Observed declines in body size have differential effects on survival and recruitment, but no effect on population growth in tropical birds.

Declines in body size can be an advantageous physiological response to warming temperatures, or a result of physiological and nutritional stress. Either way, studies often assume that these climate-induced trait changes have important implications for fitness and demography. We leveraged almost three decades of capture-mark-recapture data of 51 bird species in Panama to examine if body size has changed through time, how sensitive body size is to changes in weather, and if body size impacts population demography.

Embryonic heart rate is higher in species that experience greater nest predation risk during incubation.

Avian eggs develop outside of the female body, and therefore embryonic development is subject to multiple internal (physiological) and external (ecological) factors. Embryonic developmental rate has important consequences for survival. Within species, embryos that develop too quickly often experience deformities, disorders, or mortality, while embryos that develop slowly risk inviability and increase the time they are exposed to various sources of mortality in the nest.

Dynamic, multi-scale analyses indicate site- and landscape-level forest cover drive Yellow-billed and Black-billed Cuckoo interannual turnover.

Studies of habitat use in breeding birds often assume species have relatively stable breeding distributions. Some species, however, display considerable year-to-year variability, complicating efforts to determine suitable or preferred habitats. After returning to their breeding range, Black-billed Cuckoos () and Yellow-billed Cuckoos () are thought to range widely before nesting, resulting in high rates of interannual breeding-site turnover, potentially contributing to conflicting habitat associations found in past studies.

Water depth influences survival and predator-specific patterns of nest loss in three secretive marsh bird species.

Wetlands have become increasingly rare in the United States, negatively influencing wetland-dependent birds, and many remaining wetlands are intensively managed through seasonal dewatering mimicking historic flood pulses during spring and summer. However, water around nests may provide protection from terrestrial predators, and lowering water levels during the breeding season of wetland birds may increase predation risk and exacerbate marsh bird population declines. Understanding interactions between water depth, nesting marsh birds, and nest predators is critical to aid managers in developing a multi-species management approach in emergent wetlands.

Extensive regional variation in the phenology of insects and their response to temperature across North America.

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.

Host community-wide patterns of post-fledging behavior and survival of obligate brood parasitic brown-headed cowbirds.

The antagonistic arms races between obligate brood parasites and their hosts provide critical insights into coevolutionary processes and constraints on the evolution of life history strategies. In avian brood parasites-a model system for examining host-parasite dynamics-research has primarily focused on the egg and nestling stage, while far less is known about the behavior and ecology of fledgling and juvenile brood parasites. To provide greater insights into the post-fledging period of generalist brood parasites, we used handheld and automated telemetry systems to examine the behavior and survival of fledgling brown-headed cowbirds (Molothrus ater).

Long-term monitoring reveals widespread and severe declines of understory birds in a protected Neotropical forest.

Long-term studies on the population dynamics of tropical resident birds are few, and it remains poorly understood how their populations have fared in recent decades. Here, we analyzed a 44-y population study of a Neotropical understory bird assemblage from a protected forest reserve in central Panama to determine if and how populations have changed from 1977 to 2020. Using the number of birds captured in mist nets as an index of local abundance, we estimated trends over time for a diverse suite of 57 resident species that comprised a broad range of ecological and behavioral traits.

Ground nesting by arboreal American robins ().

Animals with dependent and vulnerable young need to decide where to raise their offspring to minimize ill effects of weather, competition, parasitism, and predation. These decisions have critical fitness consequences through impacting the survival of both adults and progeny. Birds routinely place their nest in specific sites, allowing species to be broadly classified based on nest location (e.

Referential alarm calling elicits future vigilance in a host of an avian brood parasite.

Yellow warblers () use referential 'seet' calls to warn mates of brood parasitic brown-headed cowbirds (). In response to seet calls during the day, female warblers swiftly move to sit tightly on their nests, which may prevent parasitism by physically blocking female cowbirds from inspecting and laying in the nest. However, cowbirds lay their eggs just prior to sunrise, not during daytime.

Egg Incubation Temperature Affects Development of Innate Immune Function in Nestling American Robins ().

The innate immune system provides important first-line defenses against invading pathogens and is considered especially important for developing organisms. However, we know little about how early-life conditions influence these defenses in wild animals. For oviparous species such as birds, embryonic development occurs in the egg, which can be subject to variation in thermal conditions.

Avian fitness consequences match habitat selection at the nest-site and landscape scale in agriculturally fragmented landscapes.

Habitat selection theory suggests that when choosing breeding sites, animals should choose the best available habitat; however, studies show that individuals fail to choose habitats that maximize their fitness especially in drastically altered landscapes. Many studies have focused on selection at single scales, often using a single measure of fitness. However, links between habitat selection and fitness may vary depending on the spatial scale and measure of fitness, especially in situations where agricultural land use has altered the surrounding landscape.

