Eastern Kentucky University
Wintering Eastern Bluebirds Adjust Habitat Use, Diet, and Social Behavior During Cold Weather Events
Institution
Eastern Kentucky University
Faculty Advisor/ Mentor
David Brown
Abstract
The population size of Eastern Bluebirds (Sialia sialis) in the Bluegrass Region of Kentucky has declined in recent years. To better understand the cause of this decline, I studied the winter ecology of bluebirds at the Bluegrass Army Depot (BGAD). Specifically, I collected data on home range size, group size, foraging behavior and diet, and tested for difference in habitat use based on periods of winter weather. I used mist nets and vocal playbacks to capture birds from different groups. Each bird was color-banded, and a subset of birds (N=9) were tagged with a small radio-transmitter. I also collected fecal samples from each captured bird. Several times each week I marked bird locations, recorded group size, and noted foraging behaviors. Weather data was collected from the Lexington National Weather Service Station. Using ArcGIS analysis, I determined the average group home range size (95% utilization distribution) to be 33 hectares with a much smaller average core home range of 3 hectares. Land cover analysis indicated that group home ranges consisted of 50% forested habitat and 50% open habitat. During relatively warm weather, small groups of bluebirds (2-13 individuals) maintained territories in open fields and foraged near the ground for insects. However, during cold weather events, and when the ground was snow covered, bluebirds tended to leave their core home range to join larger flocks (N= 50-100 individuals) and forage on fruit in forested habitat. This shift in habitat use has important implication for conservation of wintering bluebird populations.
Wintering Eastern Bluebirds Adjust Habitat Use, Diet, and Social Behavior During Cold Weather Events
The population size of Eastern Bluebirds (Sialia sialis) in the Bluegrass Region of Kentucky has declined in recent years. To better understand the cause of this decline, I studied the winter ecology of bluebirds at the Bluegrass Army Depot (BGAD). Specifically, I collected data on home range size, group size, foraging behavior and diet, and tested for difference in habitat use based on periods of winter weather. I used mist nets and vocal playbacks to capture birds from different groups. Each bird was color-banded, and a subset of birds (N=9) were tagged with a small radio-transmitter. I also collected fecal samples from each captured bird. Several times each week I marked bird locations, recorded group size, and noted foraging behaviors. Weather data was collected from the Lexington National Weather Service Station. Using ArcGIS analysis, I determined the average group home range size (95% utilization distribution) to be 33 hectares with a much smaller average core home range of 3 hectares. Land cover analysis indicated that group home ranges consisted of 50% forested habitat and 50% open habitat. During relatively warm weather, small groups of bluebirds (2-13 individuals) maintained territories in open fields and foraged near the ground for insects. However, during cold weather events, and when the ground was snow covered, bluebirds tended to leave their core home range to join larger flocks (N= 50-100 individuals) and forage on fruit in forested habitat. This shift in habitat use has important implication for conservation of wintering bluebird populations.