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Most of us know that the ever-popular Gouldian finch is more prevalent in captivity than in the wild, where its populations have declined steadily. It is now listed as an endangered species. The causes for this decline have not been accurately determined but in the past it has been hypothesized that habitat change (fire and rain cycles), parasitism, predation, and air-sac mite infestation could be the cause. No matter what the cause, research must continue. Yet, there is alarmingly little research on the biology of these birds in the wild. Sonia Tidemann of Batchelor College in Australia has performed most of the serious work in the Northern Territory of Australia, the only area in the world where the Gouldian finch exists in the wild. Here I summarize a recent report on the breeding biology of Gouldians as reported by Tidemann's group in the journal EMU. The longer and much more complete (and scientific) reference is:

Tidemann, S.C., C. Lawson, R. Elvish, J. Boyden, and J. Elvish. 1999. Breeding biology of the Gouldian finch Erythrura gouldiae, an endangered finch of Northern Australia. EMU 99:191-199.

Although most of the observations of the Gouldian finches were made in the early 1990's the report was just recently published. The study was based on two independent sites. The Yinberrie Hills site gets and average annual rainfall of 42.6 inches and the Newry site gets an average rainfall of 34.4 inches. The climate is considered monsoonal with around 85% of the annual rainfall coming from November to March. As for nesting sites, all but one of the nests that were found and monitored was made in Eucalyptus tree hollows. The nesting material was Sorghum grass. The parents were caught and tagged with color-coded bands so each bird could be monitored from a distance (see NFSS Bulletin Volume 16 (5): 6-9, for my article on a similar banding method). The banding also helped determine if renesting occurred within a pair in the same season and/or in subsequent years.

Nesting hollows were monitored year after year. Some could not be reused because of termite activity, fire, or fallen tree limbs. It was noted by Tidemann and her group that eggs were laid at intervals very close to 24 hours and that incubation was 14 days with the nestlings fledged after 21 days. The average clutch size (60-nest sample) was 5.2 eggs. The average number of nestlings to fledge from a successful (and note she means successful) nest was 4.8. There were no significant differences between the clutch size and the proportion of clutches that survived indicating that egg survival was not influenced by clutch size. About 75% of the nests fledged at least one young and the cause of nestling mortality could not be determined. The egg success (i.e. the number of eggs that produced a fledgling) was about 2.5 fledglings per bird per season.

Breeding time correlated well with the weather. In Newry, the number of clutches started to peak in April. In some years breeding activity would cease in June but in others it would continue until July or August. The average length of a nesting attempt was estimated to be 43 days with an interclutch break of 17 days following weaning. Interestingly, the number of clutch attempts was only two in some years but four in others. One pair did have three successful clutches, one in February, one in March, and one in May.

The study sites were of limited geographic range but were large. Interestingly, only a few banded breeding adults returned to the same study area in a subsequent year. In one case the site was skipped by an adult one year but the bird returned suggesting the "off-year" nesting site was outside the study area. Pair bonding was strong within a given year and all but one of 11 carefully studied pairs bred together for the whole breeding season. One pair had a successful clutch and then found new partners (my note: don't we wish humans could be so faithful - but then again it was only one year for the birds!). In NO case did a pair bond extend beyond one season.

Within a breeding season, a pair with a successful clutch were equally likely to find a new hollow as to stay in the same hollow. Yet, 25% of the hollows could not be reused between seasons because they were destroyed. Some hollows were reused even though a predator had taken the clutch.

Fortunately, the statistics showed that 32 to 56% nesting success was obtained and this is within the normal range for other Australian multi-brooded passerines. Losses occurred from predation but also abandonment. In fact, abandonment was a more common cause of nest failure than predation (my note: they do not state if this is caused by the pair realizing the clutch is infertile or if they are scared away from the nest and do not return). It is thought that by nesting exclusively in hollows Gouldian finches may have a bit of an advantage when compared to other species, which may be more susceptible to predators. The annual productivity of about 2.5 fledglings per bird per season is actually higher than other studied Australian passerines.

It is thought that some of the variability in annual production of young is linked to rainfall, which affects food sources. The authors state that adult Gouldians fed predominately on Sorghum seed (my note: so why don't we feed them Sorghum?) and feed Sorghum seed to their young. This grass requires a large amount of rainfall up to January for vegetative growth to be sufficient to produce large seed yields. As for other limitations to breeding success, the authors mention that the reuse of hollows by different pairs in subsequent years suggests that hollow availability is limited or that some hollows, even with the same dimensions, are more suitable for other reasons (my note: if this turns out to be true I hope they make more artificial hollows so nest sites are not the limiting factor).

They conclude by stating that the reproductive success of Gouldian pairs should not be limiting the populations. The assumption is that if populations continue to decline some other cause must be found. They suggest that until further studies indicate that the populations are increasing the status of the Gouldian finch should remain endangered.

I hope that you enjoyed the update on one of our favorite finches. Seeing the endangered Gouldian finch in the wild must be an exciting experience. We often forget that our captive populations have wild roots. We should all be aware of how import it is that these wild populations remain healthy.

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