Sitta Carolinensis Research Articles

Influence of social and physical environmental variation on antipredator behavior in mixed-species parid flocks.

Carolina chickadees (Poecile carolinensis) and tufted titmice (Baeolophus bicolor) regularly form flocks with multiple species through the winter months, including white-breasted nuthatches (Sitta carolinensis). Earlier studies found that behavior of both chickadees and titmice was sensitive to mixed-species flock composition. Little is known about the influence of background noise level and vegetation density on the antipredator behaviors of individuals within these flocks, however. We tested for the effects of vegetation density, traffic noise, and flock composition (conspecific number, flock diversity, and flock size) on antipredator behavioral responses following an alarm call playback (Study 1) and an owl model presentation (Study 2) at feeders. We recorded background traffic noise and performed lidar scans to quantify vegetation density at each site. After a feeder had been stocked with seed and a flock was present, we recorded calls produced, and we identified flock composition metrics. We coded seed-taking latency, call latency, mob latency, and mob duration following the respective stimulus presentation and tested for effects of flock composition metrics, vegetation density, and background noise on these responses. For the alarm call playback study, flock composition drove behaviors in chickadees and titmice, and vegetation density drove behaviors in chickadees and nuthatches. For the owl model study, conspecific number predicted behavior in chickadees, and mob duration was predicted by nuthatch number. The results reveal individual sensitivity to group composition in anti-predatory and foraging behavior in simulated risky contexts. Additionally, our data suggest that the modality of perceived simulated risk (acoustic vs. visual) and the density of vegetation influence behavior in these groups.

Genomic divergence and introgression between cryptic species of a widespread North American songbird.

Analysis of genomic variation among related populations can sometimes reveal distinct species that were previously undescribed due to similar morphological appearances, and close examination of such cases can provide much insight regarding speciation. Genomic data can also reveal the role of reticulate evolution in differentiation and speciation. White-breasted nuthatches (Sitta carolinensis) are widely distributed North American songbirds that are currently classified as a single species but have been suspected to represent a case of cryptic speciation. Previous genetic analyses suggested four divergent groups, but it was unclear whether these represented multiple reproductively isolated species. Using extensive genomic sampling of over 350 white-breasted nuthatches from across North America and a new chromosome-level reference genome, we asked if white-breasted nuthatches are comprised of multiple species and whether introgression has occurred between divergent populations. Genomic variation of over 300,000 loci revealed four highly differentiated populations (Pacific, n = 45; Eastern, n = 23; Rocky Mountains North, n = 138; and Rocky Mountains South, n = 150) with geographic ranges that are adjacent. We observed a moderate degree of admixture between Rocky Mountain populations but only a small number of hybrids between the Rockies and the Eastern population. The rarity of hybrids together with high levels of differentiation between populations is supportive of populations having some level of reproductive isolation. Between populations, we show evidence for introgression from a divergent ghost lineage of white-breasted nuthatches into the Rocky Mountains South population, which is otherwise closely related to Rocky Mountains North. We conclude that white-breasted nuthatches are best considered at least three species and that ghost lineage introgression has contributed to differentiation between the two Rocky Mountain populations. White-breasted nuthatches provide a dramatic case of morphological similarity despite high genomic differentiation, and the varying levels of reproductive isolation among the four groups provide an example of the speciation continuum.

Interspecific differences in the effects of masking and distraction on anti-predator behavior in suburban anthropogenic noise.

