Doi: https://doi.org/10.13157/arla.70.2.2023.ra2
Authors: Cristina RAMO, Macarena CASTRO, Alejandro PÉREZ-HURTADO, Nuria MARTÍN, Miguel A. RENDÓN, , Juan A. AMAT and Gustavo LIÑÁN-CEMBRANO
E-mail: cristina@ebd.csic.es
Published: Volume 70.2, July 2023. Pages 169-184.
Language: English
Keywords: crypsis, mud covering, shorebirds, texture analysis and visual modelling
Summary:
Predation is one of the main causes of nest failure in birds. In order to overcome this, many species lay cryptic eggs, which enhances camouflage through either background matching or shape disruption, among other mechanisms. Despite this, ground-nesting birds still suffer high nest predation rates. One possibility to alleviate this could be to soil the eggs with particles of material surrounding nests, improving the camouflage. Indeed, it has been suggested that egg soiling is a mechanism of egg protection, but it remains to be demonstrated whether egg soiling is a strategy used by birds or is an unintentional by-product after incubating adults enter nests with dirty feet, legs and/or plumage. In this study, we analysed images from infra-red camera traps placed beside Pied Avocet Recurvirostra avosetta nests, in which we had previously cleaned dirty eggs and provided mud with which the adults might have soiled the eggs, and we found no evidence of deliberate egg soiling in this case. There was a slight improvement (not statistically significant) in the camouflage of soiled avocet eggs in comparison to clean eggs, but only in one of two studied nesting sites in which the eggs were more soiled. Although egg soiling may result in improved camouflage, future studies should address its potential costs to establish why it has not apparently evolved as a deliberate strategy to improve egg camouflage in nesting shorebirds.
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