Nest Usurpation by Red-headed Woodpeckers in Southeastern Montana

2007·2.8 MB·English

by  William J Kronland

486 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 119, No. 3, September 2007
The Wilson Journal ofOrnithology 119(3):486-489, 2007
Nest Usurpation by Red-headed Woodpeckers in Southeastern Montana
William J. Kronland*
—
ABSTRACT. Red-headedWoodpeckers(Melaner- usurp nests rather than excavate their own has
pes erythrocephalus) occasionally usurp nests ofother not been investigated.
species. I compared incidence of nest usurpation in Interspecific competition among cavity
logged and non-logged treatments in a burned ponde-
rosa pine {Finnsponderosa) forest in 2004 and 2005. nesting birds can increase as nest site avail-
I predicted that usurpation would occur more often on ability decreases (Brawn 1990, Lindell 1996).
logged than non-logged sites because Red-headed Red-headed Woodpeckers tend to nest in more
Woodpeckers tend to nest in more open habitats. Red- open habitats (Smith et al. 2000) and greater
headed Woodpeckers nested more often and usurped a density of woodpeckers in logged areas may
gbtrheeaianntgenromnpo-rrloeopogrgatebiduonn{dnaonf=thoo3s)ntatsrhpeeeacs,ineosdne-silnpoitglegoeghdgoesdttr{ecnaatvm=ietnit6e.)s resIulrtecinorldiemditiendcinedsetncseiteofavnaeisltabuilsiutryp.ation by
Usurping Red-headed Woodpeckerpairs initiatednest- Red-headed Woodpeckers as part of a 2-year
ing earlier (x = 12 May ± 2 days) than pairs that study on the ecology of cavity nesting birds
excavated cavities (18 May ± 2 days) which implies in a burned ponderosa pine (Pinusponderosa)
an existing beneht to offset the cost of interspecific forest in southeastern Montana. The area had
conflict. Received14November2005. Accepted 19No- been logged in 2003 following a stand-re-
vember2006.
placement wildfire the previous year. Red-
headed Woodpeckers began arriving on the
study site in early May after most other cavity
Competition for nest sites is often intense nesters had already completed cavity excava-
among cavity nesting birds because potential
tion and nest building.
sites are limited by specific habitat require- The objective of this study was to compare
ments, such as tree decay and stand density incidence of nest usurpation by Red-headed
(Short 1979, Dobkin et al. 1997, Schepps et Woodpeckers in logged versus non-logged
al. 1999, Hutto and Gallo 2006). Once a ter- post-fire treatments. 1 predicted that usurpa-
ritory is obtained, nest cavity construction re- tion by Red-headed Woodpeckers would be
quires a substantial energetic investment with greater in the logged than non-logged treat-
excavation ranging from 3 weeks for Hairy
ment.
Woodpeckers {Picoides viUosu.s) to over a
year for Red-cockaded Woodpeckers {P. bo- METHODS
realis) (Kilham 1983, Ligon et al. 1986). The
high energetic investment appears offset by The study area was in a ponderosa pine for-
the high rate of reproductive success that cav- est —40 km southeast ofEkalaka, Montana in
ity nests provide (Nice 1957, Oniki 1979). the Long Pines unit of the Custer National
Woodpeckers may reduce the cost of ex- Forest (45° 38' N, 104° 1 1' W). The study site
cavation by usurping cavities occupied by oth- (1,320 ha) is part of a larger forested area
er species. Red-headed Woodpeckers {Mela- (28,368 ha) intermixed with pine savanna,
nerpes erythrocephalus) typically reuse or ex- open native grassland (Achnatheriim spp.,
cavate their own cavities, but may occasion- Bouteloua spp., Carex spp., and Psuedoroeg-
ally usurp nests and consume eggs or nestlings neria spp.), and drainages dominated by green
of other cavity nesting species (Beal 1911, ash {Fraxinuspennsylvanica) and quaking as-
Schwab and Monnie 1959, Smith et al. 2000). pen {Popidus tremidoides). The area consisted
The extent to which Red-headed Woodpeckers of hills and rocky buttes (elevation 1,000-
1,200 m) surrounded by lower elevation sage-
brush {Artemisia spp.) shrubland, native grass-
Uni‘vDerespiatryt,mSetn.tColfouBdi,olMogNica5l63Sc0i1e,ncUeSs,A;St.e-Cmlaoilu:dState land, and cultivated hayfields. Logged areas
[email protected] were treated in summer 2003 by removing all
SHORT COMMUNICATIONS 487
snags >25 cm diameter breast height (DBH). liveries or nestling vocalizations (nestling
Snags were defined as any tree with <50% stage) (Martin and Geupel 1993).
