Extreme cold events, which have become more frequent, can revert the direction of long-term responses to climate change. In 2021, record snowstorms swept the United States, causing wildlife die-offs that may have been associated with rapid natural selection. Our objective was to determine whether the snowstorms caused natural selection in Eastern Bluebirds (Sialia sialis). To test which mechanism most influenced their survival, we measured the morphology and coloration of fatalities and survivors at three sites. Survival was associated with a longer tarsus and with a wider, longer, and deeper beak, in support of the starvation and thermal endurance hypotheses. Additionally, bluebirds with more-ornamented plumage were less likely to have survived, perhaps because of an early energy investment in mate and site acquisition. As bluebirds encounter increasingly warm summer conditions, the longer extremities favored during the snowstorms may continue to be favored through their thermoregulatory benefits. However, the dull plumage coloration favored by natural selection during the snowstorms may be opposed by sexual selection benefits of more-ornamented plumage. Overall, responses to extreme events are difficult to predict from responses to long-term climate change, and responses to one event, such as the 2021 snowstorms, may not predict responses to a future extreme event.

Avian plumage coloration could be altered by external factors like dust accumulation, but the effect of environmental conditions on such post-moult colour changes are poorly studied. Here, we investigated how exposure to the atmosphere in habitats of differing anthropogenic pressures modifies UV/blue structural plumage coloration — a sexually selected trait in eastern bluebirds Sialia sialis . We collected feather samples from live birds and distributed them in three types of habitats: (i) urban roads with low traffic, (ii) urban roads with high traffic, and (iii) rural roads with low traffic. After 4 weeks, the brightness of feathers decreased in all types of habitats-resulting in less-ornamented coloration. Changes in UV and blue chroma, however, varied with habitat type; chroma decreased in urban areas (becoming less ornamented), but increased in rural locations (becoming more ornamented). According to physiological models of avian colour vision, however, these changes in coloration tended to be below perceptual thresholds. Our results underscore the importance of how human activity can influence plumage colour of individual birds during the period between moult cycles which could have an impact on avian visual signalling. The study opens venues for further studies focusing on how the optical properties of specific airborne particles can influence coloration of wild-living animals. Significance statement Plumage coloration plays an important role in avian visual communication. In addition to moult-based change, coloration may change between moult cycles due to exposure to external factors like, for example, dust accumulation. Ecological factors modifying a passive plumage change, however, remains poorly studied. We collected samples of structurally coloured feather from a species wherein plumage colour is sexually selected and exposed them to outdoor conditions. We demonstrate that UV/blue chroma of coloration changes differently in urban and rural habitats. It increased in rural and decreased in urban areas. On the other hand, brightness decreased in both habitat types. Using physiological models of avian colour vision, however, we found that these colour changes were likely not perceptible to birds. Our study provides the first evidence that changes in coloration of fully grown feathers may be habitat dependent.

Amphibians are renowned for the variation in the colour and patterns of their integument, both within and between species. Some amphibian taxa are well known for using conspicuous coloration to signal their unpalatability to potential predators. Amphibian integument secretions contain biologically active compounds that are the source of un-palatability. Although the selective advantages are poorly understood, salamanders are often brightly coloured and secrete mucous-like substances that may serve physiological and defensive functions. In the southern Appalachians, two closely related species, the Yonahlossee salamander (Plethodon yonahlossee) and Northern grey-cheeked salamander (P. monta-nus), display vastly different coloration; yet, the signaling function of integument coloration is not well studied. While P. yonahlossee has a large red dorsal patch, P. montanus is uniformly grey which might indicate that there is a selective benefit of this dorsal patch. Here, we test the hypothesis that the red coloration of P. yonahlossee is an aposematic signal that communicates unpalatability to potential predators and predict that avian predators will avoid depredating this spe-cies. We used plasticine models of both species to experimentally test whether predators depredate conspicuously coloured models less frequently than dull models. Avian predation rates on grey models were significantly higher compared to that of red models, suggesting that the red dorsal coloration of P. yonahlossee is interpreted as a warning signal that deters predation. Future research should address whether P. yonahlossee is unpalatable or is effectively mimicking a sympatric aposematic species.