Predation is a common threat to animal survival. The detection of predators or anti-predator communication signals can be disrupted by anthropogenic noise; however, the mechanism by which responses are affected is unclear. Masking and distraction are the two hypotheses that have emerged as likely explanations for changes in behavior in noise. Masking occurs when the signal and noise fall within the same sensory domain; noise overlapping the energy in the signal reduces signal detection. Distraction can occur when noise in any sensory domain contributes to a greater cognitive load, thereby reducing signal detection. Here, we used a repeated measures field experiment to determine the relative contributions of masking and distraction in mediating reduced anti-predator responses in noise. We recorded the approaches and vocalizations of black-capped chickadees (Poecile atricapillus), tufted titmice (Baeolophus bicolor), and white-breasted nuthatches (Sitta carolinensis) to both visual and acoustic cues of predator presence, either with or without simultaneous exposure to anthropogenic noise. Titmice increased their calling to both visual and acoustic cues of predator presence. However, there was no significant effect of noise on the calling responses of titmice regardless of stimulus modality. Noise appeared to produce a distraction effect in chickadees; however, this effect was small, suggesting that chickadees may be relatively unaffected by low levels of anthropogenic noise in suburban environments. White-breasted nuthatch calling behavior was affected by the interaction of the modality of the predator stimulus and the noise condition. Nuthatches had a delayed response to the predator presentations, with a greater calling rate following the presentation of the acoustic stimulus in quiet compared to the presentation of the acoustic stimulus in noise. However, there was no difference in calling rate between the quiet and noise conditions for the visual stimulus. Together this suggests that even moderate levels of noise have some masking effect for white-breasted nuthatches. We suggest that the mechanisms through which noise influences anti-predator behavior may depend on the social roles, foraging ecology and auditory capabilities of each species.

Muscle testosterone supply keeps male birds topped up out of season

Many creatures live life on the energetic limit, so when they don't need a particular organ, they simply allow it to wither away to save energy until required again. Snakes’ digestive tracts atrophy between meals, migrating birds also reduce the mass of their digestive systems while en route and many male birds allow their testes to downsize out of the mating season. But this does not mean that male birds are not able to brag boastfully when their testes are out of action. Male woodpeckers are still capable of high-speed drumming, powered by their strong neck muscles, to warn other males off their territories, which made Eric Schuppe (University of California, San Francisco, USA) and Matthew Fuxjager (Brown University, USA) wonder whether the woodpecker's impressive out-of-season percussive performances could be due to testosterone produced in the muscle itself.Schuppe headed out into the North Carolina woods to capture territorial downy woodpeckers (Dryobates pubescens) during and after the mating season, to measure the quantity of testosterone circulating in their blood and in various tissues – including the powerfully drumming neck muscle and their testes. Back in the lab, Schuppe and Daniel Tobiansky (Brown University) discovered that the levels of testosterone in the drumming muscle during the breading season were six times higher than in the bird's flight muscles, which are required year-round. The testosterone levels even remained high in the percussive muscle during the winter and autumn, when the hormone had all but disappeared from other tissues in the body. And when the team checked for evidence of the key enzymes that are essential for producing the potent hormone from the basic cholesterol building block, all of the key enzymes turned up in the neck muscle at high levels. Woodpeckers are capable of beefing up their masculine drumming neck muscles by producing testosterone within the muscle itself. But could the magnificent performances of other males also benefit from a boost of in situ testosterone?This time, the team turned their attention to chattering male white-breasted nuthatches (Sitta carolinensis) and zebra finches (Taeniopygia guttata), both of which serenade females, to find out whether their superfast voice box muscles benefit from a self-produced shot of testosterone. Sure enough, all of the necessary enzymes for producing the masculine hormone from scratch turned up in the trilling birds’ voice boxes. Serenading nuthatches and zebra finches probably produce testosterone in their voice box muscles to enhance their acoustic pyrotechnics to attract females.Having confirmed that testosterone can be produced in organs that become souped up to catch the attention of passing females, Schuppe, Fuxjager and colleagues wondered whether the hormone could also enhance the performance of other superfast muscles, such as those that drive swift eye swivels. Sure enough, all of the critical enzymes turned up in the fast-contracting eye muscles of lab mice and at much higher levels than occur in other muscles that never contract as fast.It seems that the organs that male birds depend upon when courting females are capable of producing their own internal testosterone supply to enhance their performance, and it turns out that some other muscles that are capable of super-fast contractions can also produce the hormone, which may enhance blisteringly fast contractions. So male woodpeckers, nuthatches and zebra finches don't need to depend on testosterone produced by their testes when defending their territories and serenading females out of season: their own internal muscle supplies keep them topped up and in tip-top condition.

