Zebra Finch Incubation: Brood Patch, Egg Temperature and Thermal Properties of the Nest

Abstract

Incubation was investigated in a wild population of Zebra Finches Taenropygia gurtata in northern Victoria and comparisons made with wild-caught birds. A data logger recorded temperature readings from thermocouples inside eggs, nests, nesting bushes and exposed positions adjacent to nesting bushes. Both sexes incubate but only the female has a brood patch; this forms at the start of incubation and regresses soon after eggs hatch. Females incubated at night and both sexes shared incubation during the day. There were no consistent differences in the temperature of developing eggs heated by the two sexes nor did the sexes differ in their ability to rewarm cold eggs; fluctuations in incubation temperature also did not differ consistently between the sexes. Incubation began the day the fourth egg was laid for clutches ≥ 5 or the day the last egg was laid for smaller clutches. Hatching was more synchronous in the wild than in captivity. The ability of the nest to maintain a temperature differential was limited: air temperatures in the roof of the nesting chamber of enclosed roosting and breeding nests followed ambient temperatures closely when conditions were mild but the nest provided an insulating effect that ameliorated low temperatures.