Effect of nestling sex ratio on the provisioning behavior of adult Eastern Bluebirds (Sialia sialis)

<p>To maximize reproductive success, parents may, in some cases, differentially invest in sons and daughters, i.e., sex-biased parental investment. Preferential provisioning behavior has been reported in one population of Eastern Bluebirds (<em>Sialia sialis</italic>) and attributed to local resource competition. To better understand this behavior, I studied the provisioning behavior of Eastern Bluebirds in Madison County, Kentucky, in 2004. I experimentally manipulated brood sex ratios in 24 bluebird nests, creating female-biased (N = 8), male-biased (N = 5), and control (N = 11) nests. Following manipulation, nests were video-taped to record adult provisioning behavior. Among experimental broods, the provisioning rates of male and female Eastern Bluebirds were not affected by brood sex ratio (P = 0.58). Similarly, for broods that naturally differed in the number of male and female nestlings (N = 9), I found no effect of brood sex ratio on provisioning rates (P = 0.34). </p> <p>Female bluebirds provisioned nestlings at higher rates than males (P = 0.0046) and the provisioning rates of adult bluebirds varied with brood size (P = 0.017); with broods of 5 fed at lower rates than broods of either 3 or 4. Because surface area exposure per nestling is reduced in larger broods, nestlings in larger broods may expend energy at lower rates and require less food from adults. </p> <p>Male and female bluebirds delivered a total of 2363 prey items to nestlings, with males delivering 821 prey items and females 1542 prey items. Of prey items I was able to identify, grasshoppers (<em>Orthoptera</italic>) were the most common prey delivered to nestlings by both male and female bluebirds. Other common prey items included Lepidopteran larvae, beetles (<em>Coleoptera</italic>), crickets (<em>Orthoptera</italic>), worms (<em>Oligochaeta</italic>spp.), spiders (<em>Araneae</italic>), and cicadas (<em>Hemiptera</italic>). Overall, male and female bluebirds delivered similar types of prey to nestlings. </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

2011

Author dc:creator

• Kieffer, Barbara Ellen

• behavior
• Easter Bluebirds
• kentucky
• nestling
• provisioning
• Sialia sialis
• Biology

Statement dc:rights

• Copyright 2011 Barbara Ellen Kieffer

Repository record dc:identifier

https://encompass.eku.edu/etd/37

OAI identifier oai:identifier

oai:encompass.eku.edu:etd-1036