Behaviour This species makes little known (Ogilvie 1997) dispersive movements (del Hoyo et al. 1992, Nelson 2005) related to water conditions (Brown et al. 1982, del Hoyo et al. 1992). It is locally nomadic in southern Africa in response to changing wetland conditions (Barnes 2000), and western African populations make northward movements into sub-Saharan steppe during the wet season, returning southwards in the dry season (Brown et al. 1982, del Hoyo et al. 1992, Johnsgard 1993). The species breeds all year round, although most start late in the wet season (del Hoyo et al. 1992, Johnsgard 1993, Nelson 2005). It is gregarious both during breeding and non-breeding (Langrand 1990), nesting in small groups or larger loose colonies of between 20 and 500 pairs (Brown et al. 1982, del Hoyo et al. 1992, Ogilvie 1997) (often alongside other species (Langrand 1990, Nelson 2005)). It roosts nocturnally in groups (Johnsgard 1993), but is more of a solitary feeder, preferring to fish singly or in small loose groups of less than 30 individuals (Langrand 1990, Johnsgard 1993, Nelson 2005). It is chiefly diurnally active, especially during the morning and evening, although it may also fish on moonlit nights (Brown et al. 1982, Langrand 1990). Habitat The species inhabits a wide range of aquatic habitats, but prefers to feed in quiet backwaters and weed-grown lagoons (del Hoyo et al. 1992) where there is shallow water and emergent vegetation (Langrand 1990), generally avoiding steep, vegetated lake margins (Nelson 2005). It shows a preference for freshwater lakes, swamps, large slow-flowing rivers, and seasonal pools (Brown et al. 1982, Langrand 1990, del Hoyo et al. 1992, Johnsgard 1993, Nelson 2005), but also frequents reservoirs (Brown et al. 1982, Johnsgard 1993), seasonally flooded land (Nelson 2005) and flood-plains near river mouths (Ogilvie 1997). It may occur on alkaline and saline lakes and lagoons (Brown et al. 1982, Langrand 1990, Johnsgard 1993, Nelson 2005), and can sometimes be found along the coast in bays (del Hoyo et al. 1992) and estuaries (Brown et al. 1982, Langrand 1990, Nelson 2005) (although seldom on open seashore) (Brown et al. 1982, Nelson 2005). The species tends to roost and breed in trees (e.g. mangroves), but will also roost on sandy islands, cliffs, coral reefs and sand-dunes (del Hoyo et al. 1992). Nesting trees are often killed by repeated nesting, which forces breeding colonies to move (although birds will usually not move far) (Brown et al. 1982, del Hoyo et al. 1992). Diet The diet of this species consists entirely of fish (of any size up to 450 g, although usually in the range of 80-290 g) (Nelson 2005), with cichlids (especially Haplochromis and Tilapia) being preferred (Brown et al. 1982, del Hoyo et al. 1992, Johnsgard 1993, Nelson 2005). Breeding site The species nests colonially in trees, reeds or low bushes along waterfronts (Brown et al. 1982, del Hoyo et al. 1992, Nelson 2005) as well as (less often) on the ground on sandy islands and in mangroves (del Hoyo et al. 1992, Nelson 2005). The nest is small and constructed of sticks (del Hoyo et al. 1992), and may be situated at elevations of 10-50 m above the ground (Johnsgard 1993). A single tree may contain many nests (Nelson 2005) that can be very close together (often touching) (Ogilvie 1997), and a single pair will refurbish and re-use the same nest from year to year if it has not collapsed (Nelson 2005).