Video evidence of siblicide and cannibalism, movement of nestlings by adults, and interactions with predators in nesting Hen Harriers

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Fernández-Bellon, Darío
Wilson, Mark W.
Irwin, Sandra
Kelly, Thomas C.
O'Mahony, Barry
O'Halloran, John
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During a nest-camera study of Hen Harriers (Circus cyaneus), we recorded siblicide, cannibalism, movement of nestlings by adult birds, and interactions with predators. We deployed cameras at 13 nests across three study areas in Ireland between 2008 and 2010. At a nest with two well-developed nestlings (approximately 25–30 d old), the older nestling killed its sibling and fed on it. This was the first documented case of siblicide in this species, to our knowledge. Recordings also revealed three other events of cannibalism in which one of the nestlings in a brood died from unknown causes and was then eaten by its siblings (n = 1), by the adult male (n = 1), or was used by the adult female to feed the remaining nestlings (n = 1). At two nests, recordings showed the adult female picking up and moving nestlings that were outside the nest cup. In addition, cameras recorded two instances of full brood predation by red fox (Vulpes vulpes) and an attack on a nest by a female Eurasian Kestrel (Falco tinnunculus) that had no apparent consequences for the nestlings or the female Hen Harrier. The behaviors reported here, which are difficult to observe directly, may have important consequences for our understanding of productivity and population dynamics of Hen Harriers.
Durante un estudio sobre patrones de actividad de individuos reproductores de Circus cyaneus realizado con cámaras para monitoreo de nidos, registramos comportamientos de fratricidio, canibalismo, movimientos de polluelos e interacciones con depredadores. Colocamos cámaras en 13 nidos distribuidos en tres áreas de estudio en Irlanda entre 2008 y 2010. En un nido con dos polluelos en un estado de desarrollo avanzado (c. 25-30 días), el polluelo de mayor edad mató al otro y se alimentó de él. Este es el primer caso documentado de fratricidio en esta especie. Obtuvimos imágenes de otros tres casos de canibalismo en que uno o más polluelos fallecieron por causas desconocidas y sus cadáveres fueron usados como alimento por los otros polluelos (n = 1), por el macho adulto (n = 1) o por la hembra adulta para alimentar a los otros polluelos (n = 1). En dos nidos, las imágenes muestran a la hembra adulta repetidamente recogiendo polluelos que se alejan del nido para intentar llevarlos al nido. Por último, las cámaras captaron dos eventos de depredación de polluelos por parte de Vulpes vulpes y un enfrentamiento entre la hembra adulta de C. cyaneus y una hembra de Falco tinnunculus sin consecuencias para los polluelos o la hembra adulta. Estos comportamientos, difíciles de detectar mediante metodologías de monitoreo tradicionales, pueden tener consecuencias para el éxito reproductivo y la dinámica poblacional de esta especie.
Hen Harrier , Circus cyaneus , Cannibalism , Nest camera , Nest defense , Nestling moving , Siblicide , Sibling aggression
Fernández-Bellon, D., Wilson, M. W., Irwin, S., Kelly, T. C., O'Mahony, B. and O'Halloran, J. (2018) 'Video evidence of siblicide and cannibalism, movement of nestlings by adults, and interactions with predators in nesting Hen Harriers', Journal of Raptor Research, 52(3), pp. 393-399. doi:10.3356/JRR-17-58.1
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