Abstracts

Presented by Aaron P. Yetter - Email: ayetter@illinois.edu

Millions of waterfowl rely on Illinois wetlands during autumn and spring migration. Harvest surveys show gadwall (Mareca strepera) and green-winged teal (Anas crecca) comprise approximately 15% of the ducks harvested in Illinois, and they are commonly in the top five duck species in the Illinois waterfowl harvest. Detailed information on spring distribution, habitat associations, food selection, and stopover duration for these species are lacking or antiquated. Therefore, we radiomarked green-winged teal (GWTE) and gadwall (GADW) during springs 20162018 using VHF transmitters. Our objectives were to determine home range size, estimate survival and stopover duration, describe daily movements, and evaluate wetland habitat use by GWTE and GADW during spring migration in the Illinois River Valley (IRV). Preliminary analyses suggest movement distance of GWTE from diurnal to nocturnal locations was 5,001 m (SE = 290) and 5,161 m (SE = 224) from nocturnal roosts to diurnal locations. Similarly, day-night and night-day movement distances for GADW were 5,650 m (SE = 374) and 5,463 m (SE = 356), respectively. Spring stopover duration was 14 days (CI95 = 1119 days) for GWTE and 27 days (CI95 = 1258 days) for GADW. Daily survival was less for second-year birds (x = 0.99, CI95 = 0.950.99) than after second-year birds (x = 1.00, CI95 = 0.991.00). We found that GWTE utilized emergent marsh (60%) most often while GADW utilized wooded wetlands (45%) most. Our estimates of home range size (95% MCP) for GWTE and GADW averaged 2,413 ha (SE = 591) and 2,791 ha (SE = 703), respectively. Greater than expected stopover duration and diurnal habitat switching suggested quality migration habitat may be limiting ducks in the IRV during spring.