BLM

BLM Technical Note 436

Recommendations for Improved Raptor Nest 

Monitoring in Association with Oil and Gas 

Development Activities
BLM/WY/ST-10/011+1110
Jeff P. Smith1

, Steven J. Slater, and Mike C. Neal

HawkWatch International, Inc.

2240 South 900 East

Salt Lake City, Utah 84106

1 Phone: (801) 484-6808 x109 

 Email: jsmith@hawkwatch.org

Prepared for:

U.S. Department of Interior, 

Bureau of Land Management

Utah State Office, Salt Lake City,

Wyoming State Office, Cheyenne, and

Colorado State Office, Lakewood

BLM Technical Note 436

Recommendations for Improved Raptor Nest 

Monitoring in Association with Oil and Gas 

Development Activities

iii Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . vii

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Data Standards and Record Keeping . . . . . . 3

Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Nest Naming Conventions . . . . . . . . . . . . . . . . . . . . . 3

Location-Data Standards . . . . . . . . . . . . . . . . . . . . . . 4

Nest-Cluster versus Nest-Centric Monitoring . . . . . . 5

Availability and Quality of Ancillary Data . . . . . . . . . 5

Survey Design and Rigor . . . . . . . . . . . . . . . . . . . 7

Nest-Cluster versus Nest-Centric Monitoring . . . . . . 7

Baseline Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Survey Extent and Timing . . . . . . . . . . . . . . . . . . . . . 7

Problems HWI Identified Concerning 

Raptor-Related Management of 

OG Development Activities . . . . . . . . . . . . . . . . . . 8

Recommendations for Improved 

Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Survey Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Continued Monitoring . . . . . . . . . . . . . . . . . . . . . . . . 17

Recommendations on the Recording 

and Storage of Data . . . . . . . . . . . . . . . . . . . . . . . 18

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Appendix A. Example field datasheets

for raptor nest monitoring. . . . . . . . . . . . . . . 21

Table of Contents

v Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

problems HWI encountered with regard to the nature of 

available data, which can be divided into three primary 

issues: 1) basic data standards and record keeping; 2) 

survey design and rigor; and 3) availability of ancillary 

data. We then provide a series of HWI recommendations 

designed to guide future monitoring programs in ways 

that, if implemented as standard practice, should 

substantially improve the potential for achieving robust 

future evaluations of oil and gas development or other 

land-use-change impacts to nesting raptors. Regardless 

of their specific application, the recommendations for 

improved monitoring should be of value to any raptor 

nest-monitoring program implemented on federal lands. 

We also identify links to examples of field datasheets and 

a relational database system designed to accommodate a 

comprehensive annual program of raptor nest 

monitoring, and provide recommendations for storage of 

collected monitoring data.

Raptor nest monitoring may be utilized to guide federal 

land-use planning, protect raptors, and assess the 

potential impacts of oil and gas development projects. 

The utility of monitoring programs is compromised 

when a program is not designed to address specific 

objectives and when the survey protocols are incomplete 

or applied inconsistently. HawkWatch International 

(HWI) and the Bureau of Land Management (BLM) 

encountered such monitoring limitations during the 

Raptor Radii Research Project, which attempted to 

analyze historic raptor nesting data from Utah and 

Wyoming in relation to past energy development 

activities on BLM-administered lands and to identify 

potential sites for experimental testing of nest-protection 

buffers. We summarize the difficulties encountered 

during this research project and provide our (HWI) 

recommendations for improvement of future nestmonitoring programs to be conducted in association with 

oil and gas development activities. We identify the basic 

Abstract

vii Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

State Office), and Wes Anderson (BLM Colorado State 

Office). Additional semi-independent reviews were 

provided by vested individuals, including Chris Colt 

(Fishlake National Forest, formerly UDWR Price Field 

Office) and Mark Fuller (U.S. Geological Survey, Idaho). 

Further independent reviews were provided by Michael 

Kochert (U.S. Geological Survey, Idaho), Gwyn McKee 

(Thunderbird-Jones & Stokes, Inc., Wyoming), and Jim 

Watson (Washington Department of Fish and Wildlife).

This document was created to address raptor nest-survey 

and data limitations the authors encountered while 

executing Phase I of the “Raptor Radii Research 

Project,” funded by the U.S. Department of Energy 

through the BLM Utah State Office (BLM Assistance 

Agreement JSA065003). This document benefited from 

reviews and suggestions provided by the Raptor Radii 

Project BLM Steering Committee, which included Dave 

Mills (BLM Utah, Richfield Field Office), Steve Madsen 

(BLM Utah State Office), Dave Roberts (BLM Wyoming 

Acknowledgements

1 Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

to locate potential study sites for an experimental 

assessment of OG-related nest disturbance thresholds as 

part of Phase II of this research project. Unfortunately, 

our inability to identify areas experiencing OG 

development that also contained reasonably complete 

raptor nest inventories and histories was a contributing 

factor in the abandonment of the Phase II effort.

In light of our experiences during the Raptor Radii 

Research Project, we have prepared this technical note in 

order to summarize the problems we encountered, 

outline exactly how they hampered our analyses, and 

translate the resulting insights into recommendations for 

improved future monitoring, specifically in relation to 

potential OG development projects. It is important to 

reflect at the outset that exactly what standards are 

applied in developing a new monitoring program 

depends entirely on the stated objectives for 

implementing the program. Numerous references are 

available in the scientific and statistical literature to help 

guide formulation of monitoring objectives and 

applicable methodological standards. It is not our goal 

for this discussion to comprise a “Monitoring 101” 

treatment. Rather, our intent is to focus specifically on 

the problems we encountered with the existing datasets 

in relation to achieving the objective of evaluating the 

effects of OG development on nesting raptors in the two 

study areas, and to recommend improved standards to 

help guide future monitoring oriented toward such an 

objective.

Raptor nest monitoring should play an integral part in 

wildlife inventory programs carried out on federal lands. 

Properly designed and implemented nest-monitoring 

programs can aid federal land managers during resource 

planning and increase the likelihood of compliance with 

the protections extended to nesting raptors by the 

Migratory Bird Treaty Act and Bald and Golden Eagle 

Protection Act. Additionally, properly designed and 

executed monitoring programs can be used to assess the 

potential impacts of various land-use activities. That 

said, monitoring programs lacking proper and consistent 

implementation can greatly compromise the value of the 

data collected. A recent effort by HawkWatch 

International (HWI) and the Bureau of Land 

Management (BLM) to assess the potential impacts of oil 

and gas (OG) development on nesting raptors was 

particularly insightful in this regard. The project, called 

the “Raptor Radii Research Project,” was designed to be 

carried out in two phases. Phase I sought to utilize 

historic nesting data to identify potential correlations 

between nest-activity patterns and OG development 

activities in the BLM Price Field Office (FO) in 

southeastern Utah and the BLM Rawlins FO in southcentral Wyoming (Smith et al. 2010). During the course 

of compiling existing nesting data from each study area, 

we discovered a number of inadequacies and 

inconsistencies, related primarily to problems with the 

survey terminology and methodology applied over the 

years, which significantly hampered the analyses and 

likely compromised the insight achievable from the data. 

