Brown-and-yellow marshbirds reduce their acceptance threshold of mimetic brood parasite eggs in presence of non-mimetic eggs

MERMOZ, MYRIAM E; HAUPT , CAROLINA; FERNÁNDEZ, GUSTAVO J.

JOURNAL OF ETHOLOGY

SPRINGER TOKYO

Lugar: Tokyo; Año: 2016 vol. 34 p. 65 - 71

0289-0771

Recognition and rejection of brood parasite eggs is one of the most reported hosts? defences. The brown-and-yellow marshbird (Pseudoleistes virescens) is a common host of the shiny cowbird (Molothrus bonariensis). This host recognizes and rejects cowbird eggs that are immaculate white, while it accepts cowbird?s spotted eggs. We assessed the acceptance threshold hypothesis that proposes that parasite egg recognition is context dependent. We experimentally parasitized host nests with a spotted cowbird egg and simultaneously added: 1) one novel egg with spots similar to those of a cowbird egg but over a blue background, or 2) one immaculate white cowbird egg. Seventy-eight percent of blue spotted and 77% of cowbird immaculate eggs were quickly recognized and rejected. The rejection frequency of spotted cowbird eggs was also high (60%) and was not related to the type of egg added with the spotted cowbird eggs. We found this rejection frequency of spotted cowbird eggs to be higher than the 21% we had previously found in similar experiments but in which the spotted cowbird egg was added singly. These results support the acceptance threshold hypothesis that predicts an adaptive modulation of the antiparasite defence when the perceived risk of parasitism is high.