Assessing Management of 

Raptor Predation for 

Western Snowy Plover Recovery

Bruce G. Marcot and Daniel C. Elbert

United States Department of Agriculture

Forest 

Service

Pacific Northwest 

Research Station

General Technical Report

PNW-GTR-910

July

2015
Authors

Bruce G. Marcot is a research wildlife biologist, U.S. Department of Agriculture, 

Forest Service, Pacific Northwest Research Station, 620 SW Main Street, Portland, 

OR 97205; Daniel C. Elbert is a fish and wildlife biologist, U.S. Department of the 

Interior, Fish and Wildlife Service, Newport Field Office, 2127 SE Marine Science 

Drive, Newport, OR 97365.

USDA is an equal opportunity provider and employer. To file a complaint of discrimination, 

write: USDA, Office of the Assistant Secretary for Civil Rights, Office of Adjudication, 

1400 Independence Ave., SW, Washington, DC 20250-9410 or call (866) 632-9992 

(Toll-free Customer Service), (800) 877-8339 (Local or Federal relay), (866) 377-8642 

(Relay voice users).

Cover photographs: (1) Adult male western snowy plover in breeding plumage, 

by Michael L. Baird, flickr.bairdphotos.com; (2) Adult female northern harrier 

preying on the eggs of a western snowy plover nest, by the Oregon Biodiversity 

Information Center.
Abstract

Marcot, Bruce G.; Elbert, Daniel C. 2015. Assessing managment of raptor 

predation management for snowy plover recovery. Gen. Tech. Rep. PNWGTR-910. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific 

Northwest Research Station. 67 p.

On February 4, 2014, a seven-member expert panel provided objective technical 

information on the potential effectiveness and feasibility of activities to manage 

raptors (northern harriers and great horned owls) to aid the recovery of western 

snowy plovers. The panel discussed and scored the 26 raptor control techniques in 

nine main categories of habitat modification, exclusions, hazing, live capture and 

relocation, nest or egg depredation, lethal hunting and removal, conditioned taste 

aversion, avicides, and combinations of techniques. The panel also identified areas 

of information that could be useful to help trigger activities for managing raptor 

predation for western snowy plover recovery, including use of cameras to detect 

raptor predation events and behavioral patterns, determining thresholds of numbers 

of predation events, better understanding of raptor nesting timing and locations, and 

other topics.

Keywords: Western snowy plover, threatened species, raptor control, predation 

effects, expert panel.
Executive Summary

On February 4, 2014, a seven-member expert panel workshop was held in Portland, 

Oregon, to provide objective technical information on potential effectiveness and 

feasibility of raptor predation management activities for aiding recovery of western 

snowy plovers (Charadrius nivosus nivosus) along the Oregon coast, and to provide 

additional information on potential monitoring and further considerations of raptor 

control for snowy plover recovery. The Pacific coast population of the western snowy 

plover was federally listed as threatened on March 5, 1993 (USFWS 1993), under the 

Endangered Species Act 1973 (16 USC 1531 et seq.), as amended. 

The panel discussed and scored the potential feasibility and effectiveness of 

26 raptor control techniques in nine main categories of habitat modification, exclusions, hazing, live capture and relocation, nest or egg depredation, lethal hunting and 

removal, conditioned taste aversion, avicides, and combinations of techniques. Each 

of these categories is defined in this report and is considered a humane and acceptable 

form of raptor predation management. For example, the category “lethal hunting and 

removal” involves the use of live and artificial lures to produce movement and sounds 

that attract raptors to a selected location where they are subsequently shot.

The panel also identified information that could help inform management 

activities including use of cameras to detect raptor predation events and behavioral 

patterns, determining thresholds of numbers of predation events, better understanding raptor nesting timing and locations, and other topics. The panel also suggested 

raptor predation management needs such as conducting inventories of raptors and 

their nests, placing monitors in the field dedicated to raptor studies, and other topics 

on predator behavior and plover demography.

The panel assessed (scored) the potential effectiveness and feasibility of each of 

the 26 raptor control techniques for controlling the two primary species, northern 

harriers (Circus cyaneus) and great horned owls (Bubo virginianus). The techniques 

with the highest average effectiveness and feasibility scores for controlling northern 

harriers were lethal hunting/removal, combinations of techniques, dho-gaza net 

trap, and Goodell’s cube trap; and the highest average effectiveness and feasibility 

scores for controlling great horned owls were lethal hunting/removal, combinations of techniques, Goodell’s cube trap, and Swedish goshawk trap. Panelists often 

differed in their scoring of specific levels of effectiveness and feasibility, which was 

not unexpected, but the overall panel mean scores provide useful guidance. 

The panelists also provided individual insights into the strength of evidence 

and areas of key uncertainty pertaining to the raptor control techniques, as well 

as on extenuating factors pertaining to corvid (i.e., American crows [Corvus 

brachyrhynchos] and common ravens [C. corax]) and raptor predation management, 
such as considerations for cost, workload, information management, planning, and 

plover recovery goals. They also provided ideas on additional points of discussion, 

concerns, and suggestions for information gathering and shared their experience in 

the use of each raptor control technique. 

The workshop was structured following the methods of Marcot et al. (2012) for 

eliciting expert knowledge in a panel setting, as has been successfully implemented 

in numerous projects. The Western Snowy Plover Expert Panel consisted of seven 

experts on the biology and ecology of the species, biology and ecology of raptors, 

and conservation planning and management of threatened and endangered species. 

Participants were drawn from federal and state wildlife agencies (U.S. Fish and 

Wildlife Service, Newport, Oregon; Animal and Plant Health Inspection Service 

Wildlife Services, Roseburg, Oregon; and the Oregon Department of Fish and 

Wildlife, Salem, Oregon) as well as nongovernmental wildlife institutions (Point 

Blue Conservation Science, Bolinas, California; Institute of Natural Resources, 

Portland, Oregon; Institute for Wildlife Studies, Arcata, California; and the High 

Desert Museum, Bend, Oregon). 
Contents

1 Introduction

5 Workshop Methods, Agenda, and Attendees

5 Workshop Extent and Participation

6 Overall Workshop Structure

6 Ensuring Knowledge Parity

6 Panel Topics

8 Results

8 Raptor Predation Management Techniques Addressed

24 Summary and Conclusions

24 Acknowledgments

25 Metric Equivalents

26 Literature Cited

28 Appendix 1: Workshop Agenda

28 Agenda–Snowy Plover Expert Panel Meeting 

“Assessing Raptor Predation Management for Snowy Plover Recovery”

28 Snowy Plover Expert Panel: 

32 Appendix 2: Letters of Invitation Sent to Each Invited 

Expert Panelist and to Each Invited Guest Observer

35 Appendix 3: List of Workshop Attendees

35 Expert Panel Participants 

35 Workshop Planning Team and Meeting Facilitators

35 Workshop Observers

35 Workshop Scribes

36 Appendix 4: List of Pre-Workshop Reading Materials Sent to Each 

Expert Panelist

37 Appendix 5: List of Potential Management Techniques 

Provided to the Panelists

37 Raptor Predation Management Techniques

for Snowy Plover Recovery

42 Appendix 6: Materials Provided to Expert Panelists During the 

Workshop: Snowy Plover Expert Panel Operation Assumptions, and 

Snowy Plover Expert Panel Key Terms

42 Snowy Plover Expert Panel Operating Assumptions

43 Snowy Plover Expert Panel Key Terms

44 Appendix 7: Worksheet Used by the Expert Panelists to Score Efficiency 

and Feasibility of Management Methods

44 Snowy Plover Expert Panel Score Sheet

46 Snowy Plover Expert Panel Score Sheet
47 Appendix 8: Summary of Data Sets on Western Snowy Plover That Are 

Currently Collected and Available for Analysis

47 Breeding Season Monitoring

47 Breeding Window Survey

47 Winter Window Survey

47 Nest Failures

48 Predator Surveys and Removal

49 Appendix 9: Results of the Expert Panel Scoring of Efficiency and 

Feasibility of Management Methods, Listed by Individual Panelists (A-G, 

Specific Names Withheld Here for Anonymity)

50 Appendix 10: Written Explanatory Notes From the Seven Expert Panel 

Participants (Denoted Here by Panelist Codes A-G), Recorded From 

Their Scoring of Efficiency and Feasibility of Management Methods

57 Appendix 11: Comments From the Seven Expert Panel Participants as 

Recorded During the Workshop by Two Independent Scribes (see app. 3)

57 Snowy Plover Expert Panel Meeting—Notes “Assessing Raptor Predation 

Management for Snowy Plover Recovery”
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Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Introduction

The western snowy plover (Charadrius nivosus nivosus) (figs. 1 through 3) is a 

small shorebird found in western North America. The Pacific coast population was 

listed as threatened under the U.S. Endangered Species Act (ESA) in 1993, and a 

recovery plan was published by the U.S. Fish and Wildlife Service (USFWS) in 

2007 (USFWS 1993, 2007). 

The Pacific coast population of the western snowy plover (hereafter, just 

“western snowy plover”) extends from the state of Washington to Baja California, 

Mexico, with most breeding birds found in California. Predation by increasing 

populations of generalist predators, including American crow (Corvus brachyrhynchos), common raven (C. corax), red fox (Vulpes vulpes), and coyote (Canis 

latrans) at coastal beaches is one of the primary threats to the western snowy plover 

(USFWS 1993). A comprehensive predation management program was established 

in 2002 (USDA and USDI 2002) to protect western snowy plovers where predation 

threatens their survival and reproductive success. 

Other suspected predators found to pose a threat to western snowy plovers, 

including raptors, have been considered in predation management planning (USDA 

and USDI 2002). The decision framework for raptor control requires resource 

managers to evaluate the magnitude of the threat and define a specific plan of action 

on a case-by-case basis. The raptor control decision framework, therefore, relies on 

expertise and capacity in the fields of raptor biology, ecology, and management, for 

which the Western Snowy Plover Working Group sought additional expertise. High 

levels of egg predation by northern harriers (Circus cyaneus) (figs. 4 and 5) during 

the 2013 breeding period (Psiropulous and Burrell 2013), and suspected predation 

Figure 2—A brood of three recently hatched western snowy plover 

chicks. The legs of western snowy plover chicks are nearly fully 

grown when they hatch and can be safely banded at this stage in 

their life cycle. Photograph credit: Kathleen Castelein, Oregon 

Biodiversity Information Center.

Figure 1—Adult male western snowy plover in breeding plumage. 

Photograph credit: Michael L. Baird, flickr.bairdphotos.com.
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GENERAL TECHNICAL REPORT PNW-GTR-910

by great horned owls (Bubo virginianus) (fig. 6), highlighted a need to better clarify 

and communicate response procedures concerning predation by raptors. 

In 2014, we convened a Western Snowy Plover Expert Panel workshop to 

provide technical information to further develop a decision analysis framework for 

informing USFWS and its conservation partners specifically about raptor predation 

management as part of this integrated predator management program. The workshop’s objectives were to (1) provide expert knowledge and advice on the efficiency 

and feasibility of management techniques as part of western snowy plover recovery 

activities, and (2) identify and prioritize needs for data collection and especially 

analysis of existing data sets, for aiding real-time monitoring of raptor impacts on 

western snowy plovers and help trigger potential management activities. 

Figure 4—Adult female northern harrier preying on the eggs 

of a western snowy plover nest. This photo was captured using 

a motion-sensitive nest camera (Reconyx PC900 Hyperfire). 

Photograph credit: Oregon Biodiversity Information Center.

Figure 5—Failed nest resulting from predation of three western 

snowy plover eggs by a northern harrier. Photograph credit: Joseph 

Metzler, U.S. Fish and Wildlife Service.

Figure 6—Great horned owl on day roost in a Douglas-fir tree. 

Photograph credit: Bruce Marcot.

Figure 3—A three-egg western snowy plover nest. Nests consist of a 

shallow scrape or depression on the surface of the beach, and are sometimes lined with shell fragments, plant debris, small pebbles, and other 

beach debris. The nest lining tends to increase as incubation progresses. 

Photograph credit: Daniel Elbert, U.S. Fish and Wildlife Service.

An expert panel 

provided information 

on raptor predation 

management to help in 

the recovery of western 

snowy plovers.
3

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

The expert panel evaluated feasibility and effectiveness of raptor predation 

management that could occur at any active breeding or nesting site along the Oregon 

coast (figs. 7 through 11). These currently include Sutton, Siltcoos, Overlook, 

Tahkenitch, Tenmile, Coos Bay North Spit, Bandon, New River, and Floras Lake. 

Sites are located on lands managed by the U.S. Department of the Interior Bureau of 

Land Management, USDA Forest Service, Oregon Department of Fish and Wildlife, 

Oregon Parks and Recreation Department, and U.S. Army Corps of Engineers, as 

well as some private lands. Current sites in Oregon are located in Lane, Douglas, 

Coos, and Curry Counties. 

Figure 10—Symbolic fencing (ropes and signs) placed 

around the dry sand portions of beaches during the 

western snowy plover breeding period on beaches 

where an abundance of western snowy plovers 

actively nest. The symbolic fencing informs the public 

about the presence of nesting western snowy plovers, 

as well as recreational use and access restrictions 

intended to reduce disturbance to the birds. 

Photograph credit: Bruce Marcot.

Figure 9—Example of a Carsonite sign 

placed near the boundary of a western 

snowy plover nesting area to inform 

the public of recreation access restrictions during the western snowy plover 

breeding period. Photograph credit: 

Bruce Marcot.

Figure 8—Ground-level view of a western snowy plover habitat 

restoration area. Photograph credit: Daniel Elbert, U.S. Fish and 

Wildlife Service.

Figure 7—Aerial view of the Western Snowy Plover Habitat 

Restoration Areas at Coos Bay North Spit, Coos County, Oregon. 

Photograph credit: Bill Bridgeland, U.S. Fish and Wildlife Service.

Figure 11—Western Snowy Plover 

Expert Panel evaluating effectiveness and feasibility of raptor control 

techniques. Photograph credit: Laura 

Todd, U.S. Fish and Wildlife Service.
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GENERAL TECHNICAL REPORT PNW-GTR-910

Although this report is aimed at aiding recovery of western snowy plovers 

along the Oregon coast, the information provided herein is general to the degree 

that it could also inform potential management of raptor predation on the species 

elsewhere within the species’ range along the U.S. Pacific coast (fig. 12). Results of 

the workshop presented here are descriptive and not intended to be prescriptive. 

Information from the workshop will be used later by USFWS in a structured 

decision analysis as one facet of western snowy plover recovery.

Figure 12—Active breeding and nesting sites of the federally threatened Pacific coast population of 

the western snowy plover along the Oregon coast.
5

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Figure 13—Range of U.S. Fish and Wildlife Service Recovery Units for the federally threatened 

Pacific coast population of the western snowy plover.

