Sex determination by morphometry of adult White-crested Elaenia (Elaenia albiceps chilensis)

Abstract

Sex determination of birds is key to understanding various aspects of the demography of a population as it may influence survival, dispersal, recruitment and other life history parameters (Gowaty 1993, Newton 1998), but sex differentiation is difficult in species with sexually monomorphic plumage, even for captured individuals. During the breeding season, the sex of most individuals of many species can be determined either by the presence or extent of a brood patch in females or the cloacal protuberance in males (Ralph et al. 1993). In some species, however, the male can develop an incubation patch, but it does not typically develop as extensively as in females (Skutch 1957, Pyle 1997). Furthermore, during the nonbreeding season these characters are not useful, although sexing birds in the non-breeding season is desirable (e.g., sex-specific migration phenologies, migration routes, and wintering habitat use). Morgan (2005) discussed the possibility of analyzing multi-modal distributions of morphological characters to differentiate sexes. This approach was used by Catry et

Migratory timing, rate, routes and wintering areas of White-crested Elaenia (Elaenia albiceps chilensis), a key seed disperser for Patagonian forest regeneration

“…For each captured individual, we measured wing chord (from the carpal joint to tip of the longest primary), and body mass. All individuals were sexed as described in Cueto et al [ 33 ].…”

How birds age? Chilean Elaenia as an example for the Neotropical bird species

“…We scored the development of the cloacal protuberance on a 4-point scale (0 = none; 1 = small, 2 = medium; 3 = large; Ralph et al 1993). We determined the sex of each individual following the recommendation of Cueto et al (2015).…”

“…This species is a long-distance migrant (Bravo et al 2017) and provides an important ecological service for forest regeneration (Cavallero et al 2013;Bravo et al 2015), because it is the main seed disperser of the forest (Armesto et al 1987;Amico and Aizen 2005). Chilean Elaenia is sexually monomorphic in plumage, but males have longer wings and tail than females, allowing sex differentiation (Cueto et al 2015). Thomson et al (2015) proposed, using the color of the palate for aging Chilean Elaenia, a method that has been used in several species in the northern hemisphere (Svensson 1992;Pyle 1997).…”

Demography of the Neotropical austral migrant Elaenia albiceps chilensis (Tyrannidae) on its breeding grounds: climate and food offer effects

“…We aged individuals by the presence (adult) or lack (juvenile) of the characteristic white crown (Schulenberg 2009). To determine the sex and reproductive status of birds, we registered the development of the incubation patch (females) and cloacal protuberance (males) following Ralph et al (1993), and used the diff erences in wing and tail length between females and males for sexing non-breeding birds following Cueto et al (2015). When an individual did not match with those criteria of sexing it was classifi ed as "unsexed adult".…”