Ecogeographic rules describe spatial patterns in biological trait variation and shed light on the drivers of such variation. In animals, a consensus is emerging that 'pioneering' traits may facilitate range shifts via a set of bold, aggressive and stress-resilient traits. Many of these same traits are associated with more northern latitudes, and most range shifts in the northern hemisphere indicate northward movement. As a consequence, it is unclear whether pioneering traits are simply corollaries of existing latitudinal variation, or whether they override other well-trodden latitudinal patterning as a unique ecogeographic rule of phenotypic variation. The tree swallow Tachycineta bicolor is a songbird undergoing a southward range shift in the eastern United States, in direct opposition of the poleward movement seen in most other native species' range shifts. Because this organic range shift countervails the typical direction of movement, this case study provides for unique ecological insights on organisms and their ability to thrive in our changing world. We sampled female birds across seven populations, quantifying behavioural, physiological and morphological traits. We also used GIS and field data to quantify a core set of ecological factors with strong ties to these traits as well as female performance. Females at more southern expansion sites displayed higher maternal aggression, higher baseline corticosterone and more pronounced elevation of corticosterone following a standardized stressor, contrary to otherwise largely conserved latitudinal patterning in these traits. Microhabitat variation explained some quantitative phenotypic variation, but the expansion and historic ranges did not differ in openness, distance to water or breeding density. This countervailing range shift therefore suggests that pioneering traits are not simply corollaries of existing latitudinal variation, but rather, they may override other well-trodden latitudinal patterning as a unique ecogeographic rule of phenotypic variation.

Climate change models often assume similar responses to temperatures across the range of a species, but local adaptation or phenotypic plasticity can lead plants and animals to respond differently to temperature in different parts of their range. To date, there have been few tests of this assumption at the scale of continents, so it is unclear if this is a large-scale problem. Here, we examined the assumption that insect taxa show similar responses to temperature at 96 sites in grassy habitats across North America. We sampled insects with Malaise traps during 2019-2021 (N = 1041 samples) and examined the biomass of insects in relation to temperature and time of season. Our samples mostly contained Diptera (33%), Lepidoptera (19%), Hymenoptera (18%), and Coleoptera (10%). We found strong regional differences in the phenology of insects and their response to temperature, even within the same taxonomic group, habitat type, and time of season. For example, the biomass of nematoceran flies increased across the season in the central part of the continent, but it only showed a small increase in the Northeast and a seasonal decline in the Southeast and West. At a smaller scale, insect biomass at different traps operating on the same days was correlated up to ~75 km apart. Large-scale geographic and phenological variation in insect biomass and abundance has not been studied well, and it is a major source of controversy in previous analyses of insect declines that have aggregated studies from different locations and time periods. Our study illustrates that large-scale predictions about changes in insect populations, and their causes, will need to incorporate regional and taxonomic differences in the response to temperature.

Cooperation between parents in species with biparental care can reduce sexual conflict and increase reproductive success. If parents cooperate in a conditional way - that is, alternate feeding visits to offspring - this should equalize parental investment and may improve nestling growth. Environmental variation, including competition for limited resources, may influence the need for, and benefits of, parental cooperation. We measured the benefits of partner coordination in offspring provisioning behavior among eastern bluebird partners (Sialia sialis) in which the strength of interspecific density varied spatially. Tree swallows (Tachycineta bicolor) are a recent (<40 years) arrival in our study area, are aggressive nestbox competitors with eastern bluebirds, and their density varies across the field site. Nesting among higher densities of tree swallows led to reduced parental feeding rates and reproductive success of bluebirds. Partner alternation, however, did not vary with tree swallow density. Additionally, alternation level and provisioning rate only influenced nestling growth in areas of high swallow density. It may be that the benefits of parental coordination may only be apparent when environmental conditions are poor. This study provides an important new perspective on the resolution of negotiations between breeding partners; environmental variation could influence the benefits of parental cooperation in a wide variety of animals.

Latitudinal differences in timing of breeding are well documented but how such differences carry over to influence timing of events in the annual cycle of migratory birds is not well understood. We examined geographical variation in timing of events throughout the year using light-level geolocator tracking data from 133 migratory tree swallows ( Tachycineta bicolor) originating from 12 North American breeding populations. A swallow's breeding latitude influenced timing of breeding, which then carried over to affect breeding ground departure. This resulted in subsequent effects on the arrival and departure schedules at autumn stopover locations and timing of arrival at non-breeding locations. This 'domino effect' between timing events was no longer apparent by the time individuals departed for spring migration. Our range-wide analysis demonstrates the lasting impact breeding latitude can have on migration schedules but also highlights how such timing relationships can reset when individuals reside at non-breeding sites for extended periods of time.