Workshop Methods, Agenda, and Attendees

Workshop Extent and Participation

The Western Snowy Plover Expert Panel workshop was held over the course of one 

day and consisted of seven invited panelists with various expertise in western 

snowy plover biology, ecology, and management; raptor ecology and management; 

and other topics such as recovery planning for threatened and endangered species 

(fig. 13). (The letters of invitation sent to prospective panelists as well as to workshop observers are presented in app. 2, and the list of workshop attendees including 

the expert panel participants and workshop observers is presented in app. 3.)
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GENERAL TECHNICAL REPORT PNW-GTR-910

Overall Workshop Structure

The panel workshop was structured following procedures of Marcot et al. (2012) 

that were previously successful for addressing issues of recovery and reintroduction 

of threatened and endangered species. These paneling procedures use a modified 

Delphi expert panel approach, wherein panelists are guided through discussions, 

brainstorming sessions, and a structured impact-scoring process. The modified 

Delphi approach provides for equal sharing and learning among panelists, but 

retains their individual and independent contributions so as to determine similarity 

or differences in knowledge and judgment among the experts, rather than forcing 

consensus that would mask individual variations.

Ensuring Knowledge Parity

Each panelist was sent a set of preworkshop reading materials (app. 4) to ensure that 

all panelists reached “knowledge parity,” that is, each panelist had exposure to the 

same suite of information. These reading materials included information on western 

snowy plover management, monitoring, recovery, and data availability; potential 

management techniques; and the intended workshop agenda, discussion topics, and 

expert paneling procedures. At the start of the panel, to further ensure knowledge 

parity among all panelists, D. Elbert provided a presentation on the western snowy 

plover’s ESA listing, threats to the species, recovery objectives and activities to date, 

monitoring data being gathered on the species, sources of nest failure and predation, 

and types of raptor predation management and control techniques (apps. 5 through 8). 

As part of the initial presentation, a flowchart was presented that denoted the 

role of the expert panel in the overall organization of western snowy plover planning (fig. 14). This was intended to help panelists better understand that they were 

to provide scientific and technical information, not to specifically advise on or 

direct management or planning actions per se. 

Panel Topics

Panel topic 1 on identification of information for raptor predation management—

The workshop agenda (app. 1) then covered three main topic sessions posed to 

the panelists. Topic 1 pertained to guided panel discussions and brainstorming of 

raptor predation and was broken into two subtopics: (1) identification of a suite 

of information that would be useful to generate real-time monitoring indices of 

raptor predation behavior and impacts on western snowy plovers, to help trigger 

potential management activities; and (2) suggestions for new data that could be 

collected to enhance the real-time monitoring indices of raptor impacts, and additional monitoring and research topics. The suggested priority of each item identified in both of the topic 1 sessions were rank-ordered by the panelists; thereafter, 

The Western Snowy 

Plover Expert Panel 

workshop followed 

rigorous procedures to 

elicit knowledge.
7

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

we calculated mean priority scores among the panelists and then sorted the themes 

by decreasing priority. 

Panel topic 2 on scoring raptor predation management techniques—

Topic 2 pertained first to listing a suite of potential raptor predation management 

approaches, then having the panelists score the degree to which each approach would 

be effective and feasible, in particular for two species known to be the main raptor 

predators of western snowy plovers along the Oregon coast: northern harriers and great 

horned owls. To do the scoring, each panelist was asked to spread 100 points across 

one or more of five categories denoting degree of effectiveness (completely ineffective, 

mostly ineffective, partially effective, mostly effective, and completely effective) and 

100 points across one or more of five categories denoting degree of feasibility (completely infeasible, mostly infeasible, partially infeasible, mostly feasible, and completely 

feasible) (see app. 6 for definitions and app. 7 for the score sheet used). Spreading 

points across two or more categories allowed the panelists to express their degree of 

uncertainty in how effective or feasible each management technique could be. In cases 

when a panelist had no knowledge of a technique, each was instructed to score it as 

total uncertainty (equal score values across all categories of feasibility or effectiveness).

Two rounds of scoring were conducted, each in silence. After the first round, the 

panelists each engaged in guided disclosure of their scores and their rationale, allowing other panelists to learn from their thinking and to ask questions. The second and 

Figure 14—Organization of western snowy plover recovery planning; WSP = western snowy plover; 

MOU = memorandum of understanding, EA = environmental assessment; USFWS = U.S. Fish and 

Wildlife Service.
8

GENERAL TECHNICAL REPORT PNW-GTR-910

final scoring round also entailed having panelists document in writing their rationale 

for the scores and what they considered to be key uncertainties, unknowns, and data 

needed (app. 7). After the second round of scoring, we gathered their score sheets 

and written documentation and later entered their scores into a database to determine patterns and trends. We also had their written documentation on rationale and 

uncertainty transcribed and compiled into one document file. 

Each panelist had been initially and randomly assigned a code letter (A, B, C, 

D, E, F, or G) which they noted on all their written forms and score sheets, in lieu 

of their names. The purpose was to keep individual identities anonymous, thus 

allowing panelists to feel at ease in offering their expertise without worry of later 

individual attribution.

Panel topic 3 on further considerations—

In the third and final portion, panelists provided their ideas on any extenuating 

factors that might be considered if raptor predation management were to be part of 

western snowy plover recovery activities. Such factors could include considerations 

for cost, personnel and training needed, stakeholder participation, public reaction, 

or any other concern, all of which were summarily not to have been considered 

during their topic 2 scoring of efficiency and feasibility of management techniques. 

Panel closeout and next steps—

At various points during the day, we also provided opportunities for invited observers to offer their ideas, perspectives, and questions. We ended the panel with a 

general discussion of how the panelists’ information could be used to inform a decision process in USFWS on raptor predation management for western snowy plover 

recovery. We also secured the day’s notes taken by our two scribes, who recorded 

much of the panelists’ discussions (without attributing specific names to each comment); we then sent the transcribed notes to the panelists for any corrections. 

Results

Raptor Predation Management Techniques Addressed

The set of management techniques discussed and scored by the panel fell into nine 

main categories, some with a number of subcategories, as follows (not listed here in 

any order of priority): (1) habitat modification; (2) exclusion (figs. 15 through 17); (3) 

hazing, including use of pyrotechnics, lasers, electric pole shockers, and scarecrows 

and bird diverters; (4) live capture and relocation, which included variants on noose 

traps (bal-chatri, phai, verbail, noosed lure, and barak), net traps (bow-net, dhogaza, net launcher, and Goodell’s cube trap), and permanent structures (Swedish 

goshawk trap and modified Australian crow trap) (e.g., figs. 18 and 19); (5) nest/egg 

depredation; (6) lethal hunting/removal; (7) conditioned taste aversion; (8) avicides 
9

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

(fig. 20); and (9) combinations of any of the above techniques. After preliminary 

review and discussion of categories and subcategories initially presented, the 

panelists chose to add five techniques (net launcher, Goodell’s cube trap, conditioned taste aversion, avicides, and combinations of techniques), resulting in the full 

set of nine main categories listed here. Each of these categories and techniques is 

defined in appendix 5, and each is considered a humane and acceptable form of 

raptor predation management (Bloom et al. 2007, Hygnstrom and Craven 1994). For 

example, the category “lethal hunting and removal” involves the use of live and 

artificial lures (figs. 18, 19, and 21) to produce movement and sounds that attract 

raptors to a selected location where they are subsequently shot.1

1 In this report, “hunting” refers to this particular method of attraction and dispatch as part 

of a predator control technique, and not to public sport hunting.

Figure 18—Setting up a self-triggering bownet with a white mouse lure for live capture 

of northern harriers. Photograph credit: Daniel Elbert, U.S. Fish and Wildlife Service.

Figure 17—Mini predator exclosure surrounding 

the nest bowl of a recently hatched western snowy 

plover nest. Photograph credit: Peter Knapp.

Figure 16—Medium exclosure protecting an active western snowy 

plover nest from predators. Photograph credit: Daniel Elbert, U.S. Fish 

and Wildlife Service.

Figure 15—Large exclosure being installed around an active 

western snowy plover nest for protection against predators. 

Photograph credit: David Lauten, Oregon Biodiversity 

Information Center.
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GENERAL TECHNICAL REPORT PNW-GTR-910

Figure 20—Chicken egg treated with compound DRC-1339 

(3-chloro-p-toludine hydrocholoride), which is a restricted-use 

avicide and is registered for control of common ravens (Corvus 

corax) and American crows (C. brachyrhynchos). Photograph 

credit: Jeremiah Psiropolous, Animal and Plant Health Inspection Service, Wildlife Services.

Figure 19—Bownet trap set with white mouse lure. Photograph credit: Daniel Elbert, U.S. Fish and 

Wildlife Service.

Figure 21—Adult male northern 

harrier successfully captured by 

Micah Bell, wildlife specialist 

with the Animal and Plant Health 

Inspection Service, Wildlife 

Services, using a self-triggering 

bownet trap with white mouse 

lure. This harrier was targeting 

western snowy plover nesting 

areas while hunting and had 

preyed on numerous western 

snowy plover eggs prior to being 

trapped. Photograph credit: 

Joseph Metzler, Animal and 

Plant Health Inspection Service, 

Wildlife Services.
11

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Panel topic 1 on identification of information for raptor predation management— 

The panelists collectively identified 25 areas of information that would be useful 

to generate monitoring indices designed to help trigger raptor predation management for western snowy plover recovery (table 1). On average, their top priority 

areas pertained to communication and information gathering on predator behavior, 

specifically (1) communication between monitors and Wildlife Services; (2) the use 

of cameras to detect predation events associated with raptors, determine behavioral 

patterns associated with predation events, and increase the frequency of such 

observations; (3) determining thresholds of the number of predation events that 

would trigger a management action; and (4) better understanding of raptor nesting 

phenology and location of raptor nests. A number of other information categories 

also ranked relatively high as suggested priorities.

The panelists also identified 21 categories of new data that could be collected to 

help enhance monitoring indices for triggering potential management actions (table 

2). The top priorities pertained again to predator study—conducting a breeding 

raptor inventory and survey to map their nests, and establishing in-field monitors 

dedicated to raptor studies. Other high-priority topics also pertained to predator 

study as well as to specific data to gather on aspects of plover demography. 

The Expert Panel 

identified key 

information needs 

for monitoring raptor 

predation effects 

on western snowy 

plovers, and evaluated 

techniques for 

managing predation by 

northern harriers and 

great horned owls.

Panel topic 2 on scoring raptor predation management techniques—

Means and variations in the panelists’ scores of effectiveness and feasibility of 

management techniques for northern harriers and great horned owls are presented 

in figures 22 through 25. 

For northern harriers (fig. 22), the techniques that the panelists, on average, 

scored high (at least 40 percent of mean score points) as completely effective or 

mostly effective included (in decreasing order of scored effectiveness): lethal 

hunting/removal, combinations of techniques, dho-gaza net trap, nest/egg depredation, and Goodell’s cube trap. Some 19 techniques were scored high (at least 40 

percent of mean score points) for feasibility; of these 19, the highest scored (at least 

60 percent of mean score points) techniques for feasibility were (in decreasing order 

of scored feasibility): lethal hunting/removal, bal-chatri noose trap, dho-gaza net 

trap, combinations of techniques, bow-net trap, net launcher, and Goodell’s cube 

trap. Thus, the techniques that seemed to score the highest for both effectiveness 

and feasibility against northern harriers were lethal hunting/removal, combinations 

of techniques, dho-gaza net trap, and Goodell’s cube trap. However, the panelists 

often differed widely in their specific scores. For the techniques scoring the highest 

for effectiveness and feasibility, disagreement of scores among the panelists ranked 

mostly medium to high (fig. 23) which, however, was generally the case among 

most categories of techniques. 
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GENERAL TECHNICAL REPORT PNW-GTR-910

Table 1—Results of panel brainstorm discussion on information that would be useful to generate monitoring 

indices to help trigger raptor predation management for western snowy plover recoverya

Priority rank by panelist

Information Theme A B C D E F G Sum Mean Rangeb

Communication between monitors and 

Wildlife Services

Communication 1 1 1 1 1 1 1 7 1.0 0

Use cameras to explore predation 

problems and to trigger a management 

response, e.g., to determine predator 

reactions to exclosures and predator 

behavior

Predator behavior 1 1 1 1 2 1 1 8 1.1 1

Determine thresholds of number of 

predation events that would trigger 

an action

Predator behavior 1 1 1 2 1 1 1 8 1.1 1

Increased frequency of observations, 

with cameras

Predator behavior 1 1 1 1 2 1 1 8 1.1 1

Understand better raptor nesting 

phenology; locate raptor nests

Predator 

phenology

2 1 1 1 1 1 1 8 1.1 1

Densities of plovers—number of nests/

unit area

Plover abundance 2 1 2 1 1 1 1 9 1.3 1

Develop demographic models of 

plovers to determine when raptor 

predation management may 

be necessary; helps determine 

compensatory vs. additive predation

Plover demography 1 1 2 2 1 1 1 9 1.3 1

Monitor raptor nests closely re: 

phenology of young production, 

for deciding on egg removal

Plover phenology 2 1 1 1 2 1 1 9 1.3 1

Camera use: trail cameras and 

video cameras

Predator behavior 1 2 1 1 2 1 1 9 1.3 1

Continue and expand camera 

observations to determine unknown 

predation sources

Predator presence 1 1 1 2 2 1 1 9 1.3 1

Measurement of plover response to 

predator removal

Plover production 3 1 2 1 1 1 1 10 1.4 2

Determine, for a given site, plover 

numbers, productivity, or density 

that could be a threshold for predator 

incursion

Plover abundance 2 1 2 1 1 3 1 11 1.6 2

Predator use of a site; determine 

predator behavior

Predator behavior 2 2 2 1 2 1 1 11 1.6 1
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Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Table 1—Results of panel brainstorm discussion on information that would be useful to generate monitoring 

indices to help trigger raptor predation management for western snowy plover recoverya (continued)

Priority rank by panelist

Information Theme A B C D E F G Sum Mean Rangeb

Correlate plover phenology and raptor 

phenology to determine when to take 

action

Predator 

phenology

1 2 3 1 2 1 1 11 1.6 2

Develop a list of raptor species in 

advance and their susceptibility to 

being trapped, removed, relocated, 

finding their nests, etc.

