Chestnut-backed Chickadee Research Articles

RADseq data reveal widespread historical introgression in four familiar North American songbirds.

Population genetic structure is influenced by a combination of contemporary and historical events; however, this structure can be complicated by ongoing gene flow. While it is well known that contemporary hybridization occurs frequently among many closely related species, it often remains uncertain as to which populations are involved in introgression events, and this can be even more difficult to infer when introgression is historical. Here we use restriction-site associated DNA sequencing to look at the level of introgression among four species of songbirds in North America: the black-capped, mountain, boreal, and chestnut-backed chickadee. Samples from both sympatric and allopatric sites across the species' ranges supported limited ongoing mixing among the four species with Bayesian clustering and principal component analyses. In contrast, f4-statistics and admixture graphs revealed extensive historical introgression among geographically structured populations. Almost all historical admixture events were among populations west of the Rocky Mountains, and almost all populations west of the Rocky Mountains, excluding island and coastal populations, showed evidence of historical admixture. The inclusion of all four chickadee species proved crucial in differentiating which species were involved in hybridization events to avoid erroneous conclusions. Taken together, the results suggest a complex pattern of divergence with gene flow.

Nest site characteristics of cavity-nesting birds on a small island, in Haida Gwaii, British Columbia, Canada

Many studies of cavity-nesting birds in North America are conducted in large continental forests and much less is known about them in island ecosystems. We describe a 29-year study of tree species, nest site characteristics, and fledge dates of cavity-nesting birds on a small island in Haida Gwaii, British Columbia (BC). Seven cavity-nesting bird species were documented on East Limestone Island and 463 nests were found in 173 different trees. Nest trees were significantly taller and had a greater diameter than a random sample of snags. Tree height did not differ among bird species but diameter at breast height was larger for trees used by Brown Creeper (Certhia americana) than for other species. Cavity-nesters selected tree decay classes 2–7 (all dead/near dead [snags]), with 85% in decay class 4 (35%) or 5 (50%), similar to the random snag sample (class 4, 32%; class 5, 42%). Cavity height ranged from 2.6 to 44.9 m and for all species, except Brown Creeper, the mean nest height was >60% of the mean tree height. Nest heights were generally greater than observed elsewhere in BC. Nest cavity orientation was random except for Red-breasted Sapsuckers (Sphyrapicus ruber), for which only 13% of the cavity entrances faced southeast. Median fledging dates ranged from 7 June (Chestnut-backed Chickadee [Poecile rufescens]) to 28 June (Northern Flicker [Colaptes auratus]). Estimated median dates of clutch completion were similar for all species. Our results show that large snags provide habitat for a high diversity of cavity-nesting birds on Haida Gwaii.

Use of created snags by cavity‐nesting birds across 25 years

ABSTRACTSnags are important habitat features for many forest‐dwelling species, so reductions in the number of snags can lead to the loss of biodiversity in forest ecosystems. Intentional snag creation is often used in managed forests to mitigate the long‐term declines of naturally created snags, yet information regarding the use of snags by wildlife across long timescales (>20 yr) is lacking and prevents a complete understanding of how the value of created snags change through time. We used a long‐term experiment to assess how harvest treatment (i.e., small‐patch group selection, 2‐story, and clearcut) and snag configuration (i.e., scattered and clustered) influenced nesting in and foraging on 25–27‐year‐old Douglas‐fir (Pseudotsuga menziesii) snags by cavity‐nesting birds. In addition, we compared our contemporary measures of bird use to estimates obtained from historical surveys conducted on the same group of snags to quantify how bird use changed over time. Despite observing created snags for >750 hours across 2 consecutive breeding seasons, we found limited evidence of nesting activity. Only 11% of created snags were used for breeding, with nesting attempts by 4 bird species (n = 36 nests); however, we detected 12 cavity‐nesting species present on our study sites. Furthermore, nearly all nests (94%) belonged to the chestnut‐backed chickadee (Poecile rufescens), a weak cavity‐excavating species that requires well‐decayed wood for creating nest cavities. Our surveys also recorded few observations of birds using created snags as foraging substrates, with only 1 foraging event recorded for every 20 hours of observation. We detected 82% fewer nests and recorded 7% fewer foraging observations during contemporary field work despite spending >7.5 times more effort observing created snags relative to historical surveys. We conclude that 25–27‐year‐old created Douglas‐fir snags provided limited opportunities for nesting and foraging by most cavity‐nesting birds, and that the period of greatest use by this group occurred within 5–15 years of creation. © 2018 The Wildlife Society.