AbstractThere have been an increasing number of observations of itinerancy in migratory songbirds, where individuals move among 2 or more widely separated areas during the “stationary” nonbreeding season. Knowledge of such movements and an understanding of what drives them are important for predicting how migratory populations will respond to environmental change. In this study, we investigated nonbreeding movements of the Tree Swallow (Tachycineta bicolor), an aerial insectivore that breeds across North America and spends the nonbreeding season around the Gulf of Mexico, Florida, Mexico, Central America, and the Caribbean. With year-round tracking data obtained from 133 light-level geolocators deployed at 12 breeding sites ranging from Alaska to Nova Scotia to North Carolina, we show that 44% of individuals made at least one large-scale movement (range: 301–1,744 km) within the nonbreeding range. The frequency of itinerancy decreased with longitude, such that 75% of individuals made a movement in the western portion of the nonbreeding range compared to only 31% in the east. Using the Normalized Difference Vegetation Index (NDVI) as a proxy for resource availability, we found that when individuals did move, they were more likely to move from sites where resources were deteriorating faster (a more negative change in NDVI prior to departure) than their destination sites. There was also evidence that individuals moved to destination sites with higher NDVI and temperature in the autumn, but not in the winter. Our results suggest movements of Tree Swallows during the nonbreeding season are influenced by resource availability, but because not all individuals used multiple nonbreeding sites, the density of individuals at a site and the level of competition may have also been a factor influencing nonbreeding season movements.

During migration, animals may experience high rates of mortality, but costs of migration could also be manifested through non-lethal carry-over effects that influence individual success in subsequent periods of the annual cycle. Using tracking data collected from light-level geolocators, we estimated total spring migration distance (from the last wintering sites to breeding sites) of tree swallows (Tachycineta bicolor) within three major North American flyways. Using path analysis, we then assessed direct and indirect effects of spring migration distance on reproductive performance of individuals of both sexes. When these data were standardized by flyway, females fledged 1.3 fewer young for every 1,017 km they traveled, whereas there was no effect of migration distance on reproductive success in males. In comparison, when these data were standardized across all individuals and not by flyway, longermigrations were associated with 0.74more young fledged for every 1,017 km traveled by females and 0.26 more young fledged for every 1,186 km migrated by males. Our results suggest that migration distance carries over to negatively influence female reproductive success within flyways but the overall positive effect of migration distance across flyways likely reflects broader life-history differences that occur among breeding populations across the tree swallow range.

ABSTRACT Although plumage displays often reliably signal individual condition and age, how these sexually selected traits vary with geographic region is not well understood. Golden-winged Warbler (Vermivora chrysoptera) populations are fragmented and declining precipitously in the Appalachian Mountains. Limited research suggests that Golden-winged Warbler facial plumage ornaments may be under sexual selection; black throat (melanin-based) coloration is associated with mate acquisition while yellow crown (carotenoid-based) coloration is associated with aggression and habitat quality. We tested whether multiple plumage traits (crown, throat, and tail coloration) (1) varied across the Appalachian breeding range, (2) varied with age class or body condition, and (3) covaried with each other and whether the covariance differed with geographic region. We found that crown and throat coloration followed a latitudinal gradient, with the more southern birds showing lower ornamentation. Moreover, after-second-year birds had tails with a greater extent of white than second-year, suggesting tail color may reliably signal age that conspecifics could assess. Males with more-ornamented crown color had more-ornamented throat coloration, suggesting that this species demonstrates some potential for both redundant (facial coloration) and independent (tail white) signaling. We found no evidence, however, that covariation between traits differed across the breeding range or that the plumage traits varied with body condition. Additional research investigating the signaling function of multiple plumage ornaments in Golden-winged Warblers across their breeding range could shed light on habitat preferences and communication. Received 28 October 2016. Accepted 4 January 2018.