Raptor ecology 2 2 1 1 1 2 2 11 1.6 1

Raptor nesting status phenology Raptor phenology 2 2 1 1 2 2 1 11 1.6 1

Plover brood survival, weekly Plover phenology 1 1 2 1 2 3 2 12 1.7 2

Employ info weekly on predator 

presence

Predator 

phenology

1 2 3 1 2 2 1 12 1.7 2

Determine predator diets and diet 

ecology

Predator behavior 2 2 2 2 1 2 2 13 1.9 1

Track numbers of predators by species 

intensively throughout to determine 

predator replacement and turnover 

within the season

Predator behavior 3 1 2 2 2 2 1 13 1.9 2

Identify individual problem 

predators—possibly mark individuals

Predator presence 3 2 3 1 2 1 1 13 1.9 2

Identify alternative prey being taken by 

predators

Predator behavior 3 2 2 2 1 3 2 15 2.1 2

Timed scan / survey to record predators 

observed or track occurrence—

predator species and numbers

Predator presence 1 1 3 2 3 3 2 15 2.1 2

Small mammal surveys as prey for 

raptors

Prey ecology 3 2 3 2 1 3 3 17 2.4 2

Avoiding decisions based on raptor 

behavior

Predator behavior 3 3 3 3 1 3 2 18 2.6 2

a Items are sorted by decreasing mean priority (= increasing mean scores).

Priority ranks:

1 = essential.

2 = important but not necessarily essential.

3 = worthwhile but of lower importance.

b Range = the difference between the maximum and minimum score values across the panelists; this is a simple indicator of the degree to which all 

panelists agreed (low range values) or disagreed (high range values). 
14

GENERAL TECHNICAL REPORT PNW-GTR-910

Table 2—Results of panel brainstorm discussion on new data that could be collected to enhance monitoring 

indices to help trigger raptor predation management for western snowy plover recovery, and suggestions for 

additional monitoring and research topics

Priority rank by panelist

Data, monitoring, and research Theme A B C D E F G Sum Mean Rangea

Breeding raptor inventory and survey to 

map nests; best time is during raptor 

hatchling/fledgling period; 2-mi buffer of 

snowy plover site and within each site

Predator study 1 2 1 1 1 1 1 8 1.1 1

Need raptor monitors dedicated to raptor 

studies; seasonality depends on techniques 

to employ, probably early in the season as 

augmenting Wildlife Services

Predator study 1 2 1 1 1 1 1 8 1.1 1

Search for raptor nests; consider using 

volunteers, bird observers

Predator study 1 2 1 1 1 2 1 9 1.3 1

Determine how harriers respond to 

exclosures; determine their behavioral 

response; via use of cameras at nests with 

and without exclosures

Predator study 1 2 1 1 2 2 1 10 1.4 1

For monitors, gather the evidence as images 

of tracks, information that pinpoints a 

particular predator species, in part to 

educate others making management 

decisions

Data 2 2 1 1 1 2 1 10 1.4 1

Do a camera study to determine predator 

behavior around plover nests

Predator 

behavior

2 1 1 2 2 1 2 11 1.6 1

Compare information on harriers and 

exclosures with other states

Data 2 2 1 1 2 2 1 11 1.6 1

Use video recordings of nest area to identify 

unknown predator

Predator study 1 2 1 1 2 2 2 11 1.6 1

Do a population viability analysis of plovers 

to determine which life stage is most 

sensitive to perturbations 

Plover 

demography

3 2 2 1 2 1 1 12 1.7 2

Tracking movements of raptors that are 

translocated

Predator study 1 1 2 1 2 3 2 12 1.7 2

Analyzing current data on site-specific 

hatch and fledgling rates, determine mean 

rates (past 5 to 10 years), to compare 

productivity of sites

Plover 

demography

3 2 2 1 1 3 1 13 1.9 2

Marking raptors in the area to determine 

problem individuals

Predator study 3 1 3 2 1 1 2 13 1.9 2
15

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Table 2—Results of panel brainstorm discussion on new data that could be collected to enhance monitoring 

indices to help trigger raptor predation management for western snowy plover recovery, and suggestions for 

additional monitoring and research topics (continued)

Priority rank by panelist

Data, monitoring, and research Theme A B C D E F G Sum Mean Rangea

Determine, map raptor use of the area; GIS; 

determine spatial and temporal use and 

overlap of use among multiple predators; 

can help to find nests as well

Predator study 2 1 3 2 2 3 1 14 2.0 2

Framework for monitoring raptors and their 

prey at plover sites, in a formalized and 

integrated protocol that would be repeated 

at different sites, e.g., once every 3 years

Framework 2 1 3 2 1 3 2 14 2.0 2

Literature review and field survey to 

determine harrier habitat suitability, to 

determine habitat modification to lessen 

habitat suitability

Predator study 3 2 2 1 2 2 2 14 2.0 2

Determine how habitat modification 

actually influences raptor habitat use or 

non-use; via telemetry

Predator study 3 1 2 2 3 1 2 14 2.0 2

Look at small mammal densities over time, 

cf. harrier densities over time; determine 

episodic nature of harrier occurrence

Predator study 2 2 3 2 1 2 2 14 2.0 2

Put up raptor perches with cameras before 

the season starts to identify frequency of 

raptor occurrence and species presence

Predator study 2 2 3 2 2 3 2 16 2.3 1

Do trapline survey of rodents; Sherman 

traps, March–August, regular interval; 

mark-recapture

Predator study 3 2 3 2 1 3 3 17 2.4 2

Telemetry of individual predators to 

determine predator nests and to track how 

they use a site for feeding

Predator study 3 2 3 3 3 1 2 17 2.4 2

Correlate weather/rainfall and vegetation, to 

track raptor activity and impact on plovers, 

to determine correlations with weather 

patterns, and to ascertain predictability 

of raptor behavior and occurrence as a 

function of weather and vegetation

Predator study 2 2 3 2 3 3 2 17 2.4 1

a

 Range = the difference between the maximum and minimum score values across the panelists; this is a simple indicator of the degree to which all 

panelists agreed (low range values) or disagreed (high range values). 

Note: Items are sorted by decreasing mean priority (= increasing mean scores). 

1 = Essential.

2 = Important but not necessarily essential.

3 = Worthwhile but of lower importance.
16

GENERAL TECHNICAL REPORT PNW-GTR-910

Figure 22—Mean scores of the seven expert panelists of effectiveness and feasibility of raptor control techniques on northern harriers.
17

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Figure 23—Degree of variation among the seven expert panelists in how they scored effectiveness and feasibility of management 

techniques on northern harriers. Values are coefficient of variation (CV) of scores among the panelists (CV = standard deviation/mean).
18

GENERAL TECHNICAL REPORT PNW-GTR-910

For great horned owls (fig. 24), the techniques that the panelists, on average, 

scored the highest (at least 40 percent of mean score points) as completely effective 

or mostly effective included (in decreasing order of effectiveness): lethal hunting/

removal, combinations of techniques, Goodell’s cube trap, bal-chatri noose trap, 

Swedish goshawk trap, and the verbail noose trap. Some 18 techniques were scored 

high (at least 40 percent of mean score points) for feasibility; of these 18, the highest 

scored (at least 60 percent of mean score points) techniques for feasibility were (in 

decreasing order of feasibility): lethal hunting/removal, Goodell’s cube trap, Swedish goshawk trap, combinations of techniques, and net launcher. Thus, the techniques that seemed to score the highest for effectiveness and feasibility against great 

horned owls were lethal hunting/removal, combinations of techniques, Goodell’s 

cube trap, and Swedish goshawk trap. As with the scores on northern harriers, the 

panelists tended to diverge on their scores on great horned owls (fig. 25). 

Thus, the techniques that ranked highest for effectiveness and feasibility 

in common for harriers and owls were lethal hunting/removal, combinations of 

techniques, and Goodell’s cube trap.

Interpreting mean and variations in panel scores— 

The divergence of panelists’ scores on raptor control techniques (figs. 22 and 24) 

does not necessarily indicate reduced confidence of the effectiveness or feasibility 

of specific management techniques. Rather, the divergence of scores more likely 

reflects differences in individual experience and expected methods of application of 

the techniques. The criteria we used to select the panelists resulted in a panel with a 

range of experience geographically and topically. 

The mean panel scores (figs. 23 and 25) are an indication of this particular 

expert community as a whole. For instance, with northern harriers (fig. 22), mostly 

or completely effective techniques pertain to live capture and relocation (technique 

numbers 4a through 4k) and to nest/egg depredation, lethal hunting/removal, 

avicides, and combinations (technique numbers 5, 6, 8, and 9), and far less to habitat 

modification, exclusion, and hazing (technique numbers 1, 2, and 3), whereas nearly 

all techniques were scored on average as being mostly or completely feasible except 

for habitat modification and use of avicides. 

U.S. Fish and Wildlife Service managers also may wish to understand how the 

knowledge and thinking of individual experts differ in the degree to which various 

management techniques may be effective and feasible. For example, consider lethal 

hunting and removal of northern harriers (technique number 6 in figs. 22 and 23). 

This technique averaged among all panelists the highest score of all techniques 

for being mostly or completely effective and mostly or completely feasible (fig. 

22). The variation among panelist scores (fig. 23) for this technique indicates much 
19

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Figure 24—Mean scores of the seven expert panelists of effectiveness and feasibility of raptor control techniques on great horned owls.
20

GENERAL TECHNICAL REPORT PNW-GTR-910

Figure 25—Degree of disagreement among the seven expert panelists in how they scored effectiveness and feasibility of management 

techniques on great horned owls; values are coefficient of variation (CV) of scores among the panelists (CV = standard deviation/mean)).
21

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

agreement among panelists, because variation among panelists was relatively low 

for extreme values of feasibility and effectiveness (e.g., completely feasible and 

completely infeasible). In this way, the score results provide a means of identifying 

raptor control techniques with high (or low) expected effectiveness and feasibility, 

and with a degree of agreement among panelists. 

Panelists also expressed a broad array of reasons for their scores of the array 

of management techniques, and they noted areas of key uncertainties and data 

needs that led to their scoring of effectiveness and feasibility (app. 10). Regarding 

lethal hunting and removal, panelists cautioned that although it could be effective 

at reducing predation caused by harriers and owls, it may still be difficult to reduce 

snowy plover nest failure if removal of territorial adult raptors results in an influx 

of additional raptors with an ability to predate snowy plover eggs, chicks, or adults. 

Panelists also cautioned that sociopolitical concerns could prevent otherwise effective and feasible techniques from being used. 

Goodell’s cube trap was a structure newly introduced to the panel by panelist 

Goodell, and few panel members had familiarity with it. In general, though, they 

felt it would be useful based on the description given, although one panelist noted 

that it may not be effective on harriers. A combination of techniques ranked high 

for harriers and owls, although which specific techniques would be combined for 

each species were not identified. 

Panel topic 3 on further considerations—

Panelists also provided a number of ideas on extenuating factors pertaining to corvid and raptor predation management, cost and workload, information management, 

planning, and plover recovery goals (table 3). Many of these points may be useful 

for the Recovery Unit 1 Western Snowy Plover Working Group and managers to 

consider if management techniques are deemed necessary and are implemented. As 

examples, the panel suggested using field personnel with raptor expertise for data 

collection, and that successfully implementing raptor predation management might 

entail considerations for finite time, cost, and staff so as to best focus raptor control 

only where and when specifically identified, thus requiring clarity on raptor monitoring goals and objectives. 

Experts varied in their 

experience with raptor 

control techniques, but 

jointly identified those 

of higher effectiveness 

and feasibility among 

a total of 26 potential 

techniques.

Overall panel discussion comments—

A number of additional points of discussion, concerns, and suggestions were raised 

by the panelists, specifically on topics pertaining to identifying information useful 

for generating indices to help trigger a raptor control decision; means of gathering 

that information; other raptor control methods to consider; rationale for scoring 

effectiveness and feasibility of raptor control methods; and further extenuating 

factors in instituting a raptor control program (app. 11). 
22

GENERAL TECHNICAL REPORT PNW-GTR-910

Table 3—Results of panel brainstorm discussion on extenuating factors that could influence real-world 

implementation of raptor predation management for western snowy plover recoverya

Extenuating factor Theme

Maintain emphasis on corvid control, and not switch resources to raptor predation 

management. Corvid management is paramount. There may be limited funds to cover 

both corvid and raptor predation management. 

Corvid management

Cost is a constraint, especially with state budgets shrinking. Large-scale raptor removal 

would not be acceptable from permitting level, public standpoint, and funding.

Cost

Will take some time to collect and analyze the information proposed. Information managementt

Would need raptor expertise, whether volunteers or agency personnel, for data 

collection.

Personnel

The existing environmental assessment (EA) constrains the existing program; would 

need to revisit the EA if there are significant changes to the program. 

Planning

Difficult to determine the decision point for harrier control specifically. Does the withinseason decision point always pertain to harrier control? We have the threshold numbers 

but need to define the process for the decision point. 

Planning

Some agencies might not wish to take part in raptor management even though they have 

a snowy plover habitat restoration area on their lands.

Planning

The case of barred owl control to recovery spotted owls may help inform the raptorplover situation.Planning

Larger landscape issues of how individual agencies are constrained by their 

jurisdictions. Need collaborative efforts and need to involve many groups. Need 

partnerships.

Planning

Could involve groups such as flying clubs and others to mobilize and and help with 

tasks. Need to look more broadly than just trained biologists for some tasks. Could help 

to reduce costs.

Planning

We focus on nest success, but do not know what the fate of chicks are, or of adults. The 

ultimate goal is population growth, not nest success per se. 

Planning

Keep perspective over the last decade on where plover recovery has come; are we 

becoming less sensitive to issues such as harrier control? Yes.

Planning

Revisit population goals for each colony, vs. managing take for individuals. For plovers, 

makes sense to have a long-term goal every 3 years or so; problem is with specific 

raptor management, not a system issue.

Plover goals

Will be a need for public review of a new raptor management plan; will be an ongoing 

issue. Will be a permitting issue.

Public

For proactive outreach, who do we need to inform? There may be outside sensitivity 

especially for harrier control. This could be a “stopping point” for a raptor control 

program.

Public

Raptor predation management cost and personnel needed: could be tail wagging the dog. 

Massive resources might still not provide successful results. 

Raptor management
23

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Table 3—Results of panel brainstorm discussion on extenuating factors that could influence real-world 

implementation of raptor predation management for western snowy plover recoverya (continued)

Extenuating factor Theme

May be difficult identifying which individual raptor may be responsible for predation; in 

so doing, this may take time and result in undue predation rates. Need to clarify goal, 

whether it is to track individual raptors’ predation behavior, vs. generally asserting a 

raptor control approach.

Raptor management

Public reaction to killing raptors may not be acceptable. Raptor management

Time management is the key factor limiting being able to actually engage in harrier 

trapping, control, finding nests, etc. This is a matter of cost. If raptor predation 

management is instituted, may need to drop some corvid control activities. But do 

need to first explore nonlethal raptor control techniques before lethal techniques are 

engaged; there is a cost factor for this. Would need to find volunteer staff, for example, 

to locate raptor nests. 

