Proximate causes of hatching asynchrony in Magellanic Penguins: the influence of egg temperature and brood patch area.

ESTEBAN FRERE; MELINA BARRIONUEVO; NAHUEL MARCHISIO

Ciudad del Cabo

Congreso; 2nd World Seabird Conference; 2015

World Seabird Union

Hatching asynchrony can influence nestling growth in many birds. Most species start full incubation before the clutch is complete, which has been proposed as the mechanism that controls hatching asynchrony, being largely assumed but not often tested. Our objectives were to determine: a) the proximate causes that affect hatching asynchrony, including the incubation temperatures of the eggs and the brood patch?which allows the transfer of heat to the eggs for their correct development; b) how the egg temperature and the brood patch interact with each other; and c) the breeding variables affecting them. We studied Magellanic Penguins (Spheniscus magellanicus) during four breeding seasons (2010- 2013) in Puerto Deseado, Santa Cruz, Argentina (47°45´S, 65°53´W). During the incubation period, we used iButtons attached to both eggs of the clutch to register egg temperature (n=61 nests, every 15 minutes), and we measured the brood patch?s temperature, its length and width in the breeding adults (n=24 nests, every 6 days). We used GLMM and LMM to analyze the data. Hatching asynchrony was positively related to the temperature of the first-laid egg (E1) during egg laying (2=5.8, P=0.02), which was below the temperature needed to start embryonic development, and with brood patch area on the laying day of E1 (2=4.4, P=0.04); and negatively related to the egg temperature difference between both eggs of the clutch during incubation (second ? first-laid egg) (2=5.6, P=0.02). Brood patch area was positively related to egg temperature during early incubation (t=4.4, P