Wintering ecology of Anatidae in the wetlands of Algerian Numidia: phenology, diurnal behavior and abiotic environmental descriptors

Abstract

To examine the ecology of wintering Anatidae in two Ramsar-listed wetlands in Algeria, Garaet Hadj Tahar (Western Numidia) and Lac des Oiseaux (Eastern Numidia), bimonthly exits were carried out during two consecutive wintering seasons (2021/22 and 2022/23). In addition, during an annual cycle extending from November 2021 to October 2022, we have studied the physicochemical and bacteriological quality of the water based on the evaluation of certain pollution indicators such as electrical conductivity (EC), dissolved oxygen (DO), nitrates (NO3-), nitrites (NO2-), ammonium (NH4+), phosphates (PO43-), biological oxygen demand (BOD5) as well as the four categories of faecal contamination indicators (total heterotrophic bacteria, total coliforms, faecal coliforms, and faecal Streptococci). A total of 14 species were recorded (12 at Garaet Hadj Tahar and 12 at Lac des Oiseaux). Most of the species (57%) were winter migrants; 21% were occasional visitors (passage visitors), and 22% were winter migrants with sedentary populations. Four of these species are listed as rare on the IUCN Red List: Endangered (White-headed duck Oxyuraleucocephala), vulnerable (Common pochard Aythya ferina), and Near Threatened (Marmaronettaangustirostris and Ferruginous duck Aythya nyroca). Analysis of the ecological indices reveals that the two bodies of water harbor a similar number of species in terms of species richness, but show a significant difference in terms of abundance, with 311 individuals observed at Garaet Hadj Tahar and 2411 individuals at Lac des Oiseaux. The Shannon-Weaver diversity index (H’) and Pielou equitability index (E) indicate that Garaet Hadj Tahar has the highest values, with a maximum of H’ = 1.66 bits and E = 0.98. These results suggest that Garaet Hadj Tahar is ecologically more balanced than Lac des Oiseaux. These wetlands are a perfect haven for these birds, as evidenced by the diurnal balances being dominated by sleeping activity. All the water samples studied showed results that exceeded the thresholds set by the WHO and Algerian standards, indicating significant pollution. Spearman's correlation shows that water parameters influence four (4) species of Anatidae in the GHT and seven (7) species in the LDO. Our research highlights the importance of the wetlands of the Algerian Numidia for the protection of Anatidae and provides valuable information for the development of effective strategies to safeguard these waterbirds and their habitats, a task that is essential for biosecurity and the prevention of waterbird epidemics.