Growth and Development of the Violaceous Euphonia and Palm Tanager in Trinidad

C.T. Collins

Abstract


The growth and postnatal development of Violaceous Euphonia (Euphonia violacea) and Palm Tanager (Thraupis palmarum) chicks were studied in Arima Valley, Trinidad. Like many tropical passerines, these two tanagers had lower growth rates (K = 0.462 and 0.386; T10-90 = 9.6 and 12 days respectively) than comparable sized temperate zone species. Palm Tanagers fledged at the age of 18 days and the Euphonias between 17 and 20 days. Both species were poikilothermic at hatching and only became homeothermic at 9-10 days post hatching. Chicks of both species gaped silently which may be an anti-predator detection adaptation. The reduced mobbing by the adult tanagers may represent an adaptive response to increase adult survival and, as a result, long-term reproductive success.


Keywords


Euphonia; violacea; Thraupis; palmarum; tanager; Trinidad; growth; thermoregulation; behaviour; begging; mobbing.

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