AbstractMany species of birds use shed snake skin in nest construction, but this behavior remains poorly understood. Ecological context is likely key for understanding how this unusual, but widespread, behavior evolved. We use comparative and experimental approaches to suggest that the evolution of this behavior is mediated by nest morphology and predator communities. First, we reviewed the literature and found that 78 species from 22 families have been reported to use shed snake skin in nest construction. All but one of these species are passerines and, using comparative analyses, we show that this behavior is disproportionately observed in cavity-nesting species. Second, we examined a subsample of North American species, all of which are reported to use snake skin in nest construction, to see whether the proportion of nests with snake skin differs between cavity- and open cup-nesting species. This analysis suggested that the proportion of nests with snake skin is roughly 6.5 times higher in cavity- than in open cup-nesting species. Finally, we used a series of experiments and comparisons to test four hypotheses whereby snake skin could award fitness benefits (nest predation, nest microbiotas, nest ectoparasites, social signaling) and found support for the predation hypothesis. Snake skin reduced nest predation in cavity, but not open cup, nests. These unequal fitness benefits highlight different ecological conditions between nest morphologies and likely explains why, across species, cavity-nesting birds show this behavior more frequently than open cup-nesting birds.

Ectotherms are particularly vulnerable to climate change because they rely on the surrounding environment for thermoregulation. In snakes, prolonged warmer temperatures and precipitation changes may lead to faster growth and smaller body size. Our goal was to assess how climate change may impact future sizes and growth rates on an endangered pitviper species as a model organism. We hypothesized that climate change-induced shifts in growing season temperature, early growing season precipitation, and snow residence time (SRT) would impact growth rate and asymptotic size in the threatened Eastern Massasauga (Sistrurus catenatus) rattlesnake. We used capture-mark-recapture data from eleven sites across the species’ range to fit a set of non-linear models evaluating the effects of these three climate variables on asymptotic size and growth coefficient in a modified von Bertalanffy growth curve. We found that longer SRT resulted in larger asymptotic size. We also found support for both a negative relationship between SRT and growth rate and a positive relationship between precipitation and growth rate. We averaged all supported models and predicted growth and size in the 2080s under a stabilization (RCP 4.5) and a high (RCP 8.5) emission scenario. Under RCP 8.5, predicted increases in female growth rate ranged from 10% to 33%, whereas decreases in female size across sites ranged from 9% to 17%. Under this scenario female lifetime reproductive success will decrease, as faster growth is associated with increased mortality, early senescence, and poor offspring quality, and smaller body sizes will result in smaller and fewer young.

Long-term avian nesting data are valuable to researchers studying various aspects of avian ecology, conservation, and management. Administered by the Cornell Lab of Ornithology, NestWatch accepts nesting data from volunteers and professionals who agree to follow its protocol and submit data in a standardized form using either the website NestWatch.org, the mobile app, or a bulk upload template. These data (N = 574,288 nest records currently spanning 1874-2023) have been used to examine geographical and temporal variation in breeding success, clutch size, nesting phenology, and other metrics of interest to researchers. When combined with other data sets (e.g., climate, land cover, maps of environmental stressors), NestWatch data have been used to explore the large-scale effects of anthropogenic change on nesting biology. These data can also be incorporated into investigations of status and trends for declining species and can potentially be aggregated with other large-scale nest-monitoring data sets to explore hemispheric or even global change. By committing these data to the public domain, we aimed to increase their use among researchers and stimulate novel studies. The NestWatch Open Data Set by the Cornell Lab of Ornithology is licensed under CC BY-NC 3.0 (creativecommons.org); users are free to copy, redistribute, remix, transform, and build upon the material in any medium or format, but must give appropriate credit, provide a link to the license, and indicate if changes were made. Users may do so reasonably, but not in any way that suggests the licensor endorses such use, and may not use the material for commercial purposes.

