New Zealand Journal of Marine and Freshwater Research abstracts

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CRITERIA FOR AGING AND SEXING NEW ZEALAND OYSTERCATCHERS

Allan J. Baker*

Department of Zoology, University of Canterbury, Christchurch, New Zealand

Abstract Criteria based on external characters are presented for aging and sexing the three New Zealand species of oystercatcher, Haematopus ostralegus finschi Martens, 1897, H. unicolor Forster, 1844, and H. chathamemis Hartert, 1927. Four classes are discerned: juveniles have brown dorsal plumage, a brown iris and grey legs; second-year birds have an orange-red iris and pale pink legs; sub-adults have a dull red iris and pink legs; adults have a scarlet iris and bright coral pink legs. The three species can be sexed by discriminant analysis of the sexually dimorphic characters bill length (Xj), bill length:bill depth (x₂) and bill length:bill width (x₃). Linear functions and discriminating values for predicting sex are: H. ostralegus finschi 0.46x,+3.15x₂+2.94x₃₎ 77.41; H. unicolor 0.12x_r|-6.52x.,+2.85x₃, 58.05; and H. chathamemis ^0.93x₁+1.50x₂+7.48x₃, "20.86. Similarly, the sexes of immature H. ostralegus finschi can be predicted: juveniles O.73x,+5.76x_z+3.10x,, 116.57; second-year birds 0.57x_t+5.12x₂+0.98x₈, 84.84; and sub-adults 0.55x_I+1.88x,,+ 1.08x₃, 65.90.'

N.Z. Journal of Marine and Freshwater Research 8 (1): 211-21.
(Received for publication 29 January 1973; revisions received 19 July and 7 September 1973

PDF file of entire paper: medium quality (663K); (scanned from paper original: notes about this process)

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