TY - JOUR
T1 - Demography and the Evolution of Cooperative Breeding in the Bicolored Wren, Campylorhynchus Griseus
AU - Austad, Steven N.
AU - Rabenold, Kerry N.
N1 - Funding Information:
1) We are most grateful to Tomás BLOHMfo r allowing us to live and work on his ranch and for his diligent efforts to preserve the natural habitat of the llanos. We also thank Veronika KIKLEVICH, Carla CHRISTENSEN, and Patricia Parker RABENOLfDo r invaluable assistance in all phases of data collection. R. Haven WILEYa nd Minna WILEY began the study of Campylorhynchus wrens at Hato Masaguaral in 1974, and they have been the source of many stimulating discussions ever since. For very helpful comments on the manuscript we thank Jerram BROWN, Patricia GOWATY, David LIGON, Bill RICE, Sandra VEHRENCAMP, Steve ZACK, and an anonymous reviewer. Our study has been supported by grants BNS77-00279 and DEB80-07710 from the U.S. National Science Foundation. 2) Present address: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge Mass. 02138, U.S.A. most often are nondispersers from previous reproductive episodes, it does not address why individuals who fail to establish themselves as breeders become "floaters" in some species but nondispersers in others. KOENIG & PITELKA (1981) suggest that a lack of marginally favorable breeding habitat limits the dispersal possibilities of maturing birds and is therefore important in favoring retention of offspring in the natal However why birds in such environments do not become within high quality territories has not been Second, the hypothesis does not address almost
PY - 1986
Y1 - 1986
N2 - 1. Two adjacent populations of the bicolored wren differ significantly in social structure. In one population 83% of groups consist of unaided pairs. The rest contain, in addition, a single male nonreproductive helper. About 43 % of the groups in the other population consist of unaided pairs. The rest contain from one to three helpers, and helpers may be of either sex. 2. Helpers are always individuals who have failed to disperse from their natal territory. In both populations they augment group reproductive success and reduce mortality among the breeding pair, although a single helper produces a reproductive enhancement as great as that of multiple helpers. 3. Group-size-specific reproduction and adult mortality do not differ between the populations, but juvenile mortality and average territory size differ significantly. 4. The population consequences of these differences suggest that group size is held below its optimum in one habitat by high juvenile mortality, whereas habitat saturation is probably responsible for the fact that about one-third of all groups in the second habitat contain more than an optimum number of members. 5. These demographic parameters suggest that habitat saturation is not a necessary condition for the maintenance of helping behavior in either population.
AB - 1. Two adjacent populations of the bicolored wren differ significantly in social structure. In one population 83% of groups consist of unaided pairs. The rest contain, in addition, a single male nonreproductive helper. About 43 % of the groups in the other population consist of unaided pairs. The rest contain from one to three helpers, and helpers may be of either sex. 2. Helpers are always individuals who have failed to disperse from their natal territory. In both populations they augment group reproductive success and reduce mortality among the breeding pair, although a single helper produces a reproductive enhancement as great as that of multiple helpers. 3. Group-size-specific reproduction and adult mortality do not differ between the populations, but juvenile mortality and average territory size differ significantly. 4. The population consequences of these differences suggest that group size is held below its optimum in one habitat by high juvenile mortality, whereas habitat saturation is probably responsible for the fact that about one-third of all groups in the second habitat contain more than an optimum number of members. 5. These demographic parameters suggest that habitat saturation is not a necessary condition for the maintenance of helping behavior in either population.
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U2 - 10.1163/156853986X00667
DO - 10.1163/156853986X00667
M3 - Article
AN - SCOPUS:0022841510
VL - 97
SP - 308
EP - 324
JO - Behaviour
JF - Behaviour
SN - 0005-7959
IS - 3-4
ER -