Within the field of Behavioral Ecology, there are many topics that pique my curiosity, but my main interest is the problem of how and why birds use song and other vocalizations. Studying communication is a way to pursue many questions simultaneously, as it is the mediator of social interactions in many settings and situations. I first became interested in song in particular when I read about the complexities of song development in brood parasites (Payne 1998) and about intraspecific song dialects (as in Treisman 1978), but it was during my undergraduate research when I was able to listen to male American Redstarts in the field when my interest became real.

I am interested in how females make pre-breeding choices about males and territories, and how song can affect these choices. In particular, I want to know whether song can affect a female's choice to stop migrating. Can she be "persuaded" to stop early if she hears an appropriate or "attractive" song? While working as an undergraduate assisting Sarah Mabey (past graduate student in the Migratory Bird Research Group), I became involved in her doctoral project on captive Eastern Kingbirds, Tyrannus tyrannus, which examined sex differences of patterns of migratory activity. A bit of serendipity resulted after she noticed a decrease in nocturnal migratory activity in females after males began to sing, and a corresponding increase when the singing males were removed. She noted that "the onset of breeding behavior and concurrent decrease in male activity suggest that the termination of spring migration is more strongly controlled on an endogenous level for male Eastern Kingbirds than it is for females. It is possible that the presence of males in breeding disposition may be an important Zietgeber for the termination of vernal restlessness in females"(Mabey dissertation 2002). I plan to address this problem in the following hypotheses in a research design with laboratory and field components.

Hypothesis 1:Females use song as an exogenous cue to terminate migration in the absence of other cues.

Prediction: If females use song as a cue to stop migration in the absence of other cues, then females prematurely exposed to song will terminate migratory restlessness before females that are never exposed to song or exposed to song later.

Hypothesis 2: Song is one of several important exogenous cues for the decision to terminate migration in females, including habitat and local cues.

Prediction 1: A female that is closer to a general breeding site goal will be more likely to be influenced by song cues than females that are a long way from their breeding grounds.

Prediction 2:Resident and partial migrant species will be more likely to orient towards song cues than long-distance migrants at a coastal stopover site on the Gulf of Mexico.

As an undergraduate I was hired as a field assistant for Rob Smith's (past graduate student in the Migratory Bird Research Group) doctoral work on how parental energetic arrival condition affects reproductive success with American Redstarts in the Upper Peninsula of Michigan. The summer after my sophomore year I worked primarily as a mist-netting assistant (with some arthropod collection). The following summer I returned to Michigan with the intent of studying American Redstart song while fulfilling my duties as a field assistant, which included foraging observations, nest searching and monitoring, and target-netting and resighting color-banded birds.

In my undergraduate thesis I used my field observations of American Redstarts to test the current hypotheses about the function of song modes in this species. American Redstarts have two song modes, a repeat mode that is sung early in the season and serial mode that is sung after copulation. Current literature suggests that the repeat mode, the only song sung when females arrive on the breeding grounds, is a female directed song (Lemon et. al 1994). However, I found that repeat mode is also the only song sung during male-male territory formation and can illicit aggressive responses to playback in males. I also found that females paired with serial sing males (not all males proceed to serial mode- see Sherry & Holmes 1997) had earlier clutch initiation than females not paired to serial singing males. These observations led me to generate a hypothesis for future tests, namely that serial singers have some advantage, perhaps physiological as song production is tied to hormone levels, that affects female choice. I also believe that the link between male-male aggression and repeat mode should be more closely examined. I presented these findings and hypotheses at a poster session at the North American Ornithological Conference in New Orleans in September 2002.

Lemon, R.E., S. Perreault, & D.M. Weary. 1994. Dual strategies of song development in American Redstarts, Setophaga ruticilla. Animal Behaviour 47:317-329. Mabey, S.E. 2002. Sex-based differential migration:An examination of proximate and ecological consequences. Ph.D. dissertation, University of Southern Mississippi, Hattiesburg. Payne, R.B., L.L. Payne, & J.L. Woods. 1998. Song learning in brood parasitic indigobirds Vidua chalybeata:song mimicry of the host species. Animal Behaviour 55:1537-1553. Sherry, T.W. & R.T. Holmes. 1997. The American Redstart. The Birds of North America. No 277. A. Poole and F. Gill, eds. Treisman, M. 1978. Bird song dialects, repertoire size, and kin association. Animal Behaviour 26:814-817.

Department of Biological Sciences
The University of Southern Mississippi
118 College Drive # 5018
Hattiesburg, MS 39406-0001
(601)266-4394
rachel.bru@usm.edu

 

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