Simplified polymerase chain reaction (PCR)-based sexing assists conservation of an endangered owl, the Norfolk Island Boobook Ninox novaeseelandiae undulata

Abstract

In 1986 a single Norfolk Island Boobook Owl Ninox novaeseelandiae undulata remained. As part of a re-establishment programme, two male New Zealand Moreporks N. n. novaeseelandiae were introduced, one of which survived to pair with the female in the wild and breed successfully. By 1995 the population numbered 12 or 13 individuals of which seven were second generation (F2). However, there were only two breeding pairs. As the 11 hybrids could not be sexed using morphometrics we developed a molecular method based on a recently described avian polymerase chain reaction (PCR)-based sexing technique. The population was found to contain six females and five males. A scarcity of mature males was established as the main factor slowing the recovery effort. Recent progress in molecular biology has revolutionized several fields, not least conservation biology (e.g. Griffiths and Tiwari 1995, Avise 1994, 1996). Among other advances, relatively simple techniques now allow accurate sexing of individuals, sometimes without the risks associated with handling (Griffiths and Tiwari 1993). Often such knowledge is critical to conservation efforts. The Norfolk Island Boobook Ninox novaeseelandiae undulata is confined to the small, isolated Norfolk Island Group, an Australian territory. It is one of about 26 of the world's owl taxa listed as endangered and currently the only endangered owl taxon in Australia (Clarke et al. 1978, Garnett 1992). On plumage characteristics, morphological and biogeographical grounds, the owl is classified as a large, distinctive subspecies of the New Zealand Morepork N. n. novaeseelandiae (Olsen 1996). Recent molecular analyses confirm that the New Zealand owl is the closest relative (L. Christidis and J. Norman pers. comm., National Museum, Victoria, Australia). In 1986 only one Norfolk Island Owl, a female, was extant (Olsen et al. 1989). As part of a re-establishment programme, two male New Zealand Moreporks were introduced, one of which survived to pair with the female and breed successfully (Olsen 1996). By late 1995, the population numbered 12 or 13 individuals of which seven were second generation (F2). However, there were only two breeding pairs. Norfolk Island owls are significantly larger than New Zealand Moreporks. Because both are sexually dimorphic, with females the larger sex, New Zealand females approach Norfolk Island males in size and weight (Olsen et al. 1989, Olsen 1996). This has created difficulties in determining the sex of the hybrid.