Discrimination of acoustically similar conspecific and heterospecific vocalizations by black-capped chickadees (Poecile atricapillus).

Chickadees produce a multi-note chick-a-dee call in multiple socially relevant contexts. One component of this call is the D note, which is a low-frequency and acoustically complex note with a harmonic-like structure. In the current study, we tested black-capped chickadees on a between-category operant discrimination task using vocalizations with acoustic structures similar to black-capped chickadee D notes, but produced by various songbird species, in order to examine the role that phylogenetic distance plays in acoustic perception of vocal signals. We assessed the extent to which discrimination performance was influenced by the phylogenetic relatedness among the species producing the vocalizations and by the phylogenetic relatedness between the subjects' species (black-capped chickadees) and the vocalizers' species. We also conducted a bioacoustic analysis and discriminant function analysis in order to examine the acoustic similarities among the discrimination stimuli. A previous study has shown that neural activation in black-capped chickadee auditory and perceptual brain regions is similar following the presentation of these vocalization categories. However, we found that chickadees had difficulty discriminating between forward and reversed black-capped chickadee D notes, a result that directly corresponded to the bioacoustic analysis indicating that these stimulus categories were acoustically similar. In addition, our results suggest that the discrimination between vocalizations produced by two parid species (chestnut-backed chickadees and tufted titmice) is perceptually difficult for black-capped chickadees, a finding that is likely in part because these vocalizations contain acoustic similarities. Overall, our results provide evidence that black-capped chickadees' perceptual abilities are influenced by both phylogenetic relatedness and acoustic structure.

Are chickadees good listeners? Antipredator responses to raptor vocalizations

Many animals gather information about predators with a variety of cues, such as visual, acoustic, and olfactory. Several species of birds, including chickadees, are good at discriminating between species of raptors using visual cues, and they can encode information about the threat level in their alarm calls. Much less is known about how birds discriminate between the calls of different species of predators. We played back the calls of three species of raptors to black-capped chickadees, Poecile atricapillus, mountain chickadees, Poecile gambeli, and chestnut-backed chickadees, Poecile rufescens, to determine whether they can discriminate between them using acoustic cues. We played the calls of two species of small, high-threat raptors, northern pygmy-owl, Glaucidium gnoma, and sharp-shinned hawk, Accipiter striatus, which have very different hunting strategies (mainly sit-and-wait ambush predator versus very fast surprise attack flights). We also played a larger, lower-threat northern goshawk, Accipiter gentilis. Black-capped and mountain chickadees responded much more to the calls of the two small, more dangerous raptors than to the northern goshawk; they also responded very differently to the calls of the two small raptors. Chestnut-backed chickadees did not respond differently to the calls of the three raptors. These results indicate that black-capped and mountain chickadees can make specific discriminations between the calls of these three raptors and that they encode information in their alarm calls in sophisticated ways.

ZENK activation in the nidopallium of black-capped chickadees in response to both conspecific and heterospecific calls.

Neuronal populations in the songbird nidopallium increase in activity the most to conspecific vocalizations relative to heterospecific songbird vocalizations or artificial stimuli such as tones. Here, we tested whether the difference in neural activity between conspecific and heterospecific vocalizations is due to acoustic differences or to the degree of phylogenetic relatedness of the species producing the vocalizations. To compare differences in neural responses of black-capped chickadees, Poecile atricapillus, to playback conditions we used a known marker for neural activity, ZENK, in the caudal medial nidopallium and caudomedial mesopallium. We used the acoustically complex ‘dee’ notes from chick-a-dee calls, and vocalizations from other heterospecific species similar in duration and spectral features. We tested the vocalizations from three heterospecific species (chestnut-backed chickadees, tufted titmice, and zebra finches), the vocalizations from conspecific individuals (black-capped chickadees), and reversed versions of the latter. There were no significant differences in the amount of expression between any of the groups except in the control condition, which resulted in significantly less neuronal activation. Our results suggest that, in certain cases, neuronal activity is not higher in response to conspecific than in response to heterospecific vocalizations for songbirds, but rather is sensitive to the acoustic features of the signal. Both acoustic features of the calls and the phylogenetic relationship between of the signaler and the receiver interact in the response of the nidopallium.

