The Graduate Program in

Communication and Nestling Sex Ratio in Songbirds

Warbler


David Hof, is a Ph.D. student is the OEB program, and studies sex ratios and communication in migrant songbirds. He focuses on a group of birds known as warblers, and in particular, the Black-throated Blue Warbler. Warblers are tiny birds that can fit in the palm of your hand, and the males but not females are usually brightly colored and sing songs to defend territories and attract mates. Warblers spend their winters in the tropics of South and Central America, and islands in the Caribbean, and travel all the way to North America to breed in the spring. The Black-throated Blue Warbler winters in Puerto Rico, Cuba, Jamaica, and Hispaniola, and can be found abundantly in the deciduous forests of New England in the spring and summer. David is investigating that if the value of sons and daughters is different, will these birds produce more of the more valuable sex. For example, if a female has a really attractive mate her sons will inherit that attractiveness, and be able to attract a lot of mates, so she will have more grandchildren if she produces sons. If her mate is not so attractive, her sons will have trouble attracting mates, but females almost never have trouble getting a mate, so she will be better off having daughters. David also studies the aggressive fighting behavior these birds exhibit. Males often fight viscously over territories that hold nesting sites and food for raising their young. However, fighting can be risky business and costs energy and potential injury. Many animals have evolved a communication system that can help settle disputes before fighting begins. Birds may communicate their fighting ability or level of aggression so others know what they might be getting themselves into. However, it would be advantageous for some birds to cheat by bluffing how good they are at fighting or how aggressive they will be because they could win the territory without having to fight. David is testing whether bluffing occurs in warbler communication or whether it is honest.

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