Sexing adult Northern Shrikes using DNA, morphometrics, and plumage

Abstract

Northern Shrikes (Lanius excubitor) are predatory songbirds found primarily in taiga regions throughout their Holarctic breeding range. The species is poorly known, especially in North America, and is generally thought to be sexually monomorphic. From 2004 to 2007, we captured 50 adults in northern Wisconsin during the nonbreeding season (December–March) and determined sex using DNA extracted from feather samples. Males had significantly longer wings, longer tails, and less black in the outer rectrix than females, but body mass did not differ between the sexes. A discriminant function equation using tail length and extent of black on the outer rectrix correctly assigned the sex of 97.4% of captured adults. Plumage dimorphism was also evident, with males having paler gray heads and backs without brown tones, whiter underparts with lighter barring, and a more distinct and horizontal border at the base of the sixth primary feather. The ability to accurately determine sex will provide opportunities to examine possible inter‐ and intrasexual differences in the behavior and ecology of adult Northern Shrikes.

Sexing Adult Pale-Winged Starlings Using Morphometric and Discriminant Function Analysis

“…Therefore a species cannot be wisely categorized as strictly monomorphic before detailed investigation [ 14 ]. Several studies show that species known as sexually monomorphic do in fact present differences between sexes: long tailed finches ( Poephila acuticauda ) [ 14 ], bay-capped wren-spinetails [ 5 ], northem shrikes ( Lanius excubitor ) [ 15 ] and Acadian flycatchers ( Empidonax virescens ) [ 16 ] for example. Birds may use features such as ultraviolet pigmentation of plumage to discriminate sexes [ 17 , 18 ].…”

Pre‐breeding diet influences ornament size in the Rhinoceros Auklet Cerorhinca monocerata

“…data). For birds with bill depths of 16–17 mm, we used a discriminant function analysis (Brady et al. 2009), with wing chord, weight, culmen and bill depth, to assign birds as either male or female (males are generally larger than females; B. Addison unpubl.…”

A morphometric model to predict the sex of virginia rails (Rallus limicola)

“…Classification efforts using morphometrics for many other bird species, including gulls (Laridae), hawks (Accipitridae), ravens (Corvidae), and cormorants (Phalacrocoracidae) have been able to achieve >90% accuracy (Mawhinney and Diamond , Donohue and Dufty , Bedrosian et al , Liordos and Goutner , Herring et al ). Still, models with >75% accuracy have been shown to be useful to understanding population demographics in terns (Sternidae), shearwaters (Procellariidae), puffins (Alcidae), shrikes (Laniidae), and finches (Fringillidae; Gucking et al , Bluso et al , Brady et al , Van Rooij and Griffith , Friars and Diamond ). We contend that our results are likely of interest and will prove useful to natural resource professionals that study secretive marshbirds, but additional work should be completed to increase our accuracy and the model's application.…”

“…For example, exposed culmen has been important for sex determination in a wide range of bird species, including several waterbirds (Herring et al , ; Fuertes et al ). Wing chord (the length of the closed, uncompressed wing) is also commonly used to differentiate between the sexes of a variety of bird species (Ryan et al , Pyle , Brady et al , Fuertes et al ). Tarsus length is often used in waterbirds, along with the combination of the middle toe (Ryan et al , Gucking et al , Fuertes et al ).…”