Graduate Student - Ph.D.

Ecology and Evolutionary Biology

Princeton University (Princeton, NJ)

Instructor

Biology

Columbia Gorge Community College (The Dalles, OR)

Michaela Hau

Hormonal Mediation of alternative phenotypes in a temperate bird.

During my doctoral research at Princeton University I am investigating the hormonal mechanisms of male and female polymorphisms. My model system is the well-known White-throated Sparrow (Zonotrichia albicollis). White-throated Sparrows possess a plumage polymorphism during the breeding season (Lowther 1961), where individuals of both sexes occur as two plumage morphs, either white or tan. The white-stripe morph has brighter crown stripes, brighter yellow lores and less striping on the throat patch than the tan-stripe morph (Lowther 1961). White-striped birds are also larger, sing more and are more aggressive than tan-striped birds (Lowther 1961; Atkinson and Ralph 1980). This polymorphism exists within both of the sexes; however, the female white-stripe morph looses her bright plumage during her post-nuptial molt and becomes tan in plumage for the winter. Conversely, the male of the white-stripe morph never looses his white plumage at any time of the year, his alternate plumage does tend to be drab, but he is still white not tan. There is a distinct bimodal distribution of white and tan plumage during the breeding season (Atkinson and Ralph 1980).
As of yet no, one has attempted to explain proximately what is allowing for the morph change in the female without the simultaneous morph change in the males, during the non-breeding season. An individual’s plumage in this species is dependent on the presence or absence of an autosomal inversion on the second chromosome (Thorneycroft 1966, 1975). But what accounts for the morph change in one sex without the synonymous change in the other sex?

1997-1999 Avian Ecologist