Climatic and population-dependent drivers of feeding activity in the wintering common shelduck (Tadorna tadorna)

Abstract

Among the wetlands designated under the Ramsar Convention in North Africa, the Sebkha of Ezzemoul stands out as a wintering site for thousands of waterbirds. However, the utilization of these habitats by the Common Shelduck (Tadorna tadorna Linnaeus, 1758) during the wintering season remains insufficiently documented. In particular, the influence of environmental factors, such as population size and climatic conditions, on its feeding behavior has been scarcely explored. A detailed analysis of wintering strategies and habitat-use dynamics is essential to enhance the ecological understanding of this species. During the 2015–2016 wintering season, weekly surveys were conducted to quantify Common Shelduck populations and monitor their diurnal behaviors. Particular attention was given to temporal variations in behavioral activity allocation, analyzed using a generalized linear mixed model (GLMM). This statistical model was employed to assess the effects of population size and climatic variables on the species' feeding behavior. The results revealed significant effects of population size, air temperature, and humidity on feeding activity, which accounted for 81.8 % of the total time budget. The study highlighted a strong correlation between feeding intensity and population size, as well as significant interactions with climatic parameters. These complex relationships suggest behavioral adaptations in response to environmental constraints, underscoring the species’ ecological flexibility in temporary and changing habitats. These findings reinforce the notion that North African wetlands play a crucial ecological role as daytime feeding habitats and refuges for wintering waterbirds. They also emphasize the urgent need for targeted conservation efforts to protect these fragile ecosystems. Ensuring the sustainability of these habitats will address the ecological requirements of migratory species and preserve the associated biodiversity.