What we know about the breeding biology of the endemic Gray-barred Wren (Campylorhynchus megalopterus)

Abstract

The Gray-barred Wren (Campylorhynchus megalopterus) remains among the most poorly known representatives of the family Troglodytidae endemic to Mexico. Little information exists on the species’ ecology and breeding biology, with only two known egg records in museum collections. Here I synthesized data from the literature and obtained 14 photographic records from citizen science databases to enhance our understanding of breeding behavior, egg morphology, and nesting habits of the Gray-barred Wren. I also critically assessed two egg collections in museum records. Only two, decades-old studies provided data on Gray-barred Wren breeding parameters, which I compared with information on 7 endemic wren species. According to the review, the Gray-barred Wren has an extended 10-month breeding season from November to August. The globular nest, cream-white egg interspersed with magenta to brownish spots, and evidence of cooperative breeding, were similar to closely-related species. However, the Gray-barred Wren had a smaller clutch size (1–3 eggs) and larger eggs (26.87 × 19.43 mm) than other endemic wren species. Notably, my critical reassessment of an egg set in the Western Foundation of Vertebrate Zoology collection that is attributed to the Gray-barred Wren, determined discrepancies in egg morphology, collection location, and associated nest description, suggesting a misidentification and incorrect species allocation. These findings highlight the importance of citizen science and museum records in uncovering essential biological data for poorly-known taxa.