Short-Term Effects 

of Fuel Reduction on 

Pileated Woodpeckers 

in Northeastern Oregon—

A Pilot Study

Evelyn L. Bull, Abe A. Clark, and Jay F. Shepherd

United States 

Department of 

Agriculture

Forest Service

Pacific Northwest 

Research Station

Research Paper

PNW-RP-564

February 2005
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Authors

Evelyn L. Bull is a research wildlife biologist, and Abe A. Clark was a biological technician, U.S. Department of Agriculture, Forest Service, Pacific Northwest 

Research Station, Forestry and Range Sciences Laboratory, 1401 Gekeler Lane, 

La Grande, OR 97850. Clark is currently a graduate student, Department of Animal Science, Oregon State University, Corvallis, OR 97331. Jay F. Shepherd is a 

research assistant, Department of Fish and Wildlife Resources, University of Idaho, 

Moscow, ID 83843.

Cover illustration by Susan Lindstedt.
Abstract

Bull, Evelyn L.; Clark, Abe A.; Shepherd, Jay F. 2005. Short-term effects of 

fuel reduction on pileated woodpeckers in northeastern Oregon—a pilot study. 

Res. Pap. PNW-RP-564. Portland, OR: U.S. Department of Agriculture, Forest 

Service, Pacific Northwest Research Station. 17 p.

To determine the short-term effects (1 to 3 years posttreatment) of fuel reduction 

on pileated woodpeckers (Dryocopus pileatus) in northeastern Oregon, we compared measures of abundance of logs, snags, stumps, and of woodpecker foraging 

in mixed-conifer stands that had undergone the following treatments: prescribed 

burning after mechanical fuel reduction, mechanical fuel reduction without prescribed burning, or no treatment. Pileated woodpecker foraging was significantly 

more abundant in the stands that were not treated or had mechanical fuel reduction 

only. Ants, the primary prey of pileated woodpeckers, were also significantly more 

abundant in these stands. 

Keywords: Fuel reduction, prescribed burns, pileated woodpecker, northeastern 

Oregon, ants, snags, logs.
Summary

With the increased emphasis on fuel reductions within forests of the Pacific Northwest, it is important to know how these altered forest stand structures will affect 

wildlife. The pileated woodpecker (Dryocopus pileatus) is a management indicator 

species that depends on snags and hollow trees for roosting; snags for nesting; and 

logs, snags, and live trees for foraging. The objective of this study was to compare 

the use of logs, snags, and stumps by pileated woodpeckers and other woodpeckers within three treatments: stands treated with mechanical fuel reduction without 

burning, the same treatment but with burning, and untreated controls in northeastern Oregon. Pileated woodpeckers foraged significantly more in the stands that 

were untreated or had mechanical fuel reduction only. Ants, the primary prey of 

pileated woodpeckers, were also significantly more abundant in these stands. At 

least in the short term, prescribed burn treatments (1 to 3 years old) resulted in a 

loss of foraging habitat and prey for pileated woodpeckers.
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Short-Term Effects of Fuel Reduction on Pileated Woodpeckers in Northeastern Oregon—A Pilot Study

Introduction

 Widespread outbreaks of the western spruce budworm (Choristoneura occidentalis) and Douglas-fir beetle (Dendroctonus pseudotsugae) in the 1980s and early 

1990s caused heavy tree mortality in stands with grand fir (Abies grandis (Dougl. 

ex D. Don) Lindl.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in northeastern Oregon (Gast et al. 1991). The outbreaks resulted in high tree mortality that 

increased the fuel loading and the risk of stand-replacement wildfires (Gast et al. 

1991). The increase in wildfires nationally in the early part of this century resulted 

in an increased emphasis on reducing fuels within forest stands. Currently, the 

primary methods of reducing fuels are the mechanical removal of trees and coarse 

woody debris (standing or down dead wood) and prescribed burning.

Certain wildlife species in northeastern Oregon, including small mammals, 

amphibians, rubber boas (Charina bottae), martens, bears, and woodpeckers, depend heavily on the coarse woody debris that is removed during these fuel reduction treatments (Tiedemann et al. 2000). American martens (Martes americana) 

frequently capture prey in accumulations of logs, and use rest and den sites in logs 

and snags (Bull and Heater 2000). Ants found in dead wood are the primary prey 

of pileated woodpeckers (Dryocopus pileatus) (Bull et al. 1992, Torgersen and 

Bull 1995). Other log-dwelling and log-associated insects, mainly ants and yellowjackets, comprise 24 percent of black bear (Ursus americanus) diet in northeastern 

Oregon (Bull et al. 2001). 

