Differences in social mating system and parental care between Northern House Wren (Troglodytes aedon) and Southern House Wren (T. musculus).

LLAMBÍAS, P.E.

Ithaca, USA

Congreso; Annual Meeting of the Association of Field Ornothologists and the Wilson Ornithological Society; 2004

Wilson Ornithological Society

Avian monogamy is usually associated with the need for biparental care. Whenoffspring can be raised by only one parent, selection should favor individuals who desertthe brood in order to become polygamous. During 2003 I studied the mating system andparental behavior of the Northern House Wren (N-H) and the Southern House Wren (SH)breeding in nest boxes in the U.S. and Argentina, respectively. Both species weredouble-brooded and had similar incubation and nestling periods. During the nestlingperiod, S-H males made significantly more feeding trips per nestling per hour than N-Hmales, while females fed at similar rates. Brood desertion by one parent was common inthe N-H: 75% of the nests were deserted after nestlings were 7 days old. Brood desertionwas the consequence of males switching to feed the nestlings of a primary or secondaryfemale (polygynous males) or of females starting a second brood with another male(sequentially polyandrous females). In the S-H, brood desertion was very rare and noinstances of polygamy were observed. Although populations differ in rates of brooddesertion and parental care, nestling condition at day 12 was similar. If differences inmating system between N-H and S-H are to be attributed to the need for biparental care,biparental care in the S-H must be essential even when nestlings are already welldeveloped. I discuss these data on parental care relative to the evolution of breedingsystems in House Wrens.