A comparison of the ecology and population dynamics of a neotropical migrant landbird, the hooded warbler, in winter and summer
Niven, Daniel Kenneth
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https://hdl.handle.net/2142/19649
Description
Title
A comparison of the ecology and population dynamics of a neotropical migrant landbird, the hooded warbler, in winter and summer
Author(s)
Niven, Daniel Kenneth
Issue Date
1996
Doctoral Committee Chair(s)
Robinson, Scott K.
Department of Study
Biology
Discipline
Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Ecology
Biology, Zoology
Agriculture, Forestry and Wildlife
Language
eng
Abstract
A central question in the study of avian ecology is to determine where and how migrant bird populations are limited. I studied the habitat selection, foraging ecology, and population dynamics of the Hooded Warbler (Wilsonia citrina) during the breeding season in Maryland, USA, and during the overwintering season in Quintana Roo, Mexico. The purpose of my study was to identify the factors limiting population growth in both winter and summer, and to examine the role of disturbance in habitat use and quality.
Overwintering Hooded Warblers segregate by habitat with males occupying more mature habitat; however, an analysis of vegetation structure in territories occupied by males and females indicated that these differences are not as pronounced as previously believed. Similar analyses in Maryland revealed that breeding territories are heterogeneous, with combinations of mature trees and dense understory vegetation. Patterns of foraging by breeding male and female Hooded Warblers support the hypothesis that foraging segregation and the occupancy of heterogeneous breeding territories result from gender-specific breeding roles rather than gender-specific adaptations to overwintering habitat.
Breeding territory size was inversely proportional to density, indicating density-dependent habitat use; however, density fluctuations and the presence of unmated males indicate that Hooded Warbler populations were not regulated by territorial behavior. Male mating success was density-dependent. Moreover, productivity seemed to be regulated by density-dependent nest success.
In Mexico, populations of territorial Hooded Warblers in both slightly damaged forest and an area decimated by fire were composed of over 70% males. There was no evidence for gender-based differences in condition or overwinter survivorship between the habitats, but densities were 25% lower in the burned forest. Overwinter survivorship was 80%. Between-winter site fidelity was over 50% in each habitat, although it may have been lower for older females. Distribution among territorial birds fit the ideal free distribution because fitness differences were compensated for by differences in density. Results of this study suggest that Hooded Warbler populations may be limited by events on both the breeding and overwintering grounds.
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