Sexing Adult and Nestling Red-Shouldered Hawks Using Morphometrics and Molecular Techniques1

Cheryl R Dykstra,Melinda M Simon,Ann R Wegman,Herman L Mays,Jeffrey L Hays

doi:10.3356/jrr-11-84.1

Cheryl R Dykstra, Melinda M Simon + Show 3 more

Open Access

https://doi.org/10.3356/jrr-11-84.1

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Abstract

Sexing of raptors is important for understanding their ecology and demography. Males and females of monomorphic species such as Red-shouldered Hawks (Buteo lineatus) may be distinguished using molecular and morphometric techniques. We collected blood samples and morphometric measurements from adult and nestling Red-shouldered Hawks in southern Ohio. We determined sex via amplification of the sex-linked chromo-helicase-DNA-binding gene and polymerase chain reaction. We used a suite of morphometric measurements to generate a recursive partitioning classification tree and in a linear discriminant analysis to determine the sex of adults and nestlings. For adults, the recursive partitioning tree utilized only mass to distinguish sexes, with an overall successful classification rate of 94%. For nestling hawks aged approximately 3 wk and older, mass and toepad (footpad) length were used to distinguish the sexes, with an overall successful classification rate of 91%. The ability to sex adults and nestlings in the field is valuable for studies of dispersal, survival, and behavior.

Highlights

ABSTRACT.—Sexing of raptors is important for understanding their ecology and demography
We studied Red-shouldered Hawks in two regions of southern Ohio
DNA extraction and/or Polymerase chain reaction (PCR) failed for six adults and three of the remaining nestlings, so these were excluded

Summary

Introduction

ABSTRACT.—Sexing of raptors is important for understanding their ecology and demography. Males and females of monomorphic species such as Red-shouldered Hawks (Buteo lineatus) may be distinguished using molecular and morphometric techniques. The recursive partitioning tree utilized only mass to distinguish sexes, with an overall successful classification rate of 94%. Usamos un grupo de medidas morfometricas para generar un arbol de clasificacion de particion recursiva y un analisis de discriminacion lineal para determinar el sexo de adultos y polluelos. El arbol de particion recursiva solo utilizola masa para distinguir los sexos, con una tasa total de clasificacion exitosa del 94%. Many Buteo species are moderately dimorphic; Red-tailed Hawk (Buteo jamaicensis) males average 82% of the size of females, and Redshouldered Hawks (B. lineatus) 85% (Ferguson-Lees and Christie 2001). If large numbers of birds must be sexed in order to gain statistically significant sample sizes, as in many banding studies where there is a low recovery/encounter rate (e.g., 4–5%, Dykstra et al 2004), the costs of DNA sexing may be prohibitive, whereas the cost of morphometric sexing is negligible

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