Cohort effect on discriminant rate: the case of greater flamingo (<i>Phœnicopterus roseus</i>) chicks sexed with morphological characters

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.

Pitfalls and advances in morphometric sexing: insights from the Adélie penguin Pygoscelis adeliae

“…Our study involved a considerably larger dataset than previous works concerning morphometric sexing in the Adélie penguin (Table 1). Sample size influences discriminatory power, with simulations conducted on several bird species showing how the chance of misclassification increases especially with less than 100 individuals (Dechaume- Moncharmont et al 2011;Boucheker et al 2020). Whilst our simulations conducted on the Adélie penguin yield a relatively stable classification power even with small samples, they show that reduction in sample size reflects a much higher uncertainty in the discriminant rate (Fig.…”

“…A simple solution would be pooling annual series of morphological measurements taken by different field researchers and address this issue through permuted discriminant analysis (Mundry and Sommer 2007) or logistic mixed models. Likewise, these approaches would make possible to account for other potentially confounding factors for which discriminant functions are often derived separately, such as different age classes/ cohorts (Boucheker et al 2020) and study areas (Valenzuela-Guerra et al 2013).…”

Legacy and emerging contaminants in flamingos' chicks’ blood from the Ebro Delta Natural Park

“…Both studies pointed to sex differences as an important factor in the measurements. Although adult flamingos present sexual dimorphism, being males larger than females, flamingos' chicks cannot be sexed through biometric measurements at this early age (Boucheker et al, 2020), therefore sex could not be assessed as a factor in the analyses. However, no differences in the metabolism of contaminants are expected due to the similar development of both sexes at this age.…”

Non-Invasive Sex Determination of Nestlings and Adult Bonelli’s Eagles Using Morphometrics

“…Different techniques have been used for sexing raptors, including methods based on the study of phenotypic characteristics such as feathers and colours [ 14 ], morphometry (e.g., [ 13 , 15 , 16 ]), molecular techniques (e.g., [ 17 , 18 , 19 ]) or the combination of them (e.g., [ 20 , 21 ]). Morphometric techniques are commonly used in the field in combination with molecular methods.…”