Climatic patterns in the establishment of wintering areas by North American migratory birds

Long-distance migration in birds is relatively well studied in nature; however, one aspect of this phenomenon that remains poorly understood is the pattern of distribution presented by species during arrival to and establishment of wintering areas. Some studies suggest that the selection of areas in winter is somehow determined by climate, given its influence on both the distribution of bird species and their resources. We analyzed whether different migrant passerine species of North America present climatic preferences during arrival to and departure from their wintering areas. We used ecological niche modeling to generate monthly potential climatic distributions for 13 migratory bird species during the winter season by combining the locations recorded per month with four environmental layers. We calculated monthly coefficients of climate variation and then compared two GLM (generalized linear models), evaluated with the AIC (Akaike information criterion), to describe how these coefficients varied over the course of the season, as a measure of the patterns of establishment in the wintering areas. For 11 species, the sites show nonlinear patterns of variation in climatic preferences, with low coefficients of variation at the beginning and end of the season and higher values found in the intermediate months. The remaining two species analyzed showed a different climatic pattern of selective establishment of wintering areas, probably due to taxonomic discrepancy, which would affect their modeled winter distribution. Patterns of establishment of wintering areas in the species showed a climatic preference at the macroscale, suggesting that individuals of several species actively select wintering areas that meet specific climatic conditions. This probably gives them an advantage over the winter and during the return to breeding areas. As these areas become full of migrants, alternative suboptimal sites are occupied. Nonrandom winter area selection may also have consequences for the conservation of migratory bird species, particularly under a scenario of climate change

A long winter for the Red Queen: rethinking the evolution of seasonal migration

This paper advances an hypothesis that the primary adaptive driver of seasonal migration is maintenance of site fidelity to familiar breeding locations. We argue that seasonal migration is therefore principally an adaptation for geographic persistence when confronted with seasonality – analogous to hibernation, freeze tolerance, or other organismal adaptations to cyclically fluctuating environments. These ideas stand in contrast to traditional views that bird migration evolved as an adaptive dispersal strategy for exploiting new breeding areas and avoiding competitors. Our synthesis is supported by a large body of research on avian breeding biology that demonstrates the reproductive benefits of breeding‐site fidelity. Conceptualizing migration as an adaptation for persistence places new emphasis on understanding the evolutionary trade‐offs between migratory behaviour and other adaptations to fluctuating environments both within and across species. Seasonality‐induced departures from breeding areas, coupled with the reproductive benefits of maintaining breeding‐site fidelity, also provide a mechanism for explaining the evolution of migration that is agnostic to the geographic origin of migratory lineages (i.e. temperate or tropical). Thus, our framework reconciles much of the conflict in previous research on the historical biogeography of migratory species. Although migratory behaviour and geographic range change fluidly and rapidly in many populations, we argue that the loss of plasticity for migration via canalization is an overlooked aspect of the evolutionary dynamics of migration and helps explain the idiosyncratic distributions and migratory routes of long‐distance migrants. Our synthesis, which revolves around the insight that migratory organisms travel long distances simply to stay in the same place, provides a necessary evolutionary context for understanding historical biogeographic patterns in migratory lineages as well as the ecological dynamics of migratory connectivity between breeding and non‐breeding locations.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149253/1/brv12476.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149253/2/brv12476_am.pd

Genetic Variation among Temporally and Geographically Distinct West Nile Virus Isolates, United States, 2001, 2002

Analysis of partial nucleotide sequences of 22 West Nile virus (WNV) isolates collected during the summer and fall of 2001 and 2002 indicated genetic variation among strains circulating in geographically distinct regions of the United States and continued divergence from isolates collected in the northeastern United States during 1999 and 2000. Sequence analysis of a 2,004-nucleotide region showed that 14 isolates shared two nucleotide mutations and one amino acid substitution when they were compared with the prototype WN-NY99 strain, with 10 of these isolates sharing an additional nucleotide mutation. In comparison, isolates collected from coastal regions of southeast Texas shared the following differences from WN-NY99: five nucleotide mutations and one amino acid substitution. The maximum nucleotide divergence of the 22 isolates from WN-NY99 was 0.35% (mean = 0.18%). These results show the geographic clustering of genetically similar WNV isolates and the possible emergence of a dominant variant circulating across much of the United States during 2002

