Alloparental behavior in three Neotropical grebes

Alloparental behavior includes a wide range of situations, from occasional fostering to adoption. It is usually the result of brood parasitism, brood adoption or brood mixing, but also due to nest switching. Interspecific alloparental behaviors are less widespread, but there are no key differences in mechanism of underlying behaviors. Some South American grebes are found sympatrically, and some of them usually reproduce on mixed colonies. Here we describe different conspecific and interspecific alloparental behaviors involving Silvery Grebe (Podiceps occipitalis), White-tufted Grebe (Rollandia rolland) and the critically endangered Hooded Grebe (Podiceps gallardoi). We discuss the implications of temporary adoption and potentially ‘true’ adoption, in particular for Hooded Grebes. Our observations show that alloparental behavior is possibly widespread among Neotropical grebes, and in the case of the Hooded Grebe we hypothesize that alloparental intraspecific feeding of non-related juveniles prior to migration could help to increase juvenile survival.