Abstract
Abstract. We used a large dataset of greater flamingo chicks banded and measured at Camargue, France, to verify the applicability of discriminant function analysis to sex this species. Males and females sexed genetically differed significantly in all of the morphological characters measured (body mass, tarsus and wing length), with males being significantly larger than females. Although the discriminant rate varied substantially from one year to another, we found that it increased with the sample size of genetically sexed individuals. Our results suggest that discriminant function analysis (DFA) does not provide an efficient tool to sex greater flamingo chicks as these relationship are highly variable across years, requiring the genetic determination of sex on a large number of individuals every year for calibrating the DFA and still providing an overall low accuracy in sex determination. Indeed, conditions at breeding seasons can vary between years and can be considered proximate causes affecting the correct discriminant rate. Like previous studies, we recommend caution in dealing with discriminant equations computed from small datasets, and our simulation suggests that 325 genetically sexed individuals are needed to obtain 80 % correctly classified greater flamingo chicks.
Highlights
The ability to correctly sex marked birds is crucial to most behavioral or ecological studies (Greenwood, 1980; Andersson, 1994; Short and Balaban, 1994; Childress and Bennun, 2002; Barbraud et al, 2003) and for the management and conservation of species (Zavalaga and Paredes, 1997; Fernandez-Juricic, et al, 2009)
Our results suggest that discriminant function analysis (DFA) does not provide an efficient tool to sex greater flamingo chicks as these relationship are highly variable across years, requiring the genetic determination of sex on a large number of individuals every year for calibrating the DFA and still providing an overall low accuracy in sex determination
Sexual dimorphism occurs in flamingos chicks with females of 1.5 to 2.5 months being already smaller than males of the same age (Studer-Thiersch, 1986; but see Bertault et al, 2000)
Summary
The ability to correctly sex marked birds is crucial to most behavioral or ecological studies (Greenwood, 1980; Andersson, 1994; Short and Balaban, 1994; Childress and Bennun, 2002; Barbraud et al, 2003) and for the management and conservation of species (Zavalaga and Paredes, 1997; Fernandez-Juricic, et al, 2009). Sex determination in immature and adult individuals where the plumage is similar in both sexes based only on external morphological characters is often difficult (Cuthill et al, 1999) To overcome this difficulty a range of techniques have been used such as laparoscopy (Petrides, 1950; Richter and Bourne, 1990; Richner, 1989), measuring the plasma testosterone levels during the breeding period (Czekala and Lasley, 1977; Bercovitz et al, 1978), vocalization analyses (Bourgeois et al, 2007), individual breeding or observation of territorial behavior (Castoro and Guhl, 1958; Flux and Innes, 2001; Fletcher and Hamer, 2003), and generalized molecular techniques (Griffiths et al, 1998; Bertault et al, 1999; Fridolfsson and Ellegren, 1999; Tomasulo et al, 2002; Dubiec and Zagalska-Neubauer, 2006; Balkız et al, 2007).
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