Breeding ecology and diet of the black-crowned night heron (Nycticorax nycticorax) in arid wetlands and aquaculture landscapes of Uzbekistan

The black-crowned night heron (Nycticorax nycticorax) is a piscivorous wetland bird capable of exploiting both natural and human-modified aquatic habitats. However, information on its breeding ecology and feeding relationships with aquatic resources in arid Central Asia remains limited. This study assessed long-term colony dynamics, reproductive ecology, and nestling diet of the species in two contrasting habitats of Uzbekistan: the riparian forests of the Zarafshan State Nature Reserve and the urbanised landscape of the Bukhara Oasis. Field observations were conducted during 2008–2022, supplemented by historical colony records extending to 2024. Breeding parameters, egg morphometrics, incubation behaviour, nestling growth and provisioning, and prey composition were assessed using standard field methods. The results demonstrated a shift from natural riparian breeding sites towards urban colonies, where suitable mature trees and access to aquatic food resources were available. Urban colonies showed a higher mean clutch size than the natural habitat, whereas egg dimensions showed comparatively limited variation. Analysis of nestling diet identified 128 prey remains, comprising both aquatic and terrestrial prey; invertebrates accounted for 57% and vertebrates for 43% of identified prey. Fourteen fish species were recorded, including commercially cultured cyprinids such as Cyprinus carpio, Hypophthalmichthys molitrix, and Ctenopharyngodon idella. The occurrence of cultured fish in the diet indicates that aquaculture ponds provide accessible supplementary foraging habitat for breeding night herons. Overall, the findings demonstrate considerable trophic and habitat flexibility of N. nycticorax in arid landscapes and highlight the ecological interaction between piscivorous birds and aquaculture systems. Integrated management combining wetland and riparian habitat conservation with targeted non-lethal measures at aquaculture facilities is recommended to balance biodiversity conservation and sustainable fish production.

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