Planning host exploitation through prospecting visits by parasitic cowbirds

We studied visits to potential host nests by two avian brood parasites, the host generalist shiny cowbird, Molothrus bonariensis, and the host specialist screaming cowbird, M. rufoaxillaris, in the periods preceding and overlapping the laying period of their hosts. Our goal was to examine the hypothesis that during pre-laying visits cowbird females form a dynamic memory library of laying opportunities, which they deploy to target suitable nests at a later pre-dawn period. We recorded presence of radio tagged females within a fixed area around nests of chalked-browed mockingbirds, Mimus saturninus (a common host of shiny cowbirds) and baywings, Agelaioides badius (the main host of screaming cowbirds), using proximity data-loggers placed at nests during prelaying, laying and early incubation. Our data confirmed that females of both species visit potential host nests prior to laying and that parasitic events occurred before dawn, earlier in screaming than shiny cowbirds but with little chance of host nests having been discovered on the laying day. There were interesting species differences: visits were less frequent in shiny than screaming cowbirds and the former rarely returned after laying, while screaming cowbirds visited nests repeatedly after laying and occasionally showed repeat parasitism. The higher frequency of re-visiting by screaming cowbirds to baywing nests is consistent with the uncommonly long and variable baywing prelaying period, and the incidence of repeat parasitism may reflect low availability of baywing nests and greater flexibility of its parental care potential thanks to it being a social breeder

Planning host exploitation through prospecting visits by parasitic cowbirds

We studied visits to potential host nests by two avian brood parasites, the host generalist shiny cowbird, Molothrus bonariensis, and the host specialist screaming cowbird, M. rufoaxillaris, in the periods preceding and overlapping the laying period of their hosts. Our goal was to examine the hypothesis that during pre-laying visits cowbird females form a dynamic memory library of laying opportunities, which they deploy to target suitable nests at a later pre-dawn period. We recorded presence of radio tagged females within a fixed area around nests of chalked-browed mockingbirds, Mimus saturninus (a common host of shiny cowbirds) and baywings, Agelaioides badius (the main host of screaming cowbirds), using proximity data-loggers placed at nests during prelaying, laying and early incubation. Our data confirmed that females of both species visit potential host nests prior to laying and that parasitic events occurred before dawn, earlier in screaming than shiny cowbirds but with little chance of host nests having been discovered on the laying day. There were interesting species differences: visits were less frequent in shiny than screaming cowbirds and the former rarely returned after laying, while screaming cowbirds visited nests repeatedly after laying and occasionally showed repeat parasitism. The higher frequency of re-visiting by screaming cowbirds to baywing nests is consistent with the uncommonly long and variable baywing prelaying period, and the incidence of repeat parasitism may reflect low availability of baywing nests and greater flexibility of its parental care potential thanks to it being a social breeder

Parasitic Behaviour of Interspecific Brood Parasitic Females

Interspecific avian brood parasites have to solve unique problems associated with their reproductive habit: they need to recognize potential hosts, search for and locate their nests, monitor nests progress and return to them at the appropriate time for egg-laying. In addition, parasitic females may improve the survival of their own eggs and chicks by removing or destroying part of the clutch content. Lastly, they should avoid egg-laying in nests parasitized by other females and remember the nests in which they have laid eggs to avoid laying two or more eggs in the same host nest to prevent harming their own previously laid eggs and generating competition between their own offspring. In this chapter we summarize information on the behaviour of parasitic females from the moment they start searching for host nests until they parasitize them (Fig. 1). We review the different hypotheses for explaining the recognition of hosts and the cues used to search for and locate their nests. We also review the different adaptive explanations for the removal or destruction of eggs as well as the information on competition among females for host nests and repeat parasitism.Fil: Reboreda, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Fiorini, Vanina Dafne. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Cecilia de Mársico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Gloag, Ros. University of Sydney; AustraliaFil: Scardamaglia, Romina Clara. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentin