|Nutritional and genetic adaptation of galliform birds: implications for hand-rearing and restocking|
Hand-rearing of gamebirds has long traditions; as early as ancient Romans and Greeks hand-reared pheasants Phasianus colchicus “for table” (Robertson 1997). Hand-rearing of gamebirds is traditionally carried out for game management purposes, and the main aim of stocking and releasing gamebirds has been increasing the size of the game bag. Of the 132 species of partridges, quails and francolins 66 are maintained in captivity, either for quarry or domestic use (Robbins 1992). Despite their economic value, gamebirds have both socially and culturally important status as well.
Besides hunting purposes, hand-rearing and releasing of animals can be used as tools for conservation of endangered species or biodiversity (Nesbitt & Carpenter 1993, Kleiman et al. 1994, Cade & Temple 1995). Sixty-eight galliform species out of 256 (27 %) are globally endangered. This includes 42 Phasianidae species (Rands 1992). The proportion of galliform birds from all hand-reared and released animal species is about 39 % (Griffith et al. 1989). Many hand-rearing and releasing programmes have been carried out, not for hunting, but to strengthen natural populations or reintroduce species (Angelstam & Sandegren 1981, Paolo & Piodi 1988, Schroth 1991, Starling 1991, Kavanagh 1998). The popularity of hand-rearing and releasing of gamebirds is undisputable: about 20 million pheasants, two million red-legged partridges (redlegs) Alectoris rufa (Tapper 1999), and about 50 000 grey partridges Perdix perdix (D. Potts, pers. comm.) are annually released solely in the United Kingdom.
Methods for rearing birds in captivity are many, and they can be tested with closely relative, non-endangered, species (Nesbitt & Carpenter 1993). Birds may be machine-reared, parent-reared or reared by a surrogate parent. They may be fostered or cross-fostered as eggs or nestlings into the nest of wild birds. Birds may be released into the wild as juveniles or adults. In ”hard” release birds are released immediately after arrival at the releasing site, whereas in ”soft” release birds are preconditioned to the releasing site. Released birds may be captive for the first or more generations (Scott & Carpenter 1987). All techniques have an impact on the success of the release.
Captive-rearing is more expensive and also more problematical than translocation (Starling 1991), or “trap and transfer” (Dowell 1992), where animals are moved from areas of high population density to areas with low or zero densities (Griffith et al. 1989). There have been some successful translocations, for example those conducted to Perthshire, Scotland, in 1836–1838. The historical translocations of 64 capercaillies Tetrao urogallus from Sweden formed the base to a population of about 2 000 birds (Starling 1991). The grey partridge population in the mid-western states of the USA is another result of successful translocations (Potts 1986), whereas every attempt to introduce grey partridge to New Zealand has failed (Westerskov 1958, Potts 1986).
Results obtained from releasing projects of hand-reared grey partridges, pheasants, and capercaillies have not been encouraging. Several studies conducted on these species have clearly shown that the survival of hand-reared individuals is poor after the release into the wild (Angelstam & Sandegren 1981, Hill & Robertson 1988, Panek 1988, Paolo & Piodi 1988, Dowell 1990, Schroth 1991, Brittas et al. 1992, Putaala & Hissa 1993, 1998, Leif 1994, Kavanagh 1998). Similar results are also obtained from species other than galliforms, e.g. the lesser white-fronted goose Anser erythropus (Lorentsen et al. 1999, Markkola et al. 1999).
|List of original papers||Factors affecting the survival of hand-reared birds after release|