Inadequate amounts and kinds of dead wood could affect the beneficial role that 

foliage-foraging ants and other forest-floor arthropods have in maintaining forest 

health. Ants also serve an important role in forest health in preying on the western 

spruce budworm, one of the most important forest-defoliating insects in the Pacific 

Northwest (Torgersen et al. 1990). Many other species of forest-floor arthropods are 

predators of the western spruce budworm, and some parasites of the western spruce 

budworm depend on the forest floor for a portion of their life cycle (Tiedemann et 

al. 2000). Populations of all forest-floor arthropods were significantly lower in areas 

that had been harvested and burned in comparison to adjacent undisturbed forests 3 

years after treatment (Fellin 1980). Prescribed burning severely affected groups of 

forest-floor fauna by directly killing the organism or by removing woody material 

and forest floor that are required by these insects for food and shelter (Fellin 1980).

Although few studies directly have investigated the results of fuel reduction 

treatments on wildlife in the Pacific Northwest, evidence suggests that some species are negatively affected by this type of management, at least in the short term, 

whereas others are unaffected or benefit. Numbers of red squirrels (Tamiasciurus 

hudsonicus), snowshoe hares (Lepus americanus), and southern red-backed voles 
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RESEARCH PAPER PNW-RP-564

(Clethrionomys gapperi) decreased in abundance, and chipmunks (Tamius spp.) 

increased after a mechanical fuel reduction treatment in lodgepole pine (Pinus 

contorta Dougl. ex Loud.) stands (Bull and Blumton 1999). Abundance of northern 

flying squirrels (Glaucomys sabrinus) in northeastern Oregon decreased after thinning treatments to reduce dwarf mistletoe (Arceuthobium spp.), whereas numbers of 

red squirrels remained constant or increased with this treatment (Bull et al. 2004). 

A better understanding of how fuel reduction treatments, particularly prescribed 

burning, affect forest communities is essential for effective management of habitat 

for wildlife (Kotliar et al. 2002).

The pileated woodpecker is a management indicator species for the Forest 

Service in the Pacific Northwest Region and is strongly dependent on coarse woody 

debris for foraging (Bull 1987, Bull and Jackson 1995). The effects of fuel reduction 

treatments on this species and its prey base are unknown. Given the lack of information available, our overall goal is to look at fuel reduction over time. In this pilot 

study, we investigated the short-term (1 to 3 years) response of pileated woodpeckers to fuel reduction treatments in stands with past insect outbreaks because these 

areas were determined to be at high risk for fire without some removal of fuel. 

We conducted this study in an area with a known density of pileated woodpeckers 

to determine if an adequate sample size of foraging sites could be located in fuel 

reduction treatments to justify a more comprehensive long-term study over a larger 

geographic area. The specific objective of this study was to compare the use of logs, 

snags, and stumps by pileated woodpeckers in stands treated within 1 to 3 years 

with mechanical fuel reduction without burning, the same treatment with burning, 

and in untreated controls on the Starkey Experimental Forest and Range (Starkey). 

Methods

Study Area, Stand Treatment and Selection 

The study was conducted on Starkey (11 400 ha), located within the La Grande 

Ranger District of the Wallowa-Whitman National Forest, 50 km southwest of 

La Grande, Oregon. In the 1980s, outbreaks of spruce budworm and subsequent 

Douglas-fir bark beetle outbreaks in the 1990s resulted in extensive mortality of 

grand fir and Douglas-fir in the 1990s on Starkey. Based on preliminary inquiries 

from geographic information system (GIS) and field work, at least 75 percent of the 

grand fir stands in existence in 1989-90 now have low canopy closure (<30 percent) because of extensive mortality on Starkey. These same stands contained 95 to 

100 percent canopy closure in the 1970s. This change in canopy closure and stand 

condition prompted the La Grande Ranger District in collaboration with the Pacific 
3

Short-Term Effects of Fuel Reduction on Pileated Woodpeckers in Northeastern Oregon—A Pilot Study

Northwest Research Station to implement fuel reduction treatments to reduce the 

amount of coarse woody debris in the stands. Starkey is a critical research area for 

a host of long-term scientific studies that require special protection. Starkey offers a 

unique research opportunity for this study because 50 stands were treated with fuel 

reduction methods (mechanical and mechanical with prescribed burning), stands 

with no treatment were available within close proximity, and home range locations 

of pileated woodpeckers were known based on past research (Bull and Holthausen 

1993). The proximity of the stands allowed a comparison of pileated woodpecker 

use among three treatments within the home range of the same pair of pileated 

woodpeckers (407 ha; Bull and Holthausen 1993).

