Pipraeidea bonariensis accepts parasitic eggs but does not successfully raise parasitic nestlings

SEGURA LUCIANO NOEL; GONZALEZ EXEQUIEL; MONGES VIRGINIA; CHIRAMBERRO ANA PAULA; GERSTMAYER PAULA AGUSTINA; COLOMBO, MARTÍN ALEJANDRO; JAUREGUI ADRIAN

Gramado

Congreso; II Ornithological Congress of the Americas; 2023

Association of Field Ornithologists, Neotropical Ornithological Society, Sociedade Brasileira de Ornitologia

Brood parasites reduce host breeding success and favor the evolution of antiparasitic defenses, such as the parasitic egg/nestling recognition and rejection. Molothrus bonariensis is a Neotropical generalist brood parasite and Pipraeidea bonariensis has been listed as its host. We monitored 82 host nests (2013-2019) in central-east Argentina and found that 35% were parasitized. Parasitic eggs were accepted in 92% of the nests and hatched in 78.5% of the nests that completed the incubation stage (alone in 18% of the nests, with a single host sibling in 27%, and with two host siblings in 55%). No parasitic nestling survived (92% due to apparent starvation between the second and sixth day of age and 8% due to predation). When the parasitic nestling shared the nest with a host sibling, we only observed the death of the parasitic nestling. In parallel, we videotaped 11 non-parasitized and seven parasitized nests during the nestling stage and observed that hosts delivered exclusively fruits (never insects). Although the ability to recognize and discriminate has been suggested as an effective antiparasitic defense mechanism, our results indicate that the null nestling parasite success was more linked to the type of food delivered than a potential parasitic nestling recognition. Our finding also highlights on the controversial strategies of parasitism of M. bonariensis in terms of host selection, since although our host did not successfully rear any parasitic nestling, the occurrence of parasitism was high, suggesting that there would be little or no host selection by the parasite.