We also identified additional difficulties while attempting 

Introduction

3 Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

Terminology

Steenhof and Newton (2007) effectively articulate 

the importance of standardized terminology and 

careful attention to defining terms used to code neststatus and productivity observations. We found great 

inconsistencies in the terminology used over the years to 

code nesting events in the Rawlins dataset, in particular, 

and more generally found that, based on notes recorded 

in the available databases, that various nest-status 

designations were not always consistently applied due 

to variations in field personnel and attendant differences 

in interpretation or levels of rigor in applying those 

designations. For example, in the Rawlins dataset, it 

became clear that designations of “used” and “active” 

were often used inter-changeably without clarity as 

to whether or not egg-laying was actually confirmed 

(accurate definition of “active,” indicating an actual 

breeding attempt), such that it was frequently impossible 

to differentiate between occupied but inactive nests/

territories and those in which a breeding attempt actually 

occurred. This lack of clarity especially hampered 

our ability to designate confidently many historical 

nest records as truly representing breeding attempts. 

Moreover, even accurate designation of nest records as 

representing an “occupied” scenario was problematic 

due to inconsistencies in what surveyors considered 

evidence of territory occupation. For example, the basis 

for designating a nest/territory as occupied was often 

limited to one brief sighting of a single bird in the general 

vicinity of a nest/territory, whereas a more rigorous and 

appropriate standard would be multiple sightings of at 

least one territorial, breeding-age adult in the immediate 

vicinity of the relevant nest cluster (sensu Smith et al. 

2009). The same basic problems applied to application of 

the designation “tended” in the Price surveys, especially 

because these classifications were based on brief, 

single visits to nests. The highly variable conditions 

that contributed to a particular nest being classified as 

“used” for our analyses, compared to the more concrete 

evidence required for a designation of “active,” may have 

contributed to the typical modeling trend we observed in 

our analyses of data from both study areas. That is, we 

typically identified more competing top models of nestcluster use compared to top models of cluster activity (see 

Smith et al. 2009). For example, for Price-area Red-tailed 

Hawks (Buteo jamaicensis) we identified 18 top “use” 

models, but only one top “activity” model.

Steenhof and Newton (2007) carefully outline appropriate 

terminology and standards for accurate designation of 

nest/territory status and productivity, and therefore we 

do not need to reiterate those here. The important point 

is that, before any monitoring program is instituted, 

applicable standardized terminology should be clearly 

articulated with unambiguous definitions, those standards 

should be rigorously applied throughout the course of 

the monitoring program, and metadata reflecting those 

standards should always accompany any resulting 

datasets. If new insight generated from future research 

dictates a need to change those standards, a careful record 

of the change must be included in the metadata associated 

with the database and a clear “cross-walk” articulated 

to describe the relationships between the old and new 

standards. Ideally, to render data of maximum utility, it 

is important to carefully distinguish among unoccupied 

nest clusters, occupied clusters in which no breeding 

attempt (eggs laid) occurred, occupied clusters in which 

a failed breeding attempt occurred, and occupied clusters 

in which a successful breeding attempt occurred. Of 

course, careful attention to and consistent application of 

standardized definitions of “occupied” and “successful” 

also is required, with the latter typically equating to 

successful rearing of at least one nestling to at least 80% 

of the average fledging age for the species (Steenhof and 

Newton 2007). Determining the actual number of chicks 

reared to 80% of fledging age would comprise the final 

ingredient for comprehensive monitoring by yielding an 

estimate of “productivity.”

Nest Naming Conventions

Developing appropriate standards for uniquely 

identifying specific nest sites also is critically important. 

Several acceptable approaches are possible. In this 

regard, the difficulty we encountered with the Rawlins 

naming system concerned incorporation of a species 

designator in the nest name. The problem arises because 

many nests are used by more than one species over the 

years. As a result, some year-specific nest records in the 

Rawlins dataset were confused because no consistent 

method was applied to identify when a given year’s 

record involved a species different from that for which 

the nest was named initially. In other words, in several 

cases we assumed that a given record related to the 

species identified in the nest code, when in fact careful 

perusing of miscellaneous notes associated with the 

Data Standards and Record Keeping
4 BLM Technical Note 436 • Recommendations for Improved Raptor Nest Monitoring

record ultimately revealed that in fact another species 

used the nest that year. For this reason, nest numbers 

should not include any reference to the species, with 

that information relegated to other year-specific fields 

in the relational database system. In the case of the 

Price dataset, no species designator was incorporated 

in the nest numbers, but problems still arose in tracking 

use by multiple species due to a simple data-structure 

issue. The initial 2006 dataset we obtained included 

status records for all survey years, but included only 

one species designator, which we discovered belatedly 

applied only to the most recent year in which the nest 

was active and the species confirmed. In other words, if 

the species using the nest changed sometime during the 

survey period, information about the earlier species was 

effectively lost in the 2006 file (although recovered once 

we finally obtained all of the original, complete, yearspecific datasets).

Beyond the species issue, our experience suggests that 

incorporating some method of systematic naming of 

individual nests is desirable. For example, nests in the 

Price dataset simply were assigned sequential nest IDs 

based on the order the nest was entered into the database. 

Although the reason is unclear, it became apparent that 

IDs given to a substantial number of Price nests in 1998 

(the first year of helicopter surveys) were associated 

with different nests in the subsequent years. We were 

able to rectify this issue by inspecting the spatial 

relationship between individual nests in a Geographic 

Information System (GIS). We suggest that some manner 

of geographic designation be incorporated in the name 

to facilitate efficient tracking of records and nests on 

the landscape, and for helping to rectify problems when 

errors in nest coordinates are discovered. For example, 

in the Rawlins database, individual nests were given 

a unique nest ID based on the township-range-section 

(TRS) location of the nest, and then a unique number that 

reflected sequential numbering within that section only 

(e.g., Nest 14911201 would be the first nest identified in 

Township 14, Range 91, Section 12).

Another example approach that works well is the 

convention HWI adopted for its Great Basin Raptor Nest 

Survey (e.g., see Smith and Hutchins 2006, 2007), where 

the nest-naming standard incorporates an initial fourletter code indicating the name of the 7.5′ topographic 

quad map in which the nest occurs, followed by a unique 

number that reflects sequential numbering within that 

quad only. In our experience, although the spatial 

resolution of the HWI naming convention is coarser 

than the section-specific naming in the Rawlins dataset, 

a potential problem with the latter is that standard 

topographic maps used for navigation do not always 

include complete TRS delineations, such that it is not 

always possible to easily identify and track the TRS in 

which a given nest occurs, but it is always possible to 

easily locate the topographic quad.

Location-Data Standards

Advancements in Global Positioning System (GPS) 

technology in the last 10–15 years have greatly improved 

our ability to locate nests accurately using relatively 

inexpensive and efficient handheld devices. The lack of 

such technology hampered accurate mapping during the 

early survey years in the Rawlins study area; however, 

despite the availability of appropriate technology for at 

least the past 10 years or so, no GPS coordinates have 

ever been collected for any of the nests in the Rawlins 

study area. Instead, all nest locations were based strictly 

on hand mapping of the approximate locations on 7.5′ 

quad maps. Although the inherent accuracy of standard 

7.5′ quad maps (±40 ft or 12.2 m; see http://erg.usgs.

gov/isb/pubs/factsheets/fs17199.html) is only marginally 

worse than that of typical, currently available handheld 

GPS units (typically ±3–5 m), when compounded with 

the inaccuracy of subjective hand mapping of apparent 

locations and deriving coordinates from the map, the 

error associated with hand mapping is likely on the order 

of at least 10 times greater than with use of basic GPS 

technology, and may amount to inaccuracies of 50 m 

or more. Such error may not represent a problem with 

regard to effective return visits to nests in low nestdensity situations; however, absent clear photographic 

records, it can render impossible the task of accurately 

distinguishing among multiple nests that are tightly 

clustered, which is often the case within Ferruginous 

Hawk (Buteo regalis) nesting territories, for example. 