Raptor management

Time, cost, and staff constraints have led to focusing raptor control only where and 

when specifically identified.

Raptor management

Raptors caught could be brought into an educational institute, but this could be seen as a 

conflict of interest.

Raptor management

There may be legal constraints on use of avicides. Raptor management

If exploring live capture techniques, how are various agencies involved in relocating 

raptors? Need to work as a team, need to discuss, and come up with a best protocol 

before the issue arises.

Raptor management

Could engage a working group to engage education especially for raptor live capture. 

Could find a good outcome for captured raptors, especially with the guidance of the 

working group.

Raptor management

Related is the work load for both predator control and monitoring. Workload

a

Items are sorted alphabetically by theme. Panel method used: structured panel discussion.
24

GENERAL TECHNICAL REPORT PNW-GTR-910

Summary and Conclusions

The expert panel provided individual and collective information on potential, new 

monitoring activities and data to gather for tracking the effect of raptor (northern 

harrier and great horned owl) predation on western snowy plovers along the Oregon 

coast. The panelists scored the effectiveness and feasibility of 26 techniques for 

controlling raptors. 

Techniques scoring the highest effectiveness and feasibility for control of northern 

harriers were lethal hunting and removal, combinations of techniques, dho-gaza net 

trap, and Goodell’s cube trap, and for control of great horned owls were lethal hunting 

and removal, combinations of techniques, Goodell’s cube trap, and Swedish goshawk 

trap. Although the panelists varied in their scoring of specific levels, they generally 

agreed on the techniques that were mostly or completely effective and feasible. 

Based on their own individual experiences, the panelists also suggested a 

number of extenuating factors to consider when instituting a raptor control program, particularly regarding the need for trained personnel; for collecting data 

consistently; for considering best allocation of finite time, funds, and staff; and for 

clarifying goals and objectives for raptor monitoring. They also noted the need for 

determining thresholds for the number of predation events that would signal when 

raptor control may be warranted. 

In general, results of the panel will be considered by USFWS managers in a 

broader risk analysis and risk management framework for monitoring and managing predation to aid in the recovery of western snowy plovers. 

Acknowledgments

We thank Michael Burrell, Carleton Eyster, Eleanor Gaines, Dave Garcelon, John 

Goodell, Martin Nugent, and Laura Todd for their participation and contributions as 

expert panelists. We also thank Jody Caicco and Vanessa Loverti for serving as scribes 

during the panel discussions, and Cindy Burns, Jody Caicco, Jeffrey Dillon, and 

Jennifer Kirkland for their kind patience and contributions as workshop observers. We 

appreciate the administrative and technical support afforded to the success of the workshop by personnel of the Oregon Fish and Wildlife Office; our thanks go particularly to 

Rollie White for supporting this work. Bruce Marcot participated under an interagency 

work agreement between the U.S. Forest Service Pacific Northwest Research Station 

and the U.S. Fish and Wildlife Service Oregon Fish and Wildlife Office. We appreciate 

the support of all the participating federal, state, and private agencies and institutions 

(please see app. 3). The structure and operating procedures of the expert panel session 

adhered to the Federal Advisory Committee Act, ensuring that panelists provided scientifically focused information, but not management direction, to the federal agencies. 

Raptor predation 

on western snowy 

plovers might be 

most effectively and 

feasibly controlled by 

direct removal, use 

of net or cube traps, 

or combinations of 

approaches.
25

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Metric Equivalents

When you know: Multiply by: To find:

Inches (in) 2.54 Centimeters (cm)

Feet (ft) 0.3048 Meters (m)

Yard (yd) 0.9144 Meters (m)

Mile (mi) 1.609 Kilometers (km)
26

GENERAL TECHNICAL REPORT PNW-GTR-910

Literature Cited

Bloom, P.H.; Clark, W.S.; Kidd, J.W. 2007. Capture techniques. In: Bird, D.M.; 

Bildstein, K.L., eds. Raptor research and management techniques. Blaine, WA: 

Hancock House Publishers: 193–219.

Hygnstrom, S.E.; Craven, S.R. 1994. Hawks and owls. In: The handbook: 

prevention and control of wildlife damage. Lincoln, NE: University of Nebraska, 

Internet Center for Wildlife Damage Management: E53–E61.

Lauten, D.J.; Castelein, K.A.; Farrar, J.D.; Breyer, M.F.; Gaines, E.P. 2013.

The distribution and reproductive success of the western snowy plover along 

the Oregon coast—2013. Draft report. Portland, OR: Oregon Biodiversity and 

Information Center, Institute for Natural Resources. 64 p. http://orbic.pdx.edu/

documents/2013-plover.pdf. (23 June 2014).

Marcot, B.G.; Allen, C.; Morey, S.; Shively, D.; White, W. 2012. An expert panel 

approach to assessing potential effects of bull trout reintroduction on federally 

listed salmonids in the Clackamas River, Oregon. North American Journal of 

Fisheries Management. 32(3):450–465.

Psiropoulos, J.; Burrell, M. 2013. Integrated predator damage management report 

for the western snowy plover (Charadrius nivosus nivosus) 2013 breeding season 

at Baker/Sutton, Siltcoos, Overlook, Tahkenitch, Tenmile, Coos Bay North Spit, 

Bandon State Natural Area, and New River Area of Critical Environmental 

Concern. Portland, OR: U.S. Department of Agriculture, Animal and Plant 

Health Inspection Service, Wildlife Services. [Pages unknown].

U.S. Department of Agriculture; U.S. Department of the Interior [USDA 

and USDI]. 2002. Predator damage management to protect the federally 

threatened Pacific coast population of the western snowy plover. Portland, OR: 

U.S. Department of Agriculture, Animal and Plant Health Protection Service, 

Wildlife Services, and the Siuslaw National Forest; and U.S. Department of the 

Interior, Fish and Wildlife Service, Region 1, and Bureau of Land Management 

Coos Bay District; in cooperation with the Oregon Department of Fish and 

Wildlife and Oregon Parks and Recreation Department. 149 p.

U.S. Fish and Wildlife Service [USFWS]. 1993. Endangered and threatened 

wildlife and plants: determination of threatened status for the Pacific coast 

population of the western snowy plover. Federal Register. 58(42): 12864–12874.
27

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

U.S. Fish and Wildlife Service [USFWS]. 2007. Recovery plan for the Pacific 

coast population of the western snowy plover (Charadrius alexandrinus nivosus). 

Sacramento, CA. xiv + 751 p. 2 vols.

Western Snowy Plover Working Group, Recovery Unit 1. 2013. Western snowy 

plover integrated predator damage management program, 2013 final action plan. 

Prepared for the U.S. Department of the Interior Fish and Wildlife Service and 

Bureau of Land Management; U.S. Department of Agriculture Forest Service 

and Animal and Plant Health Inspection Service; Oregon Department of Fish and 

Wildlife, Oregon Parks and Recreation Department, and Oregon Biodiversity and 

Information Center. Florence, OR. 17 p
28

Appendix 1: Workshop Agenda Agenda–Snowy Plover Expert Panel Meeting “Assessing Raptor Predation Management for Snowy Plover Recovery” February 4, 2014, 8:30 am – 5 pm, U.S. Fish and Wildlife Service, Portland, Oregon Prework for Snowy Plover Expert Panel: Review items sent out in advance: 2013 Snowy Plover Monitoring Annual Report; 2013 Snowy Plover Predator Management ASummary; 2013 Snowy Plover Predator Management Annual Report; Summary of data that is currently collected and available Snowy Plover Decision Analysis Project Summary Snowy Plover Expert Panel: Times are approximate and can be flexible

Time Topic Main messages Lead Objective8:30-8:50 am

WelcomeRoster Check In, introductions (SP Expert Panel; Workshop Facilitators & Advisors; Observers; Note-taker)

Introductions to the workshop.No decisions to be made.No major changes to the agenda.

Dan Elbert Goal & expectatio

workshop:To provide objectivinformation on poteffectiveness and fmanagement activPlover recovery. Overall workshop goal What you should have received/brought

Agenda reviewWelcome by USFWS Managers Welcome (Paul Henson). Local FWS 

manager(s)

8:50-9:10 am 

Overview of methodsRoles of SP expert panel, facilitators, and observers – clarify how workshop fits overall SP recovery actions

Information sharing. Dan Elbert, 

Bruce Marcot

Present flow chart overall project, and workshop fits in.
29

Time Topic Main messages Lead Objective

Summarize specific workshop objectives Scoring and written info 

(by the scribe) will be anonymous.

Workshop objectivwill address:1. How does raptor affect SP productiv2. What is the effic(effectiveness & fevarious managemeon SP recovery?

Summarize overall panel methods: guided discussions and individual scoringGrounding: define key terms and concepts to be addressed; summarize operating assumptions

Adherence to panel etiquette and assumptions.

Lunch choices

9:10-9:40 am

Background PresentationBrief review of SP recovery, including recent monitoring, and SP predator management action plan and annual report 

Presentation Dan Elbert The purpose is to e

panelists are equallthe key topics, and to ask questions (i.eelevating playing fi

Brief introduction of the topic – species involved, what is known from monitoring. Include addressing the question of whether raptor predation is compensatory or additive to other mortality sources.

Briefly summarize and knowledge of on SPs.

9:40-10:00 am

Topic 1: panel discussions of raptor predation on snowy plovers & raptor predation managementGuided panel discussion topics:What suite of information could be used to generate indices that help trigger a decision on whether to implement raptor predation management, in real time?Biological impacts (demography/productivity)Evidence that is neededSeasonal/temporal componentsWhat new data could be collected that would enhance these indices, in real time? What is the best way to gather the information? That is, suggestions for additional monitoring & researchto inform a raptor predation management program.

Expert panel discussion (Scribe will capture panel’s key discussion points)

Panel, guided by Bruce Marcot & Dan Elbert

Engage the expert guided discussion predation on SPs.Bruce will capture key ideas on each t
30

Time Topic Main messages Lead Objective 10:00- 10:20 am Break 10:20 am- 12:00 pm Topic 1: panel discussion of raptor predation effects on snowy plover productivity (continue, as needed) The panelists will 

priority scores on tdiscussed prior to 

12:00- 12:40 pm Lunch Lunch items may be brought into the panel meeting room, instead of everyone dispersing. 12:40- 1:00 pm Review of the morning’s guided topic discussion on raptor predation effects on Snowy Plovers. Also briefly solicit comments from non-panelist observers in the room. Brief review Scribe, Bruce, & Dan Quick review of th

suggested by the pthat scribed notes wall panelists later f

1:00-3:30 pm

Topic 2: panel evaluation of efficacy of raptor predation management methodsOverview of panel procedures for this session Review of panel methods. Bruce Marcot Briefly describe th

questions, scoring operating assumpt

Brief review of management techniques. Panelists may also suggest additional techniques for their evaluation.

What techniques have been, or could be used?

Dan Elbert Brief review of a s

of management tecQuestions from paensure everyone unequally.

Round one scoring: Panelists individually and silently score effectiveness and feasibility of each management technique.

Begin panel scoring. Can add combinations.

Bruce Marcot Panelists provide i

via their score valurationale for their s

Round one disclosure: 1. Panelists each disclose their scoring and rationale, uninterrupted except for clarification questions.2. Panelists then engage in more open discussion on their scoring and thinking.

Panelists each present their results.

Panelists disclose treasoning.Marcot will enter sa spreadsheet and overall results.

Round two scoring Second round of panel 

scoring. 

Round one disclosure Panelists each present their 

results.

As above.
31

Time Topic Main messages Lead Objective3:30-3:50 pm

Break

3:50-4:45 pm

Topic 3: discussion about extenuating factorsPanel to engage in a guided discussion about the following extenuating factors that FWS could consider when deciding on a raptor predation management plan for SP recovery:cost, personnel needed, & training neededstakeholder participation public reactionOpen the floor to observers for their comment, questions, and observations.

To provide to FWS a collective set of experiences and professional opinions on additional considerations for raptor predation management.

Dan Elbert Panelists to provid

experience in each engage in speculatThe method to use a “structured brainapproach whereby will be asked for thsuggestions, or cavsubsequent panelisto repeat others’ idaround the panel severyone has provideas. This can be done fabove bulleted list combinations there

4:45 pmend Wrap-up & close-out What’s next: The scribe, Dan, and Bruce will 

compile the day’s notes, discussions, and results, and send to each panelist for their review. Use of the panel’s input: develop a template for a decision process for raptor predation management for FWS.Panelists will be asked to provide any statements on the topics covered today.Panelists will be asked to briefly critique the day’s procedures, if they wish.Open the floor to all observers and non-panelists, for final comments and suggestions.End

Review next steps. Dan Elbert, 

Bruce Marcot

Panelists will have to review their inpchange their scoreInformation sharin
32

GENERAL TECHNICAL REPORT PNW-GTR-910

Appendix 2: Letters of Invitation Sent to Each Invited 

Expert Panelist and to Each Invited Guest Observer

United States Department of the Interior

FISH AND WILDLIFE SERVICE

Newport Field Office

2127 SE Marine Science Drive

Newport, Oregon 97365

Phone: (541) 867-4558 FAX: (541) 867-4551 

Reply To: Raptor Management Panelist Invitation_Example

File Name: 8181.0854G

TS Number: 14-260

January 24, 2014 

Panelist Name

Title

Organization

Street Address

City, State, Zip

Dear Panelist,

Thank you for agreeing to participate in the February 4, 2014, expert panel workshop to provide 

technical, biological, or scientific information on raptor predation management as part of the 

Pacific coast population of western snowy plover (Charadrius nivosus nivosus) recovery 

activities. Although much of the initial discussion will be based from experiences in Oregon, the 

results of this panel session will support the Service with key information for our decision 

making processes associated with managing the risk of raptor predation of snowy plovers and 

their eggs and chicks, and could also inform western snowy plover recovery activities across the 

Pacific coast range.

As part of the expert panel, you will be asked to help assess the potential effects of raptor 

predation on snowy plovers, the effectiveness and feasibility of various management techniques, 

and to identify and prioritize existing and new information that could trigger a decision on 

whether to implement raptor predation management. Please be aware that all materials and 

communications associated with this expert panel meeting will be subject to the Freedom of 

Information Act.

Dr. Bruce Marcot, research wildlife biologist with Pacific Northwest Research Station, U.S. 

Forest Service, and Daniel Elbert, endangered species biologist with the Service, will serve as 

facilitators of the workshop and for all exercises involving your assessments. Dan Elbert will 

also serve as the key contact for panel members.

