First Name:
Alexandra
Last Name:
Bentz
Major Department:
Biology
Thesis Director:
Lynn Sieffermann
Date of Thesis:
May 2010
Delayed plumage maturation occurs in many bird species and is considered an honest signal of subordinance in younger individuals. Although these younger individuals may be able to breed, they stand to benefit from avoiding aggression from older, more experienced individuals. While the significance of male plumage coloration is well studied, few studies have addressed the importance of plumage coloration in mediating female-female interactions or in signaling female quality and reproductive investment. Tree swallows (Tachycineta bicolor) are one of the few bird species to exhibit delayed plumage maturation in females, but not in males. In the present study, I used reflectance spectrometry to characterize plumage coloration of female tree swallows breeding in Watauga County, North Carolina. I tested whether age and plumage coloration influenced measures of female reproductive investment and success. Older females were more colorful than younger females. Moreover, older females were not only in better body condition, but laid eggs earlier and produced higher-quality offspring compared to younger females. Within age classes, female plumage coloration was positively related to measures of reproductive investment and offspring quality. Young females that were more ornamented laid eggs earlier in the season and had larger clutches, while older females that were more ornamented laid heavier clutches. These data demonstrate that female coloration in tree swallows is a good indicator of age and egg investment, both of which strongly affect nestling quality.