Additionally, mapping inaccuracies were partially 

responsible for our inability to use digital elevation 

models and GIS to assess how the visibility of OG 

developments from individual nests may affect raptor 

responses in this study. Even relatively small location 

discrepancies can greatly alter the landscape visible from 

a given three-dimensional point, especially when nests 

are located in areas of substantial topographic relief (e.g., 

on cliff faces).

Although not a problem in the context of our Phase 

I investigations, during our Phase II planning efforts 

carried out in the Vernal, Utah and Meeker, Colorado 

study areas, we encountered GPS technology-related 

difficulties driven by the inconsistent use of mapping 

datums and, more importantly, a failure to note the 

particular datum used. Inconsistent use of the NAD27 

and NAD83 datum standards, for example, can result 

in mismatch errors of >200 m when using the UTM 
5 Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

coordinate system. Consistency of use and maintaining 

a clear record of the datum standard used is of greatest 

importance (software to convert among datums is readily 

available), but with regard to the choice of datum, one 

other issue of importance to consider is matching the 

GPS data against other tools used to facilitate navigation. 

If handheld GIS computers or advanced GPS models 

with built-in topographic maps are available, the GPS/

computer combination may be all that is needed for 

effective navigation, in which case the datum used does 

not matter (as long as the chosen datum is recorded 

and consistently used). Such technology can be very 

expensive, however, and often the visual scale and 

resolution of view screens on such devices can hamper 

easy navigation across broad landscapes. The readily 

available and more typical approach is to combine use 

of GPS technology with navigation using topographic 

maps. In this case, the choice of datum makes a big 

difference, because most 7.5′ quad maps still utilize the 

older NAD27 datum.

Nest-Cluster versus 

Nest-Centric Monitoring

As discussed further below, it is essential that monitoring 

of nesting activity be based on a territory or “nestcluster” (see Smith et al. 2010) approach rather than a 

nest-centric approach. Neither the Price nor Rawlins 

databases made available to us were designed to 

accommodate designation of nest-cluster affiliations. 

Such should be a fundamental component of any 

database of raptor nest histories because, once identified 

through appropriate means, it provides essential 

information for future surveyors to consider as they comb 

the landscape for activity. It was apparent from our 

inspection of the Price and Rawlins databases that field 

personnel were often unaware of the potential association 

between individual nests and larger clusters. For 

example, in Price, all the nests in a particular cluster (i.e., 

spatially grouped nests) were rarely surveyed in the same 

year, even when each of the individual nests was known 

from previous years. This clearly could have affected our 

analyses, as we were forced to assign status designations 

to clusters based on this incomplete data. Of course, 

complete surveying of all nests within a cluster is less of 

an issue when definite signs of activity are documented 

at a particular nest, but may be a serious issue when this 

is not the case. For example, the classification of clusters 

as “unused” based on less than complete surveys of all 

component nests may have added noise to our data due to 

potential misclassifications

Availability and Quality 

of Ancillary Data

We easily gathered basic well-location data from the 

Wyoming Oil and Gas Conservation Commission and 

Utah Division of Oil, Gas, and Mining web sites. We 

often found the records wanting, however, in terms of 

missing or incomplete data on development initiation and 

completion dates, and insufficient information concerning 

the timing and extent of maintenance activities and 

“workovers.” In many cases, through significant effort 

we were able to fill-in the missing data by tracking 

down the original, individual well records; however, 

one problem that could not be eliminated effectively 

concerned what we presume to be discrepancies in 

reported and actual key activity dates (e.g., reported 

drilling dates that corresponded to approved targets rather 

than actual dates). For example, in both the Wyoming 

and Utah well records, we encountered well-completion 

dates that preceded spudding dates (i.e., initiation of 

drilling) by days to months.

We found that available road-network data layers were 

substantially lacking, especially concerning accurate 

and current representation of well-pad roads. Through 

hand digitizing of visible roads on 1-m-resolution 

aerial photographs taken in 2006 (U.S. Department of 

Agriculture National Agriculture Imagery Program), 

we added 270 km and 1,470 km of well-head roads, 

and an overall total of 1,063 km and 2,910 km of roads, 

in the Price and Rawlins study areas, respectively (Smith 

et al. 2010).

Although a product did become available late in the 

game, initially no useful, high-resolution vegetation 

map was available for the Rawlins study area. Highquality habitat maps are an essential backdrop for any 

study concerned with evaluating the landscape ecology 

of wildlife populations. Moreover, although we were 

eventually able to obtain high-quality vegetation maps 

for both study areas, the variation in the classification 

schemes employed in each study area required us 

to reduce the vegetation datasets to simpler, more 

compatible classifications. This was true even within 

the Rawlins study area, despite the fact that the same 

GIS laboratory produced both maps for this area. 

Unfortunately, this caused us to lose potentially valuable 

information about, for example, percentage sagebrush 

(Artemisia spp.) cover represented in the more detailed of 

the two Rawlins layers. Regardless, we found vegetation 

parameters were important in most models of nest use and 

activity (Smith et al. 2010).
6 BLM Technical Note 436 • Recommendations for Improved Raptor Nest Monitoring

Data available through the National Climatic Data Center 

(NOAA 2007) provided a means of representing coarsescale, annual variation in regional climate and drought 

severity, which worked well as a covariate in our models 

to help account for interannual variation in overall 

ecosystem condition (Smith et al. 2010). However, the 

absence of finer-scale information (i.e., from multiple 

weather stations located in the study area) sufficient to 

portray, for example, spatial variation in precipitation 

levels within each study area, effectively precluded more 

insightful modeling of the interactive influences of habitat 

condition and development levels on nesting activity.
7 Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

it is essentially impossible to determine accurately 

the landscape-level impact of development on the 

community of nesting raptors and related ecosystem 

elements (i.e., potential changes in the number, speciesspecific composition, and reproductive output of nesting 

raptors). Moreover, even once intensive surveys were 

begun in the two study areas with the goal of gathering 

data that might help evaluate the potential impacts of 

development, inadequate attention was directed toward 

ensuring consistent, representative sampling of areas 

not yet affected by development. Again, this largely 

precluded effective evaluation of the comparative activity 

levels, success, and productivity of nest clusters exposed 

to development and not exposed to development, because 

the latter generally were monitored less consistently.

For example, our analyses occasionally suggested an 

apparent positive correlation between development 

proximity/density and cluster use or activity (Smith et 

al. 2010). Due to the absence of representative, predevelopment, baseline data, there is no way to know 

whether this apparent positive association may be due 

to a correlation between development and higher quality 

nesting habitats, or if in fact the nesting raptors actually 

benefited from some aspect of development effects on 

the landscape. Moreover, if the former is the case, due 

to the lack of both pre-development baseline monitoring 

and effective, concurrent baseline monitoring in similar 

areas outside the development realm, we have no way to 

accurately discern whether nesting activity or success has 

changed due to development.

Another element of baseline monitoring that was wholly 

lacking for both study areas and comprises an essential 

element for effective evaluation of relationships between 

nesting raptors and their environment, whether affected 

by development pressures or not, is prey monitoring. 

Because prey ecology is a primary determinant of raptor 

nesting ecology (e.g., see Smith and Murphy [1979] 

and Steenhof et al. [1997]), without representative prey 

monitoring to facilitate understanding of how variation 

in prey abundance and accessibility interacts with 

development disturbance in affecting nesting raptors, 

it is very difficult to develop a confident assessment of 

development impacts.