Fuel reduction treatments were conducted on 50 stands that were in a mature, 

multilayered structure in either a grand fir/Douglas-fir/larch (Larix occidentalis Nutt.) forest type or a Douglas-fir/grand fir/ponderosa pine (Pinus ponderosa

Dougl. ex Laws.) type based on soil surveys (Burr 1960). The mechanical fuel 

reduction was a thinning from below conducted between 2001 and 2003 by using 

whole tree logging with a rubber tired skidder or by using a cut-to-length harvester 

with a forwarder. The objective was to retain 18.4 m2/ha basal area of live trees 

with an emphasis on ponderosa pine and western larch; green trees larger than 51 

cm diameter at breast height (d.b.h.) were not removed. District guidelines specified the retention of 10 to 15 snags larger than 51 cm d.b.h. (if available) and 250 to 

350 m of logs in each hectare. Logs were to be >30 cm in small-end diameter and 

>6 m long. Material that was removed included ladder fuels, some green trees 10 to 

51 cm d.b.h., dead trees larger than 10 cm d.b.h., grand fir with Indian paint fungus 

(Echinodontium tinctorium), trees with mistletoe brooms unless a tree was >15 m 

from other trees of the same species, and downed material. Downed material (>8 

cm in diameter) in excess of 33 626 to 56 043 kg/ha was to be removed from the 

site. The amount of fuels removed during harvesting and burning is shown in 

table 1.

Forty-three of the 50 harvested stands were broadcast burned in the fall between 2001 and 2003. The seven burned stands used in this study were burned 

when maximum daily temperature was between 12 and 24° C, and minimum 

relative humidity was 15 to 55 percent. The percentage of fuel moisture of 1-hour 

fuels was 4 to 11, of 10-hour fuels was 7 to 9, and of 1,000-hour fuels was 11 to 15. 

The units were ignited by hand with drip torches. Strategic ignition patterns were 

used to protect snags by not igniting near the base of snags, downslope from snags, 

or upwind from snags. 

Logs, snags, stumps, and recent woodpecker foraging activity were quantified 

in three types of treatments: (1) stands treated with mechanical fuel reduction only 
4

RESEARCH PAPER PNW-RP-564

(mechanical removal), (2) stands broadcast burned after mechanical fuel reduction 

(prescribed burn), and (3) stands with no treatment (control). Only seven stands 

that had fuels mechanically removed were not burned; consequently, this treatment 

limited the sample size to seven sets of the three treatments (i.e., 21 stands). We 

selected the nearest seven unharvested stands for control treatments and the nearest seven with a prescribed burn (table 2). The nearest stands (within 2 km) were 

selected so there was a high likelihood that the same pair of pileated woodpeckers had the opportunity to forage in the three stands with the different treatments. 

Therefore, randomization of stand selection was not desired. The seven areas were 

0.5 to 5 km apart. The stands ranged in size from 9 to 35 ha and were surveyed in 

August 2004.

Log, Snag, and Stump Quantification

We used a 1-ha plot (100 by 100 meters) in each stand to determine snag and stump 

density and 1000 m of transects within the plot to determine relative abundance of 

logs. It was not our intent to determine absolute log density because relative abundance of logs among treatments provided the desired information. It was also not 

necessary to know conditions prior to treatment because the amount of woody material currently available, rather than the percentage of original material removed, 

is the parameter relevant to woodpecker foraging opportunities (McClelland 1979). 

Control plots provided insight into current conditions without fuel reductions.

Log transects consisted of 10 parallel 100-m transects 11 m apart. Plot location was randomly assigned by walking to the middle of the unit and looking at the 

second hand on a watch. The observer then walked the number of paces indicated 

by the second hand and in the direction the second hand pointed (using the face of 

the watch as a compass), and that point was the corner of the plot. The three plots 

associated with the first area (replicate group) all had the transects run north and 

Table 1—Weight of fuels in units based on photointerpretation on the Starkey 

Experimental Forest and Range, 2001–2003a b

Pretreatment Posttreatment Postburn

Unit All fuels Logs >8 cm All fuels Logs >8 cm All fuels Logs >8 cm

Kilograms per hectare

47C 77 114 52 680 50 214 26 900 26 228 17 934

61 101 997 78 460 56 043 29 142 19 503 11 208

65 89 556 61 647 59 630 26 900 29 815 20 175

69 161 850 140 106 63 888 39 230

a Estimates were obtained prior to treatment (pretreatment), after the mechanical removal harvest (postharvest), 

and after the prescribed burn (postburn). 

b Fuel weights were not available for the remainder of the units nor for the postburn in unit 69; fuel weight data 

are on file at the La Grande Ranger District, La Grande, OR 97850.
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Short-Term Effects of Fuel Reduction on Pileated Woodpeckers in Northeastern Oregon—A Pilot Study

south, and the transects in the subsequent three plots ran east and west. The direction of the transects alternated among the rest of the areas.

