
Individual variation in response to simulated territorial challenge among territory‐holding song sparrows
Author(s) -
Nowicki Stephen,
Searcy William A.,
Krueger Terry,
Hughes Melissa
Publication year - 2002
Publication title -
journal of avian biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.022
H-Index - 76
eISSN - 1600-048X
pISSN - 0908-8857
DOI - 10.1034/j.1600-048x.2002.330307.x
Subject(s) - territoriality , biology , intrusion , seasonal breeder , variation (astronomy) , passerine , ecology , zoology , physics , geochemistry , astrophysics , geology
Lack (1946) suggested that male songbirds exhibit consistent individual differences in the vigor or manner in which they defend their territories against intrusion. The causes and consequences of such individual variation have not been incorporated into models of territoriality, however, because of a lack of experimental data confirming Lack's suggestion. In this paper, we test the possibility that male song sparrows Melospiza melodia who are successful territory holders differ consistently in the vigor with which they defend their territory, by conducting repeated song playback trials with the same set of territory‐holding subjects across a breeding season. We found only relatively weak seasonal trends in responsiveness: the amount birds sang in response to playback increased significantly across the breeding season and responsiveness was generally lower when a male's social mate was egg laying. By contrast, we found extensive variation among males in how closely they approached a simulated territorial intrusion. These individual differences remained significantly consistent across four rounds of playback trials that spanned the breeding season as determined by Kendall's coefficient of concordance. Our results confirm that some individual song sparrows are consistently more vigorous than others in territory defense, at least in one conspicuous aspect of their behavior, and suggest that further work is needed to understand the nature and consequences of variation in patterns of defense among successful territory holders.