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Constraints of landscape level prey availability on physiological condition and productivity of great egrets and white ibises in the Florida Everglades
Title
Constraints of landscape level prey availability on physiological condition and productivity of great egrets and white ibises in the Florida Everglades.
Creator
Herring, Garth, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Biological Sciences
Abstract/Description
Life history strategy suggests long lived bird species will adjust their nesting effort according to current conditions, balancing the costs of reproduction with their long-term needs for survival and future reproduction. The habitat conditions that produce these responses may differ between species, even within the same ecosystem, producing different nesting and population trends. I traced the pathway by which food availability influences the physiological condition of pre-breeding great...
Show moreLife history strategy suggests long lived bird species will adjust their nesting effort according to current conditions, balancing the costs of reproduction with their long-term needs for survival and future reproduction. The habitat conditions that produce these responses may differ between species, even within the same ecosystem, producing different nesting and population trends. I traced the pathway by which food availability influences the physiological condition of pre-breeding great egrets and white ibises through to reproductive measures, and the physiological condition of chicks. I focused on these two species with contrasting foraging strategies, in relation to foraging and habitat conditions to maximize the likelihood of application of these results to other wading bird species. Experimental food supplementation and physiology research on white ibis chicks demonstrated that in years with low prey availability white ibis were food limited, with increased levels of stress protein 60 and fecal corticosterone. This is the first study to demonstrate experimentally the response of stress protein 60 to changing levels of food availability. During a year with low prey availability (2007) white ibis adults and chick physiological condition was lower than that of great egrets. During the same year, fledging success was lower for both species (20% for white ibis versus 27% for great egret) but the magnitude of the decrease was particularly severe for the white ibis (76% decline versus 66% decline for the great egret). Results suggest white ibises modify their clutch size during years with poor habitat in accordance with life history traits of a long-lived species, whereas great egrets maintained their clutch size during years with poor habitat., Increasing recession rates, hydrological reversals, and prey densities influenced white ibis, whereas great egrets were most influenced by prey densities and recession rates, with no effect of hydrological reversal. During the same year, fledging success was lower for both species (20% for white ibis versus 27% for great egret) but the magnitude of the decrease was particularly severe for the white ibis (76% decline versus 66% decline for the great egret). Results suggest white ibises modify their clutch size during years with poor habitat in accordance with life history traits of a long-lived species, whereas great egrets maintained their clutch size during years with poor habitat. Increasing recession rates, hydrological reversals, and prey densities influenced white ibis, whereas great egrets were most influenced by prey densities and recession rates, with no effect of hydrological reversals. This study is the first to make the link between landscape hydrology patterns, prey availability, and responses in wading bird nesting. These linkages provide critical insight into how species' nesting patterns could differ given the same time and spatial constraints and how that may be related to long-term nesting trends. This knowledge could ultimately lead to novel predictions about population and community patterns of wetland birds.
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Date Issued
2008
PURL
http://purl.flvc.org/FAU/77643
Subject Headings
Bird populations, Water birds, Wetland ecology
Format
Document (PDF)
Dietary niche relationships of white ibis, tricolored heron and snowy egret nestlings in the northern Everglades
Title
Dietary niche relationships of white ibis, tricolored heron and snowy egret nestlings in the northern Everglades.
Creator
Boyle, Robin A., Charles E. Schmidt College of Science, Department of Biological Sciences
Abstract/Description
Food availability is the primary factor affecting the reproductive success in many species of birds. Diet composition can indicate diet quality, habitat use and niche requirements for breeding birds and may be variable across short and long-term time scales. Identifying primary prey types of nesting wading birds is important for the hydrologic restoration of wetlands. I collected nestling boluses during the 2008 and 2009 nesting seasons from three species of wading birds that nest in the...