The 1-ha plots were established by using a measuring tape, compass, and flagging. We quantified all snags (defined as dead standing wood ≥15 cm d.b.h. and ≥3 

m tall) and stumps (≥15 cm d.b.h. and 1 to 2.9 m tall) in the 1-ha area, and all logs 

≥15 cm in large-end diameter and ≥1 m long that crossed one of 10 transects. Logs 

that did not cross any transect were not tallied, and logs that crossed more than 

one transect were tallied only once. Tree species, large-end diameter of log, d.b.h. 

of snags and stumps, wood condition, and length or height were recorded for each 

log, snag, and stump. Wood condition was classified as sound, moderate decay, or 

extensive decay. The presence of charred wood and the presence and genus of ants 

observed along the length of each log that crossed a transect and in the basal 2 m 

of each snag in the unit were recorded. The presence of fresh dust created by ant 

excavation was recorded as an indication that ants were colonizing the log. If ants 

were actually seen, the genus of ant was classified as Camponotus spp. (carpenter 

ants), Formica spp. (red forest ants), and other, which included small brown ants 

of several genera including Lasius, Tapinoma, Leptothorax, and Aphaenogaster

(Torgersen and Bull 1995). The log was disturbed to encourage movement of ants to 

facilitate an identification. 

Woodpecker Foraging Activity

Our objective was to quantify all woodpecker foraging in logs, snags, and stumps 

within the 1-ha plots. To measure pileated woodpecker use, we quantified each log, 

snag, and stump that had been used for foraging within each unit. Logs, snags, and 

stumps with recent foraging by pileated woodpeckers located anywhere in the plot 

Table 2—Units surveyed in 2004 for pileated woodpecker foraging in three treatments 

(mechanical removal without burning, mechanical removal with prescribed burning, and 

controls) and the year the units were treated on the Starkey Experimental Forest and 

Range

 Mechanical removal Prescribed burning Controls

Unit no. Size Treatment year Unit no. Size Treatment year Unit name Size

 ha ha ha

15 21 2003 74 8 2001 Meadow 15

35 9 2001 37 3 2002 Trap 14

44 24 2002 63 9 2003 Sardine 22

47G 5 2003 47C 39 2003 Battle Flat 20

61 22 2002 61 12 2003 Little Bear 19

68 19 2002 65 35 2002 Tin Trough 16

69 13 2002 69 11 2003 Bluff 13
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RESEARCH PAPER PNW-RP-564

were marked with flagging, and the same variables listed above were quantified 

(tree species, diameter, length, wood condition, charring, and ant presence). We 

noted if a log with foraging was on a transect or not. Recent foraging excavations 

were defined as sites where foraging chips characteristic of pileated woodpeckers 

were present on top of the existing substrate. There may have been some recent 

litter covering the chips, but the chips were not embedded in the substrate or buried 

by other material. Old foraging excavations were not measured because they probably occurred before the fuel reduction or burning treatment occurred. Pileated 

woodpecker foraging was identified as (1) large rectangular excavations where 

pileated woodpeckers were typically in pursuit of Camponotus ants, (2) large surface excavations that reach into sapwood or heartwood where pileated woodpeckers 

were after wood-boring beetle larvae, (3) very shallow excavations where pileated 

woodpeckers were after bark beetles, (4) small isolated shallow excavations in 

sapwood where pileated woodpeckers located isolated ants or beetles, and (5) small, 

isolated, deep excavations where pileateds were after isolated wood-borers (Raley 

and Aubry 2004). Recent foraging activity by other woodpeckers, typically in the 

form of bark scaling, was identified on the basis of size of chips (<2 cm), smaller 

flakes of bark, smaller scat, and smaller indentations in the wood. The woodpeckers other than pileated woodpeckers most likely foraging in snags and logs in these 

stands would include hairy (Picoides villosus) and black-backed (P. arcticus) woodpeckers (referred to as Picoides spp.) (Bull et al. 1986). White-headed woodpeckers 

(P. albolarvatus) are now rare on Starkey, and the majority of foraging by northern 

flickers (Colaptes auratus) and sapsuckers (Sphyrapicus spp.) on Starkey does not 

include excavation or bark scaling (Bull et al. 1986). 

Analysis

The relative abundance of logs and the actual density of snags and stumps were 

compared among the treatments with chi-square analyses. The same analyses were 

used to compare substrates with woodpecker foraging among the treatments. Largeend diameter and length of logs, d.b.h., and height of snags were compared by using 

analysis of variance and a post-hoc Tukey’s B test (Zar 1999). Tree species, wood 

condition, and ant presence (for all ant genera combined and for each genus) in 

logs, snags, and stumps were compared among treatments by using chi-square tests. 