. Determining how migratory animals are spatially connected between breeding and non- breeding periods is essential for predicting the effects of environmental change and for developing optimal conservation strategies. Yet, despite recent advances in tracking technology, we lack compre- hensive information on the spatial structure of migratory networks across a species ’ range, particularly for small-bodied, long-distance migratory animals. We constructed a migratory network for a song- bird and used network-based metrics to characterize the spatial structure and prioritize regions for conservation. The network was constructed using year-round movements derived from 133 archival light-level geolocators attached to Tree Swallows ( Tachycineta bicolor ) originating from 12 breeding sites across their North American breeding range. From these breeding sites, we identified 10 autumn stopover nodes (regions) in North America, 13 non-breeding nodes located around the Gulf of Mexico, Mexico, Florida, and the Caribbean, and 136 unique edges (migratory routes) connecting nodes. We found strong migratory connectivity between breeding and autumn stopover sites and moderate migratory connectivity between the breeding and non-breeding sites. We identified three dis- tinct “ communities ” of nodes that corresponded to western, central, and eastern North American flyways. Several regions were important for maintaining network connectivity, with South Florida and Louisiana as the top ranked non-breeding nodes and the Midwest as the top ranked stopover node. We show that migratory songbird networks can have both a high degree of mixing between seasons yet still show regionally distinct migratory flyways. Such information will be crucial for accurately predicting factors that limit and regulate migratory songbirds throughout the annual cycle. Our study highlights how network-based metrics can be valuable for identifying overall network structure and prioritizing specific regions within a network for conserving a wide variety of migratory animals.

Conspicuous coloration coupled with secondary defensive mechanisms is known as aposematic coloration and is used in predator avoidance and defense. Classic theory argues that aposematic signals tend to be more effective in larger organisms as they are intrinsically more easily detected by predators and are also more profitable prey items. Thus, it has been hypothesized that conspicuous coloration evolves in tandem with increased body size in aposematic prey because this likely increases the visibility and efficacy of the signal. To test this hypothesis, we used a comparative phylogenetic approach to investigate associations between body size and conspicuous coloration in two North American salamander genera: Ambystoma and Plethodon, both of which secrete noxious compounds to deter predators. Our analyses showed that increased conspicuous coloration co-evolved with increased body size in Ambystoma, yet we found the opposite relationship in the Plethodon clade. We speculate this is likely because Ambystoma are generally larger than Plethodon and exhibit gregarious mating behavior. Future studies should explore the toxicity of slimy skin secretions and how this may contribute to aposematic signaling in salamanders.

Effective habitat and species monitoring programs require robust and repeatable estimates derived from standardized protocols. Hellbenders (Cryptobranchus alleganiensis) are large, long-lived salamanders endemic to highland streams in central and eastern North America. Based on historical data, it is apparent that Hellbender populations are undergoing significant, wide-spread declines; however, the ability of researchers to detect declines is limited because there has been little effort to standardize surveys and virtually no quantitative habitat data are collected during surveys. Here, we assess the efficacy of a spatially constrained transect-based method to capture Hellbenders and describe habitat conditions among years. We compared results to conventional snorkel/rock-turning surveys and tested the consistency of habitat parameters using intra-class correlations. Although the differences were not statistically significant, spatially constrained surveys captured 25% more animals and produced relative abundance estimates that were 107% higher than unstandardized surveys. By constraining surveys and carefully recording effort, we ensured technicians would search study reaches more effectively and find Hellbenders in habitats that may have been overlooked by unconstrained surveys. Intra-class correlations demonstrated that some physical habitat conditions remained consistent between years whereas others were much more variable reflecting the year-to-year variability inherent to stream ecosystems. By constraining Hellbender surveys in time and space, researchers can provide more informative estimates of abundance and habitat suitability that will improve the ability of monitoring programs to detect changes in the range and population sizes of these large but cryptic aquatic salamanders.

For at-risk wildlife species, it is important to consider conservation within the process of adaptive management. Golden-winged Warblers (Vermivora chrysoptera) are Neotropical migratory songbirds that are experiencing long-term population declines due in part to the loss of early-successional nesting habitat. Recently-developed Golden-winged Warbler habitat management guidelines are being implemented by USDA: Natural Resource Conservation Service (2014) and its partners through the Working Lands For Wildlife (WLFW) program. During 2012–2014, we studied the nesting ecology of Golden-winged Warblers in managed habitats of the eastern US that conformed to WLFW conservation practices. We evaluated five NRCS “management scenarios” with respect to nesting success and attainment of recommended nest site vegetation conditions outlined in the Golden-winged Warbler breeding habitat guidelines. Using estimates of territory density, pairing rate, nest survival, and clutch size, we also estimated fledgling productivity (number of fledglings/ha) for each management scenario. In general, Golden-winged Warbler nest survival declined as each breeding season advanced, but nest survival was similar across management scenarios. Within each management scenario, vegetation variables had little influence on nest survival. Still, percent Rubus cover and density of >2 m tall shrubs were relevant in some management scenarios. All five management scenarios rarely attained recommended levels of nest site vegetation conditions for Golden-winged, yet nest survival was high. Fledgling productivity estimates for each management scenario ranged from 2.1 to 8.6 fledglings/10 hectares. Our results indicate that targeted habitat management for Golden-winged Warblers using a variety of management techniques on private lands has the capability to yield high nest survival and fledgling productivity, and thus have the potential to contribute to the species recovery.