Preferences of avian seed-hoarders in advance of potential American chestnut reintroduction

Nut-bearing trees such as oaks (Quercus genus) and American chestnut (Castanea dentata, hereafter: chestnut) rely on scatter-hoarding animals for seed dispersal. With the pursuit of blight-resistant chestnuts for eventual reintroduction into eastern hardwood forests of the United States, it becomes important to understand how foraging preferences of avian seed-hoarders will influence chestnut dispersal in oak-dominated forests. Using six seed selection trials over three years and two “seasons” (early fall and late fall), we assess the relative seed preferences – when gathering seeds for hoarding or consumption – of five species of avian seed dispersers in southeast Ohio. In each trial, we presented an equal number of chestnuts and two species of common acorns, black (Q. velutina) and white oak (Q. alba), to wild birds on feeding platforms monitored by cameras. We used Bayesian discrete choice models to determine preferences of each species, and estimate the influence of natural variation in background mast availability (i.e., different years and seasons). Blue Jays (Cyanocitta cristata) showed a consistent preference for the seeds of black oak over chestnut over white oak, and the strength of preference for black oak increased in late season when acorns were scarce. Other species showed variable preferences, with White-breasted Nuthatch (Sitta carolinensis) the only species to prefer chestnuts over both acorns, though sample size was small (n = 26 selections). Our results suggest chestnuts are used by a host of avian seed-hoarders that may facilitate dispersal of chestnut, particularly in years of black oak mast failure.

Community science reveals biennial irruptive migration in the White-breasted Nuthatch (Sitta carolinensis)

Dunn, E., A. Dreelin, P. Heveran, L. Goodrich, D. Potter, A. Florea, B. Ewald, and J. Gyekis. 2022. Community science reveals biennial irruptive migration in the White-breasted Nuthatch (Sitta carolinensis). Journal of Field Ornithology 93(2):2. https://doi.org/10.5751/JFO-00091-930202

Evaluating the accuracy and biological meaning of visits to RFID-enabled bird feeders using video.

Radio‐frequency identification (RFID) technology has gained popularity in ornithological studies as a way to collect large quantities of data to answer specific biological questions, but few published studies report methodologies used for validating the accuracy of RFID data. Further, connections between the RFID data and the behaviors of interest in a study are not always clearly established. These methodological deficiencies may seriously impact a study's results and subsequent interpretation. We built RFID‐equipped bird feeders and mounted them at three sites in Tompkins County, New York. We deployed passive integrated transponder tags on black‐capped chickadees, tufted titmice, and white‐breasted nuthatches and used a GoPro video camera to record the three tagged species at the feeders. We then reviewed the video to determine the accuracy of the RFID reader and understand the birds’ behavior at the feeders. We found that our RFID system recorded only 34.2% of all visits by tagged birds (n = 237) and that RFID detection increased with the length of a visit. We also found that our three tagged species and two other species that visited the feeders, American goldfinch and hairy woodpecker, retrieved food in 79.5% of their visits. Chickadees, titmice, nuthatches, and woodpeckers spent, on average, 2.3 s at feeders to collect one seed per visit. In contrast, goldfinches spent an average of 9.0 s at feeders and consumed up to 30 seeds per visit. Our results demonstrate the importance of confirming detection accuracy and that video can be used to identify behavioral characteristics associated with an RFID reader's detections. This simple—yet time‐intensive—method for assessing the accuracy and biological meaning of RFID data is useful for ornithological studies but can be used in research focusing on various taxa and study systems.

Brown-headed Nuthatches (Sitta pusilla) have more fluctuating asymmetry than White-breasted Nuthatches (S. carolinensis) but no change over 75 years

Birds face many human-induced environmental challenges that we associate with population declines. Because of this, we need more ways to monitor populations before they become endangered. Several authors have proposed that fluctuating asymmetry, or nondirectional deviation from bilateral symmetry, could be used as an indicator of population declines. Fluctuating asymmetry is linked to developmental instability and stress associated with environmental challenges such as habitat loss in populations of birds and other animals. Two key premises of the argument for linking fluctuating asymmetry and population declines are that (1) fluctuating asymmetry changes over time, and (2) change over time results in overall population- or species-level differences in fluctuating asymmetry. I evaluated these premises by measuring tarsus and hallux lengths of museum specimens primarily from 1875–1950 in a pair of closely related species with different population statuses—the White-breasted Nuthatch (Sitta carolinensis) and the Brown-headed Nuthatch (S. pusilla). Since Brown-headed Nuthatch populations are decreasing whereas White-breasted Nuthatch populations are increasing, I predicted that Brown-headed Nuthatches would have increasing fluctuating asymmetry over time whereas White-breasted Nuthatches would have no change or decreasing fluctuating asymmetry over time, and this would result in Brown-headed Nuthatches having more overall fluctuating asymmetry in both morphological traits than White-breasted Nuthatches. The percent asymmetry of tarsi and halluces for Brown-headed Nuthatches were at least 1.5× higher than the corresponding values for White-breasted Nuthatches, which supported the second premise. However, since I also found that there was a great deal of interindividual variation and no change in fluctuating asymmetry over time in either species, it is still unclear whether fluctuating asymmetry could be used to help monitor populations for evidence of decline before they reach endangered status. Future studies should more broadly and deeply explore the associations between avian population declines and fluctuating asymmetry.