The post‐Pleistocene population genetic structure of a western North American passerine: the chestnut‐backed chickadeePoecile rufescens

The population genetic structure of many high‐latitude species in North America was affected by the last glaciation, and current structure reflects isolation in refugia and colonisation patterns. Large ice‐free areas, both south of the ice sheets and in the north‐west, supported numerous flora and fauna throughout this period. Fossil evidence suggests additional western glacial refugia existed both on Haida Gwaii (the Queen Charlotte Islands) and in northern Idaho. The chestnut‐backed chickadeePoecile rufescensis a songbird found along the western edge of Canada and the United States, with a linear distribution along the coast, and an isolated interior population. Mitochondrial DNA sequence data (control region and ATPase 6–8) from 10 populations (n = 122) were used to test for population genetic structure. The data supported a general north/south separation. Haida Gwaii was found to be genetically distinct from the rest of the populations, and the two northern British Columbia populations separated from all but Alaska. The interior population showed evidence of both historical isolation and secondary colonisation by birds from coastal populations. Neutrality tests suggested a past population expansion in all populations from previously glaciated areas, and a stable population in areas believed to be unglaciated. This pattern supports the use of multiple glacial refugia by the chestnut‐backed chickadee. We could not reject the use of Haida Gwaii or the interior (i.e. Clearwater Basin) as glacial refugia.

Experimental effects of structural enrichment on avian nest survival

Managers of landscapes dedicated to commodity production require information about how alternative practices can promote retention of native biological diversity. Retaining or creating structural features (e.g., snags or downed logs) needed to fulfill life history requirements may benefit populations and communities. However, demographic responses of species to alternative practices have received little research attention. We tested nest survival of cavity-dependent birds in response to experimental structural enrichment by creating snags on 28 plots, Oregon, USA, 2008–2010. Each plot represented one of six combinations of created snag density (0.5, 1, and 2snags/ha) and spatial dispersion (clumps of 5–7 snags or dispersed individual snags). We monitored 506 nests built by 10 species; three species nested in sufficient numbers for analysis. Chestnut-backed chickadee Poecile rufescens nest success was highest in the medium density clumped created snag treatment (average proportion of successful nests=0.76; 95% CI=0.61–0.87) and lowest in the low density clumped treatment (average proportion of successful nests=0.39; 95% CI=0.20–0.62). We did not find a response of either house wren Troglodytes aedon or northern flicker Colaptes auratus nest success to the experimental treatments. Period survival rates were 0.57 (95% CL: 0.39–0.72) for CBCH; 0.71 (95% CL: 0.51–0.84) for HOWR; and 0.59 (95% CL: 0.34–0.77) for NOFL. Our study suggests that creating snags in commercial harvest units is an effective practice for increasing structural complexity and supporting nesting communities of cavity-dependent birds. While leaving either clumped or dispersed created snags at a density of ∼1ha should support nest survival rates that are similar to those reported from unmanaged forests, we emphasize that this type of structural enrichment is not a panacea for species that require very large snags or snags that occur under complex forest canopies. Retention of existing structural features in reserve areas may be an appropriate practice for conserving species with nesting requirements that differ from those we evaluated in our study.

Note types and coding in Parid vocalizations: The chick-a-dee call of the chestnut-backed chickadee (Poecile rufuscens)

A first step to understanding how a species communicates acoustically is to identify, categorize, and quantify the acoustic parameters of the elements that make up their vocalizations. The "chick-a-dee" call notes of the chestnut-backed chickadee (Poecile rufescens) were sorted into four call note categories, A, C, D, and Dh notes, based on their acoustic structure as observed in sound spectrograms, and evaluated based on the syntactical ordering of the note types within calls. The notes were then analyzed using quantitative measures and it was determined which features have the potential to convey information to discriminate note type, individual, and the geographic origin of the producer. The findings were comparable to previous research of congeners in that chestnut-backed chickadee calls were produced with a relatively fixed syntax and contained similarly structured note types across all geographic regions. Overall this information will form a base for future research on chestnut-backed chickadee vocalizations and will strengthen the foundation for future comparative evolutionary studies.

