Cover December 2022

Submitted by Michi on 28 December 2022.

Get the paper!

We at Journal of Avian Biology wish you a HAPPY NEW YEAR and are glad to share the Nov/Dec issue cover featuring the artwork by Joshua LaPergola, a portrait of a black catbird. The cover shows an original watercolor of Josh's study species. Josh was motivated to take up watercolor in January 2021, a time when the raging SARS-COV-2 pandemic halted international travel, preventing fieldwork. The piece is based on a photograph taken by co-author Bob Curry during Josh's first trip to the Yucatán, when he was scouting for potential field sites and first getting to know the black catbird. 

Read more about this study by LaPergola et al. (2022) 'Extra-pair paternity correlates with genetic diversity, but not breeding density, in a Neotropical passerine, the black catbird'.



The frequency of extra-pair paternity (EPP) varies widely across socially monogamous birds, but the proximate mechanisms driving this variation remain unclear. In this study, we tested two major factors hypothesized to influence extra-pair mating—breeding density and genetic diversity—by comparing genetic mating patterns in two populations of black catbirds Melanoptila glabrirostris. This Neotropical songbird is endemic to the Yucatán Peninsula, including eastern Mexico, and its offshore islands. We sampled one mainland (Sian Ka’an Biosphere Reserve) and one island (Isla Cozumel) population and used single-nucleotide polymorphisms (SNPs) to quantify heterozygosity and genetic parentage over two breeding seasons. Moderate levels of EPP occurred in both populations (9.5 – 35% of offspring and 17 – 45% of nests). Contrary to predictions, breeding density did not affect EPP: although breeding densities were much higher on the mainland than on the island, EPP rates did not differ between populations, and local breeding density was not correlated with EPP at individual nests. In contrast, partial support emerged for the hypothesis that genetic diversity influences EPP: extra-pair offspring were more heterozygous than within-pair offspring. However, the two populations did not differ in genetic diversity, and neither the heterozygosity of social fathers nor within-pair relatedness predicted EPP. These results are consistent with recent comparative studies suggesting that breeding density is not a critical driver of EPP rates, and that not all tropical songbirds exhibit low rates of EPP.