Brown-headed Nuthatches (Sitta pusilla) have more fluctuating asymmetry than White-breasted Nuthatches (S. carolinensis) but no change over 75 years

Birds face many human-induced environmental challenges that we associate with population declines. Because of this, we need more ways to monitor populations before they become endangered. Several authors have proposed that fluctuating asymmetry, or nondirectional deviation from bilateral symmetry, could be used as an indicator of population declines. Fluctuating asymmetry is linked to developmental instability and stress associated with environmental challenges such as habitat loss in populations of birds and other animals. Two key premises of the argument for linking fluctuating asymmetry and population declines are that (1) fluctuating asymmetry changes over time, and (2) change over time results in overall population- or species-level differences in fluctuating asymmetry. I evaluated these premises by measuring tarsus and hallux lengths of museum specimens primarily from 1875–1950 in a pair of closely related species with different population statuses—the White-breasted Nuthatch (Sitta carolinensis) and the Brown-headed Nuthatch (S. pusilla). Since Brown-headed Nuthatch populations are decreasing whereas White-breasted Nuthatch populations are increasing, I predicted that Brown-headed Nuthatches would have increasing fluctuating asymmetry over time whereas White-breasted Nuthatches would have no change or decreasing fluctuating asymmetry over time, and this would result in Brown-headed Nuthatches having more overall fluctuating asymmetry in both morphological traits than White-breasted Nuthatches. The percent asymmetry of tarsi and halluces for Brown-headed Nuthatches were at least 1.5× higher than the corresponding values for White-breasted Nuthatches, which supported the second premise. However, since I also found that there was a great deal of interindividual variation and no change in fluctuating asymmetry over time in either species, it is still unclear whether fluctuating asymmetry could be used to help monitor populations for evidence of decline before they reach endangered status. Future studies should more broadly and deeply explore the associations between avian population declines and fluctuating asymmetry.

Social partners and temperature jointly affect morning foraging activity of small birds in winter

Abstract Daily foraging activity of small wintering birds is classically thought to be driven by the need to gather enough energy reserves to survive each night. A separate line of research has shown that sociality is a major driver in winter foraging activities in many species. Here, we used wintering birds as a study system to move toward an integrative understanding of the influence of energy requirements and sociality on foraging ecology. We used RFID-enabled feeders in Lincoln, Nebraska, USA in January–March 2019 to measure foraging activity in two species (downy woodpeckers, Dryobates pubescens, and white-breasted nuthatches, Sitta carolinensis). We analyzed the relationship between overnight temperature and morning foraging activity and found that lowest overnight temperature was weakly correlated with morning visitation at feeders. We then used a network approach to ask if flock associations explain similarity in birds’ foraging activity. In both species, individuals with stronger associations in a social network were more likely to share similar feeder activity, and an index of social partners’ activity explained foraging activity better than overnight temperature. This brings forth new questions about the interplay between individual response to temperature and social factors in shaping how small animals cope with harsh winter conditions.

Building a better baseline to estimate 160 years of avian population change and create historically informed conservation targets.