Reproductive Biology of the Chestnut-backed Chickadee (Poecile rufescens) in Northwestern Oregon

Abstract Chestnut-backed Chickadees were studied over a 4-y period near Portland, Oregon, and for 1 of those years near Eugene, Oregon. Data on nesting activities and nestling growth rates were obtained by monitoring nest boxes. The chickadees began nest-building activity in March, with the 1st eggs being laid in early April and nests continuing to be initiated through early July. The timing of nest initiation was bimodal with the 1st peak in late April and a 2nd, smaller peak in June, referred to as “late nests”. Late nests accounted for 14 of the 94 nests observed. Clutch size for early nests varied from 5 to 10 eggs, with 7- and 8-egg clutches occurring at nearly equal frequency and representing 67.9%. Fledge success was greatest for 9-egg clutches and lowest for the smallest (6 or fewer) and largest (10) clutch sizes. Incubation averaged 13.8 d. The nestling growth phase averaged 18.8 d. Nestling body mass at age 14 d (the growth asymptote) was not correlated with clutch size or 14-d brood size. Late ...

AVIAN NEST SURVIVAL IN COASTAL FORESTED BUFFER STRIPS ON PRINCE OF WALES ISLAND, ALASKA

Abstract In an effort to provide wildlife habitat and link blocks of forested habitat, coastal forested buffer strips in the Pacific Northwest are managed to mitigate effects of fragmentation that result from timber harvesting adjacent to a coastline. We examined the effect of coastal forest buffer strip width on avian nest survival on Prince of Wales Island, Alaska, in 2003 and 2004. We established nest monitoring plots in two buffer width treatments, narrow ( 350 m, n = 3), and monitored a total of 142 nests of six species: the Pacific-slope Flycatcher (Empidonax difficilis), Chestnut-backed Chickadee (Poecile rufescens), Winter Wren (Troglodytes troglodytes), Swainson's Thrush (Catharus ustulatus), Hermit Thrush (Catharus guttatus), and Varied Thrush (Ixoreus naevius). We modeled and compared the daily survival rate (DSR) of each species in both buffer width treatments. Point estimates for DSRs were slightly higher within wide buffers, but confidence intervals overlapped for al...

DO CROSS-SCALE CORRELATIONS CONFOUND ANALYSIS OF NEST SITE SELECTION FOR CHESTNUT-BACKED CHICKADEES?

Multiscale models of nest site selection often ignore cross-scale correlations (correlations between predictor variables at different scales). We reexamined nest site selection of Chestnut-backed Chickadees (Poecile rufescens) at two scales within territories to isolate: (1) variation associated purely with variables measured at the patch (0.031 ha) and tree scales, and (2) variation shared by variables measured at the patch and tree scales. We used conditional (fixed-effect) logistic regression to build a patch, tree, and full model, and subtracted pure and shared components of variation from the deviance explained by the full model. Tree scale and patch scale variables accounted for 85% and 9% of the total explained variation, respectively. Only 6% of explained variation in nest site locations was due to cross-scale correlations. We suggest that multiscale habitat selection studies incorporate a diagnostic tool like variance decomposition to avoid spurious results caused by lack of independence of habitat relationships.

GENETIC PATTERNS OF DIFFERENTIATION AMONG FIVE LANDBIRD SPECIES FROM THE QUEEN CHARLOTTE ISLANDS, BRITISH COLUMBIA

Abstract The Queen Charlotte Islands (QCI), British Columbia, have many putative endemic avian subspecies. We evaluated four species—Northern Saw-whet Owl (Aegolius acadicus), Hairy Woodpecker (Picoides villosus), Steller's Jay (Cyanocitta stelleri), and Pine Grosbeak (Pinicola enucleator), each with a phenotypically described endemic subspecies from QCI—for uniqueness, conservation concern, and management. The Chestnut-backed Chickadee (Poecile rufescens), with no endemic subspecies from QCI, was included for comparison. We hypothesized that the four endemics would have similar phylogeographic patterns of genetic divergence and coalescence between QCI and possible source populations, because they may share a glacial-refugium history. Cytochrome b was sequenced for all species from Alaska, Washington, and QCI. The four species with endemic phenotypes from QCI had significant genetic divergence from nearby conspecific populations, though variation in divergence times indicated varying colonization historie...