Survey Extent and Timing

To derive an unbiased estimate of raptor nesting 

parameters within a study area or population requires 

monitoring that effectively encompasses a representative 

Nest-Cluster versus 

Nest-Centric Monitoring

Because most raptor species routinely use and maintain 

a series of alternative nest sites within their breeding 

territories, with use of individual nest sites varying 

from year to year in a variety of species-specific and 

individualized patterns, it is essential that monitoring of 

nesting activity be based on a territory or “nest-cluster” 

approach rather than a “nest-centric” approach. This is 

critical to allow for accurate representation of multi-year 

history and necessary distinction of truly inactive nests/

territories from nests that are inactive only because that 

year the actual breeding attempt occurred at another 

nest in the cluster. In other words, the relationships 

among nests associated with a given nest cluster are 

not independent and highly misleading results may be 

obtained if they are treated as such. The problem is that 

accurate designation of distinct nest clusters requires 

several years of consistent monitoring to identify clearly 

the range of associated nests and cluster boundaries. In 

other words, properly setting the stage for evaluating 

the effects of specific disturbances or land-use changes 

on nesting dynamics requires a multi-year period of 

robust baseline monitoring to both clearly delineate the 

distribution of distinct nest clusters and provide indexes 

to pre-disturbance nest success and productivity patterns. 

Moreover, throughout any monitoring effort, it is essential 

that the focus always be on documenting whatever 

nesting activity is occurring in an area, not just on 

revisiting known nests, because new nests may be added 

to a territory and disused older nests may be refurbished 

and used again at any time. An apparent lack of attention 

to this facet of monitoring was abundantly apparent in the 

data from both the Price and Rawlins study areas, with 

nests that now clearly comprise single nest clusters often 

monitored inconsistently across years and, as a result, 

it was sometimes impossible to confidently determine 

from the records whether the cluster was in fact active or 

inactive in some years.

Baseline Monitoring

Perhaps the most serious limitation of both relevant 

datasets for evaluating the potential effects of OG 

development was a lack of robust, pre-development, 

baseline monitoring data. Such information is essential 

for accurately portraying the initial conditions that existed 

before widespread OG development began to affect 

the relevant ecosystems. Without such information, 

Survey Design and Rigor
8 BLM Technical Note 436 • Recommendations for Improved Raptor Nest Monitoring

suite of nests, in terms of both spatial and temporal 

aspects, and reflects application of a consistent approach 

for all monitored nests. A critical facet of representative 

monitoring that is often overlooked or at least poorly 

achieved for various reasons concerns effective coverage 

to document initial territory occupation and early nesting 

failures. The available Price dataset was fundamentally 

flawed for this reason, because a single mid-season 

survey simply is not adequate to provide representative 

sampling of early season failures. On the one hand, the 

stated motivation for limiting the helicopter surveys to a 

later period to avoid unnecessary early season disturbance 

of nesting birds (C. Colt pers. comm.) may have been 

appropriate. On the other hand, not pursuing other lessintrusive, ground-based surveys to accomplish needed 

early season monitoring substantially limited the value 

of the data collected. Generally, beginning surveys in 

early to mid-March effectively encompasses the early 

season activities of most raptor species in the region of 

interest. The only diurnal species for which this may 

not be true are Bald Eagles (Haliaeetus leucocephalus) 

and Golden Eagles (Aquila chrysaetos), which in some 

years and areas of the interior west may begin nesting as 

early as January (e.g., Buehler 2000, Kochert et al. 2002, 

Keller 2005). One logistical problem that researchers 

may confront in accomplishing effective early season 

monitoring of these species is inaccessible roadways 

(due to snow cover, etc.), which ironically advocates for 

helicopter surveys (from a safe, non-intrusive vantage 

point), if that resource is available.

Although not as much of an issue relative to achieving 

representative sampling, ensuring adequate late-season 

coverage also is critical if robust nesting-success and 

productivity indexes are desired. The standard for 

deriving reliable estimates of nesting success and 

productivity for raptors requires confirmation of status 

once chicks have reached at least 80% of fledging 

age (Steenhof and Newton 2007). To accomplish this 

consistently, especially when species-specific timing 

within a given study area may vary by as much as several 

weeks, generally requires at least three visits per season to 

each nest. The first early season visit would be designed 

to document nest initiation or early incubation, and the 

second midseason visit would be designed ideally to 

confirm hatching and derive an initial age estimate for 

the chicks. These first two visits would then provide 

an essential basis for predicting when the chicks should 

reach 80% of fledging age, and therefore identify the 

window of opportunity for conducting the final visit to 

confirm nest success and productivity. Again, the single 

midseason visit that was the standard for the Price surveys 

substantially limited the value of these data because it 

effectively precluded evaluating relationships between 

development patterns and nest success and productivity. 

Similarly, in the Rawlins area insufficient coverage and 

attention to the timing of follow-up visits often precluded 

reliable estimates of final nest success and productivity, 

especially for species other than the Ferruginous Hawk 

(historically the species of primary interest in this region).

Another facet of survey coverage that limited our 

investigations was inconsistent interannual survey 

histories for most nests and nest clusters. A welldesigned, representative, randomized annual sampling 

regime could in theory support a wide variety of analyses 

designed to investigate the effects of land-use changes 

such as OG development, while reducing the effort 

required of field personnel. For example, such monitoring 

would support evaluating how study-area-wide nesting 

activity levels, nesting success, and productivity varied 

from year to year in relation to changing development 

levels or other aspects of changing habitat quality. 

Assuming the extent of surveys and development activity 

was sufficient to yield appropriate sample distributions, 

such a survey program may also support evaluation of 

facets such as how nesting activity varies with habitat 

type, in relation to time since proximate development 

occurred, or in relation to development proximity or 

density. Nevertheless, consistent, multi-year, pre- and 

post-development monitoring of representative suites 

of nest clusters may yield additional advantages. For 

example, such would allow for detection of relatively 

subtle responses to development such as changes in the 

locations of “preferred” nest sites or long-term changes in 

the frequency of nesting within clusters. In many cases, 

such an approach may also prove valuable because the 

cluster sample sizes needed to support robust statistical 

analyses under a repeated-measures, pre- and postdevelopment tracking scenario would generally be less 

than for a randomized, multi-year sampling scenario.

Problems HWI Identified Concerning 

Raptor-Related Management of OG 

Development Activities

Based on our collective experiences working in the 

Rawlins Field Office for several years (M. Neal), brief 

exposure to on-going raptor surveys in the Price study 

area, and our recent work developing plans for and 

assessing the efficacy of implementing Phase II of 

the Raptor Radii Project across study areas in Utah, 

Wyoming, and Colorado, below we identify some of the 

key issues pertaining to management of OG development 

activities and overall raptor management in the study 

area:
9 Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

•	 Inconsistent application of raptor stipulations across 

and within management areas.

•	 Field personnel are not always adequately trained 

in the collection of standardized field data and the 

subtleties of terminology, nest-observation and nestrelocation protocols, and record keeping necessary for 

rigorous monitoring of raptor nesting activity.

•	 Field-Office biologists frequently do not have 

adequate time or resources available to them to 

accomplish the intensive monitoring of raptors and 

associated landscape conditions required for robust 

analyses of energy-development effects on nesting 

raptors.

•	 Adequate BLM and industry resources are necessary 

to assure a clear understanding by both about the 

required stipulations and to ensure there are no 

disconnects among agency personnel, industry 

planners, and the personnel actually responsible for 

conducting operations on the ground. Individuals 

at the site must be aware of specific stipulations or 

conditions, raptor nest locations, and other protected 

resources associated with a development site.