Globally, anthropogenic land-cover change has been dramatic over the last few centuries and is frequently invoked as a major cause of wildlife population declines. Baseline data currently used to assess population trends, however, began well after major changes to the landscape. In the United States and Canada, breeding bird population trends are assessed by the North American Breeding Bird Survey, which began in the 1960s. Estimates of distribution and abundance prior to major habitat alteration would add historical perspective to contemporary trends and allow for historically based conservation targets. We used a hindcasting framework to estimate change in distribution and abundance of 7 bird species in the Willamette Valley, Oregon (United States). After reconciling classification schemes of current and 1850s reconstructed land cover, we used multiscale species distribution models and hierarchical distance sampling models to predict spatially explicit densities in the modern and historical landscapes. We estimated that since the 1850s, White-breasted Nuthatch (Sitta carolinensis) and Western Meadowlark (Sturnella neglecta) populations, 2 species sensitive to fragmentation of oak woodlands and grasslands, declined by 93% and 97%, respectively. Five other species we estimated nearly stable or increasing populations, despite steep regional declines since the 1960s. Based on these estimates, we developed historically based conservation targets for amount of habitat, population, and density for each species. Hindcasted reconstructions provide historical perspective for assessing contemporary trends and allow for historically based conservation targets that can inform current management.

Correlates of bird collisions with buildings across three North American countries.

Collisions with buildings cause up to 1 billion bird fatalities annually in the United States and Canada. However, efforts to reduce collisions would benefit from studies conducted at large spatial scales across multiple study sites with standardized methods and consideration of species- and life-history-related variation and correlates of collisions. We addressed these research needs through coordinated collection of data on bird collisions with buildings at sites in the United States (35), Canada (3), and Mexico (2). We collected all carcasses and identified species. After removing records for unidentified carcasses, species lacking distribution-wide population estimates, and species with distributions overlapping fewer than 10 sites, we retained 269 carcasses of 64 species for analysis. We estimated collision vulnerability for 40 bird species with ≥2 fatalities based on their North American population abundance, distribution overlap in study sites, and sampling effort. Of 10 species we identified as most vulnerable to collisions, some have been identified previously (e.g., Black-throated Blue Warbler [Setophaga caerulescens]), whereas others emerged for the first time (e.g., White-breasted Nuthatch [Sitta carolinensis]), possibly because we used a more standardized sampling approach than past studies. Building size and glass area were positively associated with number of collisions for 5 of 8 species with enough observations to analyze independently. Vegetation around buildings influenced collisions for only 1 of those 8 species (Swainson's Thrush [Catharus ustulatus]). Life history predicted collisions; numbers of collisions were greatest for migratory, insectivorous, and woodland-inhabiting species. Our results provide new insight into the species most vulnerable to building collisions, making them potentially in greatest need of conservation attention to reduce collisions and into species- and life-history-related variation and correlates of building collisions, information that can help refine collision management.

Traffic noise and responses to a simulated approaching avian predator in mixed‐species flocks of chickadees, titmice, and nuthatches

AbstractTraffic noise likely reaches a wide range of species and populations throughout the world, but we still know relatively little about how it affects anti‐predator behavior of populations. We tested for possible effects of traffic noise on responses to predator acoustic cues in Carolina chickadees (Poecile carolinensis), tufted titmice (Baeolophus bicolor), and white‐breasted nuthatches (Sitta carolinensis) near 14 independent feeding stations in eastern Tennessee. We compared anti‐predator calling and seed‐taking behavior in response to playbacks of predator stimuli (screech owl calls) at sites naturally exposed to traffic noise and at sites that faced relatively little traffic noise. The screech owl call playback was designed to simulate the approach of this dangerous predator to a feeder being used by these small songbirds. We found that chickadees responded consistently to the owl stimuli across different levels of traffic noise. However, titmice, and nuthatches exhibited different behavioral responses to the predator stimulus, suggesting that traffic noise masked these low‐frequency predator calls. Overall, chickadees and nuthatches showed the broadest anti‐predator behavioral responses in comparison to titmice, corroborating earlier published work with an Indiana population. Finally, populations exposed to traffic noise overall seemed less able to detect predator cues potentially masked by that noise, and future work will need to assess likely seasonal variation in these responses as well as species‐level variation in anti‐predator responses in mixed‐species groups.

