A comparison of annual patterns of behaviour and physiology between partially migratory and non-migratory subspecies of the Australian silvereye zosterops lateralis, in captivity

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NO FULL TEXT AVAILABLE. Access is restricted indefinitely. ----- This study recorded and compared the behaviour and physiology of the partially migratory Tasmanian subspecies, Zosterops lateralis lateralis, and the sedentary mainland subspecies, Zosterops lateralis familiaris, of the Australian silvereye over an extended period in captivity. Tasmanian birds were held in captivity for a total of 17.5 months, while the mainland birds were kept for 13 or 16 months, dependent on date of capture. During this time orientation behaviour, locomotor activity, fat deposition, body weight, food consumption and moult of each subspecies were recorded. The Tasmanian birds displayed significant seasonally appropriate orientation during each of the three migratory periods and also during the breeding and moult period. In contrast, the mainland birds did not display significant orientation at any time. Graphing of the locomotor activity revealed several trends in the daily and annual activity patterns of each subspecies. During the first year in captivity the Tasmanian birds exhibited elevated activity levels during the migratory periods, which is most likely due to migratory restlessness and their activity patterns were similar to those of diurnal migrants. The Tasmanian birds were significantly fatter and heavier than the mainland birds and during the first year in captivity; the Tasmanian birds displayed increased fat deposition during the migratory periods and the overwintering period. During the second year in captivity, after moult, both subspecies failed to develop the levels of activity recorded during the previous year and also weighed significantly less. This was especially apparent during the second autumn migration period. During this time the Tasmanian birds also failed to gain the fat levels of the previous year. Captivity appeared to affect both subspecies and influenced the development of migratory activity and fat deposition in the Tasmanian birds. Both subspecies showed similar levels and patterns of consumption of nectar, apple and a protein-mix and nectar consumption had a significant inverse relationship with temperature. The subspecies differed in their consumption of mealworms, with the Tasmanian birds consuming mealworms, in higher numbers and with greater frequency than the mainland birds. Both subspecies moulted at the same time as wild birds. The Tasmanian birds commenced and completed moult earlier than the mainland birds and exhibited less variation between individuals. Overall the differences between the subspecies were consistent with their differing lifestyles and the adaptation of the behaviour and physiology of Tasmanian silvereyes to their migratory habit.
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