•	 Many current RMPs and management plans require 

no spatial disturbance buffers outside of the breeding 

season or outside the development stage. As a result, 

nests sometimes are destroyed, but more frequently 

are rendered unusable due to the proximity of 

development allowed to occur between breeding 

seasons, regardless of nest-use history. Additionally, 

current stipulations rarely account for continued 

disturbance activities that occur during the production 

phase of an OG project.

•	 On-site visits to assess the merits of industry 

exception, waiver, or modification requests often 

occur too early in the nesting season to ensure 

accurate assessments of nesting activity.

•	 Re-use intervals for specific nests and nest clusters 

often extend to several years or more; however, some 

agency management scenarios allow for nest spatialbuffer encroachment following as few as three years 

of apparent inactivity.

•	 Whether intentional or inadvertent, misclassification 

of nest status (e.g., used or unused for reproduction 

in a given year) has serious consequences for raptor 

conservation efforts and for evaluating the efficacy 

of management actions. Field biologists should 

establish unambiguous criteria for assessing nest 

status and develop categories for data that clearly 

indicate the manner by which surveyors assign a use 

category to a nest.

11 Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

Spatial domain: extending 5–10 km outside of proposed 

development area with comparable representation of 

habitats.

Required to:

•	 Enable adequate identification of nest clusters 

that may overlap the development area.

•	 Provide reference or “control” monitoring data 

for comparing against data from the development 

area. Satisfying this need may not require a 

comprehensive, radial extension of the survey 

area, but may require careful attention to 

selecting areas and an overall geographic extent 

beyond the development area that provides 

comparable coverage of habitats and sufficient 

nest-cluster sample sizes within those habitats 

for all focal species to support robust control–

treatment statistical analyses.

Data requirements:

1) Comprehensive nest inventory for a 

representative suite of species (i.e., reflecting 

a reasonable range of ecologies and expected 

sensitivities to disturbance).

•	 The choice of which species to focus on may 

vary depending on:

a) The species known to occur in the area, 

their conservation status, and prior 

knowledge of their relative abundance in 

the area.

b) The nature of the planned development/

disturbance (i.e., what habitats will 

be affected, nocturnal versus diurnal 

activities, hypothesized impacts, spacing 

of disturbance, etc.).

c) Logistical considerations and practical 

constraints with regard to the efficacy 

of gathering robust monitoring data for 

certain species.

Presented below are HWI’s recommendations for 

improved monitoring of nesting raptors, which draw on 

the conclusions presented in our previous overview of the 

existing data and the survey limitations we experienced 

during the course of this study. HWI recognizes that 

BLM Field Offices and personnel frequently are faced 

with limited resources with which to conduct wildlife 

and other types of surveys. In this light, we present the 

following recommendations for an ideal, comprehensive 

monitoring strategy, and highlight the most important and 

minimum-necessary components to help land managers 

establish monitoring priorities.

To set the stage effectively for rigorously evaluating 

the impacts on nesting raptors of a new, planned 

disturbance, such as OG development, requires solid 

baseline inventory and monitoring data. The following 

comprise HWI’s recommendations for necessary and 

desired characteristics of baseline monitoring and 

associated survey protocols needed to facilitate robust 

evaluations of the effects of land-use practices on nesting 

raptors in landscapes typical of those managed by the 

BLM in the interior western United States. Most of 

the described characteristics also would apply equally 

well to monitoring that would need to occur during 

and after application of relevant disturbance regimes or 

development activities.

Pre-development monitoring period: 3–5 years, optimally, 

or as many years as possible prior to the onset of energy 

development activities.

Required to:

•	 Enable effective, initial delineation of nest 

clusters.

•	 Accommodate typically intermittent nesting of 

species such as Golden Eagles.

•	 Allow reasonable time for capturing territory 

turnover and reoccupancy of abandoned 

territories by other species.

•	 Obtain reasonable baseline data on speciesspecific population densities, habitat associations, 

and nest success and productivity rates for the 

study area prior to development.

Recommendations for Improved Monitoring
12 BLM Technical Note 436 • Recommendations for Improved Raptor Nest Monitoring

•	 The inventory database should include the 

following information, initially recorded 

on standardized field data forms (which are 

carefully and meticulously archived) and 

then transferred to an appropriate, electronic, 

relational database system compatible with a 

GIS:

a) A unique nest name/number that does 

not include a species designation but 

does help place the nest geographically 

at a relatively fine-scale; e.g., includes a 

Township-Range-Section designation or a 

code indicating the 7.5’ topographic map 

within which the nest lies.

b) Precise (±3–4 m or better) GPS location 

coordinates for all nest sites recorded 

in a consistent coordinate system 

(preferably UTM coordinates using 

a consistent datum; i.e., NAD27 or 

NAD83), with meticulous metadata 

recorded concerning the resolution of 

the GPS device, coordinate system, 

and datum used. For nests located on 

high cliffs or in locations that otherwise 

preclude direct access to the nest or 

positions directly above or below the 

nest for acquisition of accurate nest 

coordinates, coordinates should be 

recorded from the closest accessible 

point near the nest and combined with 

a bearing reading and distance estimate 

derived from a laser rangefinder. In such 

cases, hand plotting of the estimated 

nest location on a 7.5′ topographic map 

may also help refine the location data 

upon plotting within a GIS. Although 

we recognize that not all monitoring 

programs may be able to achieve 

the same levels of accuracy and that 

some situations preclude the accurate 

recording of locations, we advocate 

that surveyors record locations with the 

highest feasible accuracy and keep clear 

records concerning said accuracy levels.

c) Township-Range-Section-Quarter Section 

location information whenever known to 

serve as back-up location data in case of 

error in recording GPS coordinates.

d) GPS coordinates for “ideal” viewing 

of nests from a distance (to avoid 

unnecessary disturbance, early season 

monitoring requires viewing from at 

least 400–800 m away, depending on the 

species).

e) Field drawn map and/or verbal 

description of the nest location relative 

to proximate roads, other relevant 

features (e.g., topographic or vegetation 

features), and view coordinates.

f) Substrate type and height above ground. 

Descriptions of nest substrate should 

be as detailed as possible (e.g., the 

species of tree, or at least evergreen or 

deciduous, rather than simply “tree”) to 

facilitate nest re-location and insights on 

the relative value of different substrates 

in the project area and their vulnerability 

to OG development.

g) Nest type (e.g., stick nest or scrape), 

estimated size (height, width, depth), 

location on substrate (top of tree, 

lateral branch, cliff ledge or pothole, 

etc.), height above ground, direction 

of exposure to and degree/nature 

of protection from the elements, 

accessibility to humans and groundbased predators, and current condition. 

A basic estimation of nest size (we are 

not advocating for the actual physical 

measurement of individual nests) can 

be helpful in distinguishing between 

proximate nests and in determining 

the likely species associations of 

inactive nests. Although assessment 

of nest accessibility is subjective, this 

assessment is critical to assessing the 

relative value and vulnerability of 

various nest substrates to development, 

as well as to potential nest predators. 

Such information may also aid in 

planning for equipment needed to 

conduct detailed nest checks for 

productivity assessments or to plan 

additional research that requires handling 

chicks (e.g., for health monitoring or 

banding).

h) Notes on known or hypothesized 

relationships to other proximal nests; 

i.e., is the nest believed to be part of a 

larger nest cluster.
13 Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

i) Standardized assessment of the primary 

habitat types and conditions surrounding 

the nest at 1-km radius.

j) A series of high-resolution digital photos 

taken at various distances from the nest 

(including data on the location from 

which each photo was taken and the 

estimated distance and bearing to the 

nest) to facilitate future relocation and 

provide a photographic record of the 

structural and location characteristics of 

each nest.

2) Annual monitoring data for all known and newly 

discovered nests for all focal species.

