Occurrence and density of mallard and green-winged teal in relation to prey size distribution and food abundance

We studied patterns of prey size and abundance among 60 lakes that differed with respect to occupancy by mallards (Anas platyrhynchos) and teal (A. crecca crecca). Size distributions of prey in lakes with and without mallards did not differ in the way they deviated from the prey size distribution found in the average diet of the species; the same was true also for teal. However, in lakes with abundant food, average teal diet differed more from what was found in the environment than in lakes with less prey; in the mallard there were no differences in this respect. The densities of mallard and teal correlated positively rather than negatively with each other irrespective of food abundance, suggesting that interspecific competition, at least in ecological time, between the species may not be important in determing their abundance and distribution.