Rapid and Low-Cost Molecular Sexing of a Corvid Songbird Using a Single Protocol with Two Universal Primer Sets

Summary. The absence of sex dimorphism in many bird species complicates sex determination by direct observation, hindering sex-specific studies. Standard protocols for molecular sexing include polymerase chain reaction (PCR) amplification of intron regions of the Chromodomain-Helicase DNA-binding protein 1 (CHD1) gene. While several methods have been studied, their usefulness for songbirds (Passeriformes) has not been consistent and has largely depended on target species and on time-consuming primer-set specific optimisation of available protocols. We tested a molecular sexing protocol with two universal primer sets (P2/P8 and 2550F/2718R) in a corvid songbird: the Plush-crested Jay Cyanocorax chrysops. The protocol was rapid and inexpensive as well as highly effective. Using 2550F/2718R, females were revealed by two bands separated for some 200 base pairs (bp) that resolved easily on 0.8% agarose gel. Conversely, P2/P8 female amplicons differed in roughly 30 bp and a more expensive 3% agarose gel was necessary to reveal them. Our results are contextualised with an up-to-date literature survey of molecular sexing in other corvids. The primer set 2550F/2718R is found to be effective, providing a reliable and low-cost method for sexing jays and other corvids. —Lois-Milevicich, J., Gómez, R.O., Ursino, C.A., Lois, N.A. & de la Colina, A. (2021). Rapid and low-cost molecular sexing of a corvid songbird using a single protocol with two universal primer sets. Ardeola, 68: 501-510.