•	 During the pre-development inventory 

and monitoring period (ideally 3–5 

years), monitoring data should be 

spatially comprehensive to facilitate 

accurate delineation of nest clusters, 

habitat relationships, climate effects, and 

associated population dynamics. Once a 

solid, comprehensive inventory and initial 

monitoring database has been compiled, it 

then should be possible to develop a spatially 

less-intensive but representative sampling 

regime for gathering future monitoring data 

that will allow for effective evaluation of the 

effects of development activities.

•	 An ideal monitoring regime should include 

a minimum of three visits to all nests/nest 

clusters, with the timing depending on the 

species involved. Simply documenting nest 

activity does not provide land managers 

with an adequate tool to assess the potential 

negative impacts of disturbances such as 

OG development; i.e., active nests that 

subsequently fail are indistinguishable from 

successful nests, and successful nests in 

different habitats/development scenarios may 

experience different levels of productivity.

a. For most species (e.g., Bald and Golden 

Eagles, Red-tailed and Ferruginous 

Hawks, Prairie Falcons [Falco 

mexicanus], and Peregrine Falcons 

[F. peregrinus]) first visits should occur 

from March through early April to 

document initial territory occupancy, 

courtship and nest-building/tending 

activities, and preferably actual nestinitiation (i.e., egg laying and initial 

incubation). Although earlier visits for 

early-nesting species such as the Golden 

Eagle may be valuable for the detection 

of early nest failures, such visits are 

often logistically infeasible. For other 

late-nesting species, such as Swainson’s 

Hawks (Buteo swainsoni) and Burrowing 

Owls (Athene cunicularia), nest initiation 

typically does not occur until late April 

through May, so the timing of first visits 

would need to be adjusted accordingly. 

To avoid unnecessary disturbance 

during the most sensitive period in the 

nesting cycle, observers should attempt 

to achieve most early nest monitoring 

activities at distances of at least 800 

m (0.5 mile) from nests of most raptor 

species. We suggest this distance as 

a general rule of thumb and recognize 

that closer observation of some species, 

such as the American Kestrel (Falco 

sparverius), Barn Owl (Tyto alba), and 

Prairie Falcon, may be acceptable, while 

endangered or threatened species should 

be given a wider berth (Romin and Muck 

2002). We also suggest that nest-viewing 

distances may be adjusted based on the 

specific conditions at a particular nest 

(e.g., topography, vegetation screening, 

etc.). Regardless, this type of relatively 

long-distance monitoring is dependent on 

the use of high-quality spotting scopes 

and often extended observation periods to 

acquire accurate information. Ensuring 

adequate early season monitoring is the 

most critical component of any survey 

regime, because deriving an accurate 

index of annual nesting activity requires 

knowledge of early failures, which 

cannot be gleaned from only mid- or 

late-season monitoring. These visits 

should focus on both revisiting all known 

nesting areas and observing for signs of 

activity in other areas of suitable habitat 

that may not have been used or known as 

nesting areas previously.

b. Second, mid-season visits are designed 

ideally to confirm hatching success or 

failure and to obtain initial age estimates 

for chicks and initial brood sizes. These 

visits also provide the first opportunities 

to safely intrude more closely into 
14 BLM Technical Note 436 • Recommendations for Improved Raptor Nest Monitoring

nesting habitats to identify other nesting 

that may have been missed during 

distant, early-season monitoring. These 

visits typically should occur from midApril through early June, depending 

on the species and indications of cycle 

timing derived from early season visits. 

We consider these first two visits the 

minimum necessary to confirm annual 

numbers of breeding events in a study 

area.

c. Third visits are designed to confirm 

nesting success and productivity. They 

should be timed based on knowledge of 

egg-laying or hatching dates to allow 

for confirmation of nestlings reaching 

80% of the average fledging age for the 

species. Waiting until after chicks are 

likely to have fledged may still yield 

confirmation of nesting success if one 

or more fledglings are found in the area, 

they can be accurately distinguished 

from adults, and there is no chance of 

confusing fledglings from different nests, 

but often precludes accurate confirmation 

of productivity (i.e., the actual number 

of chicks fledged). These third visits 

may be considered discretionary if 

the monitoring objective is limited to 

documenting annual breeding levels; 

however, doing so will substantially limit 

the value of inferences drawn concerning 

effects of development. We suggest 

that the minimum strategy should entail 

confirming nesting success.

•	 All monitoring data must conform to 

standardized and meticulously documented 

terminology standards and recording 

protocols (see Steenhof and Newton [2007] 

for further guidance), and be collected by 

adequately trained personnel to ensure longterm consistency and conformity to the 

adopted standards. This may require annual 

training of new or inexperienced employees. 

Along with being familiar with terminology 

standards presented in Steenhof and Newton 

(2007), we suggest that field personnel also 

have a basic understanding of species-specific 

raptor behaviors and nesting ecology, which 

can easily be gleaned from reviewing relevant 

Birds of North America accounts (see http://

bna.birds.cornell.edu/BNA). It is particularly 

important to adopt and ensure conformity to 

rigorous standards designed to distinguish 

“occupied” and “unoccupied” nest clusters 

or territories, and to confirm actual breeding 

events (i.e., eggs laid):

a. Whether or not an actual breeding event 

occurs, identification of “occupied” 

nest clusters ideally should be based on 

repeated observations of one or more 

breeding-age adults in the immediate 

vicinity of the nest cluster, preferably 

combined with evidence of territorial 

behavior, courtship/pair-bonding 

activities, and/or nest tending. Digital 

photo records of nests from the previous 

year may assist in identifying recently 

“improved” or “tended” nests through 

comparison of nest sizes, the nature of 

materials present, and whitewash signs. 

Otherwise, absent actual observations 

of an adult at or working on a nest, one 

must be very careful in classifying nests 

as tended or occupied without multiple 

lines of evidence supporting such a 

classification. For example, perceived 

additions of new nest material or the 

presence of apparently fresh whitewash 

are not sufficient evidence alone, as both 

can be very difficult to discern depending 

on lighting, viewing angles, and the 

relative exposure of the nest to the 

elements. In addition, use of certain nests 

by more than one species in different 

years is common, particularly where 

buteo and raven nests are concerned, so 

one must also be careful not to assign 

activity to a former species in the absence 

of confirming use by that species in the 

current year. Positive evidence of nest 

tending also does not confirm an actual 

breeding event.

b. Confirmation of an actual breeding event 

must be based on evidence that egg 

laying occurred. Such evidence may 

include direct confirmation of eggs or 

chicks in the nest (or perhaps freshly 

hatched or broken eggs or dead chicks 

under the nest), witnessing an obviously 

incubating adult, prey deliveries to 

the nest and/or obvious chick-feeding 

behavior, and as a last resort obvious 

late-season signs that the nest was 
15 Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

occupied for a long period by nestlings 

(e.g., heavy, fresh whitewash deposits, 

extensive prey remains, and/or obvious 

downy chick feathers in or under the 

nest).

3) Annual, representative prey-monitoring data.

•	 Prey abundance and accessibility often are 

the primary drivers of raptor nesting activity 

and especially success and productivity 

(Smith and Murphy 1979, Steenhof et al. 

1997, Smith et al. 2010). Therefore, an 

absence of knowledge concerning spatial 

and temporal patterns and trends in prey 

availability may seriously compromise 

efforts to evaluate accurately the impacts of 

other factors such as OG development on a 

population. Achieving adequate and truly 

representative prey monitoring often is a very 

challenging proposition, however, and so 

rarely has been achieved, especially at larger 

landscape scales. It is not our goal here to 

advocate one particular survey method over 

another, but rather point out that various 

techniques exist for these species and that, 

whenever feasible, prey monitoring should be 

considered an integral part of any raptor nestmonitoring program.

