Gadwall nesting and brood ecology at Waterhen Marsh, Saskatchewan / James E. Hines

The nesting and brood ecology of the gadwall (Anas strepera L.) was investigated during the period May to September of 1972 and 1973 at Waterhen Marsh. Gadwalls were present on the study area in early May with a sex ratio of 112 males to 100 females. Pairs dispersed about the marsh according to the availability of suitable heterogeneous habitat.The peak of nest initiation occurred during the last week of May in 1972 and in the first week of June in 1973. The delay in nesting in 1973 corresponded with cooler weather during the pre-nesting period for that year. The peak of hatching was during the week of July 8 to 14 in 1972 and July 15 to 21 in 1973. The earliest broods could fly by the week of August 11 to 18 and all broods could fly by September 22, during both years. The average size of 295 first clutches (dump nests excluded was 10.37 +- 0.08 (SE) eggs. Twenty-seven renest clutches averaged significantly fewer eggs than did first clutches - 8.00 +- 0.19.Thirty-three dump nests co