I Butll. GCA 14: 59-61,1997 Black-crowned Night-herons Nycticorax Inyclcorax feeding on carcasses

D. PAREJO

The diet of the Black-crowned Night-heron Nycticorax nycticorax is based rnostly on fish, arnphibians and insects, though in sorne populations the herons cornrnonly take srnall birds. Two records are here reported of night-herons feeding on bird carcasses in the west of Badajoz Province (Extrernadura, Spain). The rnain factor causing the absence of reports of night-herons using this food source rnay be the rnethodology traditionally used to study the diet of the species, based on the collection of food boluses or chick regurgitates but rarely on direct observation.

Key words: Black-crowned Night-heron, Nycticorax nycticorax, food, carcasses, Extremadura.

Deseada Parejo. G.I.C. Área de Biologia Animal. Dpto. de Ciencias Morfológicas, Biologia Celular y Animal. Facultad de Ciencias. Universidad de Extremadura. Avda. de Elvas s/n. E-06071 Badajoz. Rebut: 10.07.98; Acceptat: 30.10.98

The diet of the Black-crowned Night- (Martinez et al. 1992). In this note I report heron Nycticorax nycticorax is based mostly observations of Night-herons feeding on on fish, amphibians, insects, crustaceans bird carcasses, a type of food that has not and small mammals (Voisin 1991), thou,gh previously been reported, in a heronry in small birds may on occasion constitute a the west of Badaioz Province (Extremadura, significant part (Allens & Mangels 1940, Spain). Wolford & Boag 1971). In its American On 05.08.96 two one-year-old night- range this species also commonly takes herons were observed feeding on the corpse eggs and young birds (Becketi 1964, Kale of a conspecific near the trees of a heronry 1965, Collins 1970, Wolford & Boag 1971, located on the Guadiana River in Badajoz Hunter & Morris 1976, Andrews 1981). In city (38"53'N-6'58'E). The colony contained Spain, birds in the diet of this heron have Cattle Egrets Bubulcus ibis, Little Egrets only been reported for the Ebro Delta Egretfa garzetta and Black-crowned Night- population, based on chicks' regurgitations herons. At the same colony, but the next year Butll. GCA 14,1997

(08.05.97), an adult Night-heron used its RESUM bill to pick up the corpse of a young Little Egret from the ground and went into colony Martinets de nit Nycticorax nycticorax vegetation, presumably to eat the bird. alimentant-se de carronya Necrophagy has not previously been L'alimentació del Martinet de nit es basa reported in this species, though the fonamentalment en peixos, amfibis i methodology that has traditionally been insectes encara que en determinades used to study its diet could have precluded poblacions és comuna la ingestió de joves its detection, as the collection of chicks' d'altres ocells. Aqui es descriuen dues regurgitates (Fasola et al. 1981, Martinez observacions de martinets alimentant-se et al. 1992) or food boluses by means of d'ocells morts en una colonia de I'oest de neck collars (Pérez et al. 1991) are the most Badajoz. El fet que no existeixin descripcions commonly used methods. These previes de l'ús d'aquest tipus de menjar per observations support the idea of the Night- part dels martinets probablement és perque heron as an opportunistic feeder (Wolford la metodologia emprada tradicionalment & Boag 1971, Fasola et al. 1981): per a I'estudi de la dieta d'aquesta especie es basa en la recollida de restes de menjar com egagropiles o regurgitacions, utilitzant ACKNOWLEDGEMENTS molt poc I'observació directa.

Jesús Avilés revised and improved the original manuscript. Emilio Costillo REFERENCES accompanied me in the field. Juan Carlos Senar and an anonymous reviewer offered ALLEN, R. & MANGLES, F. i? 1940. valuable suggestions to the manuscript. Studies of the nesting behavior of the Black- crowned Night-heron. Proc. Linn. Soc. N. Y. 50: 1-28. RESUMEN ANDREWS, S. 1981. Black-crowned Martinetes Nycticorax nycticorax ali- Night-heron predation on Black-necked mentándose de carroria Stilt. Elepaio 41 : 86. La alimentación del Martinete se basa fundamentalmente en peces, anfibios e in- BECKm, T. A. 1964. Black-crowned Night- sectos, aunque en determinada~poblacio- heron feeding behaviour. Chat 28: 93-94. nes es común la ingestión de juveniles de otras aves. Se describen aqui dos observa- COLLINS, G. T. 1970. Black-crowned ciones de martinetes alimentándose de aves Night-heron as predator of tern chicks. Auk muertas en una colonia del oeste de 87: 584-585. Badajoz. El hecho de que no existan des- cripciones previas del uso de este tipo de FASOLA, M., GALEOllI, F?, BOGLIANI, alimento por parte de 10s martinetes pro- G. & NARDI, i? 1981. Food of Night Heron bablemente se debe a que la metodologia (Nycticorax nycticorax) and Little Egret tradicionalmente empleada para el estudio (Egreita garzetta) feeding in rice fields. Riv. de la dieta de esta especie se basa en la Ital. Om. 51: 97-1 12. recogida de restos alimentarios como egagrópilas o regurgitados, utilizándose HUNTER, R. G. & MORRIS, R. D. 1976. raramente la observación directa. Nocturnal predation by Black-crowned Black-crowned Night-herons feeding on carcasses

Night-heron ata Cornrnon Tern colony. Auk PEREZ, J. J., DE LOPE,F., TUREGANO, B. 93: 629-633. & DE LA CRUZ, C. 1991. La alirnentación de 10s pollos de Martinete (Nycticoraxnycticorax) KALE, H. W. 1965. Nesting predation en Extrernadura. Ardeola 38: 277-287. by herons in a Georgia heronry. Oriole 30: 69-70. VOISIN, C. 199 1. The Herons of Europe. London: Poyser. MART~NEZ,C., RUIZ, X. & JOVER, L. 1992. Alirnentación de 10s pollos de Mar- WOLFORD, J. W. & BOAG, D. A. 1971. tinete (Nycticorax nycticorax) en el Delta del Food habits of Black-Crowned Night-Herons Ebro. Ardeola 39: 25-34. in Southern Alberta. Auk 88: 435-437.