In addition, the amount of charring on logs and snags with and without ants and 

with and without pileated woodpecker foraging was compared by using t-tests and 

Levene’s test for equality of variances (Zar 1999). A probability of 0.05 was used 

for significance.
7

Short-Term Effects of Fuel Reduction on Pileated Woodpeckers in Northeastern Oregon—A Pilot Study

Results 

The objective of the fuel reduction treatments was to decrease stem density and 

coarse woody debris, so it was logical that significant differences occurred in the 

number of logs, snags, and stumps among the three treatments (X2 = 208.01, 4 df, 

P < 0.01) with the highest number of each occurring in the control stands (fig. 1). 

Figure 1—Mean number of logs on 1000 m of transects in seven stands and the mean number of 

snags and stumps in a 1-ha plot in seven stands in control, mechanical removal, and prescribed burn 

treatments on the Starkey Experimental Forest and Range in northeastern Oregon, 2004.

Logs

We tallied 1,764 logs in the control plots, 693 in the mechanical removal plots, and 

299 in the prescribed burn plots. Significant differences occurred among the treatments in log large-end diameter (F = 20.59, P < 0.01), length (F = 329.16, P < 0.01), 

species (X2 = 48.36, P <0.01), and wood condition (X2 = 49.84, P < 0.01). Logs 

remaining after the mechanical removal treatment were significantly larger (mean 

= 33 cm, standard error = 0.54) than in either the control (mean = 29 cm, standard 

error = 0.31) or burn treatments (mean = 29 cm, standard error = 0.75). Logs in the 

control treatment were significantly longer (mean = 9 m, standard error = 0.12) than 

those in the burn and mechanical removal treatments (burn: mean = 5 m, standard 

error = 0.29; mechanical: mean = 4 m, standard error = 0.13). In all treatments, 

83 to 91 percent of the logs were in the intermediate decay class, with the highest 

proportion of logs with advanced decay (16 percent) occurring in the mechanical 

removal treatment. 
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RESEARCH PAPER PNW-RP-564

Snags

We tallied 879 snags in the control plots, 65 in the mechanical removal plots, and 63 

in the prescribed burn plots; there were no significant differences in snag numbers 

between the two fuel reduction treatments (fig. 1). Significant differences occurred 

in snag diameter (F = 40.66, P < 0.01), height (F = 13.51, P < 0.01), species (X2 = 

16.29, P < 0.01), and condition (X2 = 10.51, P < 0.01) among the treatments. Although the stands with either fuel reduction treatment had fewer snags than the 

control, a higher percentage of the snags that occurred in these treatments were 

larger than 50 cm d.b.h. compared to the control treatments. Snag d.b.h. differed 

significantly among all the treatments. The mean d.b.h. of snags was 35 cm (standard error = 0.63) in the control treatments, 46 cm (standard error = 2.88) in the 

prescribed burn treatments, and 55 cm (standard error = 3.17) in the mechanical 

removal treatments. Sixty-three percent of the snags in the control treatments were 

less than 35 cm d.b.h., whereas 35 percent of those in the prescribed burn treatments and 25 percent of those in the mechanical removal treatments were this size. 

Snags in the control treatment were significantly shorter (mean = 9.3 m, standard 

error = 0.17) than those in the prescribed burn/mechanical removal treatments 

(mean = 12.4 m, standard error = 0.90) or the mechanical removal treatments (mean 

= 11.3 m, standard error = 0.87), which is consistent with snags in the control treatments being smaller in diameter. Wood condition differed significantly among the 

treatments where the burn treatments contained 11 percent of recently dead trees 

compared with 2 percent and 4 percent in the mechanical removal and control treatments, respectively. 

Stumps

We tallied a total of 379 stumps in the control plots, 154 in the mechanical removal 

plots, and 57 in the prescribed burn plots (fig. 1). Significant differences occurred 

in stump diameter (F = 14.74, P < 0.01), height (F = 8.35, P < 0.01), and species 

(X2 = 27.28, P < 0.01) among the treatments. Although the stands with either fuel 

reduction treatment had fewer stumps, the average diameter was 38 cm (standard 

error = 2.24) in the prescribed burn treatments, 41 cm (standard error = 1.78) in the 

mechanical removal, and 32 cm (standard error = 0.80) in the control treatments. 

