Song sharing, song dialects and reproductive success in bobolinks (Dolichonyx oryzivorus).

The ecological and behavioral significance of song sharing was investigated in a population of bobolinks (Dolichonyx oryzivorus) in Michigan. Bobolinks have song dialects that are characterized in terms of song syllable structure and order. Songs for each dialect are distributed over large, discrete geographical areas (30-100 km$\sp2$) that correspond to disjunct patches of nesting habitat. Approximately 25% of the population sang non-local songs. Fourteen percent of these apparent immigrants sang the songs of a nearby dialect. Song sharing in bobolinks was associated with greater nest success. Differences in nest success may be a result of the significantly earlier arrival and longer residence period of song-sharing males in comparison with non-sharing males. There was no association between size and nest success or song sharing. Although associative, these results represent an important first step in understanding the fitness consequences of song sharing. A new hypothesis, the social experience hypothesis, is developed. It proposes that experience with unshared songs is important for subsequent recognition of and response to novel unshared songs. It predicts that only males experienced with unshared songs will respond strongly to playback of unshared songs. Several mechanistic hypotheses proposed to explain advantages of song sharing predict a stronger response to unshared playback songs than to shared playback songs. The new hypothesis explains the general finding, from previous playback experiments, that males responded weakly to unshared songs. The social experience hypothesis and the dialect mechanisms were both supported by the results of a song playback experiment in bobolinks, in which response to playback of shared and unshared songs was compared within the context of the test subject's previous experience with unshared songs. The results of a song learning experiment provide no strong evidence that bobolinks learn their songs. Bobolinks were captured as juveniles and were held in captivity throughout song development. They had no exposure to adult song in captivity. Most captive males developed songs similar to those of the dialect area where they were captured.PhDBiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104412/1/9513511.pdfDescription of 9513511.pdf : Restricted to UM users only