acceptable to some wild birds. Released parakeets, and wild males paired to
released females, have readily accepted nest-boxes. The reluctance with which
the wild Echo Parakeets have accepted nest-boxes is mirrored by the experience
of others working with wild parrots. For example, efforts with three Amazona
parrot species in Mexico, with St Lucia Parrots Amazona versicolorand Puerto
Rican parrots have almost all failed (N. Snyder personal communication).
However, by contrast, Blue and Gold Macaws Ara araraunareadily accepted
nest-boxes (Munn 1992) as did Green-rumped Parrotlets Forpus passerinus
(Beissinger and Bucher 1992). Nest-boxes increased the number of breeding
pairs of the Green-rumped Parrotlet, and were more secure than natural holes.
Birds nesting in boxes had more frequent and larger broods. This is a common
finding with nest-boxes where predation rates are often lower. In addition cavity
size may influence clutch and brood size.
Artificial ledges and cavities have been successfully constructed for many cliff
nesting bird species, including Northern Bald Ibis Geronticus eremita(Hirsch
1978) and various raptors. In Germany artificial sites suitable for Peregrine Falcons
Falco peregrinushave been made in quarries and cavities have been blasted in cliff
faces (Hepp 1988) so that about 80% of eyries in the Black Forest area were in
artificial sites, where breeding success was “distinctly higher than in natural
nests” (Brucher and Wegner 1988).
Competition over cavities can be severe. The size of the entrance hole is often
important, and for most species the smallest hole through which they can enter
is the safest, since this excludes larger species. Minimizing the entrance hole was
used to exclude White-tailed Tropic Birds, which were competing for nest-sites
with the smaller and much rarer Bermuda Petrel Pterodroma cahow(Wingate
1978). The exclusion of the tropic birds led to improved breeding success and
numbers of petrels, with pairs increasing from 18 in 1962, when management
first started, to 26 in 1977 (Wingate 1978) and an estimated 180 birds (53 breeding
pairs) by 1997 (Stattersfield and Capper 2000).
Nest-boxes are widely used in Europe and have resulted in increases in popula-
tions of many hole-nesting birds, including Pied Flycatcher Ficedula hypoleuca,
Collared Flycatcher F. albicollis, Redstart Phoenicurus phoenicurus, various tits Parus
spp., Tree Sparrow Passer montanus, and Starling Sturnus vulgaris(Newton 1994).
In North America nest-boxes have resulted in a steady increase in the populations
of Bluebirds Sialiaspp. (Zeleny 1978, Newton 1998). Nest-boxes represent an
alternative to natural hollows, but are not always an adequate replacement because
they do not reflect the diversity of natural hollows (Gibbons and Lindemayer
2002). Some species prefer natural cavities to nest-boxes (e.g. Treecreeper Certhia
familiaris), and for these more research is needed on nest-box design.
276 |Conservation management of endangered birds