Stumps in the control stands were significantly taller (mean = 2.2 m, standard 

error = 0.04) than those in the prescribed burn treatments (mean = 2.0 m, standard error = 0.11) or the mechanical removal (mean = 1.9 m, standard error = 0.06) 

largely because most of the stumps in the treated stands were a result of the harvesting treatment.
9

Short-Term Effects of Fuel Reduction on Pileated Woodpeckers in Northeastern Oregon—A Pilot Study

Presence of Woodpecker Foraging and Ants

Pileated Woodpeckers—We detected 534 dead wood substrates (i.e., logs, snags, 

and stumps) with pileated foraging. The majority (71 percent) of the foraging activity in all substrates involved large rectangular or deep excavations where pileated 

woodpeckers appeared to be foraging on ants or wood-boring beetle (cerambycids 

and buprestids) larvae, 17 percent were shallow excavations where bark beetles 

likely had been present, and the remainder were small, isolated shallow excavations. 

Overall, we detected 216 logs with recent pileated woodpecker foraging; 200 

of those logs were on transects and 16 did not cross a transect. The majority of 

these logs with foraging occurred in the control treatment (fig. 2). Pileated foraging in logs was significantly more abundant in the control and mechanical removal 

treatments than in the prescribed burn treatments (control versus prescribed burn: 

X2 = 4.34, 1 df, P = 0.04; mechanical removal versus prescribed burn: X2 = 3.82, 

1 df, P = 0.05). Pileated woodpeckers selected substrates with ants. Forty-three percent of transect logs had ants, whereas 62 percent of logs with pileated woodpecker 

foraging had ants (X2 = 33.83, 1 df, P < 0.01). Ants were significantly more abundant in logs in the control and mechanical removal treatments than in the prescribed 

burn treatments (X2 = 28.92, P < 0.01). Ants occurred in 46 percent of transect logs 

in the control, 44 percent in the mechanical removal treatments, and in 29 percent 

in the prescribed burn treatments. The presence of charring on logs influenced the 

occurrence of ants and pileated woodpecker foraging activity. Logs with ants had 

Figure 2—Mean number of logs, snags, and stumps with pileated woodpecker foraging in 1-ha 

plots in seven stands in control, mechanical removal, and prescribed burn treatments on the 

Starkey Experimental Forest and Range in northeastern Oregon, 2004.
10

RESEARCH PAPER PNW-RP-564

significantly less charring than logs without ants (t = 3.56, 2,758 df, P < 0.01). The 

percentage of charring on logs with pileated foraging was significantly less than on 

logs without pileated foraging (t = 2.80, 306 df, P < 0.01).

Eighty-six percent of an overall total of 239 snags with recent pileated woodpecker foraging occurred in the control treatment with <10 percent in the other 

treatments (fig. 2). Pileated woodpeckers selected snags with ants, as 33 percent 

of all snags had ants, whereas 59 percent of snags with pileated woodpecker foraging had ants (X2

 = 99.79, 1 df, P < 0.01). Thirty-four percent of the snags in control 

treatments, 29 percent in the mechanical removal treatments in contrast to only 14 

percent of the snags in the prescribed burn treatments, contained ants. No statistical 

differences occurred in the percentage of charring and the occurrence of ants and 

pileated foraging in snags.

We detected a total of 79 stumps with recent pileated woodpecker foraging 

where 62 percent of the stumps in the control treatments had foraging activity, 29 

percent in the mechanical removal treatments, and 9 percent in the prescribed burn 

treatments (fig. 2). Although significantly more stumps in the control treatments 

contained ants (X2 = 6.07, 2 df, P = 0.05), there was no significant difference in the 

number of stumps with foraging among the treatments with 12 to 15 percent of the 

stumps in each treatment containing pileated woodpecker foraging. No statistical 

differences occurred in the percentage of charring and the occurrence of ants and 

pileated foraging in stumps.

Ant species—We identified Camponotus in 112 logs, snags, and stumps; Formica

in 399; and other in 58. The occurrence of Camponotus and Formica ants differed 

significantly among treatments with the highest percentage occurring in the control 

treatments (X2 = 8.48, 2 df, P = 0.01; X2 = 11.90, 2df, P < 0.01, respectively). Of 

the Camponotus, 81 percent occurred in the control treatments, 15 percent in the 

mechanical removal treatments, and 4 percent in the prescribed burn treatments. Of 

the Formica ants, 76 percent occurred in the control treatments, 18 percent in the 

mechanical removal treatments, and 6 percent in the prescribed burn treatments. No 

significant differences occurred among treatments in the presence of other ants.

