Sexual Dimorphism, Habitat Use and Molt in Wintering Black Skimmers (Rynchops niger) in the Lagoa do Peixe, Southern Brazil

Sexual dimorphism is the phenotypic difference between males and females of the same species, characterized by different body size and plumage. Black Skimmers (Rynchops niger, n = 44 adults, n = 14 juveniles) were captured between December 2010 and April 2012 with mist nets during the non-breeding p...

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Bibliographic Details
Published in:Waterbirds (De Leon Springs, Fla.) Fla.), 2013-12, Vol.36 (4), p.438-447
Main Authors: Scherer, Angelo L, Scherer, Janete F. M, Petry, Maria V, Valiati, Victor H
Format: Article
Language:English
Subjects:
adults
biometrics
Black Skimmer
body size
Brackish
color
estuaries
females
fish
habitat preferences
habitats
head
juveniles
Lagoa
males
Marine
molting
plumage
Rynchops niger
sex characteristics
sex determination
sex determination analysis
sexual dimorphism
sexual size dimorphism
wintering grounds
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Summary:Sexual dimorphism is the phenotypic difference between males and females of the same species, characterized by different body size and plumage. Black Skimmers (Rynchops niger, n = 44 adults, n = 14 juveniles) were captured between December 2010 and April 2012 with mist nets during the non-breeding period in the Lagoa do Peixe estuary, southern Brazil. Black Skimmers showed conspicuous sexual size dimorphism, with males being significantly larger than females. Males were 29% heavier than females and significantly larger in six measurements (% sexual size dimorphism = 7–26%). We developed two discriminant functions, both correctly identifying the sex of > 97.7% of the individuals tested and found that head + bill length alone was sufficient to predict the adult sex. The preferred habitat of Black Skimmers in this area was the barra region of the Lagoa do Peixe, where they can take advantage of the abundance of fish in the shallow water. Active molt was recorded in 62.5% of captured Black Skimmers. The molt scores of the primaries and the capture date showed a positive correlation, with lower scores observed in November/December and the highest scores in March/April. We found the intensity of red coloration of the culmen was not a good method for Black Skimmer sex determination in the field compared to molecular sexing, misclassifying 31.0% of individuals overall.
ISSN:1524-4695
1938-5390
DOI:10.1675/063.036.0401