Lay Summary center dot Feeding wild birds is a popular household activity in North America, but it can have positive and negative consequences for birds. center dot We looked for effects of wild bird feeding during the breeding season on three key aspects of reproduction: timing of egg-laying, clutch size, and survival of nests. center dot Our 6-year study focused on three species commonly fed across most of their breeding range: Black-capped Chickadee, Carolina Chickadee, and Eastern Bluebird. center dot We found that Eastern Bluebirds with access to human-provided food started laying eggs earlier and had better nest survival than those without, but clutch size was unaffected. Access to food was unrelated to the three reproductive measures for either chickadee species in our study. center dot Our results suggest that reproductive impacts of feeding birds vary by species, likely due to dietary differences. center dot Supplemental feeding during the nesting season may only be a viable conservation strategy for food-limited populations. Wild bird feeding is a popular and growing activity, with approximately half of households participating in nations including the United States, Canada, the United Kingdom, New Zealand, and Australia. Supplemental feeding can increase survival and reproductive success of birds (which is often a goal of supplemental feeding efforts), but it raises concerns about phenological mismatch and possible increased risk of nest predation. Our objectives were to test whether access to supplemental food during the breeding season was correlated with (1) advanced egg-laying phenology, (2) increased clutch size, or (3) improved nest survival of 3 cavity-nesting species (Carolina Chickadee [Poecile carolinensis], Black-capped Chickadee [P. atricapillus], and Eastern Bluebird [Sialia sialis]) at a large spatial scale (the United States and Canada; spanning 22 degrees latitude and 55 degrees longitude). We examined data from 24,528 nest attempts submitted to NestWatch from 2014 to 2019. For Eastern Bluebirds, birds with access to supplemental insects initiated clutches 5.83 +/- 0.89 (mean +/- SE) days earlier than birds without access to food subsidies, whereas predicted nest survival was 5% greater for birds with access to supplemental insects (probability of nest success = 0.79, 95% CI: 0.77-0.81) than for birds without (0.74, 95% CI: 0.72-0.75). Clutch size of Eastern Bluebirds did not differ between birds with and without access to supplemental insects. For chickadees, supplemental feeding (of seeds, suet, insects, or fruit) was not correlated with phenology, clutch size, or nest survival. Our results suggest that supplemental feeding of insects can be an effective tool for increasing nest survival in Eastern Bluebirds and potentially other food-limited insectivores. However, the efficacy of supplemental feeding for improving reproductive success varies across taxa, likely related to diet. Despite widespread feeding of Black-capped and Carolina Chickadees, supplemental food had no discernable effect on timing of egg-laying, clutch size, or nest survival.

Globally, billions of U.S. dollars are spent annually to provide food for wild birds. The variety of foods offered continues to diversify, yet the consequences for wildlife of this widespread human activity are relatively unexplored, as are the relative benefits of different types of supplemental food. To investigate the potential implications of supplemental feeding for reproductive success, we experimentally examined the effects of providing supplemental insect prey on nestling mass for two species of birds across two nesting seasons (2016-2017) in Tompkins County, New York. Nesting adults in the experimental group were provided with 10 grams of insect larvae (mealworms, Tenebrio molitor) per day from the day eggs hatched until nestlings fledged. Results were mixed, with nestling Eastern Bluebirds (Sialia sialis) having 5.2% greater mass at fledging in supplemented nests, on average, than those in nests not receiving supplemental food. In contrast, no difference in mass was detected between treatment and control groups of nestling Black-capped Chickadees (Poecile atricapillus). Models also supported variation in bluebird mass depending on weather conditions, with greater mass at higher mean temperatures and during periods with less precipitation. Although people who feed wild birds are often motivated by a desire to contribute to conservation and help birds, the consequences of supplementing birds vary, and feeding may not have the desired effects across taxa. People seeking to improve the condition of nestlings should not assume that feeding is universally beneficial and should also consider making habitat improvements, keeping cats indoors, and limiting access of predators to nest boxes by installing predator guards. Implementing a suite of conservation behaviors may be more effective at promoting reproductive success than feeding alone.