Mimicry-dependent lateralization in the visual inspection of foreign eggs by American robins.

Brain lateralization, or the specialization of function in the left versus right brain hemispheres, has been found in a variety of lineages in contexts ranging from foraging to social and sexual behaviours, including the recognition of conspecific social partners. Here we studied whether the recognition and rejection of avian brood parasitic eggs, another context for species recognition, may also involve lateralized visual processing. We focused on American robins (Turdus migratorius), an egg-rejecter host to occasional brood parasitism by brown-headed cowbirds (Molothrus ater) and tested if robins preferentially used one visual hemifield over the other to inspect mimetic versus non-mimetic model eggs.

Estimating apparent survival of songbirds crossing the Gulf of Mexico during autumn migration.

Many migratory bird species are declining, and the migratory period may limit populations because of the risk in traversing large geographical features during passage. Using automated radio-telemetry, we tracked 139 Swainson's thrushes () departing coastal Alabama, USA and crossing the Gulf of Mexico to arrive in the Yucatan Peninsula, Mexico during autumn. We estimated apparent survival and examined how extrinsic (weather variables and day of year) and intrinsic (fat load, sex and age) factors influenced survival using a mark-recapture approach.

Incubation temperature impacts nestling growth and survival in an open-cup nesting passerine.

For oviparous species such as birds, conditions experienced while in the egg can have long-lasting effects on the individual. The impact of subtle changes in incubation temperature on nestling development, however, remains poorly understood, especially for open-cup nesting species with altricial young. To investigate how incubation temperature affects nestling development and survival in such species, we artificially incubated American robin () eggs at 36.

Correction: Does flooding effect the apparent survival and body condition of a ground foraging migrant passerine?

[This corrects the article DOI: 10.1371/journal.pone.

Rates of parasitism, but not allocation of egg resources, vary among and within hosts of a generalist avian brood parasite.

Brown-headed cowbirds (Molothrus ater) deposit their eggs into the nests of other birds, which then raise the cowbird chick. Female cowbirds thus have limited options for impacting their offspring's development via maternal effects compared to most other passerines. Cowbirds can impact their offspring's phenotype by choosing among potential host nests, and by adjusting egg resources based on host characteristics.

Does flooding effect the apparent survival and body condition of a ground foraging migrant passerine?

Natural disturbances play a fundamental role in maintaining habitat and landscape heterogeneity; however, these events can also have negative effects on some species. While we know that disturbances can reduce habitat quality for many species, leading to diminished populations and altered community structure, the effect of these events on individuals that continue to occupy affected areas remains unknown. We focused on understanding the impact of flood-mediated reduction of habitat quality on Swainson's Warblers (Limnothlypis swainsonii).

Fat, weather, and date affect migratory songbirds' departure decisions, routes, and time it takes to cross the Gulf of Mexico.

Approximately two thirds of migratory songbirds in eastern North America negotiate the Gulf of Mexico (GOM), where inclement weather coupled with no refueling or resting opportunities can be lethal. However, decisions made when navigating such features and their consequences remain largely unknown due to technological limitations of tracking small animals over large areas. We used automated radio telemetry to track three songbird species (Red-eyed Vireo, Swainson's Thrush, Wood Thrush) from coastal Alabama to the northern Yucatan Peninsula (YP) during fall migration.

Patch size and edge proximity are useful predictors of brood parasitism but not nest survival of grassland birds.

Declines of migratory birds have led to increased focus on causative factors for these declines, including the potential adverse effects of habitat fragmentation on reproductive success. Although numerous studies have addressed how proximity to a habitat edge, patch size, or landscape context influence nest survival or brood parasitism, many have failed to find the purported effects. Furthermore, many have sought to generalize patterns across large geographic areas and habitats.

Juvenile survival in a neotropical migratory songbird is lower than expected.

Attempts to estimate and identify factors influencing first-year survival in passerines, survival between fledging and the first reproductive attempt (i.e. juvenile survival), have largely been confounded by natal dispersal, particularly in long-distance migratory passerines.

Implications of spatial patterns of roosting and movements of American robins for West Nile virus transmission.

The arrival of West Nile virus (WNV) in North America has led to interest in the interaction between birds, the amplification hosts of WNV, and Culex mosquitoes, the primary WNV vectors. American robins (Turdus migratorius) are particularly important amplification hosts of WNV, and because the vector Culex mosquitoes are primarily nocturnal and feed on roosting birds, robin communal roosting behavior may play an important role in the transmission ecology of WNV. Using data from 43 radio-tracked individuals, we determined spatial and temporal patterns of robin roosting behavior, and how these patterns related to the distribution of WNV-infected mosquitoes.

Identifying predators clarifies predictors of nest success in a temperate passerine.

1. Nest predation negatively affects most avian populations. Studies of nest predation usually group all nest failures when attempting to determine temporal and parental activities, habitat or landscape predictors of success.