live green crown cover (U.S. Department of I monitored active cavities from time of lo-
Agriculture 2003). Aspen and green ash trees cation to completion of the nesting effort by
were not harvested, and a 15-m no-cut buffer observing nestling and adult behavior from
was left on either side of drainages to main- >30 m. A nest was considered successful if
tain watershed quality (U.S. Department of fledglings were observed <20 m from the
Agriculture 2003). Non-logged areas were not cavity, or if the fledgling date was known and
treated because of inaccessibility or excessive the cavity did not show signs ofpredation (en-
slope. larged cavity entrance or feathers at base of
I examined incidence of nest usurpation by tree) (Dudley and Saab 2003). Nests failed if
Red-headed Woodpeckers on logged (437 ha) predation was observed, or if nest stage was
and non-logged (444 ha) treatments from mid- known and inactivity occurred before the like-
April through 1 July in 2004 and 2005 (2 and ly fledgling date. Nest failures were probably
3 years post-fire). I recorded the number and underestimated because signs of predation are
status (alive or dead) of trees in circular plots frequently not evident. A nest was considered
(radius = 11.3 m) in 2005 to compare trees usurped ifRed-headed Woodpeckers were ob-
and snags per ha between treatments. I cen- served breeding in a cavity last used by a host
tered plots at random points (control: n =15, species before fledging could have occurred.
salvage: n = \9) generated with a Minnesota I estimated nest initiation for cavities discov-
Department of Natural Resources (DNR) ex- ered after the laying period by backdating
tension for ArcView 3.0 software. Three sub- from a known nest stage transition (Ehrlich et
plots were arranged 120° from each other and al. 1988, Martin et al. 1997). I did not ex-
m
30 from a central subplot (Martin et al. amine nest success ofRed-headed Woodpeck-
1997). ers because nest failures or fledglings were not
I searched for nest cavities from 22 April observed before the survey period ended.
to 1 July by using a random numbers table to I pooled data from 2004 and 2005 and clas-
place two plots (45-52 ha) in each treatment sified each Red-headed Woodpecker nest cav-
in 2004 and 2005. Landscape and salvage ity as either usurped or excavated. I compared
characteristics dictated the availability and incidence of nest usurpation versus cavity ex-
size of contiguous search plots on the study cavation between salvage and control treat-
site, which were smaller than the standard ments with Pearson’s Chi-square test. Sample
protocol for monitoring cavity nesting birds sizes were small and I used Fisher’s exact test
(200-400 ha) and likely reduced sample sizes to examine statistical significance. I also used
(Dudley and Saab 2003). Plots were inten- a r-test to compare date of initiation for each
sively searched every 1-2 days and nests were Red-headed Woodpecker nest effort between
located by observing adults and systematically pairs that usurped and excavated cavities.
searching for cavities (Martin and Geupel
RESULTS
1993). Potential host species included North-
ern Flicker (Colaptes auratus). Hairy Wood- The logged treatment contained fewer live
pecker, Eastern Bluebird (Sialia sialis). Moun- trees (T = 3.1 ± 1.3 [SE]) and snags (x =
tain Bluebird (S. ciirrucoides), and European 44.7 ± 4.9) per ha than live trees (12.2 ± 3.8)
Starling (Sturnus vulgaris). I recorded the lo- and snags (90.8 ± 8.5) on the non-logged
cation of active nests with a Garmin E-trex treatment. Average size (cm) of green trees
Global Positioning System (GPS) receiverand did not differ between treatments (logged: x
flagged a bearing tree no closer than 30 m. = 5.5 DBH ± 13, non-logged: 15.5 ± 18),
Each cavity was visited every 3 days for up but snags were smaller in logged (x = 16.7 ±
to 30 min, or until nest status (active or in- 1.9) than non-logged (23.7 ± 3.7) areas. I lo-
active) could be ascertained by observing an cated and observed 91 active nest cavities in
adult or nestling inside the cavity. I estimated 2004 and 2005. Red-headed Woodpeckers
nest phenology from courtship displays and were the only species that nested more often
duration of adult visits to the nest (courtship in the logged than non-logged treatment (Ta-
and egg laying vs. incubation), and food de- ble 1). Red-headed Woodpeckers accounted
488 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 119, No. 3, September2007
TABLE 1. Number of observed nest cavities per identical between treatments, but Red-headed
species in salvage logged and non-logged treatments Woodpeckers nested more often and usurped
in aburnedponderosapineforest, CusterNationalFor- a greater percentage of hosts in logged than
est, Montana, 2004 and 2005. non-logged areas, despite host cavities being
more abundant in the control.