PRESENCE OF SALMON INCREASES PASSERINE DENSITY ON PACIFIC NORTHWEST STREAMS

Abstract The annual migration of Pacific salmon (Oncorhynchus spp.) to freshwater streams and lakes provides an important nutrient subsidy to terrestrial systems in North America. We investigated the effects of salmon and other habitat variables on abundance of Winter Wren (Troglodytes troglodytes), Swainson's Thrush (Catharus ustulatus), Varied Thrush (Ixoreus naevius), Pacific-slope Flycatcher (Empidonax difficilis), Golden-crowned Kinglet (Regulus satrapa), and Chestnut-backed Chickadee (Poecile rufescens) on the central coast of British Columbia. In our comparisons of salmon-bearing and non-salmon-bearing reaches of two rivers that had waterfall barriers to salmon partway upstream, we found that position above or below the falls and proximity to the stream were the major predictors of songbird abundance. Each species, except for Chestnut-backed Chickadee, had higher densities below the falls at both rivers. Our results suggest that salmon-derived nutrients influence songbird density, and thus benefit ...

Habitat attributes and chestnut-backed chickadee nest site selection in uncut and partial-cut forests

We examined the relationship between habitat attributes and nest-site selection by chestnut-backed chickadees ( Poecile rufescens (Townsend, 1837); hereinafter chickadees) in uncut and partial-cut forests in northwest British Columbia. We described the characteristics of uncut sites and compared them with structurally modified partial-cut sites (mature and old forests). We then compared the use and selection of habitat by chickadees at uncut and partial-cut sites at three spatial scales: (1) the stand (19–24 ha uncut or partial-cut stand), (2) the nest patch (a 0.031 ha patch centered on nest trees), and (3) the nest tree. At the stand scale, we found no correlation between the density of breeding chickadees and the characteristics of uncut and partial-cut sites. At the nest-patch scale, chickadees in uncut and old partial-cut sites selected nest patches with higher densities of broken-top trees compared with available habitat within territories. At the nest-tree scale, chickadees selected nest trees with boring insects and broken tops in uncut and mature partial-cut sites and large trees with boring insects in old partial-cut sites. Our results suggest that chickadees exhibited flexibility in resource selection but also selected resources with similar attributes at the nest-patch and nest-tree scales. Managed stands that maintain a range of tree species and conditions, including live trees with areas of disease, insect attack, and damage, will provide the specific structural attributes used for nesting by weak cavity excavators such as the chickadee.

Nest Survival of Chickadees in Managed Forests: Habitat, Predator, and Year Effects

Abstract We examined the influence of year, habitat, and predators on nest survival by monitoring 69 natural cavity nests of the chestnut-backed chickadee (Poecile rufescens) across a range of uncut and partial cut stands in northwest British Columbia during 2000–2003. We considered 3 spatial scales of habitat: 1) the stand (19–24 ha of uncut and partial cut stands), 2) the nest patch (a 0.03-ha patch centered on nest trees), and 3) the nest tree. At each scale we hypothesized that nest survival time of chickadees differed among years, as a result of harvest treatment, habitat characteristics, and predator activity. Nest predation rates fluctuated among years: 56% in 2000, 64% in 2001, 10% in 2002, and 12% in 2003. We identified the red squirrel (Tamiasciurus hudsonicus) as the dominant nest predator. At the stand and nest patch scales, only the covariate year reliably predicted survival time: Risk = 1.81 (Year 2001) for both models. At the nest tree scale, we found the most support for a model with year ...

Effects of Pleistocene glaciations on population structure of North American chestnut‐backed chickadees

The postglacial recolonization of northern North America was heavily influenced by the Pleistocene glaciation. In the Pacific Northwest, there are two disjunct regions of mesic temperate forest, one coastal and the other interior. The chestnut-backed chickadee is one of the species associated with this distinctive ecosystem. Using seven microsatellite markers we found evidence of population structure among nine populations of chestnut-backed chickadees. High levels of allelic variation were found in each of the populations. Northern British Columbia and central Alaska populations contained a large number of private alleles compared to other populations, including those from unglaciated regions. The disjunct population in the interior was genetically distinct from the coastal population. Genetic and historical records indicate that the interior population originated from postglacial inland dispersal. Population structuring was found within the continuous coastal population, among which the peripheral populations, specifically those on the Queen Charlotte Islands and the central Alaska mainland, were genetically distinct. The pattern of population structure among contemporary chickadee populations is consistent with a pioneer model of recolonization. The persistence of genetic structure in western North American chestnut-backed chickadees may be aided by their sedentary behaviour, linear distribution, and dependence on cedar-hemlock forests.

