Does climate or habitat affect the frequency of cooperative brood rearing in Canada geese?

Citation
Al. Gosser et Mr. Conover, Does climate or habitat affect the frequency of cooperative brood rearing in Canada geese?, ETHOLOGY, 106(3), 2000, pp. 235-246
Citations number
19
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Animal Sciences","Neurosciences & Behavoir
Journal title
ETHOLOGY
ISSN journal
0179-1613 → ACNP
Volume
106
Issue
3
Year of publication
2000
Pages
235 - 246
Database
ISI
SICI code
0179-1613(200003)106:3<235:DCOHAT>2.0.ZU;2-A
Abstract
Canada geese (Branta canadensis) are unusual because individuals use either of two different brood-rearing behaviors: cooperative broods (two or more merged broods attended by more than three parents) or two-parent families. We tested whether cooperative broods form in response to habitat or climati c conditions by examining variation in cooperative brood frequencies among Canada geese nesting in Connecticut from 1982 to 1996. Percent of goslings raised in cooperative broods ranged from 0 to 100% at a given site in diffe rent years, but the pattern of annual variation was different at each site. The sites were in close proximity to each other and had similar climates; thus, the differences in annual variation among sites was not likely to be a response to climatic conditions. Cooperative brood frequencies also varie d among sites in each individual year, but sites with the most gang broodin g in one year often had the least the next. Such would not be expected if g ang brooding occurred in response to non-ephemeral habitat characteristics. Sites where gang brooding occurred and where it did not have similar food resources and predation risks. These findings failed to support the hypothe ses that gang broods form in response to food competition or predation. Sit es where gang broods occurred had more parent geese and more goslings than sites where they did not occur. Furthermore, the proportion of goslings rai sed in gang broods was correlated with the number of goslings and parents a t the site. Our results support the hypothesis that gang broods form from t he inadvertent mixing of goslings. This single factor, however, was not suf ficient to account for all of the observed variation in gang brooding frequ encies.