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

FRERE, E. & BARRIONUEVO, M.

Conferencia; 2nd World Seabird Conference; 2015

World Seabird Union

Hatching asynchrony can influence nestling growth in many birds. Most species start full incubationbefore the clutch is complete, which has been proposed as the mechanism that controls hatchingasynchrony, being largely assumed but not often tested. Our objectives were to determine: a) theproximate causes that affect hatching asynchrony, including the incubation temperatures of the eggsand 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 breedingvariables affecting them. We studied Magellanic Penguins (Spheniscus magellanicus) during fourbreeding seasons (2010- 2013) in Puerto Deseado, Santa Cruz, Argentina (47°45´S, 65°53´W). Duringthe incubation period, we used iButtons attached to both eggs of the clutch to register eggtemperature (n=61 nests, every 15 minutes), and we measured the brood patch´s temperature, itslength and width in the breeding adults (n=24 nests, every 6 days). We used GLMM and LMM toanalyze the data. Hatching asynchrony was positively related to the temperature of the first-laid egg(E1) during egg laying (Chisq=5.8, P=0.02), which was below the temperature needed to startembryonic development, and with brood patch area on the laying day of E1 (Chisq=4.4, P=0.04); andnegatively related to the egg temperature difference between both eggs of the clutch duringincubation (second - first-laid egg) (Chisq=5.6, P=0.02). Brood patch area was positively related toegg temperature during early incubation (t=4.4, P