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Correspondence

Twinning and embryonic mortality in a free-living kaka (Nestor meridionalis)

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Page 39 | Received 18 Sep 2001, Published online: 22 Feb 2011
 

Abstract

Compared to mammals, twinning in birds is rare. The reported incidence in domestic chickens (Gallus gallus) is 0.11 % (Byerly and Olsen Citation1934) and in pigeons (Columba livia) only 0.07% (Riddle Citation1923). Monozygotic twins occur following the fission of an early embryo and may or may not share the same yolk. Dizygotic twins are thought to occur following 2 simultaneous ovulations or perhaps by the slow passage of an ovum down the oviduct, resulting in it being caught by a succeeding yolk and then being incorporated into the same membrane and shell (Harrison Citation1986). Regardless of their origin most avian twins do not survive beyond hatching.

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