Species Logged Non-logged
Red-headed Woodpecker pairs that usurped
Northern Flicker 6 6
cavities initiated nesting earlier than pairs that
HRaeidr-yheWaodoeddpWeocokdeprecker 207(6)^ 111(33)“ excavated cavities. Early nesting correlates
Eastern Bluebird 3 5 with larger clutch sizes in cavity nesting birds
Mountain Bluebird 5 10 (Dijkstra et al. 1982, Nilsson 1991). The ben-
European Starling 2 3 efit derived from usurping a nest was possibly
^Red-headedWoodpeckernestsacquiredbyusurpation. countered by the risk associated with inter-
specific conflict. For example. Northern Flick-
ers and Hairy Woodpeckers aggressively de-
for 65% {n = 11) of nest failures of other fended their cavities from Red-headed Wood-
cavity nesters by depredating two and usurp- peckers. However, Mountain Bluebirds were
ing nine nests. More nests were usurped in the seldom seen defending cavities against Red-
logged {n = 6) versus unlogged {n = 3) treat- headed Woodpeckers and were usurped al-
ment, but incidence of nest usurpation versus most twice as often as Hairy Woodpeckers,
construction by Red-headed Woodpeckers was despite nests of the two species having oc-
similar between treatments (x“ = 0.03, df = curred at similar abundances on each treat-
1, P = 1.0). Nest cavities of potential host ment.
species were more abundant in the non-logged Interspecific competition can increase as
(/z = 37) than logged treatment {n = 23). nest site availability decreases among cavity
Thus, Red-headed Woodpeckers usurped a nesters (Brawn 1990, Lindell 1996). It seems
greater proportion of cavities in the logged logical that the similarity in incidence ofusur-
(26%) than the non-logged (8%) treatment. pation versus excavation on my study site
Mountain Bluebirds were usurped most often could be explained by availability ofnest sites
(/? = 5), followed by Hairy Woodpeckers (/z between treatments. An examination of nest
= 3) and Northern Flickers (zz = 1). Red- site selection and availability by Red-headed
headed Woodpeckers were unsuccessful in Woodpeckers was beyond the scope of this
their attempt to usurp one Hairy Woodpecker study, but may be influenced by abundance of
and one Northern Flicker nest cavity. burned aspen stands (Vierling and Lentile
1 used backdating to estimate nest initiation 2006) or large relatively isolated conifer snags
for one cavity that was discovered after the (pers. obs.). Most Red-headed Woodpecker
egg-laying period in 2005. The cavity was nests were in large ponderosa pine snags (ex-
originally excavated by Hairy Woodpeckers cavated: n = 20, usurped: n = 6) rather than
the year before and, according to field notes, aspen stands which were rare across the study
was probably unoccupied before Red-headed area and infrequently used (excavated: n = 2,
Woodpeckers enlarged the entrance and began usurped: n = 3). Better understanding of the
nesting. Red-headed Woodpecker pairs that importance of hardwoods and distribution of
usurped cavities initiated nesting earlier (.v = snags is needed before nest site availability
12 May ± 2 days, n = 9) than pairs that ex- can be used to explain incidence ofusurpation
cavated cavities (18 May ± 2 days, n = 22; t by breeding Red-headed woodpeckers in
= 2.04, df = 21, P = 0.054). burned ponderosa pine forests.
ACKNOWLEDGMENTS
DISCUSSION
I predicted that incidence of usurpation I thank Thomas Whitford for initiating and support-
would be greater in logged than non-logged ing the study. Brent Haase contributed fieldassistance,
areas because Red-headed Woodpeckers tend and the Sioux RangerDistrictprovidedhousingduring
field seasons. Jorge Arriagada, Leonard Onyiah, and
to nest in open habitats (Smith et al. 2000, Marco Restani commented on the draft manuscript. D.
Doherty and Grubb 2002). Incidence of nest J. Ingoldand K. E. Millerreviewedthemanuscriptand
usuipation versus construction was nearly providedcomments. FundingwasprovidedbytheU.S.
SHORT COMMUNICATIONS 489
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