Thinning alters avian occupancy in piñon–juniper woodlands

ABSTRACT Natural resource managers are increasingly applying tree reduction treatments to piñon–juniper woodlands to meet a range of ecological, social, and economic goals. However, treatment effects on woodland-obligate bird species are not well understood. We measured multiscale avian occupancy on 29 paired (control/treatment) sites in piñon–juniper woodlands in central Colorado, USA. We conducted point counts at 232 stations, 3 times each season in 2014 and 2015. We used hierarchical multiscale modeling to obtain unbiased estimates of landscape and local occupancy (i.e. probability of use) in treated and untreated sites for 31 species. Treatments reduced the occupancy of conifer obligates, including Mountain Chickadee (Poecile gambeli), Clark’s Nutcracker (Nucifraga columbiana), and White-breasted Nuthatch (Sitta carolinensis), and increased occupancy of Lark Sparrow (Chondestes grammacus) and Mountain Bluebird (Sialia currucoides). Occupancy of Virginia’s Warbler (Oreothylpis virginiae) and Gray Flycatcher (Empidonax wrightii), two piñon–juniper specialists, decreased at the landscape scale in treated sites, and Pinyon Jay (Gymnorhinus cyanocephalus) occupancy decreased at the local scale. Tree reduction treatments in piñon–juniper woodlands have the potential to reduce habitat quality for a suite of bird species of conservation concern. We suggest that treatments designed to retain higher tree density and basal area will benefit conifer-obligate and piñon–juniper specialist bird species.

Flocking propensity by satellites, but not core members of mixed-species flocks, increases when individuals experience energetic deficits in a poor-quality foraging habitat.

Mixed-species bird flocks are complex social systems comprising core and satellite members. Flocking species are sensitive to habitat disturbance, but we are only beginning to understand how species-specific responses to habitat disturbance affect interspecific associations in these flocks. Here we demonstrate the effects of human-induced habitat disturbance on flocking species’ behavior, demography, and individual condition within a remnant network of temperate deciduous forest patches in Indiana, USA. Specifically, we characterized the following properties of two core species, Carolina chickadees (Poecile carolinensis) and tufted titmice (Baeolophus bicolor), across a secondary-forest disturbance gradient: foraging time budgets, home range size, fat scores, fledgling counts, survival rates, and abundance. We also report fat scores for two satellite species that flock with the core study species: white-breasted nuthatches (Sitta carolinensis) and downy woodpeckers (Dryobates pubescens). Finally, we assess mixed-species flock sizes and composition, in addition to avian predator call rates, across the disturbance gradient. Foraging time budgets and home range size were highest and fat scores were lowest for core species in the most-disturbed site. Fat scores of two satellite species followed the same pattern. Additionally, the number of tufted titmice fledglings and winter survival rate of Carolina chickadees were lowest at the most-disturbed site. These results suggest that core species in the most-disturbed site experienced energetic deficits. Moreover, cumulative calling rate of raptors was lowest at the most-disturbed site, and none of the individual raptor species call rates were higher at the most-disturbed site—suggesting that perception of predation risk does not contribute to these patterns. Surprisingly, the satellites continued associating with mixed species flocks through the breeding season at the most-disturbed site. Total flock size and interspecific association patterns were otherwise consistent across the gradient. The fact that satellites continued to flock with core species during the breeding season suggests foraging niche expansion resulting from mixed-species flocking is important in disturbed sites even beyond the winter season. Our study reveals mechanisms underlying flock composition of birds surviving in remnant forest and links the mechanisms to degradation of foraging habitat. These findings offer important insight into the relative impact potential of forest disturbance on mixed-species flocks in the North Temperate Zone.

Ten new species of Brueelia Kéler, 1936 (Phthiraptera: Ischnocera: Philopteridae) from nuthatches (Aves: Passeriformes: Sittidae), tits and chickadees (Paridae), and goldcrests (Regulidae).

