Reproduction in a Zebra Finch Colony in South-eastern Australia: the Significance of Monogamy, Precocial Breeding and Multiple Broods in a Highly Mobile Species

Abstract

The reproductive demography of a colony of Zebra Finches Taeniopygia guttata was studied in farmland over four breeding seasons in south-eastem Australia. The colony was an open breeding assembly with much mobility of members. Breeding lasted from seven to nine months, spanning early spring to late autumn. Clutch size was smaller in the autumn half of the breeding season. Seed supplements did not affect clutch size. Clutches larger than modal size were the most productive. Re-nesting was frequent due to high nest predation (66%); losses between fledging age and independence were 69%. Young were capable of breeding at 60 to 70 days after hatching and their breeding success was no different from that of older birds. Young hatched in the spring half of the breeding season constituted 44% of pairs breeding in the autumn half of the season. Current breeding effort was traded-off against future breeding potential in young hatched in the autumn half of the season. Pairs mated for life (n = 144). The breakup of 50 pairs happened only on the presumed death of the partner; yet, repairing was frequent. Except for one brother-sister mating, mates were unrelated. Sexes did not differ significantly in natal dispersal, age at pair formation, number of mates acquired or breeding success. Estimates of 'lifetime' reproductive success were limited to the term a bird was present at the study colony and did not differ between the sexes. In their short, highly social and mobile lives Zebra Finches live in a state of tight, life-long social monogamy where high mortality is compensated for by multiple broods of mediumsized clutches produced by precocial, highly productive young.