Estimating sexes of New Holland and White-cheeked Honeyeaters from head-bill measurements.

We tested the degree to which New Holland and White-cheeked Honeyeaters could be sexed on the basis of head-bill measurements. Both species showed bimodal distributions of head-bill measurements, with inter-modal troughs at 41.25 mm in New Holland Honeyeaters and at 40.75 mm in White- cheeked Honeyeaters. We proposed that birds with head-bill measurements greater than the inter-modal trough were probably males, and tested this method on birds whose sexes were known from brood patches or observations of nesting behaviour. Of 77 New Holland Honeyeaters (22 male, 55 female) and 47 White-cheeked Honeyeaters (11 males, 36 females), 91 per cent of birds were correctly sexed from their head-bill measurements. We investigated the possibility of using this technique on Yellow-faced Honeyeaters, but found this species to have a unimodal distribution of head-bill lengths.

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