USe of morphometric parameters for the determination of sex of Adelie penguins.

Abstract

The sex of Addie penguins, Pygoscelis adeliae, may be determined by cloacal examination during the early part of the breeding season. Later in the season it becomes increasingly difficult to determine the sex of penguins by this method as the structures used for identification regress. Discriminant analysis of morphometric characters has been suggested as an alternative. This technique was examined for breeding birds of known sex near Mawson Station, Antarctica. The sex of 89% of breeding birds could be correctly determined by comparing the discriminant score D = 0.582 Bl + 1.118 Bd + 0.219Fw, where Bl is bill length, Bd is bill depth and Fw is flipper width, with a mean discriminant score (MDS) of 55.39. In all, the sexes of 87% were correctly determined by means of length and depth only (D=0.601Bl+ 1.154Bd, MDS=44.96). The sex of juvenile birds could not be determined. Determination of sex by discriminant analysis is shown to give acceptable estimates of morphometric characters divided by sex where only the mean and variance of these variables but not the sexual identity of individual birds is required. Where absolute accuracy in sex determination is required, 80% of the birds in our samples would have to be discarded to be 90% confident of the sex of the remainder.

A new sex determination method using morphological traits in adult chinstrap and gentoo penguins on King George Island, Antarctica

“…Among phenotypic parameters, we excluded "maximum gap of the bill" (Renner et al 1998) and "total length from bill to tail" (ValenzuelaGuerra et al 2013) since these were difficult to estimate due to the animals' movements and varied largely among repeated measurements. Instead, we used middle toe length, which was used in Adélie penguin sex determination, easily distinguished on the ventral surface from the tarso-metatarsal joint to the end of middle toe claw (Kerry et al 1992, for measurement; see Figure 1). For analysis, we used bill length, bill depth, flipper length and middle toe length (for measurement pictures of bill and flipper size, see Amat et al 1993 for chinstrap and ValenzuelaGuerra et al 2013 for gentoo).…”

“…Thus, past studies have developed techniques to determine sex via combining several morphological differences in bills or flippers (e.g. Kerry et al 1992 for the Adélie penguin, Pygoscelis adeliae; Hull 1996 for Royal penuigns, Eudyptes schlegeli, and Rockhopper penguins, Eudyptes chrysocome; Arnould et al 2004 for the Little penguin, Eudyptula minor). Although recent molecular sexing techniques have enabled us to distinguish the sexes, morphological traits must still be used when surveying colonial birds under harsh field conditions.…”

Inter-colony and sex differences in the effects of parental body condition and foraging effort on the brood growth of Ad�lie penguins

“…These birds were designated as MONI-TORED birds. Bill depth, bill length, and head length were measured with calipers to 0.1 mm and flipper width was measured to 1 mm (CCAMLR 1991;Kerry et al 1992). The sexes of parents were determined by their sizes following Kerry et al (1992).…”

“…Bill depth, bill length, and head length were measured with calipers to 0.1 mm and flipper width was measured to 1 mm (CCAMLR 1991;Kerry et al 1992). The sexes of parents were determined by their sizes following Kerry et al (1992). We arbitrarily sampled pairs at Syowa 95 in the period of 23-27 December in 1995 (16 pairs with two chicks and 4 pairs with a single chick), and those brooding two chicks at Syowa 96 in the period of 23-30 December 1996 (17 pairs) and at DDU 96 during 29-31 December 1996 (10 pairs).…”

“…The body mass did not decrease after 3-7 flushings, indicating that most of the stomach contents were removed. These birds were designated as TRIP birds and sexed following Kerry et al (1992). Soon after the flushing, the stomach contents were drained through sieves, weighed to 0.1 g with an electronic balance, and sorted (Watanuki et al 2002).…”