Enclosed with this letter is a packet of background materials that includes a draft workshop 

agenda, pre-reading materials and a scoring-sheet. Although we intend to cover some of these 

items in presentations at the front end of the workshop we ask that you familiarize yourself with 

these materials ahead of time. Additionally, we ask that you score biological effectiveness and 

technical feasibility of each management technique and to not consider cost, political sensitivity, 

management budgets, etc., as described on page 6 of the agenda. 
33

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

United States Department of the Interior

FISH AND WILDLIFE SERVICE

Newport Field Office

2127 SE Marine Science Drive

Newport, Oregon 97365

Phone: (541) 867-4558 FAX: (541) 867-4551 

Reply To: 8181.0854G

File Name: Raptor Management Guest Invitation_Example

TS Number: 14-260

January 24, 2014 

Invited Guest 

Title

Organization

Street Address

City, State, Zip

Dear Invited Guest, 

We would like to invite you or your agency representative to attend an expert panel session that will 

provide technical, biological, and scientific information on raptor predation management as part of 

the Pacific coast population of western snowy plover (Charadrius nivosus nivosus) recovery 

activities. Although much of the initial discussion will be based from experiences in Oregon, the 

results of this panel session will support the Service with key information for our decision making 

processes associated with managing the risk of raptor predation of snowy plovers and their eggs and 

chicks, and could, therefore, inform western snowy plover recovery activities across the Pacific coast 

range. 

Implementation of a multi-agency integrated predator management program is a prime example of 

the type of commitment and cooperation that is moving the plover towards recovery in Oregon, and 

much of the credit for this improvement lies with of our State and Federal land management partners. 

As key agencies actively involved in western snowy plover recovery activities, I encourage you to 

attend this important event. As an invited guest you will have the opportunity to observe the 

development of the expert knowledge-based decision model and be given ample opportunity to 

speak, ask questions and provide ideas at certain points during the panel session.

The panel session will be held in Portland at our Oregon Fish and Wildlife Office (2600 S.E. 98th 

Avenue, Suite 100, Portland, OR, 97266) on February 4, 2014, from 8:30 am to 5:00 pm. In order to 

ensure that all attendees receive further directions, please provide us a list of attendees and their 

email addresses to Daniel Elbert, daniel_elbert@fws.gov, or Laura Todd, laura_todd@fws.gov. 

Thank you for your support in the conservation of the western snowy plover, and we look forward 

seeing you in February. 

 Sincerely

 Laura L. Todd, Field Supervisor

Pre-reading materials include: 2013 Snowy Plover Predator Management Action Plan; 2013 

Snowy Plover Monitoring Draft Annual Report; 2013 Snowy Plover Predator Management 

Annual Report; Summary of data that is currently collected and available for analysis; and a 

peer-reviewed article describing procedures applicable to expert paneling in general.

The panel session will be held in Portland at our Oregon Fish and Wildlife Office (2600 S.E. 

98th Avenue, Suite 100, Portland, OR, 97266) on February 4, 2014, from 8:30 am to 5:00 pm. If 

you are not from the Portland/Vancouver area and will need accommodations, a convenient hotel 

is the Residence Inn 1710 NE Multnomah Street, Portland 1-503-288-1400. A Shuttle will be 

available if you will need a ride from the airport or to the Oregon Fish and Wildlife Office. We 

will provide coffee and refreshments during the panel session, and will have menus from a 

nearby restaurant to order in (please bring cash). After the conclusion of the panel session you 

are also invited to join us for a social gathering.

Thank you for your support in the conservation of the western snowy plover, and we look 

forward seeing you on February 4. Please contact Dan Elbert (541-867-4558 x239, 

daniel_elbert@fws.gov) if you have any further questions.

Sincerely

Paul Henson

State Supervisor 
34

GENERAL TECHNICAL REPORT PNW-GTR-910

United States Department of the Interior

FISH AND WILDLIFE SERVICE

Newport Field Office

2127 SE Marine Science Drive

Newport, Oregon 97365

Phone: (541) 867-4558 FAX: (541) 867-4551 

Reply To: 8181.0854G

File Name: Raptor Management Guest Invitation_Example

TS Number: 14-260

January 24, 2014 

Invited Guest 

Title

Organization

Street Address

City, State, Zip

Dear Invited Guest, 

We would like to invite you or your agency representative to attend an expert panel session that will 

provide technical, biological, and scientific information on raptor predation management as part of 

the Pacific coast population of western snowy plover (Charadrius nivosus nivosus) recovery 

activities. Although much of the initial discussion will be based from experiences in Oregon, the 

results of this panel session will support the Service with key information for our decision making 

processes associated with managing the risk of raptor predation of snowy plovers and their eggs and 

chicks, and could, therefore, inform western snowy plover recovery activities across the Pacific coast 

range. 

Implementation of a multi-agency integrated predator management program is a prime example of 

the type of commitment and cooperation that is moving the plover towards recovery in Oregon, and 

much of the credit for this improvement lies with of our State and Federal land management partners. 

As key agencies actively involved in western snowy plover recovery activities, I encourage you to 

attend this important event. As an invited guest you will have the opportunity to observe the 

development of the expert knowledge-based decision model and be given ample opportunity to 

speak, ask questions and provide ideas at certain points during the panel session.

The panel session will be held in Portland at our Oregon Fish and Wildlife Office (2600 S.E. 98th 

Avenue, Suite 100, Portland, OR, 97266) on February 4, 2014, from 8:30 am to 5:00 pm. In order to 

ensure that all attendees receive further directions, please provide us a list of attendees and their 

email addresses to Daniel Elbert, daniel_elbert@fws.gov, or Laura Todd, laura_todd@fws.gov. 

Thank you for your support in the conservation of the western snowy plover, and we look forward 

seeing you in February. 

 Sincerely

 Laura L. Todd, Field Supervisor
35

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Appendix 3: List of Workshop Attendees

Expert Panel Participants 

Michael Burrell, District Supervisor, APHIS-Wildlife Services, Roseburg, Oregon

Carleton Eyster, Snowy Plover Biologist, Point Blue Conservation Science (formerly Point Reyes Bird Observatory), Bolinas, California

Eleanor Gaines, Zoology Projects Manager, Institute of Natural Resources, 

Portland, Oregon

Dave Garcelon, President, Institute of Wildlife Studies, Arcata, California

John Goodell, Curator of Natural History, High Desert Museum, Bend, Oregon

Martin Nugent, Threatened and Endangered/Sensitive Species Coordinator, 

Oregon Department of Fish and Wildlife, Salem, Oregon

Laura L. Todd, Field Supervisor, Newport Field Office, U.S. Fish and Wildlife 

Service, Newport, Oregon

Workshop Planning Team and Meeting Facilitators

Daniel C. Elbert, Endangered Species Biologist, Newport Field Office, U.S. 

Fish and Wildlife Service, Newport, Oregon

Bruce G. Marcot, Research Wildlife Biologist, Pacific Northwest Research 

Station, USDA Forest Service, Portland, Oregon

Workshop Observers

Cindy Burns, Wildlife Biologist, Siuslaw National Forest, Central Coast Ranger 

District / Oregon Dunes Natural Recreation Area, USDA Forest Service, 

Reedsport, Oregon

Jody Caicco, Forest Resources Division Manager, Oregon Fish and Wildlife 

Office, U.S. Fish and Wildlife Service, Portland, Oregon

Jeffrey A. Dillon, Endangered Species Division Manager, Oregon Fish and 

Wildlife Office, U.S. Fish and Wildlife Service, Portland, Oregon

Jennifer Kirkland, Wildlife Biologist, Coos Bay District, USDI Bureau of Land 

Management, North Bend, Oregon

Workshop Scribes

Jody Caicco, Forest Resources Division Manager, Oregon Fish and Wildlife 

Office, U.S. Fish and Wildlife Service, Portland, Oregon

Vanessa Loverti, Wildlife Biologist Shorebird Coordinator, Migratory Birds and 

Habitat Programs, Pacific Regional Office, U.S. Fish and Wildlife Service, 

Portland, Oregon
36

GENERAL TECHNICAL REPORT PNW-GTR-910

Appendix 4: List of Pre-Workshop Reading Materials 

Sent to Each Expert Panelist

1. “A Decision Analysis Approach to Raptor Management for Snowy Plover 

Recovery: Project Summary” by Dan Elbert and Bruce G. Marcot (internal 

white paper).

2. 2013 Snowy Plover Predator Management Action Plan (Western Snowy 

Plover Working Group, Recovery Unit 1, 2013)

3. 2013 Snowy Plover Monitoring Draft Annual Report (Lauten et al. 2013)

4. 2013 Snowy Plover Predator Management Annual Report (Psiropoulos and 

Burrell 2013)

5. Summary of data that is currently collected and available for analysis (see 

app. 11).

6. Peer-reviewed article describing procedures applicable to expert paneling in 

general (Marcot et al. 2012)

7. Contact list of all invited panelists (see app. 4)

8. Snowy Plover Expert Panel Workshop agenda (see app. 1)

9. Snowy Plover Expert Panel Workshop scoring sheet (see app. 7)

10. List of management techniques (see app. 5)

11. Snowy Plover Expert Panel Workshop Operating Assumptions and Key 

Terms (see app. 6)
37

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Appendix 5: List of Potential Management Techniques 

Provided to the Panelists

Raptor Predation Management Techniques

for Snowy Plover Recovery

4 February 2014

Strategies and techniques were identified and defined primarily using the 

following sources: 

Ash, L. 2014. Traps and trapping. The modern apprentice: falconry, ecology 

education. http://www.themodernapprentice.com/

Bloom, P.H.; W.S. Clark, and J.W. Kidd. 2007. Capture techniques. In: Bird, 

D.M.; Bildstein K.L. eds. Raptor research and management techniques, Blaine,

WA: Hancock House.

Hygnstrom, S.E.; Craven S.R. 1994. Hawks and owls. Handbook: Prevention and 

Control of Wildlife Damage. Paper 63.

1. Habitat Modification

This strategy involves altering the abundance and availability of key components of

raptor habitat, raptor prey habitat, or raptor food sources, in order to make snowy

plover nesting areas and adjacent areas less attractive to raptors, resulting in less

use by raptors.

2. Exclusion

This strategy involves the use cages constructed of 2′′× 4′′ welded wire that are

centered around plover nests in order to restrict access of predators to plover nests

and eggs. Exclosures can be categorized into three general sizes: mini-exclosure (≤

2′× 2′× 2′), medium exclosure (≈ 4′× 4′× 2′), and large exclosure (≥ 6′× 6′× 4′).

3. Hazing

This strategy involves the use of scare tactics to frighten, disturb or harass a raptor

sufficiently that a change in behavior occurs, resulting in the avoidance of the

target area.

3a. Pyrotechnics: Pyrotechnics include a variety of exploding or noise-making 

devices. The most commonly used are shell crackers, which are 12-gauge shotgun 

shells containing a firecracker that is projected 50 to 100 yards (45 to 90 m) before it 

explodes. Noise, whistle, and bird bombs are also commercially available. They are 

fired from pistols and are less expensive to use than shell crackers, but their range is 

limited to 25 to 75 yards (23 to 68 m).
38

GENERAL TECHNICAL REPORT PNW-GTR-910

3b. Lasers: Using lasers with very bright beams and very low divergence that appears 

as a physical danger to the raptor, causing the raptor to fly away in order to avoid the 

laser beam. Lasers can be used to scare birds from a long distance (100 m to 1 km).

3c. Electric pole shockers: Each unit consists of a ground wire running 1 inch (2.5 

cm) from and parallel to a wire that is connected to an electric fence charger. When 

a raptor lands on a pole, it receives an electric shock and is repelled from the immediate area. Other perching sites in the area should be removed or made unattractive. 

Shocking units are energized from dusk until dawn for owls and during daylight 

hours for hawks. The electric pole shocker keeps raptors from perching within a 

threatened area but does not exclude them from nesting in or using a nearby area. 

Most hawks and owls are highly territorial. A pair that is allowed to remain will aggressively defend the area and usually exclude other hawks and owls. Thus, farmers may actually find it beneficial to coexist with a pair of hawks or owls that have 

learned to avoid an area protected by pole shockers.

3d. Scarecrows and bird diverters: Scarecrows are effective at repelling raptors 

when they are moved regularly and used in conjunction with shotgun fire or pyrotechnics. Bird diverters discourage birds from roosting on utility poles, towers, 

street lights, and other structures. 

4. Live Capture and Relocation

This strategy can involve the use of a variety of trapping techniques in order to nonlethally capture raptors, which are subsequently relocated and released.

Noose traps

4a. Bal-chatri: The bal-chatri is a small cage, often in a half cylinder, conical, or 

rectangular shape, with many monofilament nooses attached to the exposed surfaces. A lure animal, such as a mouse or non-native bird is placed in the cage. The trap 

is then deployed within sight of a perched raptor. The movement of the lure animal 

will attract the raptor, and when the raptor lands on the trap, the nooses will ensnare 

the raptor’s toes and feet.

4b. Phai: The phai is a hoop made out of a rigid material (e.g., metal or wood), and 

has many upright nooses placed along its length. A lure animal, such as a non-native bird, is placed (tethered) in the center of the hoop. The trap is deployed within 

sight of a raptor. The movement of the lure animal will attract the raptor and it will 

make a stoop down to capture the lure. As the raptor extends its legs to grab the 

lure, its legs are ensnared by the hoop’s nooses. This trap can capture a raptor from 

any angle of approach.
39

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

4c. Verbail: The verbail trap is mounted to a pole that is deployed in an open area 

away from any other perches of similar or greater size, which attracts raptors that 

use perches for hunting to land on the trap. The perch is collapsible and acts as the 

triggering mechanism. When tripped, the body of the trap flips a padded noose 

around the leg(s) of the raptor. Two spring-wired arms tied to the noose simultaneously spring out in opposite directions, tightening the noose and holding the bird 

firmly. A separate line attached to the noose allows the trapped raptor to flutter to 

the ground, while remaining tethered to the pole.

4d. Noosed lure: A lure animal, such as a non-native bird, is equipped with a 

jacket that is covered in nooses. The jacket is then tied to a weight using a shock 

cord that tethers the pigeon in place so that it can fly up to 5 or 10 feet (1.5 to 3 m), 

but no further. The weight is heavy enough that the raptor is not be able to drag it. 

The movement of the lure animal attracts the raptor, which will make a stoop down 

to capture the lure. As the raptor strikes the lure animal, it's toes and feet become 

entangled in the nooses.

4e. Barak: The barak is a trained decoy raptor equipped with a noosed feathery 

ball disguised as prey. The barak is flown within sight of a target raptor. The barak 

stimulates a kleptoparasitic response in the target raptor, which tries to rob the 

barak of its “prey” and subsequently becomes ensnared in the nooses of the feathery ball, and the two raptors fall to the ground where they can be retrieved.