•	 The choice of what prey species to monitor 

may depend on the focal raptor species of 

interest; however, we suggest that targeting a 

few key species or species groups generally 

should provide a well-rounded assessment 

of relevant prey-composition and trends 

that will be useful for at least typical diurnal 

raptor communities in the interior West. 

These include:

a. Rabbits and hares. Throughout much of 

the interior West, black-tailed jackrabbits 

(Lepus californicus), white-tailed 

jackrabbits (Lepus townsendii), and 

various cottontail species (Sylvilagus

spp.) are of great importance to Golden 

Eagles (Kochert et al. 2002). Snowshoe 

Hares (Lepus arcticus) are an important 

prey species for raptors at higher latitudes 

and elevations. Various techniques are 

available for surveying rabbits and hares, 

including nighttime spotlighting on road 

transects (e.g., Smith and Nydeggar 

1985), walking transects (e.g., Gross et 

al. 1974), pellet counts (e.g., Prugh and 

Krebs 2004), and more intensive markrecapture techniques.

b. Squirrels. Ground squirrels 

(Spermophilus spp.) and prairie dogs 

(Cynomys spp.) in open habitats and tree 

squirrels in forested habitats constitute 

important prey items for many mediumsized raptors such as buteos, the larger 

accipiters, and Prairie Falcons, as well 

as Golden Eagles. Visual animal counts 

may be more effective than burrow 

counts for both prairie dogs and ground 

squirrels (see Van Horne et al. [1997] 

and Severson and Plumb [1998]). 

Walking transects for visual and/or aural 

detections may be useful for monitoring 

tree squirrels (e.g., Burnham et al. 1980).

c. Small rodents. Various mice, voles, and 

rats are key constituents in the diets of 

many small to medium-sized raptors. 

Various types of live or lethal trapping 

arrays are effective tools for monitoring 

the species diversity and abundance 

patterns of this group of species (e.g., 

Pearson and Ruggiero 2003).

d. Birds. A variety of birds are important 

prey species for many raptors, ranging 

from primarily small songbirds for 

species such as the Sharp-shinned Hawk 

(Accipiter striatus) and American Kestrel, 

to larger grouse and pheasants for eagles, 

goshawks, and some larger buteos. 

Visual and aural point counts are an 

effective method for monitoring species 

occurrence and the relative abundance 

of communities of especially small to 

medium sized birds (e.g., Reynolds et 

al. 1980), whereas walking transects are 

often the most productive method for 

surveying species such as grouse and 

pheasants.

•	 Once a representative array of species 

or species groups is selected for prey 

monitoring, decisions must be made about 

the nature of data desired. To be useful, prey 

monitoring should minimally provide robust, 

study-area-wide, annual indexes of relative 

abundance for each focal species or species 

group to help account for annual variation 
16 BLM Technical Note 436 • Recommendations for Improved Raptor Nest Monitoring

in raptor nesting activity, success, and 

productivity related to this important factor. 

Ideally, sampling also would provide for 

discrimination of relative prey diversity and 

abundance across different habitat types or 

otherwise distinct segments of the study-area 

landscape that are relevant to nesting raptors. 

During or after development has occurred, 

an appropriate sampling regime may be 

to target areas around subsets of “control” 

and “treatment” nest clusters for each focal 

raptor species to provide comparative data 

for modeling landscape characteristic around 

each.

4) Annual, representative climatic and landscapecondition data.

•	 Annual climatic summary data for general 

landscape regions across the U.S. are 

generally readily available through the 

National Climatic Data Center, and can serve 

well in providing monthly to annual indexes 

of general climatic conditions (e.g., drought 

severity levels and precipitation totals) in the 

region of interest.

•	 Finer-scale information sufficient to 

discriminate variation in, for example, 

moisture and drought severity levels 

across habitat types would further assist 

in accounting for (in a modeling sense) 

the effects of within-study area variation 

in habitat condition that is unrelated to the 

disturbance factor of interest. Acquiring such 

data would require, however, placement of 

a representative array of automated weather 

stations throughout the study-area landscape, 

which may be cost prohibitive.

•	 Accurate, annual mapping of fire histories 

can be another important tool for qualifying 

landscape condition.

•	 Standardized, annual assessments of range 

condition may be another effective means for 

helping to quantify annual and potentially 

within-study-area spatial variability in 

landscape condition. Effective, spatially 

explicit tracking of annual livestock stocking 

levels also may be of great interest, as 

landscape alterations from livestock grazing 

can significantly alter the distribution and 

abundance of key raptor prey species.

•	 If other forms of human disturbance are 

prevalent in the study area (e.g., recreational 

activities, wind farms, quarries, etc.), 

annual, spatially explicit monitoring and 

quantification of such activities also may be 

important to provide a truly robust basis for 

evaluating the effects of a new disturbance 

such as OG development.

5) Other desired GIS data layers describing the 

study-area landscape:

•	 High-quality 10–30-m resolution vegetation/

landcover data layer(s) derived from 

classified satellite imagery. At least one 

representative and reasonably contemporary 

map is essential, but multiple versions 

prepared to represent change at 3–5-year 

intervals are ideal. When the BLM funds 

the preparation of GIS data layers such as 

these, we suggest that careful attention be 

paid to existing layers to avoid the loss of 

information that necessarily occurs when 

attempting to combine data with different 

levels of detail and varying classification 

schemes. We recognize that the continual 

improvement in the resolution of aerial and 

remote sensing data should naturally lead 

to more detailed and refined data layers; 

however, we suggest that if some attention 

is paid to previously used classification 

schemes, it could facilitate the more direct 

linking of various datasets (e.g., greater 

refinement in newer datasets might simply 

be represented by sub-classifications of 

previously used schemes).

•	 Minimum 30-m resolution Digital Elevation 

Model to represent landscape topography.

•	 Current, comprehensive road-network data 

layer, with all roads classified in terms of 

type (e.g., primary paved, secondary gravel, 

dirt two-track, oil and gas road, etc.), and 

preferably including dates of first appearance 

or construction, and some indication of 

relative traffic levels.

•	 Current, comprehensive data layer 

representing the distribution of power and 

telephone lines, with lines classified by type 

(e.g., high-voltage transmission, distribution, 

etc.).
17 Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

•	 Current, comprehensive OG well-location 

data layer, with all wells classified by type 

(oil, conventional natural gas, coalbed 

methane, etc.), and including accurate 

and precise construction, spudding, major 

workover, and capping dates, as relevant.

Survey Methods

In our experience, ground-based surveys generally are 

the most cost-effective, efficient, and least disturbing 

means of obtaining accurate monitoring data for multiple 

species. This is particularly true if any species other than 

eagles or Ferruginous Hawks are targeted, because most 

other species are simply too cryptic for aerial surveys 

to be productive. That said, if managed appropriately, 

aerial surveys, particularly helicopter surveys, can be a 

very efficient and productive, though very costly, tool 

for surveying species such as eagles and in many cases 

Ferruginous Hawks, whose large nests are generally 

located in situations where they can be seen easily from 

the air. Moreover, aerial surveys may be a particularly 

useful tool to achieve early-season monitoring in areas 

where snow cover or otherwise poor road conditions 

preclude easy access early in the year. Aerial surveys 

may also be particularly useful for gaining visual 

confirmation of the contents of highly elevated nests. 

With this said, research has documented the potential 

for nest disturbance associated with close passage of 

aircraft, although some species may habituate to this type 

of disturbance relatively quickly (Andersen et al. 1989). 

