Breeding Fidelity and Landscape Effects on Distribution of Mallards and Duck Broods in the Nebraska Sandhills

I investigated aspects of mallard (Anas platyrhnchos) breeding ecology in the Nebraska Sandhills during 2007-2008. Previous work in this region suggests that nest success is low for a large area of intact grassland such as the Sandhills. My goal was to conduct a local-scale examination of age distribution and return rates of mallards, and a large-scale examination of brood distribution in the Sandhills region as a whole. This information will help explain factors contributing to the low nest success previously observed, determine relationships between landscape composition and spatial distribution of waterfowl in the Sandhills, and predict productivity and abundance of ducks in the Sandhills from a spatial model. I used decoy traps to capture mallard ducks prior to nesting to ascertain age ratios and return rates for captured birds. I captured and banded 820 unique ducks representing 6 species during 2005-2008. Age distribution (SY:ASY) of mallards in 2007 was 0.9:1 for males and 6:1 for females and 0.8:1 for males and 2.3:1 for females in 2008. Mallard recapture rate was 7.4% and recovery rate was 30%. Mallard survival was 79.5% with a fidelity rate of 61.8%. I conducted road-count brood surveys consisting of three survey routes extending across the Sandhills. These presence/absence surveys were used to document the abundance and distribution of duck broods in the Nebraska Sandhills. Nine different duck species broods were observed on the survey routes in 2008. The 4 most common duck species broods observed on the survey routes were the mallard, blue-winged teal, gadwall (A. strepera), and redhead (Aytha americana). Results from the brood survey allowed me to produce a thunderstorm map predicting the probability of brood occurrence across the Sandhills. Analysis of the thunderstorm map suggests that waterfowl productivity is at its highest in the eastern Sandhills. This map will be one tool to help managers identify high priority wetland habitat that can be protected through various habitat conservation strategies by private or governmental agencies. Adviser: Larkin A. Powel