Net traps

4f. Bow-net: The bownet is a circular, spring loaded, and netted trap, that lies folded on the ground. The trap is baited with a lure animal that is tethered to the center 

of the trap, in order to attract the attention of a passing raptor. The movement of the 

lure animal (natural or stimulated by pulling a line attached to the tethered animal) 

will attract the raptor and it will make a stoop down to capture the lure. The trap is 

sprung just as the raptor arrives at the lure, causing one half of the circle to release 

over the raptor, creating a net over the now trapped bird. These traps can be sprung 

manually by pulling a rope or line connected to a pin that holds the trap folded 

together, using a remote controlled release mechanism, or can have an automatic 

release that is tripped by the raptor.

4g. Dho-gaza: The dho-gaza is a small net attached at its four corners to a pole 

frame. The net is attached in such a way as to be easily pulled off the pole frame 

(e.g., clothepins, paperclips, etc.). A cinch-line string attached at one end of the 

pole frame is run through the outer mesh squares of the net along all four sides, 

and then attached again to the frame. A lure animal is tethered to the ground 
40

GENERAL TECHNICAL REPORT PNW-GTR-910

near the base of the trap. Prey species such as sparrows and starlings, or predator species such as great horned owls can be used to attract the raptor. The trap 

is positioned within sight of a raptor, and perpendicular to the path the raptor is 

expected to take to get the lure animal. The lure animal is placed on the opposite side of the net from the raptor. The movement of the lure animal (natural or 

stimulated by pulling a line attached to the tethered animal) will attract the raptor and it will make a stoop down to capture the lure. Before the raptors gets to 

the lure, the raptor will hit the net, which detaches from the pole frame, and the 

cinch-line string will close the net behind the raptor, effectively forming a net bag 

around the raptor.

4j*. Net launcher: A trapper sits in a blind and projects a net over the target raptor 

from a hand-held device using a 308 cartridge.

4k*. Goodell’s cube trap: This trap consists of caged box with a separate compartment housing a lure animal and a funneled top with a perch. The target raptor enters the trap and cannot escape. Because of its size, the trap can be left unattended 

like a Swedish goshawk trap. (Source: J. Goodell, pers. comm., 4 February 2014.)

Permanent structures

4h. Swedish goshawk: A large box made of wood and wire mesh, which has a top 

that opens up. This construction typically measures approximately 1 x 1 x 1 m and 

can be a permanent structure. Bait is set inside the box, or in a separate wire mesh 

compartment under the main area of the box, and the hawk or owl drops in from the 

top. The raptor entering the trap triggers the two pieces of the roof to close behind 

it, trapping the raptor in the box.

4i. Modified Australian crow trap: A large box constructed of wood and poultry 

netting with sloped roofs leading to a thin opening that runs the length of the trap, 

and baited with lure animals such as non-native birds. This construction typically 

measures approximately 2 x 2 x 2 m, and results in a permanent structure. The raptor is attracted to the trap from the movement and sound of the lure animals inside 

the trap. The raptor is funneled to the thin opening between the sloped roofs, enters 

the trap through the opening, and becomes trapped inside. 

5. Nest/egg depredation

This strategy aims to inflict nest failure and cause breeding raptor(s) to abandon an 

area. This strategy requires that the nest site is located and can involve interrupting 

nest construction, addling or removal of eggs, or removal of nestlings.
41

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

6. Lethal hunting and removal

Involves the use of live and artificial lures to produce movement and sounds that 

attract raptors to a selected location where they are subsequently shot.

7. Conditioned taste aversion1

This strategy involves the use of a non-lethal chemical compound (repellent) applied 

to a bait that would non-lethally affect the target raptor that preys on the bait and 

thereby teach them to avoid a specific food source.

8. Avicide1

This strategy involves the use of a lethal chemical compound (toxicant) applied to 

a bait that would lethally affect the target raptor, similar to what is used to control 

corvids.

9. Combination1

A combination of any of the previously identified strategies and techniques to manage raptor predation.

1 Categories of techniques added by the expert panelists during the panel session.
42

GENERAL TECHNICAL REPORT PNW-GTR-910

Appendix 6: Materials Provided to Expert Panelists 

During the Workshop: Snowy Plover Expert Panel 

Operating Assumptions, and Snowy Plover Expert 

Panel Key Terms

Snowy Plover Expert Panel Operating Assumptions

4 February 2014

Panel etiquette 

Respect everyone’s views and ideas; we are not here to critique each other. Let 

everyone finish their statements without interruption.

Invited guest etiquette

Invited observers will be expected to be courteously silent during the formal panel 

procedures, but toward the end of the day everyone present will be given ample 

opportunity to speak, ask questions and provide ideas.

Equal say

Each panelist will have equal opportunity and adequate time to express their ideas, 

and will be encouraged to think individually (no “group think” allowed).

Expert panel method

Panelists will be asked to follow the agenda and structure for guided discussions 

and scoring.

Panelists will be given opportunity and time to explain and discuss their ideas 

and scores, to best learn from each other.

However, scoring will be done silently and individually, not as a group consensus.

Contributions will not be attributed by individual panelists’ names. 

Expert judgments

Panelists will provide their best technical and scientific judgments.

Panelists will expressly not consider cost or political circumstances when scoring effectiveness and feasibility of potential management techniques.

Panelists will not second-guess management availability (budgets, personnel, etc.).

Panelists will not consider agency-specific issues (USFS, BLM, ACOE, OPRD), 

and will assume that the same treatment will be applied to all of the Oregon sites; 

that is, the set of Oregon sites will not differ significantly in effectiveness or feasibility of potential management techniques.
43

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Snowy Plover Expert Panel Key Terms

Raptor—Any diurnal or nocturnal bird of prey (hawk, eagle, falcon, owl) that 

could prey on Snowy Plover eggs, young, or adults, or otherwise cause harassment 

to Snowy Plover nesting. 

Effectively, however, only two species have been observed to be anything like 

consistent predators on Snowy Plovers along the Oregon coast: Northern Harriers 

(Circus cyaneus) and Great Horned Owls (Bubo virginianus).

Terms and levels used in scoring management techniques (see Appendix 6):

Effectiveness—The degree to which executing a particular management technique 

will result in significantly lessened mortality of Snowy Plover eggs, young, and/or 

adults, and/or lessened harassment of nesting Snowy Plovers. 

a. Completely ineffective: neither mortality nor harassment of Snowy Plovers by

raptors are reduced in any way.

b. Mostly ineffective: only a minority of mortality and harassment events on

Snowy Plovers by raptors are eliminated.

c. Partially effective: about half of mortality and harassment events on Snowy

Plovers by raptors are eliminated.

d. Mostly effective: the majority of mortality and harassment events on Snowy

Plovers by raptors are eliminated.

e. Completely effective: mortality and harassment of Snowy Plovers by raptors

are fully eliminated.

Feasibility—The degree to which a particular management technique can be technically implemented, regardless of cost, politics, and agency operations and personnel. “Technical” can refer to equipment, operational methods (e.g., efficacy of 

netting a bird), or other biological circumstances. 

a. Completely infeasible: the management technique cannot be implemented

due to technical impediments.

b. Mostly infeasible: the management technique can be only partially implemented due to technical impediments.

c. Partially feasible: the management technique can be mostly implemented, but

with technical impediments that may or may not be solvable.

d. Mostly feasible: the management technique can be fully implemented once

one or more minor technical impediments are resolved.

e. Completely feasible: the management technique can be fully implemented

with no technical impediments.
44

Appendix 7: Worksheet Used by the Expert Panelists to Score Efficiency and Feasibility of Management Methods Snowy Plover Expert Panel Score Sheet Panelist code: Date: Place your score(s) to sum to 100 Place your score(s) to su

Effectiveness Feasibility Management Technique a. Completely ineffective b. Mostly ineffective c. Partially effective d. Mostly effective e. Completely effective a. Completely infeasible b. Mostly infeasible c. Partially feasible d

Mf

1. Habitat modification a. alter perch abundance & availability

b. alter key elements of

prey habitat

c. alter prey abundance

& availability

2. Exclusion

a. mini-exclosure

(≈ 24”x24”x24”)

b. medium exclosure

(≈ 4’x4’x2’)

c. large exclosure

(≥ 6’x6’x4’)

3. Hazing

a. pyrotechnicsb. lazersc. electric pole shockersd. scarecrows & bird

diverters

4. Live capture &relocation

a. noose trap: bal-chatrib. noose trap: phaic. noose trap: verbail
45

Effectiveness Feasibility

Management Technique

a. Completely ineffective

b. Mostly ineffective

c. Partially effective

d. Mostly effective

e. Completely effective

a. Completely infeasible

b. Mostly infeasible

c. Partially feasible

dMf

d. noose trap: noosed luree. noose trap: barakf. net trap: bow-netg. net trap: dho-gazah. structure: Swedish 

goshawk

i. structure: Mod. Austr. 

crow trap

5. Nest/egg depredation6. Lethal hunting/removal7. Net launcher8. Conditioned taste aversion9. Goodell’s Secret Cube Trap10. Avicides11. Combination
46

GENERAL TECHNICAL REPORT PNW-GTR-910

Snowy Plover Expert Panel Score Sheet

Panelist code: Date: 

Management Technique Rationale for your scores Key uncertainties, unknowns, & data needed
47

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Appendix 8: Summary of Data Sets on 

Western Snowy Plover That Are Currently 

Collected and Available for Analysis

Breeding Season Monitoring

The Oregon Biodiversity and Information Center (ORBIC) has conducted over 20 

years of intense nest, demographic, and population monitoring at every plover site 

in Oregon. Nearly every bird produced in Oregon has been banded. Individualbased data on demography, parentage, and reproductive success are available in 

electronic databases managed by ORBIC. Plover monitors survey each nest site 

multiple times per week and report observations of breeding activity in electronic 

databases on a weekly basis during the breeding season. 

Breeding Window Survey

All currently occupied and historical breeding sites are surveyed to count the number of snowy plovers present. Each site is surveyed in one pass during a one-week 

window in mid to late May following the rangewide protocol. In addition to counting the number of snowy plovers present, additional information about the presence 

and abundance of potential predators is recorded. This survey has been conducted 

in Oregon every year for at least the past 20 years. These data are available in 

electronic databases managed by USFWS.

Winter Window Survey

All currently occupied and historical wintering sites are surveyed to count the 

number of snowy plovers present. Each site is surveyed in one pass during a oneweek window in mid to late January following the rangewide protocol. In addition 

to counting the number of snowy plovers present, additional information about the 

presence and abundance of potential predators is recorded. This survey has been 

conducted in Oregon every year for at least the past 20 years. These data are available in electronic databases managed by USFWS.

Nest Failures

When plover nests fail, ORBIC plover monitors identify the source of the nest failure when feasible. Nest failures have been attributed to factors including predation 

(e.g., corvid, coyote, red fox, raccoon, avian predator, rodent predator, unknown 

predator, etc.), nest abandonment, one egg nests, infertile, overwashing, burial 

by sand, and others. These data are compiled in electronic databases managed by 

ORBIC. These data are reported on a weekly basis, and are compiled in an annual 

report after the conclusion of the breeding season.
48

GENERAL TECHNICAL REPORT PNW-GTR-910

Predator Surveys and Removal

APHIS-WS wildlife specialists conduct predator surveys and management activities 

on a daily basis from late February through August. Data recorded include the total 

number of hours spent on predator management activities at specific nesting sites 

each day (e.g., predator survey, raven or crow calling, setting traps, etc.). APHISWS wildlife specialists also collect and record data on the number of individuals 

by predator species that are removed from a nesting site every two weeks. These 

data are compiled in electronic databases managed be APHIS-WS. These data 

are reported on a bi-weekly basis, and are compiled in an annual report after the 

conclusion of the breeding season.
49

Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Appendix 9: Results of the Expert Panel Scoring of 

Efficiency and Feasibility of Management Methods, 

Listed by Individual Panelists (A-G, Specific Names 

Withheld Here for Anonymity)

Data tables displaying the 7 panelists’ individual scoring of efficiency and 

feasibility of management methods are available in a supplementary document 

from the authors of this report upon request.
50

GENERAL TECHNICAL REPORT PNW-GTR-910

Appendix 10: Written Explanatory Notes From the Seven Expert Panel 

Participants (Denoted Here by Panelist Codes A-G), Recorded From Their 

Scoring of Efficiency and Feasibility of Management Methods

Snowy Plover Expert Panel Score Sheet Panelist code: A Date: 2/4/2014

Management technique Rationale for your scores Key uncertainties, unknowns, & data needed

Habitat Modification I think perch alteration/removal could be 

accomplished, but would be only effective 

for GHOW1. Don’t really see altering 

prey/habitat as effective, and changes the 

ecosystem for a multitude of species.

Establishing a food plot some distance away 

might serve as an attractant for GHOW/NOHA2, 

but could also attract corvids to the area. Doing 

a study plot might be in order.

Exclusion Certainly some threats for adult plovers. 

Don’t know enough about size of 

exclosures vs. potential dangers to provide 

a strong support for this idea.

Hazing Probably not that effective for raptors—

hard to do for owls and harriers are 

moving quickly through areas so would 

be hard to target.

Live Capture & Relocation Trap types are species specific, hence 

the score differences. The right traps are 

highly effective... given enough time and 

with trained personnel.

Translocation still has a lot of unknowns, 

especially with regard to birds returning 

to original site, and raptor survival. More 

data needed based on satellite telemetry. 

Transmitters placed on translocated birds.

Nest/Egg Depredation If effort put into finding nests, this 

could help reduce plover losses as adults 

would not be foraging to feed young. 

However, adults still present and could 

still kill plovers.

Lethal Hunting Is mostly effective, but still difficult for 

both of these species. Not necessarily 

easier than trapping.

Removal of territorial adults can cause an 

influx of floater birds or territory expansion 

by adjacent territory holders. These are 

good reasons to know that you are removing 

individual that are taking plovers/nests.

Others Avicides—Not legal for raptors.

Taste Aversion— might work well for 

harriers if they eat eggs.

1

 GHOW = great horned owl

2

 NOHA = Norther harrier
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Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Snowy Plover Expert Panel Score Sheet Panelist code: B Date: 2/4/2014

Management technique Rationale for your scores Key uncertainties, unknowns, & data needed

Habitat Modification In simple habitat feaure like “perches” & 

“cover” (removal) the technique/method 

is effective and feasible. If it is making 

raptor habitat less “desirable”, we do 

not usually know enough about species/

habitat interaction to make changes. 

Removing “cover” from beaches to avoid 

predator cover maybe ineffective as young 

plovers benefit from vegetation/logs for 

protection too.

Often unable to determine which elements of 

habitat to manipulate (remove or enhance).

Exclusion Not sure about this. Small exclosures can 

be effective at protecting nests/eggs but no 

good for fledglings. Large exclosures may 

provide perches for harriers or owls.