Perhaps more importantly, the high cost of helicopter 

surveys, and specifically the cost of time spent in the air, 

may limit the rigor and thoroughness of aerial survey 

programs.”

The observational period required to determine nest status 

depends on the species and nest situation. During early 

season monitoring when nests cannot be approached 

closely or whenever the nest location precludes direct 

observation of nest contents or easy detection of an 

incubating adult on the nest from an appropriate distant 

vantage point, a minimum 1-hour observation period 

will usually be required to confirm the status of the nest 

through observation of nest switching by incubating 

adults, an adult adjusting its position on the nest, or, 

during brood-rearing, the chicks standing up to stretch 

or adjust their positions or the adults bringing prey. 

However, the necessary observation period may need 

to extend to two hours for species such as Peregrine 

Falcons when they are nesting in hidden cliff cavities. 

Additionally, once both adults can be away from the nest 

to forage for their chicks, observation periods of several 

hours may be required to confirm the status of Golden 

Eagles nests.

Besides a high-quality spotting scope and mounting 

system, binoculars, a digital camera, a reliable handheld 

GPS unit, a laser range finder, and a compass, another 

very important survey tool relevant to gathering accurate 

nest-monitoring data is a telescoping mirror pole (4–5 m 

extension range) that can be used to inspect the contents 

of many nests from above or below.

Continued Monitoring

After initial baseline data have been collected, nests 

should be assigned to clusters based on proximity and 

history of use. Ideally, all known clusters should be 

monitored (within and outside the development project 

boundary) as development proceeds. If comprehensive 

annual monitoring is not achievable, we would instead 

advocate use of representative random sampling of known 

nesting areas on an annual basis, with the sampling 

regime designed to achieve the following:

•	 Annual monitoring of at least 15–20 nest clusters 

representing each species, primary habitat types, 

and both “control” and “treatment” regions. 

These sample sizes reflect the minimum number 

necessary to detect changes in nest productivity 

of 50% or more between groups (i.e., control 

and treatment nests), as suggested by statistical 

power analysis and fledgling-production effects 

sizes estimated from five years of intensive nest 

monitoring data collected for the same species 

by HWI in the northern Great Basin of Utah 

and Nevada (Smith and Hutchins 2006, 2007). 

Note that this approach still requires an initial 

gathering of relatively complete, area-wide 

baseline information to facilitate the selection of 

cluster samples.

•	 Both re-checking of known nesting areas and 

nest clusters, and searches for potential new nests 

in suitable areas. A quadrat-based sampling 

strategy should be able to provide insight into 

general habitat conditions, nesting densities, and 

reproductive output based on a subsample of the 

full landscape.

•	 Representative subsets of species-specific nest 

clusters that are monitored every year to obtain 

information about consistency of cluster use and 

nest-switching rates.
18 BLM Technical Note 436 • Recommendations for Improved Raptor Nest Monitoring

•	 Either sampling that ensures all areas are 

re-inventoried at least every five years, or 

alternatively that a comprehensive re-inventory 

occurs every five years, to maintain accurate and 

current knowledge of all nest locations across the 

landscape of interest.

•	 Representative annual monitoring as long as 

development activity continues to expand across 

the landscape of interest, and continuation for 

at least another 3–5 years following cessation 

of new development activity to provide for an 

assessment of stabilization tendencies.

Otherwise, standardized monitoring of prey populations 

and other landscape-condition indices should continue 

on an annual basis along side any raptor monitoring that 

occurs. Augmentation of effort or sampling locations 

to better correspond to specific “treatment” locations 

may be desired at this stage, if resources allow and it is 

relevant to achieving research objectives associated with 

evaluating the effects of development or other human 

activities. Additionally, longer-term post-development 

monitoring also may be desirable, if the evaluation of 

the potential efficacy of post-development reclamation 

activities also is a goal of the monitoring program.

Lastly, HWI recommends that protecting historic nest 

sites, especially those with a lengthy history of use, 

should be considered a priority regardless of the current 

condition of the actual nest or the length of time the nest 

has been inactive. Even when historic nests become 

highly degraded or collapse entirely, that site may still be 

preferentially chosen by new breeders for re-occupation 

and rebuilding because it is a particularly attractive 

location. While we recognize that it may be impractical 

to protect all nest sites indefinitely, we do suggest 

that protections be extended to account for potential 

fluctuations in nest activity as related to prey abundance, 

climatic fluctuations, etc. (e.g., Romin and Muck [2002] 

advocate for protection of inactive nests for at least 

seven years).

Recommendations on the 

Recording and Storage of Data

During the course of our own (HWI) nest survey efforts, 

we created and refined field datasheets which can be 

used to facilitate the recording of nest and nest-site 

characteristics previously outlined in the Improved 

Monitoring section. We provide example datasheets 

in Appendix A, which may be used directly by field 

personnel or as a template to guide the production of 

similar datasheets for specific monitoring programs. We 

also developed a Microsoft Access relational database 

system for storing and querying nest location and 

monitoring data; a template of this database system is 

readily available to any interested parties at http://www.

hawkwatch.org/conservation-science/tools-and-resources. 

We strongly advocate that any nest-monitoring plan 

also budget time and personnel for regular electronic 

entry of data to facilitate ease of data retrieval and use 

in conjunction with other data layers and mapping 

software. Collected data should be archived in both 

hardcopy and electronic form, preferably in distinct 

physical locations, to prevent the potential complete 

loss of data. We also recommend that detailed metadata 

accompany the database and any database or mapping 

products derived from the collected data. Detailed 

metadata should serve to reduce the likelihood of the 

unintentional misinterpretation or misuse of collected 

data and associated products. Perhaps more importantly, 

it should also facilitate the maintenance of consistent 

data-collection standards and the continued, effective 

implementation of established monitoring programs, even 

in the face of potential turnover of field and programoversight personnel.
19 Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

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21 Recommendations for Improved Raptor Nest Monitoring • BLM Technical Note 436

Appendix A.

Example field datasheets

for raptor nest monitoring.

Figure A1. Example “nest location” data form (front [previous page] and back [this page] sides) used to record detailed nest and nest-site 

characteristics of newly found raptor nest. Editable electronic versions of this data form are available at http://www.hawkwatch.org (find download 

link associated with listing of this manuscript in the publications section accessed from the Conservation Science menu).

Figure A2. Example “nest history” data form (front [previous page] and back [this page] sides) used to record data from multiple nest-check visits. 

Editable electronic versions of this data form are available at http://www.hawkwatch.org (find download link associated with listing of this manuscript 

in the publications section accessed from the Conservation Science menu).



The mention of trade names or commercial products does not constitute endorsement

or recommendation for use by the Federal Government.
BLM Technical Note 432 Raptor Nesting Near Oil and Gas Development:

An Overview of Key Findings and Implications

for Management Based on Four Reports by

Hawk Watch International 

BLM Technical Note 433 An Assessment of the Effects of Oil and Gas Field 

Activities on Nesting Raptors in the Rawlins, 

Wyoming and Price, Utah Field Offices of the 

Bureau of Land Management

BLM Technical Note 434 Artificial Nest Structures as Mitigation for NaturalGas Development Impacts to Ferruginous Hawks 

(Buteo regalis) in South-Central Wyoming

BLM Technical Note 435 Accipiter Use of Pinyon–Juniper Habitats for 

Nesting in Northwestern Colorado

BLM Technical Note 436 Recommendations for Improved Raptor Nest 

Monitoring in Association with Oil and Gas 

Development Activities

These five documents are an integrated series.