Avian plumage represents some of the greatest diversity in integument coloration of all animals. Plumage signals are diverse in function, including those that allow for assessing potential mates or the mitigation of agonistic interactions between rivals. Many bird species possess multiple ornamental traits that have the potential to serve as multiple or redundant signals. For example, male golden-winged warblers (Vermivora chrysoptera) have brilliant carotenoid-based yellow crowns, melanin-based black throats, and structurally based white patches on their outer tail feathers. Using a correlative approach, we investigated whether plumage ornaments have the potential to reliably signal ability to acquire higher quality territory, aggressive response to simulated territorial intrusions, and reproductive success. We found that both crown chroma and tail brightness were significantly related to habitat quality and aggression; more ornamented birds held territories with higher quality habitat and were less aggressive toward simulated conspecific stimuli. Older birds sang less threatening songs than younger birds and were more likely to sing their mate attraction song type (type 1) rather than songs typically reserved for agonistic interactions (type 2). Finally, despite our previous research demonstrating that habitat strongly predicts reproductive success in this warbler population, we found no evidence of a direct link between ornamentation and reproductive success. Overall, these data suggest that younger males, and those with lower quality ornaments, compensate with more aggressive behaviors. Additional research is needed to investigate the dynamics between behavioral traits and ornaments to better understand complex signaling and how golden wing signals function in conspecific interactions (male–male interactions and mate-choice).

Aggressive interference competition for limited resources is frequently observed among animals. However, these behavioral interactions within (intraspecific) and between (interspecific) species are costly as they can be energetically expensive and cause injury or death. To avoid these agonistic interactions, numerous species alter their behaviors and resource requirements. Spatial variation in nest site competition allows for investigation of concurrent variation in territorial defense behavior. Further, among species with bi-parental nest defense, behavioral similarity in territorial defense may benefit pairs. Here, we studied territorial aggression between two eastern bluebird (Sialia sialis) populations (North Carolina and Alabama, USA) that differ in avian community structure; those in North Carolina have recently begun to experience strong interspecific competition for nesting cavities by tree swallows (Tachycineta bicolor), a competitive pressure that is relatively new for North Carolina bluebirds (~35-40 years) and is absent in Alabama populations. We found that bluebirds in North Carolina are more aggressive to simulated territorial intrusions compared to their Alabama counterparts. Behavioral similarity (here, in aggression) between partners is strong and similar in both populations. These results suggest that bluebirds in North Carolina may have to maintain higher baseline aggression during territory establishment and nest construction to co-occur with highly aggressive tree swallows, but that, in both populations, behavioral similarity between partners may be adaptive. Finally, we acknowledge the preliminary nature of this study and the need for expanding the behavioral studies to other sites in the southeastern United States. Greater regional coverage would exclude the possibility of alternative drivers of the observed behavioral differences between the North Carolina and Alabama populations.

Anthropogenic landscapes negatively impact stream habitats by altering hydrologic, sediment, and nutrient cycling regimes, thereby reducing or displacing populations of sensitive biota. The hellbender (Cryptobranchus alleganiensis) is an imperiled salamander endemic to eastern and central North American streams. Although once widespread, hellbender distributions have contracted and populations have declined in the past several decades. Hellbenders are considered indicators of stream quality; however, few studies have empirically linked hellbender presence to stream habitat or water-quality. We examined the ability of catchment-scale land-use and local physical and chemical habitat parameters to predict hellbender occurrence in an Appalachian headwater river drainage. Generalized linear models revealed that water-quality, local habitat, and catchment land-use are informative predictors of hellbender site occupancy. Because broad-scale land-use changes likely affect hellbender populations at multiple levels, management and conservation should focus on protecting streams at the catchment scale. In this system, ex-urban development appears to be the primary threat to hellbenders. However, threats to hellbender populations may be mitigated by management regulations targeting economically important outdoor recreational activities including trout fishing as well as existing streamside development guidelines.