Hazing Cannot see how these techniques could 

ever be effective or precise to affect 

predators & not plovers too.

Live Capture Not familiar enough to review individual 

techniques. May have a role to play in 

combination. Also a challenge if used in 

combination with relocation. Relocation 

has all sorts of issues relating to birds 

returning/homing to some nesting area 

within the same nesting season. May do 

more to “look good” politically. Trapping 

is difficult to achieve practically.

Nest/Egg Depredation Nest/egg removal of harriers or eggs 

may be worthwhile although difficult to 

find. May reduce predation if adults are 

not provisioning their young with prey 

(plover chick). Harriers would remain 

present and prevent other harriers (or 

owls) filling the vacant vacuum. May 

prevent re-nesting if repeated.

Lethal Hunting/Removal Likely to be very effective in outcome 

and in cost/return. Will remove birds 

that are doing the damage. The downside is political & P.R. which would be a 

necessary element to plan/prepare for.

Live capture etc. Could be a useful tool.

Conditioned-taste aversion May play a role to reinforce or combine 

with other techniques. Placing additional 

eggs in the environment may add to risk 

and attraction of predators.

Avicides Very effective & practically feasible, but 

is unlawful. Therefore is not an option.
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GENERAL TECHNICAL REPORT PNW-GTR-910

Snowy Plover Expert Panel Score Sheet Panelist code: C Date: 2/4/2014

Management technique Rationale for your scores Key uncertainties, unknowns, & data needed

Habitat Tremendous undertaking to alter prey 

habitat and abundance. Uncertain how 

such change could impact local ecosystem 

beyond plovers.

Exclusion Exclusions have been known to minimize 

corvid predation but could cause adult 

plover mortality by raptors. Raptors cue 

in exclosures.

Uncertain how harriers would respond to 

exclosures. Certain owls would benefits with 

exclosure use.

Hazing All in all, poor, short-term and laborintensive with little effectiveness.

Live Capture Relocate Each trap is species specific. All timeintensive when dealing with individual 

raptor. Harrier nest location essential if 

technique implemented.

Uncertain on relocation sites, who is responsible 

for relocating, etc.

Egg Depredation Better option is capture adults. Uncertain of effectiveness, vs. time to find nest.

Lethal Removal Most effective technique. Selectively 

target individual.
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Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Snowy Plover Expert Panel Score Sheet Panelist code: D Date: 2/4/2014

Management technique Rationale for your scores 

(General note: Tended to not consider 

most options completely feasible or 

infeasible)

Key uncertainties, unknowns, & data needed

Habitat Modification Considered this to be methods to 

reduce habitat suitability—Partially 

effective. All would have mostly partial 

effectiveness and depending on site & 

conditions, partially feasible.

Unclear if prey habitat manipulations would also 

affect plovers. Unclear if altering raptor prey 

abundance meant increasing or decreasing prey.

Exclusion Mostly ineffective, could reduce predation 

but could actually increase predation of 

adults. Large exclosures include predation 

& too hard to effect.

Not sure if mini-exclosures would work in OR 

conditions. Comparison of the threshold at 

which benefits of exclusions outweigh the loss 

of nests/adults.

Hazing Most would also affect plovers. Most 

have not worked consistently when tried 

in the past. Time-intensive & person 

needs to be present.

Not sure if we could use electric shockers given 

the sand/salt environment.

Live Capture & Relocation Many techniques I had little knowledge 

of. Ranked the ones I thought had been 

tried with mixed success in California, 

relocated birds mostly return so decreased 

effectiveness scores.

Don’t know how many techniques would work. 

Least experience with trapping. How likely 

would it just come right back?

Nest Depredation Thought NOHA may abandon area if nest 

was removed, but changed core when 

others thought it wouldn’t.

Not sure how owl would be affected or if nests 

would be found. Not entirely sure how GHOW/

NOHA would respond, whether they would 

leave the area or continue to prey on plover.

Lethal Seems to be most effective and feasible. 

Concerned about feasibility if a large 

response is needed (lots of owls or 

harriers).

Unclear how it would affect predator 

populations. Not sure if other owls or harriers 

would replace those killed. Unclear about how 

timing alters effectiveness.

Others—Goodell’s Goodell’s trap seems like it would be 

effective.

Not familiar with how the technique compares 

to other trapping techniques.

Combination Considered using nest location with 

trapping adult.

Seems like it would be effective, but not sure how 

feasible based on time and resources required.
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GENERAL TECHNICAL REPORT PNW-GTR-910

Snowy Plover Expert Panel Score Sheet Panelist code: E Date: 2/4/2014

Management technique Rationale for your scores Key uncertainties, unknowns, & data needed

Habitat

 Prey abundance/

availability

Increasing attractive prey at adjacent 

area will draw raptors away from SNPL. 

Irrigated alfalfa or irrigated grass.

Habitat management Addresses underlying phenomenon 

constant

B-C trap Opportunistically effective for NOHA. 

Regularly effective for GHOW. Regularly 

effective for other hawks.

Dho-gaza Regularly effective for NOHA at nest and 

all raptors at nest & falcons with prey 

lures.

Funnel type box-type trap Regularly effective for GHOS and most 

buteo & accipiter.

Individual raptor 

management

Circumstantial, skill dependent, always 

changing

Management Framework

1. Manage for population goals vs. management response based on raptor take of SNPL circumstance.

2. Establish demographic “sweet-spot” for each colony.

3. If colony drops below goals (avg. over x years) then WS is engaged to manage individual raptor depredation scenarios.
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Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Snowy Plover Expert Panel Score Sheet Panelist code: F Date: 2/4/2014

Management technique Rationale for your scores Key uncertainties, unknowns, & data needed

Exclosures Small exclosures wouldn’t work in OR 

because of wind—nests get buried. 

Large exclosures are very time intensive 

to erect – lots of disturbance of adults. 

Predators have been able to get into large 

exclosures. Medium exclosures work well 

against corvids. Do not work with owls. 

Exclosures do not benefit survival to 

fledgling. If chicks fledge into habitat with 

high predation, adult effort wasted—may 

reduce fitness.

Unsure how well they work against harriers. 

Uncertain effectiveness against harriers, but 

suspect harriers hunting style would lead to 

increased adult depredation. Need to identify 

how much potential adult loss offsets improved 

nest success. Also how successful are we at 

getting chicks to fledge after exclosure use. Do 

exclosures attract some predators?

Habitat Modification Give plovers more open space, improve 

camouflage. Probably not reasonable to 

remove non-plover prey. But could make 

habitat less attractive to predators.

Trapping & Relocation This method is effective from a plover’s 

perspective. But it is not effective to 

relocate raptor—they die or come back...

Not sure on specific methods, but overall this 

seems an option. Lots of work. Do relocated 

birds come back? Is this just a temporary fix?

Lethal Control Likely to improve plover success at all life 

stages.

Do other predators just fill in?

Nest/Egg Depredation Could be effective if it kept non-problem 

birds on a territory, & kept predator 

population down.

For all these techniques, need to make sure they do not divert funding/time/attention from ongoing management (e.g., 

corvid control).
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GENERAL TECHNICAL REPORT PNW-GTR-910

Snowy Plover Expert Panel Score Sheet Panelist code: G Date: 2/4/2014

Management technique Rationale for your scores Key uncertainties, unknowns, & data needed

Habitat Perches (including nest sites for owls). 

Balance removing vegetation cover for 

prey with maintaining plover chick cover.

Regional owl population? Impact of nesters vs. 

nonbreeders?

Exclusion Loss of Adults

Most adult loss likely due to raptors.

Need for frequent monitoring.

Reduced effectiveness (not effective for 

owls).

Likely high risk with NOHA.

Small exclosure not effective with high 

wind, coyotes.

Frequency of use will likely lead to 

increased problems observed (adult loss)/

Review literature (PIPL).

Hazing Limited effectiveness of lasers by day. Fog 

can reduce effectiveness of electric poles.

Feasibility on owls?

Live Capture Feasibility reduced over large 

landscape scale.

Question of whether relocating leads to death 

of raptor.

Nest Removal Difficulty of locating all owl nests in 

some areas. Owls nest early. Provides 

time (buys time) and increases options.

Assess usefulness for keeping “favorable” 

raptor pair (territorial).

Lethal Must ID & get target individual.

Goodell’s Trap Not effective for NOHA

A combination of all techniques would be most effective.
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Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Appendix 11: Comments From the Seven Expert Panel 

Participants as Recorded During the Workshop by Two 

Independent Scribes (see app. 3)

Snowy Plover Expert Panel Meeting—Notes “Assessing Raptor 

Predation Management for Snowy Plover Recovery”

February 4, 2014, 8:30 am–5:00 pm

U.S. Fish and Wildlife Service, Portland, Oregon

Introduction

Two scribes were asked to capture the content of the discussion as it was divulged 

during the expert panel discussion topics. These notes were not necessarily intended 

to present a linear progression of thought, but were intended as an additional tool to 

gather information and expertise for later use. At times, this methodology resulted 

in successive comments that contradicted preceding comments. Additionally, the 

identities of the panelists and invited guests were intentionally kept anonymous, in 

order to promote an open and candid exchange of information and expertise that 

might otherwise have been inhibited if the scribes had been asked to attribute the 

comments and questions to individuals.

Attendees

Cindy Burns Invited Guest US Forest Service cburns@fs.fed.us

Michael Burrell Panelist APHIS-Wildlife Services michael.b.burrell@aphis.usda.gov

Jody Caicco Scribe US Fish and Wildlife Service jody_caicco@fws.gov

Jeff Dillon Invited Guest US Fish and Wildlife Service jeffrey_dillon@fws.gov

Daniel Elbert Facilitator US Fish and Wildlife Service daniel_elbert@fws.gov

Carleton Eyster Panelist Point Blue Conservation Science ceyster@pointblue.org

Eleanor Gaines Panelist Oregon Biodiversity and Information Center egaines@pdx.edu

David Garcelon Panelist Institute of Wildlife Studies garcelong@iws.org

John Goodell Panelist High Desert Museum jgoodell@highdesertmuseum.org

Jennifer Kirkland Invited Guest Bureau of Land Management jkirkland@blm.gov

Vanessa Loverti Scribe US Fish and Wildlife Service vanessa_loverti@fws.gov

Bruce Marcot Facilitator US Forest Service bmarcot@fs.fed.us

Martin Nugent Panelist Oregon Department of Fish and Wildlife martin.nugent@state.or.us

Laura Todd Panelist US Fish and Wildlife Service laura_todd@fws.gov
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GENERAL TECHNICAL REPORT PNW-GTR-910

Morning Session

8:30-8:50 am—Welcome and introductions

8:50-9:10 am—Overview of methods

Background presentation

Questions generated from presentation: 

What is the average hatch rate for western snowy plover (SNPL)? Recent hatch rate 

is 45%. How does that compare with CA? Not known for the entire state. 

Would like to add a clarification, in previous years we have had rodent predation 

on SNPL. Rodents are a predator on plover eggs at these sites. Some of the predation 

of SNPL nests may be attributed to rodent, harriers or other species not identified. 

What are the long-term goals for SNPL/predator management? Are there sites 

that are putting a lot of resources into addressing predation issues with little return? 

If we (managers) intervene at critical stages (managing predation) that we will grow 

plovers. The recovery plan does have recovery goals for each site. 

What are some non-lethal techniques that have been used for raptor management? Bal-chatri traps, bow net, multiple traps have been used and baited with 

anything from mice to quail. We have also used audible devices to draw in predators during the study (two week period); audible devices ran for 6 to 8 hours a day. 

The issues are that Northern Harrier densities are so low that observations and 

opportunities to trap are few. 

Density dependent mortality could be a concern at some of these sites. 

Is there a reference site for harriers (a colony or typical harrier site that has been 

identified)? We do not know? It becomes difficult because density changes with 

latitude and longitude. As you go south and north there are fewer birds (harriers) 

and the population is not as dense/concentrated. 

9:40-10:00 am—topic 1: panel discussions of raptor predation on snowy plovers 

& raptor predation management

What suite of information could be used to generate indices that help trigger a decision on whether to implement raptor predation management, in real time?

Note: Called upon each panelist to provide top 2 ideas to generate indices.

Utilize cameras to observe and document unknown predations. Track individual predators that were seen at the site (trouble birds). 

Determine best time to take action (during harrier hatching/fledgling season?). 

At what point in the predator’s biology correlates with plover nesting/timing. Is 

there a timing issue?

We need information on raptor nesting phenology (to ID nesting status, we need 

monitoring). Could be helpful to look at weekly brood survival to see what suites of 
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Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

chicks are disappearing due to predation (kind of hard to document ultimate cause). 

It may be possible to identify an individual predator by a specific unique character.

Use of cameras needs to incorporate a high level of follow through to accurately 

documenting depredations of plover nests. Need to be hiring volunteers to survey 

raptors, specifically. Need a greater capacity for monitoring (need to increase 

frequency of observations). 

Are densities of plovers nesting in a particular area influencing predation by 

harrier (increased incidents)? It seems like we may be seeing an increase in predation because of density. Can we collect a density of nest per unit area to see if there 

is a correlation? These observations are very important for Wildlife Services (WS).

When raptors target prey, what number of events needs to be documented on 

a nest before a response is initiated? We need to agree on a tolerance level for WS 

to respond. Number of events documented to trigger a response or action (lethal or 

non-lethal). For example, Ravens are not given an opportunity to trigger an action, 

they are just taken (shot) if they are in the area, but with harriers what do we do 

with the trigger. 

At the Pendleton site we tried to get a handle on recording corvids and harriers. 

Mark Colwell had incorporated predator surveys at specific time intervals to record 

any predator species observed and also to look for predator tracks (predator surveys 

include species and numbers). This provides us with a random sample of what goes 

on at individual nest sites or what species are present (baseline). 

Locate raptor nests soon as possible, ID nest site, and then use a dho-gaza to trap 

the bird (harrier). New info may enhance predator management. If you knew where 

the nests were then you would have new info to take action – knowing where the 

nest is increases our options (addle eggs, etc.). Use cameras as an info gathering tool. 

Is there any effort to demographically model when to take action on harriers? We 

need to provide the drivers and to determine what the harrier population is doing?

Use cameras to document predator behavior at under varying circumstances. 

Suggestion to develop a study looking at use of enclosures and non-enclosures. Also, 

should consider other management that is occurring at the site, where enclosures are 

utilized (should we be cautious and more sensitive at these sites). 

Should be noting what predator monitors are observing and document 

(relayed back to decision makers). Also, need to include small mammal surveys 

(prey for raptors). 

