I have a large outdoor aviary which is becoming overpopulated with zebra finches. I am reluctant to give the birds away if they are likely to end up in small domestic cages, and wonder whether it would be kinder to release them into the wild. What would be their chance of survival if I released them into the wild after being born and bred in captivity?
Coromandel Valley (This letter was not addressed to me!)
I understand the aviary is so large that the feathered inmates and candidates for the wild have had enough flying exercise and are strong enough to meet the demands of life in the wild. The question is: Have they been able, in captivity, to develop the skills of finding food and shelter without human aid, i. e. are they able to feed on half ripe and ripe grass seeds and build breeding and sleeping nests in bushes? If yes, the birds can indeed be released into the wild, but not in Adelaide: The climate there is not really suitable for Zebra Finches since it is too cool and wet in winter and too dry in summer.
However, Zebra Finches do occur just a two hours' drive north of Adelaide or a bit further north, depending on the time of the year. It is here that they have the southern boundary of their distribution range. Therefore it would be possible to release a flock of well prepared Zebra Finches e. g. on a trip to the Flinders Ranges, which is an ideal terrain for wild animals. I have but one reservation about such an action: Birds bred in captivity often deviate from the genotype of the wild form even if the phenotype looks exactly the same. So, in order to protect the wild Zebra Finches from degeneration, no captive birds should be released into the wild as long as it is not absolutely (!) sure that there is and has been no colour or other variation in the breeding stock.
As for overpopulation, a breeder should not let the birds raise more than three or four broods a year. This can be achieved by replacing a complete (!) clutch with white ceramic or plastic eggs of the same size. Of course, one could also remove all the nests and nesting material, but in a large outdoor aviary Zebra Finches can make do with all kinds of materials and nesting sites, and by nature, they spend their nights in sleeping nests.