HABITAT USE BY RIPARIAN AND UPLAND BIRDS IN OLD-GROWTH COASTAL BRITISH COLUMBIA RAINFOREST

The value of riparian habitats to birds differs among ecosystems. I tested whether riparian habitat near large streams and rivers in the Pacific Northwest supported a higher abundance and diversity of birds than adjacent upland forest. From 1996 to 1998, I surveyed breeding birds at four 9-ha sites in coastal western hemlock forest on western Vancouver Island, British Columbia. Five species of forest generalists dominated both riparian and upland bird communities: Winter Wren (Troglodytes troglodytes), Chestnut-backed Chickadee (Poecile rufescens), American Robin (Turdus migratorius), Swainson's Thrush (Catharus ustulatus), and Pacific-slope Flycatcher (Empidonax difficilis). Species richness and total abundance were similar over the riparian-to-upland gradient, whereas abundances of riparian specialists and aerial foragers declined with distance from the river. To explore whether vegetation composition and structure explained bird distribution patterns, I sampled three locations along both riparian and upland transects at each site. Riparian areas had higher densities of deciduous trees; conifer and snag densities were higher in upland areas. Salmonberry (Rubus spectabilis) cover was marginally higher in riparian areas and blueberry (Vaccinium spp.) cover was higher in upland areas. There was little effect of distance from the river on most bird species, but there were stronger associations of birds with specific vegetation attributes. Tree and snag densities explained the most variation in abundance of aerial foragers, and eight of nine individual species, whereas distance from the river and shrub cover were important predictors of Hammond's Flycatcher (Empidonax hammondii) abundance. Apart from riparian specialists and a few species with strong vegetation associations, bird assemblages in riparian and upland habitats of this moist forest type were dominated by similar sets of generalist species.

BREEDING BIRDS OF RESEARCH NATURAL AREAS IN SOUTHEASTERN ALASKA

Abstract The Tongass National Forest encompasses a large expanse of temperate rainforest in southeastern Alaska and contains 12 designated Research Natural Areas (RNAs). Existing in as near a natural condition as possible, RNAs receive minimal commercial and recreational use. Because few bird studies have been conducted on RNAs, we used point counts and area searches to determine the occurrence and abundance of breeding landbirds present in vegetation communities of RNAs. Of 49 species of small landbirds detected during area searches, the most widely distributed birds among RNAs were rufous hummingbird (Selasphorus rufa), chestnut-backed chickadee (Poecile rufescens), winter wren (Troglodytes troglodytes), golden-crowned kinglet (Regulus satrapa), Swainson's thrush (Catharus ustulatus), hermit thrush (C. guttatus), varied thrush (Ixoreus naevius), and Townsend's warbler (Dendroica townsendi). The 8 most abundant species recorded on 187 point counts (>0.5 birds/point) were Pacific-slope flycatcher (Empidon...

Effects of Commercial Thinning on Breeding Bird Populations in Western Hemlock Forests

Bird populations and habitat structure were compared between three commercially thinned and three unthinned western hemlock (Tsuga heterophylla) stands to assess short-term effects of commercial thinning on breeding bird communities. Thinning reduced the density of small trees and snags (≤30 cm dbh), but did not affect the density of large trees or snags (>30 cm dbh). The overstory canopy was more open and cover of forbs, grasses and seedlings was higher in thinned than unthinned stands. Winter wrens (Troglodytes troglodytes), dark-eyed juncos (Junco hyemalis), chestnut-backed chickadees (Parus rufescens) and red-breasted nuthatches (Sitta canadensis) were more abundant in thinned than unthinned stands, but total bird density did not differ between thinned and unthinned stands. Commercial thinning thus enhances habitat conditions for some bird species while having minimal effects on other bird species.