Need to stress our management goal as the key trigger. Identify if there is a 

sweet spot at any given site (for predators). Identify the predator trigger (i.e., over 90 

plover nests?). Monitor over a 3 to 5 year window then reassess. Raptors - document 

point source circumstances. 
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GENERAL TECHNICAL REPORT PNW-GTR-910

Assess and identify alternate prey for harriers (e.g., if you have a lot of vole species or ducks at a site). Make alternatives more available for harriers (one strategy)?

Predator behavior is not the trigger. Avoid decisions, pending further information 

on raptor behavior. Developing lists of species in advance ranked by trap, relocate, or 

kill. Take into consideration what predator you are targeting, their suitability of being 

trapped and removed. Some species will be more difficult to trap than others. 

Phenotypic means of identifying predators (harriers) (capture and marking) mark 

with dye spray type markers. Need to know what are the predators actually feeding 

on at each site (through the season would be an idea (site specific). How can we make 

the site less attractive for predators? Again, how are harriers actually using the site? 

Need emphasis on the behavior of the raptors. 

What could you do if plover depredations increase? Are there options to remove 

nests and/or young? We would need to monitor raptor nests closely and make a 

management decision to remove eggs or young. Strategy may be to track harrier 

numbers intensively throughout site (e.g. by removing 10 ravens - are you having an 

effect on plover success). We could track regional response (likelihood) to determine predator replacement during the season. 

10:20 am–12:00 pm—topic 1: Panel discussion of raptor predation effects on 

snowy plover productivity

What is the best way to gather the information?

Investigate how harriers respond to exclosure (do they respond as other raptors do). Test to see how they respond to exclosure – direct observations, cameras, 

e.g., Owls perch on enclosure, so do harriers do this too? Are they attracted to the 

exclosures? Use cameras to document predation with and without nest exclosures. 

Need a raptor observer/staff/monitor dedicated to raptor research. Monitoring 

would need to be employed early in the season to track raptors (during most essential/appropriate time).

Analyze current plover data from the past 5 to 10 years (to compare productivity data and site specific hatch rates/fledge rates). Area suggestion - example ~10 mi 

at Coos Bay, OR. Erect raptor perches before the season starts to observe frequency 

of raptor species/occurrence (critically important). 

Is there a correlation (harrier’s taking plovers) with vegetation and or rainfall 

or weather patterns (look at historical data)? Could track raptor impacts on plovers 

with weather patterns to better predict predation events based of weather and/or 

vegetation changes.

Track movements of raptors (harriers) that are translocated (after removal) 

to evaluate removal technique and determine if translocation is a viable option 

for management. 
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Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Compare SNPL nest exclosure information with other states. Search for raptor 

nests to document locations. Utilize volunteers to survey (look at ways to collect 

data without funding). Gather new data (e.g., images of tracks) gather evidence to 

document what is occurring so that management decisions can be developed. . 

Run a population viability analysis (PVA) of plovers to see at what stage they may 

be susceptible to management actions (at what life stage). Do a camera study to look 

at predator behaviors around nests (marking problem individuals in plover areas). 

Small mammal live-trap line for small rodents and then a survey for raptors 

(suggestion to use Sherman traps from March to Aug at regular intervals). Small 

mammal trapping should be done the year prior (prior to what?), when harriers are 

hatching/feeding and fledging young. Area for trapping should include a 2-mile area 

+ 2 miles out from plover boundary. 

Package the prey and predator survey/monitoring into a single protocol to make 

repeatable and integrate into perpetuity. Develop a framework for a long-term 

monitoring for raptors and prey (includes small mammals etc.). Reevaluate the 

formalized protocol once every three years. 

Good to have telemetry to see how they use the area (primary predator species). 

Find where the nests are. How do they use the entire area? Map where focused 

individuals are located and problem areas for plover predation. GIS Data layer (use 

of the area). Detail of mapping effort- down to the individual plover nest. 

Conduct a literature review and survey. One option is to make habitat less 

attractive for raptors (tree removal) —habitat management suitability. Use telemetry 

on harriers and owls and follow-up on results. 

Observer Note: Use video cameras over a broad area (in addition to a trail 

camera). Would work at some sites and not so well as other. Maybe useful if you 

have an unknown predator taking plovers....

Look at small mammal densities and raptor numbers over time (is there 

a correlation).

Other methods of trapping noted:

Using a net launcher to capture harriers. Sit in a blind. Use a .308 cartridge. While 

we only tried this once, we attempted using a net gun (Coda; powered by a .308 

blank cartridge) to try to capture harriers. Not suggesting it is the best trapping 

method by any means, but it is another trick in the bag.

Use condition taste aversion (this is a compound that will affect any bird that 

preys on eggs). 

Use Avicide to kill birds similar to what is used to control corvids.

Create a list of trapping techniques that are species specific (advise best 

approach for each species). Develop a list of trap types and species that are good 

candidates for us.
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GENERAL TECHNICAL REPORT PNW-GTR-910

Afternoon Session

12:40 pm–1:00 pm—Review of the morning’s guided topic discussion of raptor 

predation effects on snowy plovers 

Went over the mornings scoring—including data, monitoring and research. There 

was a spread among the panelists- which is fine.

The group needed additional time to finish scoring.

1:00 pm–3:30 pm—topic 2: panel evaluation of efficacy of raptor predation 

management

1St round of scoring. The panelists then disclosed how they scored:

Habitat modification—not a lot of experience in dealing with raptors in terms of 

altering habitat. 

Removing perches may be feasible and possible. Removing perches may 

help with some raptor species; perhaps not so much with harriers as they are not 

perch hunters. 

Harriers maybe not so much. 

Changing prey may be too difficult and only partially effective. 

Exclusionary devises are unknown at this point. Perhaps smaller cages could 

reduce adult mortality—ranked the smaller ones more effective.

Hazing—no experience—just don’t know.

Pole shockers may be a good idea and effective.

Scare crows may be effective—things that move are better than things that 

don’t move. 

Live capture-relocation very effective and feasible. 

Nest egg depredation didn’t score real high. Removing offspring would potentially reduce the amount of hunting the adults would have to do, but still have the 

adults themselves who are hunting. 

Habitat modifications more broadly—perhaps partially effective. How much 

area do you treat? Difficult to deal with in a landscape setting 

Exclusions—effectiveness on habitat exclosure with eggs—problem with fledgings. Larger structure versus smaller make a difference. 

Hazing—can cause disturbance to plovers as well. Not effective technique to 

be precise.

Live capture and relocation—not enough experience to say. 

Lethal hunting and removal—very effective from a practicable point of view. 

Could be an overwhelming public relations problem.

Taste aversion—can be an effective tool. Positive elements but labor intensive.

Avicides—right substances can be highly effective, but restrictions may deter use. 
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Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Combination may be the preferred approach. 

Habitat modification—overall would rate ineffective—altering perches feasible 

and something that is done. 

Feasibility of habitat manipulation and prey abundance would be difficult.

Exclusion—great horned owls—having exclosures could benefit the owl. 

Very ineffective.

Hazing—pyrotechnics, lasers, not feasible. 

Electric pole shocker—don’t know enough about.

Scare crows could work in certain circumstances but have to combine with lethal.

Live capture—feasible, but very labor intensive. 

Nest egg depredation—could be effective, but how would change behavior?

Lethal hunting—very effective

Taste aversion—don’t know, but not likely very effective.

Trapping—very effective

Net launcher—ineffective with the large landscapes—better luck with a traps. 

Habitat modification—partially effective.

Exclusions—minimally effective and potentially loss of adults.

Hazing is not effective.

Scare crows—ineffective.

Traps—depends on conditions and time of year—and question feasibility.

Nest depredation—could be effective for harriers.

Lethal hunting—effective. 

Taste aversion—don’t expect it will work.

Avicides—no idea if will work.

Combination—most feasible.

Habitat modification—removing perches may work. Consider planting alfalfa 

spring summer window—very feasible and effective. Artificial food plot or native 

habitat approach. 

Hazing—minimal effective for raptors.

Live capture—there are differences between harriers and owls. May be 

effective depending on methods.

Nest depredation—would not recommend.

Lethal hunting—practicable measure.

Taste aversion may work for scavengers.

Habitat modification could be effective long term strategy—improve plover 

habitat reasonable.

Altering prey abundance does not seem practicable.

Exclosures—small would not work—too much sand—medium may work, but 
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GENERAL TECHNICAL REPORT PNW-GTR-910

not with owls and may not harriers—larger exclosures—a lot of work and disturbance to the birds.

Hazing—not certain that scarecrows or pyrotechnics will work.

Capture and relocation—viable option—but are the birds going to come back?

Nest and egg depredation—may work.

Lethal hunting and removal—good solution for our situation.

Avicides—not feasible.

Taste aversion—sounds interesting.

Habitat modification only partially effective and may not be feasible—challenge of veg cover for the plover chicks—depends on the landscape.

Exclosures—risk to the adults is well documented. Need frequent monitoring—

not feasible—medium exclosure may be best compromise.

Hazing—not effective and difficult to employ at an appropriate scale.

Live capture—question if feasible? 

Nest egg depredation a viable option of disrupting the nest.

Lethal—effective and highly feasible- targeting appropriate individuals is 

often difficult.

Taste aversion—low feasibility.

Time factor in when the bird is caught. 

Questions from panelists or observers?

Could increase the density of birds with irrigated alfalfa? Longer term it would support those birds that are drawn into the area. Cost benefit could be feasible—concern 

bring more raptors to the area, and perhaps increasing corvids in the area as well. 

Where would we be relocating these raptors to? Have the ability to travel great 

distances—and would they return? Interstate transfers as an issue? Do they survive? Removed 33 birds last year. Have not seen any birds return yet. May depend 

on the species and how far you move them. 

Removed a harrier or owl—how long does it take for them to return? Don’t 

know—would take a lot of work to determine rates of return. 

Have any harriers been removed and return over the cascades? Not sure...

Taste aversion? Raven experiment discussed. 

2nd Round of Scoring. Disclosure and sharing opportunity; Explained what you 

changed and why.

Modified feasibility for live capture and relocation because of the difficulty in 

catching harriers in a large landscape.

Ranked a combination of techniques to be the most effective.

Switched scores by lumping a bit more. Made exclosures less effective because 

of owls.
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Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Lethal removal as the most effective and feasible option.

Made changes to egg depredation to partially effective and feasible for both species.

Lethal control—great horned owls are a native invader—removal may open 

other window of conservation for other species. 

Dropped avicides down to overall feasibility issues. Taste aversion bumped up a bit.

Mini exclosures reduced down—less effective- uncertainty of threshold of 

benefits v. risks.

Live capture—relocation- adjusted. 

Nest egg depredation—reduced effectiveness for the owl.

Lethal removal—ranked higher.

Combination—variety of methods more effective. 

Without constraints, all options feasible

Changed the capture techniques a bit. 

Not too many changes in the ranking—downgrading the overall ranking a bit 

due to uncertainties. 

Made a few adjustments—exclusions—smaller size impacts to the birds. 

3:50 pm–4:45 pm—topic 3: Discussion about extenuating factors: 

Overarching subject of population goals of other factors- what are the goals for each 

colony? Is there a window of what are targets? Figure out if we can withstand the 

take. Manage the premise of take of individuals of plovers– have more of a long 

term goal that you may revisit every 3 years. Overall don’t believe raptors behavior 

is a systemic problem. Is it a frequent occurrence? Tail wagging the dog of raptor 

issues—ton of resources being spent for tricky situation. Uphill battle as a management decision. Look at population of plovers first and avoid too many situations of 

tackling the raptor situation.

Do we have population goals for plovers? Yes, the numbers are in the recovery 

plan – agencies manage for population goals–time period targets–do have a range 

the agencies have to target at each site. Numbers are not in place for every site. 

Clarification provided. 

Maintain emphasis on corvid control—would be concerned if resources 

switched to raptor management. Why is that a concern? Money is an issue—talking about diverting funds from corvids to raptors is a concern. How does raptor 

management fit into—concern of competition for funds to cover both corvids and 

raptors. Also workload of control and monitoring is of concern. 

Will take time to collect and analyze the information.

Only a few raptors that are causing problems in CA—sometimes difficult to 

know if which raptor is responsible. Caution of what is it going to take action—decide 

what really is the goal—possible to know – what is it going to take to take action?
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GENERAL TECHNICAL REPORT PNW-GTR-910

Public reaction—killing raptors in CA will be difficult. 

Trying to give direction to staff of how to deal with this—funding issues—

don’t see an intensive project of proactively removing raptors. Look forward to 

finding something in the middle—going to have people responding to corvids and 

dealing with raptors is not possible. Time management—checking traps daily. Not 

much time to do both. Will go where the biggest priority is—if a harrier, will likely 

have to drop corvid stuff. Our existing Environmental Assessment gives direction 

of exploring non-lethal techniques in addition to lethal. Need to take care of the 

problem before it gets bigger. All comes down to costs. If we are really going to 

look for nests this year we need to get started. Only target raptors where they are 

impacting a colony. Don’t have the staff to react proactively.

Educational institutions to take harriers into captivity—option to consider. 

Funding constraints – trying to figure out how to manage the population 

within budget. Not acceptable to consider removing all raptors. Important to 

develop a protocol – 

Will be review for public review of a new raptor management plan. 

We already have an EA which limits us to how and what we can do—expand 

beyond the existing program—workload concerns (if there are significant changes 

to the program). We need raptor expertise—need data collection and raptor observation expertise and action items. Need that resource somehow.

Decision points along the way—really looking at additive losses as the season 

unfolds. At what point do we trigger decision points of harrier control? Get to some 

decision point at a certain loss during the season—given the losses from other 

sources, the harrier one will be at some point later in the season—what are the 

decision points that allows the management action to take place? How do we get to 

the threshold for a decision to take place?

Outreach—who do we inform? A lot of people watching what we do—early 

phase of harrier issues—who do we communicate with? Proactive outreach—

potential limitation.

If certain agencies don’t want to partake in the management plan, could be a 

major issue.

Legal issues associated with avicides—labeling, etc.

Exploring live capture technique? Who is involved? Time constraints associated 

with capture—part of protocol—work with all the agencies—

Larger landscape issues—agencies constraints within jurisdictions—collaborative approach, partnerships to address larger scale issues.
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Assessing Management of Raptor Predation for Western Snowy Plover Recovery, 2015

Are there ways to get around some of the costs associated with capture and 

relocation, volunteer groups to help to defray some of the increased costs of the 

program by having them transport the birds?

Most of what was discussed was related to nest success, but important to 

remember overall population growth. Keep in mind all that is unknown—overall 

goal is population goal, not nest success.

Working group—education—airport group—objective way to find a good 

outcome for the birds. Committee formed that could be from a variety of stakeholders. Harriers are under-represented in the raptor education world. 

Big picture —are we getting higher production of young—keep sensitive to 

such issues such as harrier control.

Wrap Up & Close-Out

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