Female condition: A predictor of hatching synchrony in the House Wren?

The degree of hatching synchrony in clutches of passerine birds frequently varies among species and among individuals of the same species. Many hypoth eses have been proposed to explain why some eggs hatch several days after o thers in a clutch. We tested one of these hypotheses, the energetic-constra ints hypothesis, which proposes that females in poor physical condition pos tpone initiating incubation and hatch their clutches synchronously, whereas females in good condition begin incubation early and hatch their clutches asynchronously. We tested the hypothesis using the House Wren (Troglodytes aedon) because recent studies have found little difference in productivity between synchronously and asynchronously hatching clutches in this species, suggesting that the degree of hatching synchrony varies for reasons unrela ted to nestling growth and survival. We used logistic regression to test th e dependence of the degree of hatching synchrony on each of two measures of female condition. We found no relationship between female condition and de gree of hatching synchrony. These results and two other lines of evidence a xe inconsistent with the energetic-constraints hypothesis as an explanation for variation in degree of hatching synchrony in this House Wren populatio n.