In North America, nest site competition from invasive cavity-nesting birds can limit the opportunities for successful nesting by native birds. Managing invasive species is costly and complex, requiring input from biologists, decision makers, and the public. An informed and engaged public can play an important role in mitigating the negative effects of invasive avian species. However, little is known regarding the publics' knowledge, attitudes, and behaviors toward non-native bird species. We examined the association between participating in a citizen science project and enjoyment, knowledge, and management of two non-native avian species in North America: European starlings (Sturnus vulgaris) and house sparrows (Passer domesticus). We administered a pre and post survey to 947 people who monitor nest boxes in the United States and Canada, 30% of whom were also reporting their observations to NestWatch, a citizen science project focused on nesting birds. We found that NestWatch participants were more likely to have negative views of non-native species, score higher on bird identification tasks, and manage for invasive species than non-participants. The most important predictor for undertaking management activities was respondents' perceptions of whether they believed non-native birds to be a problem at the continental scale, underscoring the important role of individual factors such as perception. Our study also highlights the important role citizen science may play in shaping attitudes and behaviors and increasing knowledge. We propose a conceptual model describing the mechanisms by which citizen science can be leveraged for management of invasive species.

Invasive species are a threat to global biodiversity, yet the impacts of invasive birds on the native birds with which they compete are understudied. Humans have a long history of providing and managing nest boxes to support native birds; however, their management of non‐native birds has received limited research attention. We surveyed people who maintain nest boxes in North America to examine the extent of interference competition for nest sites between native and non‐native birds and the human behaviors intended to reduce nest site competition. Our specific objectives were to examine observations of nest usurpation of native birds by non‐native birds across the United States and Canada, to ascertain whether and how people who maintain nest boxes control non‐native bird species in favor of native species, and to quantify various factors correlated with the likelihood of engaging in management activities. We found that nearly one‐third of the 871 respondents had observed a non‐native species usurp a nest box occupied by a native species. Among respondents who reported nest usurpations, species‐specific nest usurpation rates varied (range = 3–35%). We found that witnessing a nest usurpation is the most important predictor of whether or not someone will engage in management activities. Management activity was also associated with the extent to which respondents believed non‐native birds to be a problem at the continental scale. Our study shows that people's observations of threats from introduced species are correlated with the environmental management actions people take, and that these actions can mitigate the threats, and potentially support the survival of native birds.

The House Sparrow (Passer domesticus), native to Europe and Asia, has been introduced globally and is now one of the most ubiquitous birds in the world. In North America, these invasive passerines compete with native species for nest cavities, which are often limited. Because of the difficulties of extirpating an invasive species and the growing desire from the public to help in conservation matters, we sought to test a potential technique for managing invasive cavity-nesting passerines that could be successfully deployed by professionals and citizen scientists alike. Previous studies demonstrate that applying vegetable oil to eggs is a nontoxic management technique often used to manage unwanted waterfowl. Further, egg oiling is a technique that is acceptable to a large segment of the public. This study assesses the efficacy of applying vegetable oil for preventing House Sparrow eggs from hatching, reducing the number of fledged young, prolonging incubation time, and delaying renesting attempts by the adults. We sprayed treatment clutches once with approximately 0.8 ml of vegetable oil early in the developmental period and subsequently monitored nests every 3-4 days. The application of vegetable oil to treated eggs was 100% effective at preventing hatching and, thus, preventing any offspring from fledging. Furthermore, the adults in the treatment group incubated their eggs for nearly twice as long as the adults at control nests, reducing their opportunity to produce more clutches later in the season. Given the availability, low cost, and effectiveness of applying vegetable oil to eggs to prevent the reproductive output of invasive cavity-nesting passerines, we propose that this method can be easily implemented by wildlife managers as well as trained nest box stewards.

Long-term demographic data are important for conserving populations of threatened and endangered species. Collecting data specific to the population of interest can improve conservation success by allowing managers to make informed decisions, evaluate the efficacy of habitat management, and assess extinction risk. Population viability analysis (PVA), a tool commonly used to estimate extinction risk in threatened populations, is most informative when precise, population-specific data are available. We used mark-recapture data spanning ten years (2008–2017) to estimate annual adult survival rates in a population of threatened Eastern Massasauga rattlesnakes (Sistrurus catenatus) in Barry County, Michigan. Using these survival estimates and ten additional parameter values obtained from our site and a nearby population, we modeled population viability over the next 100 years. We performed sensitivity analysis using Latin hypercube sampling, followed by logistic regression to assess the relative influence of model parameters on extinction risk. We estimated annual apparent survival rates of 0.79 (95% CI = 0.69–0.87) for adult males and 0.78 (95% CI = 0.69–0.85) for adult females, which are higher than expected given the population's locality. Results of our sensitivity analysis suggest that actions promoting high survival of adult females should be a management priority, followed by activities that facilitate high reproductive output and neonate survival. We recommend focusing future research and monitoring efforts on these parameters.