Prevalence and Diversity of Avian Hematozoan Parasites in Asia: A Regional Study

Tissue samples from 699 birds from three regions of Asia (Myanmar, India, and South Korea) were screened for evidence of infection by avian parasites in the genera Plasmodium and Haemoproteus. Samples were collected from November 1994 to October 2004. We identified 241 infected birds (34.0%). Base-on-sequence data for the cytochrome b gene from 221 positive samples, 34 distinct lineages of Plasmodium, and 41 of Haemoproteus were detected. Parasite diversity was highest in Myanmar followed by India and South Korea. Parasite prevalence differed among regions but not among host families. There were four lineages of Plasmodium and one of Haemoproteus shared between Myanmar and India and only one lineage of Plasmodium shared between Myanmar and South Korea. No lineages were shared between India and South Korea, although an equal number of distinct lineages were recovered from each region. Migratory birds in South Korea and India originate from two different migratory flyways; therefore cross-transmission of parasite lineages may be less likely. India and Myanmar shared more host species and habitat types compared to South Korea. Comparison between low-elevation habitat in India and Myanmar showed a difference in prevalence of haematozoans

(Micro)evolutionary changes and the evolutionary potential of bird migration

Seasonal migration is the yearly long-distance movement of individuals between their breeding and wintering grounds. Individuals from nearly every animal group exhibit this behavior, but probably the most iconic migration is carried out by birds, from the classic V-shape formation of geese on migration to the amazing nonstop long-distance flights undertaken by Arctic Terns Sterna paradisaea. In this chapter, we discuss how seasonal migration has shaped the field of evolution. First, this behavior is known to turn on and off quite rapidly, but controversy remains concerning where this behavior first evolved geographically and whether the ancestral state was sedentary or migratory (Fig. 7.1d, e). We review recent work using new analytical techniques to provide insight into this topic. Second, it is widely accepted that there is a large genetic basis to this trait, especially in groups like songbirds that migrate alone and at night precluding any opportunity for learning. Key hypotheses on this topic include shared genetic variation used by different populations to migrate and only few genes being involved in its control. We summarize recent work using new techniques for both phenotype and genotype characterization to evaluate and challenge these hypotheses. Finally, one topic that has received less attention is the role these differences in migratory phenotype could play in the process of speciation. Specifically, many populations breed next to one another but take drastically different routes on migration (Fig. 7.2). This difference could play an important role in reducing gene flow between populations, but our inability to track most birds on migration has so far precluded evaluations of this hypothesis. The advent of new tracking techniques means we can track many more birds with increasing accuracy on migration, and this work has provided important insight into migration's role in speciation that we will review here

Introductions of West Nile Virus Strains to Mexico

Complete genome sequencing of 22 West Nile virus isolates suggested 2 independent introductions into Mexico. A previously identified mouse-attenuated glycosylation variant was introduced into southern Mexico through the southeastern United States, while a common US genotype appears to have been introduced incrementally into northern Mexico through the southwestern United States

Collision Mortality Has No Discernible Effect on Population Trends of North American Birds

Avian biodiversity is threatened by numerous anthropogenic factors and migratory species are especially at risk. Migrating birds frequently collide with manmade structures and such losses are believed to represent the majority of anthropogenic mortality for North American birds. However, estimates of total collision mortality range across several orders of magnitude and effects on population dynamics remain unknown. Herein, we develop a novel method to assess relative vulnerability to anthropogenic threats, which we demonstrate using 243,103 collision records from 188 species of eastern North American landbirds. After correcting mortality estimates for variation attributable to population size and geographic overlap with potential collision structures, we found that per capita vulnerability to collision with buildings and towers varied over more than four orders of magnitude among species. Species that migrate long distances or at night were much more likely to be killed by collisions than year-round residents or diurnal migrants. However, there was no correlation between relative collision mortality and long-term population trends for these same species. Thus, although millions of North American birds are killed annually by collisions with manmade structures, this source of mortality has no discernible effect on populations

First serological evidence of West Nile virus in human rural populations of Gabon

