How do Southern House Wrens achieve polygyny? An experimental approach

PAULO LLAMBÍAS

INTERNATIONAL JOURNAL OF ORNITHOLOGY

SPRINGER

Año: 2012 p. 571 - 578

1519-888X

I designed two experiments to evaluate how polygyny is achieved in Southern HouseWrens (Troglodytes aedon musculus) breeding in a south-temperate population. In thefirst experiment I manipulated territory attractiveness by adding high quality nestingsites (nest-boxes) to 50% of monogamous territories (n = 24) and evaluated if malescan attract a second female when defending high quality resources. In the secondexperiment, I simulated high male mortality early in the breeding season by removing30 territorial males in plots where wrens had been breeding in nest-boxes (n = 47territories). The first experiment did not induce polygyny: although females switchedfrom breeding in tree cavities to nest-boxes when boxes were erected in their territory,none of the neighbouring females who did not receive a box moved to breed as asecondary female. The male removal experiment did induce polygyny; of 21experimentally widowed females, 38% bred as secondary females of neighboringmales?who expanded their territories in the absence of a defending male?andaccepted polygyny even in the presence of neighbouring territories held by bachelormales. Secondary females mated to polygynous males were rarely helped by the malewhile feeding nestlings, but primary and secondary females did overlap very little in theuse of space. Hence, females mated to polygynous males may share parental caredisproportionally but not territorial resources. Female attachment to territories andexclusive use of space together with male´s expansion of territories to achievepolygyny suggests that Southern House Wrens engage in sublease polygyny.