Ten new species of chewing lice in the genus Brueelia Kéler, 1936, are described from hosts in the families Paridae, Regulidae, and Sittidae. They are: Brueelia johnsoni n. sp. from Poecile sclateri eidos (Peters, 1927); Brueelia juniperi n. sp. from Baeolophus ridgwayi ridgwayi (Richmond, 1902); Brueelia kabulica n. sp. from Sitta tephronota tephronota Sharpe, 1872; Brueelia mpumalangensis n. sp. from Melaniparus niger niger (Vieillot, 1818); Brueelia nazae n. sp. from Parus cinereus caschmirensis Hartert, 1905; Brueelia oxyrhyncha n. sp. from Sitta nagaensis nagaensis Godwin-Austen, 1874; Brueelia picea. sp. from Parus major excelsus Buvry, 1857; Brueelia ragusica n. sp. from Sitta neumayer neumayer Michahelles, 1830; Brueelia regulicida n. sp. from Regulus calendula grinnelli Palmer, 1897; Brueelia sittacola n. sp. from Sitta carolinensis carolinensis Latham, 1790. Brueelia regulicida is the first Brueelia-complex louse to be described from the host family Regulidae. Collectively, the Brueelia of parid, regulid, and sittid hosts show two peculiar patterns. Firstly, lice on closely related hosts appear to be distantly related. Secondly, lice on most hosts in these families appear to be more closely related to lice on other host families than to each other. This contradicts the traditional view that Brueelia-complex lice on closely related hosts are themselves closely related. Potentially, the tendency of the hosts to participate in mixed-species feeding flocks may explain some of these patterns.

A decade of emerald ash borer effects on regional woodpecker and nuthatch populations

The emerald ash borer (EAB) Agrilus planipennis, first detected in 2002 in the vicinity of Detroit, Michigan, USA, has spread throughout much of eastern and midwestern North America as of 2016, resulting in widespread mortality of ash trees in the genus Fraxinus. We investigated the effects of this newly available, exotic food source on populations of six species of largely resident insectivorous birds, including five species of woodpeckers and white-breasted nuthatch (Sitta canadensis), using North American Breeding Bird Survey data for breeding season estimates and Audubon Christmas Bird Counts for winter season estimates. We found evidence for relatively modest and variable effects of EAB invasion on the populations of these birds during the breeding season, but highly significant numerical increases during the winter that in several cases appeared to be increasing as the EAB invasion has progressed. Our results confirm that the EAB invasion is resulting in increased populations of several insectivorous birds, primarily during the winter. They also suggest that the numerical response of woodpeckers to EAB may be such that avian predation, which represents a significant, and possibly the largest, morality factor affecting some EAB populations, may continue to increase and help control the EAB epidemic as the invasion continues.

Ranges of the Subspecies of the White-breasted Nuthatch in California

Ranges of the Subspecies of the White-breasted Nuthatch in California

Winter Space Partitioning of Woodpeckers and Nuthatches in Wisconsin

Abstract Woodpeckers and nuthatches are resident species sharing similar year-round habitat in northeastern North America, but little is known about how these species distribute themselves within the same wintering area. From 2009 to 2015, we conducted a mark—recapture study of 7 Downy Woodpeckers, 15 Hairy Woodpeckers, 9 Red-bellied Woodpeckers, and 39 White-breasted Nuthatches to determine geographical winter home-range partitioning between and within species. We used multinomial log-linear models to estimate the likelihood of capturing each species in a particular baited trap when other species had been caught in the same trap during the same year. Our results show the presence of each species influenced the likelihood at least 1 other species would inhabit the same area. Most of these relationships were positive and indicate active sharing of the same space. However, Hairy Woodpeckers appeared to deter White-breasted Nuthatches, and Red-bellied Woodpeckers avoided conspecifics. Little evidence of spac...

Diversity in mixed species groups improves success in a novel feeder test in a wild songbird community

Mixed-species groups are common and are thought to provide benefits to group members via enhanced food finding and antipredator abilities. These benefits could accrue due to larger group sizes in general but also to the diverse species composition in the groups. We tested these possibilities using a novel feeder test in a wild songbird community containing three species that varied in their dominant-subordinate status and in their nuclear-satellite roles: Carolina chickadees (Poecile carolinensis), tufted titmice (Baeolophus bicolor), and white-breasted nuthatches (Sitta carolinensis). We found that chickadees and titmice were more likely to obtain seed from the novel feeder with greater diversity of species composition in their mixed-species flocks. For successful chickadee flocks, furthermore, the latency to obtain seed from the novel feeder was shorter the more diverse their flocks were. These results in a natural setting indicate that diversity, per se, can benefit individuals in mixed-species groups in biologically meaningful contexts such as finding food in novel places.