THE TIME COMPONENT IN WATERFOWL DIET ANALYSES

Zuur B. J.

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Abstract:

Five species of waterfowl (Ma11ard Anas platyrhynchos, Tea1 A.crecca> Tufted Duck Ayrhya fuligula> Pochard A.ferina, and Coot Fulica atra) showed dai1y f1uctuations in the abso1ute and relative abundance of consumed food types. lf these f1uctuations are not taken into account in diet analyses, dietary differences usua11y attributed to demogra - phic, seasona1 or other variab1es may actua11y be due to the norma1 dai1y feeding patterns. Some species fed large1y at.night (t he :.11a1- 1ards and the Pochards) and the importance of nocturnally conaumed foods will be underestimated in norma l diet analyses. The Teal had ap' parently altered its feeding behaviour to feed outside the peak shoo~ ting time. lt is recommended that the population investigated be sampled throughout the day, and that the feeding times be weighed in sub sequent analysis according to the amount of food consumed and not according to the number of birds shot. The integraI of the time/food curve is an ideaI way of describing a diet, alt houg h this may be difficult to apply in pract i ce , lt is po in: tless and misleading to present diets calculated. from incomplete and uneven data as "exac t " percentages.