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Global migrations of diverse animal species often converge along the same routes, bringing together seasonal assemblages of animals that may compete, prey on each other, and share information or pathogens. These interspecific interactions, when energetic demands are high and the time to complete journeys is short, may influence survival, migratory success, stopover ecology, and migratory routes. Numerous accounts suggest that interspecific co-migrations are globally distributed in aerial, aquatic, and terrestrial systems, although the study of migration to date has rarely investigated species interactions among migrating animals. Here, we test the hypothesis that migrating animals are communities engaged in networks of ecological interactions. We leverage over half a million records of 50 bird species from five bird banding sites collected over 8 to 23 y to test for species associations using social network analyses. We find strong support for persistent species relationships across sites and between spring and fall migration. These relationships may be ecologically meaningful: They are often stronger among phylogenetically related species with similar foraging behaviors and nonbreeding ranges even after accounting for the nonsocial contributions to associations, including overlap in migration timing and habitat use. While interspecific interactions could result in costly competition or beneficial information exchange, we find that relationships are largely positive, suggesting limited competitive exclusion at the scale of a banding station during migratory stopovers. Our findings support an understanding of animal migrations that consist of networked communities rather than random assemblages of independently migrating species, encouraging future studies of the nature and consequences of co-migrant interactions. [ABSTRACT FROM AUTHOR]

As the climate changes, global systems have become increasingly unstable and unpredictable. This is particularly true for many disease systems, including subtypes of highly pathogenic avian influenzas (HPAIs) that are circulating the world. Ecological patterns once thought stable are changing, bringing new populations and organisms into contact with one another. Wild birds continue to be hosts and reservoirs for numerous zoonotic pathogens, and strains of HPAI and other pathogens have been introduced into new regions via migrating birds and transboundary trade of wild birds. With these expanding environmental changes, it is even more crucial that regions or counties that previously did not have surveillance programs develop the appropriate skills to sample wild birds and add to the understanding of pathogens in migratory and breeding birds through research. For example, little is known about wild bird infectious diseases and migration along the Mediterranean and Black Sea Flyway (MBSF), which connects Europe, Asia, and Africa. Focusing on avian influenza and the microbiome in migratory wild birds along the MBSF, this project seeks to understand the determinants of transboundary disease propagation and coinfection in regions that are connected by this flyway. Through the creation of a threat reduction network for avian diseases (Avian Zoonotic Disease Network, AZDN) in three countries along the MBSF (Georgia, Ukraine, and Jordan), this project is strengthening capacities for disease diagnostics; microbiomes; ecoimmunology; field biosafety; proper wildlife capture and handling; experimental design; statistical analysis; and vector sampling and biology. Here, we cover what is required to build a wild bird infectious disease research and surveillance program, which includes learning skills in proper bird capture and handling; biosafety and biosecurity; permits; next generation sequencing; leading-edge bioinformatics and statistical analyses; and vector and environmental sampling. Creating connected networks for avian influenzas and other pathogen surveillance will increase coordination and strengthen biosurveillance globally in wild birds. [ABSTRACT FROM AUTHOR]

Migratory birds are exposed to a diverse pathogen fauna by virtue of their long-distance travels. Although the immune system is an organism's primary defense against pathogenic microorganisms, few studies have investigated avian immune function during migration, much less shown seasonal differences in immune function. We describe the immunological condition of three intercontinental migratory species, Swainson's Thrush (Catharus ustulatus), Veery (C. fuscescens), and Wood Thrush (Hylocichla mustelina) during spring migration. In addition, we compare their immunological condition with conspecifics captured during fall migration and during the breeding season to provide a frame of reference for the spring immunological data. Measures of immunological condition presented include total leukocyte count, heterophil:lymphocyte (H:L) ratio, heterophil and lymphocyte counts, hematocrit, and IgG titers. In addition, we assessed each bird's energetic condition by measuring body mass and calculating a size-corrected condition index. Migrating birds had lower leukocyte and lymphocyte counts, lower hematocrit, reduced fat stores, and higher H:L ratios relative to nonmigrating individuals sampled during the breeding season. We also found that birds sampled during spring migration had lower lymphocyte counts and reduced fat stores, and higher heterophil counts and H:L ratios than fall migrants. Our results suggest that migrating birds are immunocompromised compared with conspecifics during the breeding season. Furthermore, compared with conspecifics sampled after a shorter overland flight, migrants sampled after crossing the Gulf of Mexico exhibited higher H:L ratios, which is indicative of heightened energetic stress. [ABSTRACT FROM AUTHOR]