Dissertation Defense Seminar - Alexander Sharp

COASTAL AND MARINE SYSTEM SCIENCE PROGRAM
DEPARTMENT OF PHYSICAL AND ENVIRONMENTAL SCIENCES
TEXAS A&M UNIVERSITY-CORPUS CHRISTI

SUBJECT: Movement patterns of wading birds as a mechanism linking freshwater wetlands and coastal ecosystems in the greater Everglades

MAJOR ADVISOR: Dr. Dale Gawlik

ABSTRACT

Migratory wading birds rely on a network of wetland habitats across great geographic ranges, serving as important biological connectors linking wetland systems as they move. Approximately 50% of the waterbird species found in North America are in decline, threatened by habitat loss and degradation, increasing urbanization, wetland salinization, altered hydrology, and global climate change. Without a clear understanding of a species annual cycle movement patterns and associated habitat needs at each stage, management plans will be insufficient for addressing declining populations. In this dissertation, I quantify the annual cycle movements and habitat selection patterns of GPS tagged Little Blue Herons from two important wintering sites on the Gulf Coast of Florida. Specific objectives of this dissertation included 1) describing annual cycle movements, space use, phenology and nonbreeding site fidelity, 2) quantifying and contrasting annual cycle selection patterns of wetland habitats, emphasizing the link between coastal wetlands and freshwater habitats, 3) determining the influence of urbanization on the availability of foraging habitat and daily movements during the nesting period, and 4) quantifying habitat selection patterns during the wintering period. Herons wintering in coastal South Florida established nesting colonies in freshwater and coastal wetlands throughout the southeast United States and Cuba. During the nesting period, herons displayed a strong dependency of freshwater habitats, supporting an increased focus on the management of freshwater wetlands for Little Blue Heron populations in any system. In addition, foraging habitat during the nesting period was selected nonrandomly, with herons selecting low elevation, high wetland potential habitats, while avoiding non-wetland, anthropogenic habitats such as developed areas or agriculture. Foraging habitat around nesting colonies was influenced by urbanization, with the availability of habitat decreasing as the amount of anthropogenic habitat proximate to the colony increases and on landscapes with a low density of large anthropogenic patches. During the wintering period, individuals maintained small home ranges, did not make any significant within-season movements to other locations, displayed strong inter-year site fidelity, and used these locations for approximately half of the annual cycle, highlighting the disproportionate importance of wintering sites for heron populations. Habitat selection patterns during this period were strongly site-dependent, however attributes such as land cover class, foraging habitat availability, distance to the nearest island and wetland, and NDWI are all important predictors of heron habitat use.