To investigate West Nile virus (WNV) circulation in rural populations in Gabon, we undertook a large serological survey focusing on human rural populations, using two different ELISA assays. A sample was considered positive when it reacted in both tests. A total of 2320 villagers from 115 villages were interviewed and sampled. Surprisingly, the WNV-specific IgG prevalence was high overall (27.2%) and varied according to the ecosystem: 23.7% in forested regions, 21.8% in savanna, and 64.9% in the lakes region. The WNV-specific IgG prevalence rate was 30% in males and 24.6% in females, and increased with age. Although serological cross-reactions between flaviviruses are likely and may be frequent, these findings strongly suggest that WNV is widespread in Gabon. The difference in WNV prevalence among ecosystems suggests preferential circulation in the lakes region. The linear increase with age suggests continuous exposure of Gabonese populations to WNV. Further investigations are needed to determine the WNV cycle and transmission patterns in Gabon

Optimal Conservation of Migratory Species

Background. Migratory animals comprise a significant portion of biodiversity worldwide with annual investment for their conservation exceeding several billion dollars. Designing effective conservation plans presents enormous challenges. Migratory species are influenced by multiple events across land and sea-regions that are often separated by thousands of kilometres and span international borders. To date, conservation strategies for migratory species fail to take into account how migratory animals are spatially connected between different periods of the annual cycle (i.e. migratory connectivity) bringing into question the utility and efficiency of current conservation efforts. Methodology/Principal Findings. Here, we report the first framework for determining an optimal conservation strategy for a migratory species. Employing a decision theoretic approach using dynamic optimization, we address the problem of how to allocate resources for habitat conservation for a Neotropical-Nearctic migratory bird, the American redstart Setophaga ruticilla, whose winter habitat is under threat. Our first conservation strategy used the acquisition of winter habitat based on land cost, relative bird density, and the rate of habitat loss to maximize the abundance of birds on the wintering grounds. Our second strategy maximized bird abundance across the entire range of the species by adding the constraint of maintaining a minimum percentage of birds within each breeding region in North America using information on migratory connectivity as estimated from stable-hydrogen isotopes in feathers. We show that failure to take into account migratory connectivity may doom some regional populations to extinction, whereas including information on migratory connectivity results in the protection of the species across its entire range. Conclusions/Significance. We demonstrate that conservation strategies for migratory animals depend critically upon two factors: knowledge of migratory connectivity and the correct statement of the conservation problem. Our framework can be used to identify efficient conservation strategies for migratory taxa worldwide, including insects, birds, mammals, and marine organisms

Conservation of Forest Birds: Evidence of a Shifting Baseline in Community Structure

Quantifying changes in forest bird diversity is an essential task for developing effective conservation actions. When subtle changes in diversity accumulate over time, annual comparisons may offer an incomplete perspective of changes in diversity. In this case, progressive change, the comparison of changes in diversity from a baseline condition, may offer greater insight because changes in diversity are assessed over longer periods of times. Our objectives were to determine how forest bird diversity has changed over time and whether those changes were associated with forest disturbance.We used North American Breeding Bird Survey data, a time series of Landsat images classified with respect to land cover change, and mixed-effects models to associate changes in forest bird community structure with forest disturbance, latitude, and longitude in the conterminous United States for the years 1985 to 2006. We document a significant divergence from the baseline structure for all birds of similar migratory habit and nest location, and all forest birds as a group from 1985 to 2006. Unexpectedly, decreases in progressive similarity resulted from small changes in richness (<1 species per route for the 22-year study period) and modest losses in abundance (-28.7 - -10.2 individuals per route) that varied by migratory habit and nest location. Forest disturbance increased progressive similarity for Neotropical migrants, permanent residents, ground nesting, and cavity nesting species. We also documented highest progressive similarity in the eastern United States.Contemporary forest bird community structure is changing rapidly over a relatively short period of time (e.g., approximately 22 years). Forest disturbance and forest regeneration are primary factors associated with contemporary forest bird community structure, longitude and latitude are secondary factors, and forest loss is a tertiary factor. Importantly, these findings suggest some regions of the United States may already fall below the habitat amount threshold where fragmentation effects become important predictors of forest bird community structure