Causes of geographic variation in the house wren social mating system

LLAMBÍAS, P.E.

Ithaca, USA

Congreso; 12th International Behavioral Ecology Congress; 2008

International Society of Behavior Ecology

Males could be constrained to social monogamy by organismal, demographic orecological factors. For example, monogamy could be obligate when food is limiting andbiparental care is essential. However, monogamy may be facultative when males areconstrained by the distribution of nesting sites or the competition for and availability ofmates. During 2003-2007, I studied the social mating system and parental behavior of apolygynous population of Northern House Wrens (N-H) in the U.S. and a monogamouspopulation of Southern House Wrens (S-H) in Argentina. To evaluate the effects of foodlimitation on social mating systems I induced polygyny in the S-H by removing malesfrom their territories. Polygynous males in the S-H fledged significantly more nestlingsthan did monogamous males. Hence the food limitation hypothesis cannot explain thedifferences in polygyny rate between both populations since it predicts that S-Hpolygynous males should produce less offspring than monogamous ones. Habitatsaturation rather than food limitation seems to constrain S-H male to monogamy since thepolygyny rate of plots where males were removed differed significantly from thepolygyny rate in the control plots. Habitat was more saturated in Argentina than in theUSA where 10% of the males removed where replaced by non-territorial males while inArgentina, 67% of the replacements were non-territorial males. I suggest that monogamyin the S-H is facultative and that the social mating system is constrained by demographicfactors.