ABSTRACT Humans have long provided nest boxes in a widespread and popular effort to augment nesting sites for cavity‐nesting birds. Nest boxes, however, may provide easy access for predators and thereby create ecological traps for nesting birds. Predator exclusion techniques are often deployed at nest boxes to reduce nest predation, but few studies have tested their performance. For the first time, we test the effectiveness of predator guards in promoting the nesting success of multiple species of birds at a large spatial scale (United States and Canada). We used nest fate data from 24,114 nest records submitted from 2014 to 2016 to NestWatch, a citizen‐science program focused on quantifying nesting success, to determine whether installing predator guards on nest boxes is an effective management technique. Across all species, top models predicting daily nest survival rates suggest a positive influence of predator guards, with a nearly 7% increase in nest success for attempts in boxes with guards versus attempts in boxes without guards. At the species level, nest survival was greater for individuals nesting in boxes with guards in 7 of 9 species, with no effect in the remaining 2 species. Although all types of guards were correlated with improved nesting success, birds nesting in boxes with cone‐type baffles, stovepipe baffles, or entrance hole extenders were most likely to result in successful nesting. Further, birds nesting in boxes with multiple predator guards were more successful, on average, than birds nesting in boxes with only a single guard. Our results can help managers of cavity‐nesting birds incorporate science‐based evidence into decision‐making and allocate resources more effectively. © 2017 The Wildlife Society.

Elucidating how life history traits vary geographically is important to understanding variation in population dynamics. Because many aspects of ectotherm life history are climate-dependent, geographic variation in climate is expected to have a large impact on population dynamics through effects on annual survival, body size, growth rate, age at first reproduction, size-fecundity relationship, and reproductive frequency. The Eastern Massasauga (Sistrurus catenatus) is a small, imperiled North American rattlesnake with a distribution centered on the Great Lakes region, where lake effects strongly influence local conditions. To address Eastern Massasauga life history data gaps, we compiled data from 47 study sites representing 38 counties across the range. We used multimodel inference and general linear models with geographic coordinates and annual climate normals as explanatory variables to clarify patterns of variation in life history traits. We found strong evidence for geographic variation in six of nine life history variables. Adult female snout-vent length and neonate mass increased with increasing mean annual precipitation. Litter size decreased with increasing mean temperature, and the size-fecundity relationship and growth prior to first hibernation both increased with increasing latitude. The proportion of gravid females also increased with increasing latitude, but this relationship may be the result of geographically varying detection bias. Our results provide insights into ectotherm life history variation and fill critical data gaps, which will inform Eastern Massasauga conservation efforts by improving biological realism for models of population viability and climate change.

The Dark-eyed Junco (Junco hyemalis) is one of the most abundant birds in North America and exhibits versatility in its selection of nest sites. Although typically ground-nesting birds, juncos also nest occasionally in trees, on buildings, and in natural recesses such as rock crevices. To our knowledge, juncos have never been reported nesting in a fully enclosed nest box specifically provided for songbirds. We report the first record of nest box adoption by Dark-eyed Juncos, supported by photographic evidence. A nest box containing a nest attended by a pair of Dark-eyed Juncos was monitored in 2016 in western Washington, USA, and reported to the Cornell Lab of Ornithology's NestWatch program, a national citizen-science program wherein volunteers submit data on wild nesting birds. The nest in question hatched successfully, and three nestlings fledged from the box. Cavity nesting in New World sparrows appears to be very rare, and we found only four additional observations of juncos utilizing natural cavity nests (i.e., a tree hole). Engaging the public to monitor large numbers of nests is the most likely approach to documenting novel nest sites, and citizen science provides the infrastructure for individuals to share observations.

