Incubation routines and foraging-trip regulation in the Grey-faced Petrel Pterodroma macroptera gouldi

In Grey-faced Petrels Pterodroma macroptera gouldi parental care during the 55-day incubation period is mainly achieved by three long shifts (two by the male) when one partner is ashore while the other forages at sea. This situation would seem to carry high risks of parental desertion and failure of the hatching chick to receive a meal before its yolk sac is exhausted. We examined incubation routines of 51 pairs of Grey-faced Petrels to investigate factors implicated in parental desertion and in the duration of the final foraging trip before hatching. The duration of the final long foraging trip (by the female) during incubation is not predicted by the time spent fasting on the nest but by the time elapsed since laying. Desertions accounted for 6.5% of egg losses. Eggs were deserted not after the delay of the foraging bird to return to the nest, but when the incubating bird departed early in the incubation spell. Desertions were not a response to critically depleted energy reserves.