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The image on the left depicts an adult male cowbird singing an undirected song during the breeding season.  This male’s history is typical of many birds used in our studies. He was captured as a wild adult male in the summer of 2000. He participated in two aviary experiments where he mated successfully and in the summer of 2002 he was released. Birds that have resided in aviaries make the transition to the life of a wild bird successfully. Banding studies we have conducted reveal that birds released in the summer frequently reappear at the lab the following year after having migrated south for the winter.

 

The image on the right depicts an adult female cowbird. She was captured as a juvenile in the summer of 1999 when she was approximately 50 days old. She has participated in a number of aviary studies where she has bred successfully. She currently is still in the lab and is serving as a mentor to juvenile females. Young birds learn a great deal from adults from how to forage to how to communicate. In this case, NY is serving as a mentor to juvenile birds that were hand raised from the egg. In this way, we are able to have a great deal of control over the socialization process of the young.

 

The image on the left depicts three female cowbirds. Females use subtle visual signals to communicate with one another and with males.  Thus, what may appear to be three females doing little may well be three females reacting to each others visual signals, as well as the behavior of other birds in the area.  It is quite possible that one way females learn preferences for specific males is by watching other females reactions to males vocal and social behavior. Recent studies in our lab indicate that females are very competitive among themselves for the attention of males and there may be many parallels between the development of female preferences and the development of male song production.

The image on the right depicts four male cowbirds singing to one another. This communicative interaction is of great significance to the establishment of male social order but also appears to be a very important way for males to stimulate and attract female cowbirds. These two photographs are instructive of gender differences in the nature of communication in this and many species.  The male communicative behavior is obvious, competitive, and can be overtly aggressive. The female behavior is subtle, and difficult to observe. This is one reason why much more is known about development and function of male communication. In the end, much of the male behavior is designed to impress the female. 

      

      

   

In the sequence above, a male sings a series of songs to a female, which elicit a copulation solicitation posture. The male then maneuvers around the female and copulates with her.

Time-frequency spectrograms made using Igor Pro and BSound software written by Brian Nelson.

BSound is available at http://homepage.mac.com/bsnelson/Igor/BSound.html

 

This is a spectrogram of the actual song used to elicit a female copulation solicitation posture followed by a series of whistles that are sometimes produced when the male mounts the female.  In the far left of this spectrogram the song is labeled as well as the introductory notes, which trigger the solicitation posture in the female. The whistle sequence is also labeled. High-ranking males use the whistle sequence much more than low ranking males who may frequently use no whistle advertisement at all.

 

BABIES BETWEEN 10-15 DAYS OLD

 

 

  

    

BABIES BETWEEN 20-25 DAYS OLD

These baby cowbirds were hand reared from the egg. The eggs were collected from nests, which we placed in aviaries during the breeding season. We place fake eggs in the nests, which encourages the females to lay their eggs in these nests. These baby birds will be raised in our aviaries where they will choose mates and breed in the following spring. After microsatellite parentage analysis is performed to determine their parents, we will be able to investigate group and individual level effects on reproductive success and the quality of the young produced. Recent work indicates that the reproductive success of the individual cannot be predicted without an understanding of group level social effects.

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