We report the first record of presumed twinning in eastern bluebird ( Sialia sialis ) and provide a review of previously reported twinning events in wild birds. A nest containing twin eastern bluebird nestlings was monitored in 2013 in central Pennsylvania and reported to the Cornell Lab of Ornithology’s NestWatch program, a national program where volunteers submit data on wild nesting birds. A presumed double-yolked egg of a free-living eastern bluebird pair hatched successfully, and twin nestlings lived for 11 days in a nest box shared by three siblings. Due to the rarity of twinning in wild birds, engaging the public to monitor large numbers of nests is the most likely approach to documenting twinning in wild populations, and citizen science provides the infrastructure for individuals to share observations.

Decisions affecting wildlife management and conservation policy of imperiled species are often aided by population models. Reliable population models require accurate estimates of vital rates and an understanding of how vital rates vary geographically. The eastern massasauga (Sistrurus catenatus catenatus) is a rattlesnake species found in the Great Lakes region of North America. Populations of the eastern massasauga are fragmented and only a few areas harbor multiple, sizable populations. Eastern massasauga research has typically focused on single populations or local metapopulations but results suggest that demographic parameters vary geographically. We used 21 radiotelemetry datasets comprising 499 telemetered snakes from 16 distinct locations throughout the range of the eastern massasauga to characterize geographic patterns of adult survival using the known-fate model in Program MARK. Annual adult survival ranged from 0.35 to 0.95 (mean?=?0.67) and increased along a southwest to northeast geographic axis. Further analysis of 6 datasets indicated no consistent difference in survival between males and females. Our results provide a better understanding of the relationship between survivorship and geography for the eastern massasauga and suggest that such variation should be incorporated into population models as well as local and regional management plans. (c) 2012 The Wildlife Society.

The eastern massasauga rattlesnake (Sistrurus catenatus catenatus) has experienced population declines throughout its range and is now a candidate for federal protection. However, little is known about massasauga habitat selection in Michigan, particularly in actively managed landscapes. Our objectives were to: 1) quantify whether massasaugas in southwestern Michigan select certain vegetation types disproportionately to their availability and 2) quantify whether the vegetation structure associated with snake locations differed between managed (e.g., burning, woody species removal) and unmanaged stands. We implanted radio transmitters in 51 snakes from 2004 to 2005 and 2008 to 2009. We quantified second-order resource selection using compositional analysis, and modeled the effect of habitat management efforts on vegetation using 4 structural variables. All snakes selected cover types disproportionately to their availability (P = 0.001); a ranking matrix ordered the vegetation types, from most to least used, as: early-mid successional deciduous wetland > early-mid successional deciduous upland > developed > late successional mixed lowland forest > late successional deciduous upland forest. We found that snakes in managed areas were associated with greater amounts of dead herbaceous cover (P = 0.005) and less woody stem density (P < 0.001) and tree dominance (P < 0.001) than were snakes in unmanaged areas; however, live herbaceous cover was comparable. Our results can be used by regional managers to provide early and mid successional habitat with structure similar to that selected by snakes in Michigan. © 2011 The Wildlife Society.

The Eastern Massasauga rattlesnake, Sistrurus catenatus catenatus, is a candidate for US federal listing and is legally protected in every state or province in which it occurs. Habitat degradation and human persecution have contributed to range-wide population declines. Survival estimates are essential for a thorough understanding of population dynamics, yet are rarely reported for S. c. catenatus in the peer-reviewed literature. There has been little research on massasauga survival in managed areas of Michigan, USA, the state considered to be the last S. c. catenatus stronghold. Our objectives were to estimate survival of massasaugas during the active season (May October) in southwestern Lower Michigan and describe causes of mortality. We captured (mid-May to late August), radiomarked, and monitored 27 adult massasaugas in 2008 and 2009 and pooled data for analyses. We observed snakes throughout the active season and estimated survival (Mayfield method) for that period (11 May-29 October; 168 d). Cause-specific mortality was investigated qualitatively. Estimated survival probability for the active season was 0.9472 (CI = 0.8518-1.0000), higher than any estimate for similar studies of which we are aware. The single mortality event observed was caused by predation. We suggest that the high massasauga survivorship in this area might be attributable to habitat management for S. c. catenatus combined with a relative lack of infrastructure and human persecution. Our results suggest that adult S. c. catenatus survival is potentially geographically variable and can be high in areas not well-investigated, such as southwestern Lower Michigan. More research would yield long-term survival trends for the studied population as well as throughout their range.