Winter Behavior and Ecology of Eastern Bluebirds (<i>Sialia sialis</i>): Home Ranges, Habitat Use, and Effect of Weather on Foraging Behavior

<p>Eastern bluebirds (<em>Sialia sialis</em>) are widespread across eastern North America, but populations appear to be susceptible to extreme winter weather. Declines in population following cold winters in states like Kentucky suggest the need to better understand winter-specific habitat requirements and behavioral responses to inclement weather. My objectives were to 1) describe the size and habitat composition of the home ranges of wintering bluebirds, and 2) examine the effects of weather (i.e., temperature, wind speed, and snow presence) on habitat occupancy, group size, and foraging behavior. My study was conducted at the Blue Grass Army Depot in Madison County, Kentucky. I radio-tracked 19 bluebirds during January and February 2010 and 2011 and recorded their locations, the size and composition (males vs. females) of groups, and foraging behavior. Mean home range size (± SE) was 29.2 ± 2.36 ha (N = 9), which is smaller than previously published estimates for wintering bluebirds. Home ranges consisted of an average (± SE) of 39.6 ± 2.6% wooded habitat and 60.4 ± 2.6% open habitat (N = 9), and edge habitat between these areas was likely an important additional component. Insectivory was the most frequently observed foraging behavior (>65% of all observations, N = 235), although shifts to frugivory were observed during periods of low temperatures, low wind speeds, and the presence of snow. Hackberry (<em>Celtis occidentalis</em>), mistletoe (<em>Phoradendron leucarpum</em>), and red cedar (<em>Juniperus virginiana</em>) were the most commonly consumed fruits, but high winds may restrict their potential as a food resource. High winds, when combined with low temperatures and substantial snow cover, potentially lower the efficiency of both insectivory and frugivory to sub-optimal levels, thus representing especially challenging winter conditions for bluebirds. In addition to changing foraging strategies, bluebirds appeared to respond to weather conditions by adjusting group sizes, a tactic which may enhance foraging efficiency, allow individuals to locate food resources, or both. These responses to weather occurred without an apparent shift in habitat occupancy, thus the ability of bluebirds to survive extreme winter weather may be constrained by available food resources and interacting weather conditions that may restrict foraging options. </p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Master's

Discipline thesis:degree_discipline

Biological Sciences

Grantor dc:publisher

Eastern Kentucky University

Year

2013

Author dc:creator

• Weinkam, Todd J.

• bluebird
• foraging
• fruit
• sialia
• weather
• winter
• Ecology and Evolutionary Biology
• Ornithology

Statement dc:rights

• Copyright 2013 Todd J. Weinkam

Repository record dc:identifier

https://encompass.eku.edu/etd/144

OAI identifier oai:identifier

oai:encompass.eku.edu:etd-1143