Show moreFood availability is the primary factor affecting the reproductive success in many species of birds. Diet composition can indicate diet quality, habitat use and niche requirements for breeding birds and may be variable across short and long-term time scales. Identifying primary prey types of nesting wading birds is important for the hydrologic restoration of wetlands. I collected nestling boluses during the 2008 and 2009 nesting seasons from three species of wading birds that nest in the northern Everglades: White Ibis, Tricolored Herons and Snowy Egrets. White Ibis bolus composition was dominated by crayfish in both years, but exhibited some variation with landscape water depth in 2009; fish use was greatest when the wetland landscape was relatively dry. In contrast, the prey of Tricolored Herons and Snowy Egrets were primarily fish and their respective diets did not differ from one another in either fish species composition or size structure.
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Date Issued
2010
PURL
http://purl.flvc.org/FAU/2953207
Subject Headings
Wetland ecology, Bird populations, Water birds
Format
Document (PDF)
Hierarchical resource selection and movement of two wading bird species with divergent foraging strategies in the Everglades
Title
Hierarchical resource selection and movement of two wading bird species with divergent foraging strategies in the Everglades.
Creator
Beerens, James M., Charles E. Schmidt College of Science, Department of Biological Sciences
Abstract/Description
Seasonal variation in food availability is one of the primary limitations to avian populations, particularly during the breeding season. However, the behavioral responses between species may differ based on foraging strategies. I examined the influence of food availability on landscape-level habitat selection, patch-level habitat selection, and movements of two wading bird species with divergent foraging strategies, the Great Egret and White Ibis. On a landscape scale, there appeared to be a...
Show moreSeasonal variation in food availability is one of the primary limitations to avian populations, particularly during the breeding season. However, the behavioral responses between species may differ based on foraging strategies. I examined the influence of food availability on landscape-level habitat selection, patch-level habitat selection, and movements of two wading bird species with divergent foraging strategies, the Great Egret and White Ibis. On a landscape scale, there appeared to be a relationship among resource availability, the temporal scale of the independent variable, and whether the response was similar or different between species. At the patch level, results demonstrated a relationship between resource availability and the spatial scale of the independent variables selected by birds. Species movements were consistent with the differing strategies. This study is the first to make the link between landscape hydrology patterns, prey availability, and responses in wading bird habitat selection at multiple spatial scales.
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Date Issued
2008
PURL
http://purl.flvc.org/FAU/172667
Subject Headings
Water birds, Habitat, Habitat selection, Bird populations, Wetland ecology
Format
Document (PDF)
Territory size of the Florida Scrub-jay (Aphelocoma coerulescens) at Savannas Preserve State Park
Title
Territory size of the Florida Scrub-jay (Aphelocoma coerulescens) at Savannas Preserve State Park.
Creator
Smith, Theresa E., Harriet L. Wilkes Honors College
Abstract/Description
The Florida Scrub-jay is the only bird endemic to the state of Florida, and is entirely restricted to pyrogenic xeric oak scrublands. The species is listed as Threatened, and all populations throughout the state are in decline. The major causes of decline are habitat modification due to development and fire suppression. Preservation and proper fire management is crucial for the continued survival of the species. The territories of three families of Florida Scrub-jays at Savannas Preserve...
Show moreThe Florida Scrub-jay is the only bird endemic to the state of Florida, and is entirely restricted to pyrogenic xeric oak scrublands. The species is listed as Threatened, and all populations throughout the state are in decline. The major causes of decline are habitat modification due to development and fire suppression. Preservation and proper fire management is crucial for the continued survival of the species. The territories of three families of Florida Scrub-jays at Savannas Preserve State Park were delineated, and the area calculated using 100% MVCP analysis and compared to work previously published by Cowan (2005). The results of this study show that Savannas Preserve State Park oak scrub habitat is deteriorating, but that aggressive fire management can restore the scrub to optimal Florida Scrub-jay habitat.
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Date Issued
2007
PURL
http://purl.flvc.org/FAU/11599
Subject Headings
Savannas Preserve State Park (Fla.), Florida Scrub-jay, Distribution, Bird populations, Wildlife conservation
Format
Document (PDF)