Migratory bird communities are sensitive to landscape alteration. Urban development significantly impacts bird communities on breeding grounds, as well as en-route during migration. One current theory is that Neotropical migratory birds are not limited by breeding or wintering habitat constraints but by food and habitat availability along major migration routes. The eastern flyway is the route taken by neotropical land-birds through eastern North America that follows coastal areas denoted by intense urban development. Coastal areas funnel birds to major departure points along the northern coast of the Gulf of Mexico and the western coast of Florida. Birds were monitored for 12 consecutive months along a decadal time gradient of urban development. Cypress domes are present through a broad scale of urban development in Hillsborough County creating ideal natural sampling units for long term monitoring of wetland bird communities in urban areas. Residential non-migratory bird communities were least influenced by development and did not change significantly with urban development. Neotropical and short-distance migratory birds, however, declined significantly for both richness and bird abundance with increased urban land cover. Migratory birds positively correlated with forested area at a spatial scale of 500 meters surrounding sites. Wintering migrants hit a critical point in development between 10 and 20 years of age, after which they disappeared. Neotropical migrants were most sensitive to declines significantly at sites classified as heavily degraded by the UMAM (Uniform Mitigation Assessment Method) a 'wetland integrity index'.

As Neotropical migratory birds, Prothonotary Warblers are exposed to parasites in both tropical and temperate regions and may act as dispersal agents between geographic areas. This study identifies the prevalence of Haemosporidia, West Nile Virus (WNV), and St. Louis Encephalitis virus (SLEV) in this species. A total of 71.6% of captured Prothonotary Warblers were infected with Haemosporidia during the 2008 breeding season, and infection prevalence increased throughout the season. This temporal change in prevalence is likely due to infection relapse and transmission of new infections. No correlations between reproductive effort and infection status were observed, nor were any associations between infection prevalence and nest box location identified. WNV and SLEV were present in 37.5% and 6.3% of sampled Prothonotary Warblers, respectively. These results warrant more detailed analyses of pathogen transmission dynamics in this population, physiological mechanisms that affect infection susceptibility, and spatial and temporal trends in infection that may exist.

Blackburnian Warblers (Dendroica fusca) were observed in their wintering grounds in a High Andean native secondary forest in Colombia between September 1993 and May 1994. The main objective of the study was to determine the relationships between the Blackburnian Warblers and the habitats where they were found. Size and composition of the mixed-species flocks joined by Blackburnian Warblers were also compared to habitat features. Habitat variables were measured in circular plots centered where a Blackburnian Warbler was first seen. The same set of variables was measured in randomly located paired plots to compare the two sets. The results obtained in Colombia (wintering grounds) were compared to similar data available from North America (breeding grounds). Ninety-six mixed-species flocks with Blackburnian Warblers were detected. Some of the habitat variables measured differed between plots used by the birds and the random plots. Density of trees in all dbh (diameter at breast height) categories, density of snags and density of native trees and shrubs were higher at the bird-centered plots. Percentage vegetation density (understory foliage volume) from O-1m, 1-2m and 2-3m were lower at bird-centered plots. There was no significant difference for maximum and mean canopy height between bird-centered and randomly selected paired plots. At Los Amarillos, Blackburnian Warblers avoided Eucalyptus spp. trees. They preferred the higher part of the trees and trees in the middle and high abh classes. They avoided the smallest dbh size class (3-8cm dbh). Comparisons were made between the data from Los Amarillos and data available from northern central Minnesota (Collins et al. 1982). Percent ground cover, densities of trees 15.1-23, 23.1-38 and 38.1-53 cm dbh and total density of trees were significantly higher in Minnesota. Trees 7.5- 15, 53.1-68 and > 68.1 cm dbh were higher in Los Amarillos. Percent canopy cover was not different between the two Sites. Blackburnian Warblers selected for closed canopy cover (about 75%) and large trees in each individual site. They selected larger trees in Minnesota. This selection may be related to nesting requirements of the species. / Master of Science