RESUMO

Monarch butterflies in eastern North America have declined by 84% on Mexican wintering grounds since the observed peak in 1996. However, coarse-scale population indices from northern US breeding grounds do not show a consistent downward trend. This discrepancy has led to speculation that autumn migration may be a critical limiting period. We address this hypothesis by examining the role of multiscale processes impacting monarchs during autumn, assessed using arrival abundances at all known winter colony sites over a 12-y period (2004-2015). We quantified effects of continental-scale (climate, landscape greenness, and disease) and local-scale (colony habitat quality) drivers of spatiotemporal trends in winter colony sizes. We also included effects of peak summer and migratory population indices. Our results demonstrate that higher summer abundance on northern breeding grounds led to larger winter colonies as did greener autumns, a proxy for increased nectar availability in southern US floral corridors. Colony sizes were also positively correlated with the amount of local dense forest cover and whether they were located within the Monarch Butterfly Biosphere Reserve, but were not influenced by disease rates. Although we demonstrate a demographic link between summer and fine-scale winter population sizes, we also reveal that conditions experienced during, and at the culmination of, autumn migration impact annual dynamics. Monarchs face a growing threat if floral resources and winter habitat availability diminish under climate change. Our study tackles a long-standing gap in the monarch's annual cycle and highlights the importance of evaluating migratory conditions to understand mechanisms governing long-term population trends.

Assuntos

RESUMO

Around forty bird species habitually reproduce in the Northern Hemisphere during summer, and migrate to the Southern Hemisphere during northern winter. These migrating birds fly together in large or small groups until they have reached the Caribbean, Central American, or Brazilian shores. Charadrius semipalmatus, Bonaparte 1825, is one of these migrating species that uses resting and feeding areas along eastern and western coasts of North and South America, with several records for the Brazilian coast, and very few for the inland country. On November 24, 2011, an individual of this species was observed on the banks of one of the lakes that compose a complex of about 40 temporary lakes within the Karst of Lagoa Santa Environmental Protection Area. On October 29 and 30, 2012 a single individual of Gelochelidon nilotica, Gmelin 1789, was also observed in Sumidouro State Park. We suggest that these specimens have used the Atlantic Ocean migration route, following the São Francisco River Basin, until the karst area. Although highly impacted, the temporary lakes within the Karst of Lagoa Santa still harbor a significant number of bird species, and serve as resting and feeding places for migratory or errant species that are still eliciting new records.

Cerca de 40 espécies de aves se reproduzem no hemisfério Norte durante o verão e migram durante o inverno, desse hemisfério, para o hemisfério Sul. Essas aves migratórias se reúnem em grandes ou pequenos bandos até atingir o Caribe, América Central e região costeira do Brasil. Charadrius semipalmatus, Bonaparte 1825, é uma das migratórias que usa áreas de repouso e alimentação ao longo das costas leste e oeste das Américas do Norte e do Sul, tendo vários registros no litoral brasileiro e muito poucos no interior do país. No dia 24 de novembro de 2011, um indivíduo da espécie foi observado nas margens de uma das lagoas que compõem um complexo de cerca de 40 lagoas temporárias da Área de Proteção Ambiental (APA) Carste de Lagoa Santa. Nos dias 29 e 30 de outubro de 2012 um indivíduo de Gelochelidon nilotica, Gmelin 1789, foi observado na lagoa do Sumidouro, no Parque Estadual do Sumidouro. Sugerimos que os indivíduos utilizaram a rota do Oceano Atlântico para a migração, seguindo a bacia do rio São Francisco até atingir a área da APA Carste de Lagoa Santa. Apesar de altamente impactadas, as lagoas temporárias da APA Carste de Lagoa Santa ainda abrigam expressiva riqueza em espécies e servem como local de repouso e alimentação para espécies migratórias ou errantes ocasionais que continuam sendo registradas.

Assuntos

RESUMO

Around forty bird species habitually reproduce in the Northern Hemisphere during summer, and migrate to the Southern Hemisphere during northern winter. These migrating birds fly together in large or small groups until they have reached the Caribbean, Central American, or Brazilian shores. Charadrius semipalmatus, Bonaparte 1825, is one of these migrating species that uses resting and feeding areas along eastern and western coasts of North and South America, with several records for the Brazilian coast, and very few for the inland country. On November 24, 2011, an individual of this species was observed on the banks of one of the lakes that compose a complex of about 40 temporary lakes within the Karst of Lagoa Santa Environmental Protection Area. On October 29 and 30, 2012 a single individual of Gelochelidon nilotica, Gmelin 1789, was also observed in Sumidouro State Park. We suggest that these specimens have used the Atlantic Ocean migration route, following the São Francisco River Basin, until the karst area. Although highly impacted, the temporary lakes within the Karst of Lagoa Santa still harbor a significant number of bird species, and serve as resting and feeding places for migratory or errant species that are still eliciting new records.(AU)

Cerca de 40 espécies de aves se reproduzem no hemisfério Norte durante o verão e migram durante o inverno, desse hemisfério, para o hemisfério Sul. Essas aves migratórias se reúnem em grandes ou pequenos bandos até atingir o Caribe, América Central e região costeira do Brasil. Charadrius semipalmatus, Bonaparte 1825, é uma das migratórias que usa áreas de repouso e alimentação ao longo das costas leste e oeste das Américas do Norte e do Sul, tendo vários registros no litoral brasileiro e muito poucos no interior do país. No dia 24 de novembro de 2011, um indivíduo da espécie foi observado nas margens de uma das lagoas que compõem um complexo de cerca de 40 lagoas temporárias da Área de Proteção Ambiental (APA) Carste de Lagoa Santa. Nos dias 29 e 30 de outubro de 2012 um indivíduo de Gelochelidon nilotica, Gmelin 1789, foi observado na lagoa do Sumidouro, no Parque Estadual do Sumidouro. Sugerimos que os indivíduos utilizaram a rota do Oceano Atlântico para a migração, seguindo a bacia do rio São Francisco até atingir a área da APA Carste de Lagoa Santa. Apesar de altamente impactadas, as lagoas temporárias da APA Carste de Lagoa Santa ainda abrigam expressiva riqueza em espécies e servem como local de repouso e alimentação para espécies migratórias ou errantes ocasionais que continuam sendo registradas.(AU)

Assuntos

RESUMO

Many migratory animals are experiencing rapid population declines, but migration data with the geographic scope and resolution to quantify the complex network of movements between breeding and nonbreeding regions are often lacking. Determining the most frequently used migration routes and nonbreeding regions for a species is critical for understanding population dynamics and making effective conservation decisions. We tracked the migration of individual Wood Thrushes (Hylocichla mustelina) (n = 102) from across their range with light-level geolocators and, for the first time, quantified migration routes and wintering regions for distinct breeding populations. We identified regional and species-level migratory connectivity networks for this declining songbird by combining our tracking results with range-wide breeding abundance estimates and forest cover data. More than 50% of the species occupied the eastern wintering range (Honduras to Costa Rica), a region that includes only one-third of all wintering habitat and that is undergoing intensive deforestation. We estimated that half of all Wood Thrushes in North America migrate south through Florida in fall, whereas in spring approximately 73% funnel northward through a narrow span along the central U.S. Gulf Coast (88-93°W). Identifying migratory networks is a critical step for conservation of songbirds and we demonstrated with Wood Thrushes how it can highlight conservation hotspots for regional populations and species as a whole.

Assuntos