Picoides foraging—We detected evidence of foraging by Picoides woodpeckers in 

3 percent of 2,779 logs on transects, in 23 percent of 1,007 snags, and in 11 percent of 590 stumps. Evidence of foraging by Picoides woodpeckers in logs, snags, 

and stumps did not differ significantly among treatments, although the majority of 

Picoides foraging occurred in snags in the control treatments (fig. 3). Significant 

differences occurred in the presence of Picoides foraging in snags (X2

 = 4.03, 1 df, 
11

Short-Term Effects of Fuel Reduction on Pileated Woodpeckers in Northeastern Oregon—A Pilot Study

P = 0.04) and stumps (X2 = 6.04, 1 df, P = 0.01) with and without evidence of ants. 

Picoides foraged more in snags and stumps without ants than snags and stumps 

with ants. In snags, 62 percent of the foraging occurred with no evidence of ants 

versus 38 percent with ants. In stumps, 56 percent of the foraging occurred with no 

evidence of ants versus 44 percent with ants. Picoides foraging in logs did not differ 

with or without evidence of ants. The percentage of charring in the prescribed burn 

treatments differed significantly between stumps with Picoides foraging (mean of 

22 percent charring) and stumps without Picoides foraging (mean of 56 percent 

charring) (t = 3.21, 40 df, P < 0.01).

Discussion

Both the control treatments and the mechanical removal treatments provided 

significantly more foraging habitat for pileated woodpeckers, whereas the prescribed burn treatments provided significantly less. The higher incidence of ants in 

the control treatments and mechanical removal treatments explains the greater use 

by these woodpeckers. In this study area, pileated woodpeckers are known to forage 

primarily on ants, specifically Camponotus and Formica (Bull et al. 1992). The 

higher incidence of pileated woodpecker foraging in substrates with ants suggests 

Figure 3–Mean number of logs on 1000 m of transects in seven stands and the mean number 

of snags and stumps in a 1-ha plot with foraging evidence of Picoides woodpeckers in control, 

mechanical removal, and prescribed burn treatments on the Starkey Experimental Forest and 

Range in northeastern Oregon, 2004.
12

RESEARCH PAPER PNW-RP-564

that their foraging is not random and that they were able to detect ants in substrates. 

Consequently, their foraging is more efficient than random selection of substrates, 

and the energy they expend foraging is therefore minimized. 

A significant difference in foraging habitat of the smaller Picoides woodpeckers 

was not detected among the treatments (fig. 3), except in their avoidance of charred 

stumps in the prescribed burn treatments. Unlike the pileated woodpecker, these 

woodpecker species do not concentrate their foraging extensively on ants, likely 

because the Camponotus and Formica ants are inside dead wood, which would be 

largely unavailable to these woodpeckers. Both the black-backed and hairy woodpeckers forage extensively by bark scaling and pecking on trees in Starkey and seldom excavate in the interior wood (Bull et al. 1986). Black-backed woodpeckers are 

frequently associated with recent stand-replacement fires (Hutto 1995, Kotliar et al. 

2002, Saab and Dudley 1998), and recent mortality of trees killed by burning would 

result in an increase in bark beetles and wood-boring beetles, which the Picoides

species of woodpeckers forage on. Black-backed woodpeckers feed extensively on 

larvae of wood-boring beetles (buprestids, cerambycids), engraver beetles, and bark 

beetles (scolytids; Dixon and Saab 2000, Murphy and Lehnhausen 1998). Hairy 

woodpeckers forage on larvae of bark beetles, codling moth, pupae of cecropia 

(Hyalophora cecropia), as well as ants (Jackson et al. 2002).

In a comparison of prescribed burning and harvesting in southeastern British 

Columbia, Machmer (2002) found no difference in woodpecker foraging among 

treatments after partial harvesting and burning in the short term (1 to 2 years). 

After treatments, she detected increases in insect species diversity in Buprestidae, 

Cerambycidae, and Scolytidae, which are all species that inhabit dead and dying 

wood and serve as prey for woodpeckers. The increase in insects was most pronounced in the burn only treatment, followed by harvest and burning, and then 

by harvest only. Prescribed burns in northern Idaho resulted in most of the small 

woody fuels and 15.5 t/acre (34 746 kg/ha) of large woody fuels being consumed 

(Reinhardt et al. 1991). In spruce (Picea spp.) ecosystems in Alaska, Werner (2002) 

found that both fire and timber harvest attracted woodborers and bark beetles the 

first year after disturbance, but populations then decreased to levels below those in 

undisturbed sites.

The absence of management activities in the control treatments in our study 

resulted in an abundance of logs, snags, and pileated woodpecker foraging (figs. 1 

and 2). Because no logs or snags were removed from the control treatments, the 

average diameter and height or length of snags and logs were smaller than in the 

fuel reduction treatments where the smaller snags and logs were targeted for 

removal. However, the control treatments actually contained a larger number of 
13

Short-Term Effects of Fuel Reduction on Pileated Woodpeckers in Northeastern Oregon—A Pilot Study

large-diameter snags and logs compared to the fuel reduction treatments. The 

control treatments also contained the highest number of logs and snags with all 

species of ants, including Camponotus and Formica, which provided the most 

foraging habitat for pileated woodpeckers.

