How dare you? Broad-billed Rollers Eurystomus glaucurus usurp a threatened Cape Parrot Poicephalus robustus from a nest cavity in the Limpopo province of South Africa

Abstract

This study documents the first recorded instance of interspecific competition for nesting cavities between the endangered Cape Parrot Poicephalus robustus and the Broad-billed Roller Eurystomus glaucurus. Both are secondary cavity-nesters occupying overlapping habitats in southern Africa. Despite the Cape Parrot’s earlier breeding season, which theoretically affords it priority access to cavities, a roller pair was observed attempting to use an actively occupied Cape Parrot nest. This rare interaction reveals potential interspecies conflict where nest-site selection overlaps. Additional examples from both African and Australasian regions suggest that breeding season timing and cavity characteristics often mitigate competition among avian species. The impact of the roller usurping a Cape Parrot nest was significant as only three out of 13 known nest sites were active in 2024 and only one was known to be successful. Therefore, with Cape Parrot populations having dwindled to fewer than 2,000 individuals and breeding success vulnerable to habitat damage and predation, understanding all limiting factors, including interspecific interactions, is vital for conservation. Long-term monitoring across regional nodes underscores the importance of protecting preferred nesting sites to ensure reproductive success and species longevity.