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Summary This paper reviews the occurrence of nocturnal activity, particularly foraging, in wildfowl (Anseriformes) and shorebirds (Charadrii), and discusses its significance. Many duck species are mainly active at night while others regularly feed during both the day and night. Some ducks and geese are normally day feeders and occasionally forage during darkness. In a few duck species, courtship also has been observed at night. Most shorebirds forage both by day and night, in temperate and in tropical latitudes. Some are mainly crepuscular and nocturnal feeders and also display at dusk and at night. Some species may use their daytime territory at night. A few shorebird species, including some visual peckers and long‐billed tactile probers, use the same foraging method to detect and capture food by night as by day. However, some long‐billed species that forage visually during daytime modify their feeding techniques and rely completely or partly on tactile means for detecting prey at night. Large eyes seem an advantage to plovers and other sight feeders for night feeding. Numerous touch‐sensitive corpuscles in the bill of ducks and many scolopacid species favour tactile feeding. Some ducks, geese and shorebirds may especially use moonlit nights for feeding though, in a few species, moonlight seems to have no effect. The possible role of bioluminescence is also discussed. Nocturnal activity may occur for two reasons. The night may be preferred because foraging is more profitable or safest from predators. Alternatively, birds may be forced to forage at night because they fail to collect all their food requirements during the day. The evidence for both hypotheses is reviewed. Nocturnal activity does appear to allow wildfowl, and perhaps shorebirds, to avoid diurnal predators (including man). Shorebirds, and some ducks also seem to take advantage of prey that are more abundant and/or accessible at night. The main evidence for the supplementary feeding hypothesis comes from studies of seasonal variations in the occurrence of nocturnal feeding, about which rather little is known at present. The increasing availability of modern night‐viewing equipment may help to fill this gap. There are two important implications arising from the widespread occurrence of nocturnal activity in wildfowl. Most knowledge on time and energy budgets is based on daytime studies, and so may need to be revised. Wintering dabbling ducks and shorebirds, at least in some regions, may use different habitats by day and by night. If confirmed, there would be a need to preserve some wintering habitats which, although little used by ducks and shorebirds during the day, may be intensively used at night.

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Temporal variation in bird abundance was studied during a complete annual cycle in a thorn scrub, a thorn woodland and a deciduous forest in northeastern Venezuela. Abundance of site‐attached and transient birds from different feeding guilds was determined by mist‐netting at 2‐week intervals. Diets were investigated by regurgitated samples. The overall avifauna was characterized by a low number of species but they were present all year despite showing strong seasonal fluctuations in abundance. The number of bird species and individuals peaked before and after the reproductive period. These high values probably were associated with movement of species feeding on plant food during the late dry season and the post‐breeding dispersion of juveniles. Bird richness and abundance were lowest during the breeding season and in the early dry season when food abundance was low. Birds from different feeding guilds showed distinct patterns of seasonal abundance which tended to be similar at all three sites. Transient birds represented a large portion of the avifauna, particularly in nectarivores, frugivores and granivores during the dry season. We used a canonical correspondence analysis to demonstrate that bird abundance was correlated with breeding activity, rainfall seasonality and food abundance, with the influence of each parameter varying according to feeding guilds, spatial behaviour of individuals and habitats. Despite a great turnover in the occurrence of the diverse food types available, species composition remained strikingly constant during the year, with birds responding to seasonal changes primarily through a generalist feeding habit and a highly variable rate of transience.