The Reproductive Ecology of the Black-Crowned Night Heron in Numidia, North-Eastern Algeria

This study examines the breeding ecology of the Black-crowned Night Heron Nycticorax nycticorax in north-eastern Algeria, focusing on factors influencing breeding performance across a network of wetlands. Between 2003 and 2007, we monitored four colonies in marshes shared with four to five other heron species. Night Herons nested in trees, mainly Salix atrocinerea and Tamarix africana, and in Phragmites australis reedbeds, typically initiating breeding earlier than other herons and using higher nest positions. Mean clutch size was 3.3 ± 0.7 eggs (n = 174), hatching success was 87.7%, and successful nests fledged on average 2.5 ± 1.0 chicks (n = 105) to 12–15 days of age. Breeding performance varied among colonies and years and was highest at Lake Fetzara, the largest wetland in the region, underscoring the importance of habitat quality. Generalised additive models showed that clutch size was relatively constant across colonies and years but strongly and positively related to both the number of hatched eggs and fledgling output, whereas laying date, nest height and site-year (Event) had no detectable effects once clutch size was included. Despite an approximate tenfold regional population increase over the past decade, ongoing pressures on heron populations and wetlands highlight the need for continued monitoring and targeted conservation.