|Nutritional and genetic adaptation of galliform birds: implications for hand-rearing and restocking|
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Wild and hand-reared capercaillies differed from each other in many morphological and physiological features (I). Similar results were obtained on grey partridges (Putaala & Hissa 1995). Thus, the difference between wild and traditionally hand-reared gamebirds may be considered as well documented. Hand-rearing affects GI tract as well as the flight muscles in both of these species.
Grey partridge chicks fed a diet rich in invertebrates were heavier than chicks fed a low-insect diet or a fish diet. They also had better developed wing primaries, and a superior temperature regulation ability (II). This result highlights the importance of natural food for the growing chicks. Grey partridge chicks should be provided with invertebrates at least during the first weeks of their life.
The abrupt change in diet from pelleted commercial poultry food to natural food (III, V) caused a mass loss in grey partridges, and the body mass stayed at a lower level during the feeding trial than in control birds. They also had to increase their food intake to compensate the high fibre and low energy content of the natural food compared with the commercial food. However, feeding on natural foods only improved the gizzard mass in grey partridges. Plasma analyses did not reveal any dramatic disparities between traditionally or naturally fed grey partridges (III, V). As a consequence of these feeding trials we may summarise, that preconditioning of birds to natural food is beneficial, but a six-week period may not be long enough for acclimation of the birds.
The parameters used for studying power production showed a clear difference between wild and hand-reared capercaillies. The cytochrome-c oxidase activity, glycogen content of the muscles and the size of the heart may reflect differences in take-off and flying abilities. High plasma thyroxine concentration can indicate low metabolic level, which may affect the power production and flying ability. These results support the earlier suggestions about the benefits of large rearing aviaries, where birds can exercise their muscles and heart. It would probably be worth trying to teach hand-reared birds to recognize predators, as a valuable adjunct to predator-naïve birds after release (Dowell 1989, McLean et al. 1995, Griffin et al. 2000).
An interesting finding in this study was the slight impact of introductions that could be seen despite the centuries long introduction actions in Europe. The genetic disparity between wild and hand-reared Finnish grey partridges in the mtDNA was considerable deep. The control region 1 differed by 13 substitutions and 1 deletion/insertion between wild main eastern and hand-reared main western birds (VI). The history of hand-rearing and releasing of grey partridges is long; birds have been moved from one place to another, and it was of great interest to find some of the Irish grey partridges to be identical to those from Finland, Bulgaria, Russia or Greece. The crash of the grey partridge population in Finland may be a consequence – at least partly – of the use of more southern subspecies for introductions. The Finnish natural population represents, without any doubts, a more eastern mtDNA lineage. Genetic compatibility of released birds to the native population of the releasing site should be ensured before any releasing actions are put into practice.
Some of the game management economics are addressed to hand-rearing and releasing gamebirds. However, the survival of hand-reared birds after the release is poor. Hand-reared birds differ from their wild conspecifics in many morphological, physiological and behavioural ways, which may explain their high mortality. Before any releasing activities are started, it is more important to take care of the habitat. There is no use in trying to reintroduce galliform birds to areas where the habitat has become unsuitable or even hostile because of human activity, farming or forestry practices. It may be a strong statement to advocate predator-control (Maa- ja metsätalousministeriö 1999). It is preferable to determine how habitat changes have negatively affected gamebirds, and then direct management to reverse these negative changes.
If hand-rearing and releasing are carried out for hunting purposes only, the quality of birds is not of great importance. However, if the aim is to increase the population size, or even to reintroduce a species, the quality of the birds is vitally important. According to this study, more natural rearing methods are preferable. Hand-reared birds should be fed natural food, and should be able to exercise their flying muscles and heart, for which an adequate area for flying is required. However, the most important thing is to ensure that the birds represent proper subspecies. Further, grey partridges should be managed population-by-population. Releasing birds without any genetic adaptation to the environmental conditions, into which they are released, is a waste of time and money.
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