Breeding Biology of the Night Heron Nycticorax Nycticorax in the South-west of Spain

The Night Heron Nycticorax nycticorax is widespread across the Palaearctic region though its population has decreased during the last century (Cramp & Simmons, 1977). In the Iberian Peninsula it has a threatened status (Blanco & González, 1992) and its reproduction is concentrated in no more than thirty colonies in the North, Northeast and Southwest (Palacios, 1997). Currently, population estimates for the Mediterranean region (29000-37000 pairs) show an increasing trend (Perennou et al., 1996), while population estimates for Spain give values between 1480 and 2210 pairs that oscillate between years, which makes this species very vulnerable (Fernández-Cruz & Fernández, 1991). Some information about the breeding biology of this species in the Palaearctic region has been published in recent years (Fasola & Hafner, 1997; Kazantzidis et al., 1997; Fasola, 1998), although part of the available information was restricted to a general framework about the breeding biology of herons (Schönwetter, 1967; Fasola & Barbieri, 1975; Hafner, 1977; Voisin, 1979). In Spain only Prósper & Hafner (1996) reported on the breeding phenology of the species in a coastal area, while there is no information for inland areas despite the high occurrence of inland Night Heron colonies in the Iberian Peninsula (FernándezCruz, 1975; Farinha & Leitâo, 1996; Parejo & Sánchez, 1999). The aim of this study is to describe the breeding biology of Night Herons in an inland area Ardeola 48(1), 2001, 19-25