| Publication Type: | Journal Article |
| Year of Publication: | 1978 |
| Authors: | Vehrencamp, SL |
| Journal: | Behavioral Ecology and Sociobiology |
| Volume: | 4 |
| Issue: | 1 |
| Date Published: | 1978 |
| ISBN Number: | 03405443 |
| Keywords: | Crotophaga, Crotophaga sulcirostris, Cuculidae |
| Abstract: | 1. A two-year field study of Groove-billed anis was conducted to determine the advantage of communal group nesting versus solitary pair nesting. The following specific hypotheses were tested: a) groups have better territories than pairs; b) groups defend their nests better against predators; c) groups can feed nestlings more efficiently; d) groups can raise more broods per season; e) adult survival is higher in groups. 2. Large groups (3+ pairs) were found to occur primarily in second growth and marsh portions of the study area, single pairs and small groups primarily in the pastureland areas. Vegetation cover, territory size, and nest height differed significantly in these two habitats, but food abundance during the breeding season was similar. The two habitats were analyzed separately to separate out group size effects and habitat effects. 3. Groups in the pasture habitat had significantly lower nest predation than pairs, but there was no significant difference in predation rate between groups and pairs in the marsh. 4. Groups in the pasture were less successful in raising nestlings than pairs, but there was no significant difference in juveniles raised per pair for large and small groups in the marsh. 5. In both habitats, pairs were more likely to attempt second broods than groups. Second broods were much more frequent in the pasture than in the marsh. 6. Annual reproductive success (juveniles/pair/year) was the same for all commonly occurring group sizes within each habitat, but was higher in the pasture than in the marsh because of the high frequency of second broods. 7. In the marsh habitat, adult survival was considerably higher for females and subordinate males than for dominant males, providing a possible incentive for group formation in this habitat. In the pasture, females had slightly lower survival than males. It is hypothesized that the advantage of communal nesting is the reduction of parental care costs, particularly the risk of mortality during incubation. |
| URL: | http://www.jstor.org/stable/4599186 |
| Short Title: | Behavioral Ecology and Sociobiology |
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