Ornis Hungarica. vol.27(1). (2019) p.85-98.
Diurnal feeding strategies of the Ferruginous Duck (Aythya nyroca) in Lake Tonga (Northeastern Algeria)
Although the Ferruginous Duck (Aythya nyroca) has thoroughly been studied, the foraging behaviour of this species is still not completely known. In the present paper we studied the diurnal feeding behaviour of ducks. We monitored the annual cycle of birds through two fieldtrips per month. The instantaneous behaviour of birds was recorded in regular 30-minute intervals from 7 a.m. to 4:30 p.m., amounting a total of 456 observation hours. Food searching activity corresponds to a quarter of the total diurnal time budget of the Ferruginous Duck. Foraging behaviour was classified into five categories dominated by the “diving”, which is almost 45.61% of the total search time. Foraging activities at the water surface considered to be secondary activities, including feeding by “bill”, “neck and head”, and “beak and head” in a rate of 19.86%, 14.53%, and 13.98%, respectively. The “toggle” remains a minor activity and represents only 5.99% of foraging time. The feeding behaviour of this species correlated to several environmental parameters (rainfall, temperature and wind velocity), and linked to the group size of ducks visiting the lake. Regarding the food intensity, our results show the highest values for “bill and head” behaviour. “Diving” has the longest feeding interval (16.16±14.1 minutes), while foraging by “bill” has the shortest (0.69 ± 0.48 minutes).