First documented case of pseudo-egg incubation by Coragyps atratus (Cathartidae) in a semiarid environment in Northeastern Brazil

Abstract Birds occasionally incubate inanimate objects, a behavior known as pseudo-egg incubation. This study documents the first case of pseudo-egg incubation by a black vulture ( Coragyps atratus ) in the Brazilian semi-arid region. An unbanded adult vulture exhibited nesting behavior and tolerance to close human approach while incubating an empty snail shell. A month later, an unbanded adult vulture was observed at the same location near the shell, consistent with the species’ incubation period. The most plausible hypothesis for this behavior is mistaken-egg, where birds misidentify objects as eggs due to visual similarities, given the shell’s morphological similarity to a vulture egg. This record expands knowledge on this behavior in birds of prey and, as it was observed during a birdwatching excursion, highlights the value of citizen science in generating novel ornithological discoveries.