Although foraging by pileated woodpeckers in mechanical removal treatments 

was not as common as in the control treatments, there was significantly more 

foraging than in the prescribed burn treatments. The presence of Camponotus

and Formica ants in the mechanical removal treatment provided prey for pileated 

woodpeckers. The removal of standing trees alone did not prevent pileated woodpeckers from using the stands. The larger diameter logs and snags found in these 

stands, as well as in the burn treatment, were retained during harvesting owing to 

management guidelines and to their low susceptibility to wildfire and high value to 

wildlife. The shorter length of logs and the higher incidence of logs in the advanced 

decay class found in this treatment likely resulted from the logging equipment running over the logs and breaking them.

The lower occurrence of ants in logs, snags, and stumps in the prescribed burn 

treatment suggests that the burning either directly eliminated the ants or rendered 

the habitat unsuitable for ants. In the burn treatment, the logs in the advanced decay 

class would probably have been consumed. Our observation that logs with ants had 

less charring than logs without ants suggests that charring on logs may make the 

logs less attractive to ants or that ants were extirpated from the general area by fire. 

The lower abundance of ants in the burn treatments resulted in significantly less 

pileated woodpecker foraging activity.

In our study, the average number of snags was about the same in both fuel 

reduction treatments (fig. 1), although the higher number of recently dead snags in 

the prescribed burn treatments suggests that some live trees were killed and some 

existing snags were consumed. Trees continued to die more than a year after the 

burn owing to woodborer and bark beetle activity in them. The recent mortality of 

live trees created foraging habitat for Picoides woodpeckers because woodborers 

were present in the dead and scorched live trees in the 2003 prescribed burn treatments. We did not detect woodborers still present in the 2001 or 2002 prescribed 

burn treatments. 

Prescribed burning in this study area did not allow the degree of control in 

retaining coarse woody debris that the mechanical reduction treatment allowed. 

In one of the 43 burned stands on Starkey, more than 10 pileated woodpecker nest 

trees located in a previous study (Bull and Holthausen 1993) were consumed by the 

fire in an 18-ha area. A snag used by great gray owls (Strix nebulosa) for nesting 

was burned in one of the stands used in this study. Although some combustible fuel 
14

RESEARCH PAPER PNW-RP-564

was removed from the base of some snags as recommended by Conner and Locke 

(1979), the nest trees burned. Weather conditions can change rapidly and reduce the 

amount of control that managers have over a prescribed burn and result in the loss 

of logs, snags, and live trees that were designated for retention. 

The results of this pilot study indicate that it is feasible to determine the effect of fuel reductions on pileated woodpecker foraging in relatively small plots. It 

would be beneficial to conduct a similar study over a much larger geographic area 

to determine if the results of this study are applicable on a landscape scale and 

over the long term. It would be beneficial to know when Camponotus and Formica

colonize areas that had prescribed burn treatments. If maintaining biodiversity and 

management indicator species is an objective, it is important to know the consequences of fuel reduction treatments on specific wildlife species, particularly those 

that depend on the coarse woody debris that is removed during these treatments. 

Alternative measures may be available to ensure the retention of structures that 

specific wildlife species depend on and allow managers to meet multiple objectives 

simultaneously. Additional research is needed on the long-term effects of fuel reduction treatments on specific wildlife species, amounts and kinds of fuels to retain 

for wildlife, and additional measures that can be taken to protect specific habitat 

structures.

Acknowledgments

Cathy Nowak assisted with fieldwork. Personnel at the La Grande Ranger District 

supervised the mechanical fuel reduction and prescribed burning treatments, and 

Arlene Blumton, Tom Burry, Bob Clements, and Mike Johnson provided additional 

information on prescriptions. Jim Barrett, Nicole Nielsen-Pincus, Torolf Torgersen, 

Barbara Wales, and Andy Youngblood reviewed an earlier draft of the manuscript. 

English Equivalents

When you know: Multiply by: To find:

Centimeters (cm) 0.394 Inches 

Meters (m) 3.28 Feet

Kilometers (km) .62 Miles

Hectares (ha) 2.47 Acres

Kilograms per hectare (kg/ha) .89 Pounds per acre 

Square meters per hectare (m2

/ha) 4.37 Square feet per acre

Celsius (°C) 1.8 + 32 Fahrenheit
15

Short-Term Effects of Fuel Reduction on Pileated Woodpeckers in Northeastern Oregon—A Pilot Study

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