The issue of whether unusual birds are escapers
/ releasees or wild birds is best solved by an understanding of their population
in adjacent natural areas and the number of them kept in captivity. Therefore
the ratio of occurrences of different species to how popular they are in
captivity, combined with how well they survive post-release, will impact on how
many occur. For example, although Budgerigars are more common in captivity than
Cockatiels, it is the Cockatiels that are observed much more often as escapers.
These issues are explored in my paper: (1991) ‘The
changing status of the Rainbow Lorikeet Trichoglossus haematodus in
South-east Australia: the role of wild and escaped birds’, Australian
Bird Watcher 14: 3–9. and more so in my book:
Canberra Birds: A Report on the first 21 years of the Garden Bird Survey.
The latter provides data over 1316 observer years, of occurrences of all species
and shows that incidence of escaped birds relates primarily to how popular they
are in captivity. This is complicated by the situation when some of these
species also occur naturally (usually marginally,) in nearby habitats. Also it
is notable that escaped parrots commonly associate with similar native
(to the area) species.
By the way, the plural of escapee is escapees, DEFINATELY NOT escapee's (which only makes sense followed by a noun, to mean some
property of the escapee). Also by usual grammar, one who escapes should
be called an escaper (even if that word is not generally used). The
escapee is the one to whom an escape occurs, that is the prior owner.
If the bird is released, the bird is a
releasee and the person releasing it is a releaser.