Relationships of habitat patch size to predator community and survival of duck nests

We studied duck nest success and predator community composition in relation to size of discrete patches of nesting cover in the Prairie Pothole Region (PPR) of die United Slates in 1993-95. We focused on nests in uplands that were seeded to perennial grasses and forbs and enrolled in the Conservatio n Reserve Program (CRP) in Minnesota, North Dakota, and South Dakota. We es timated daily survival rates (DSRs) of upland duck nests and indices of act ivity for red foxes (Vulpes vulpes), coyotes (Canis latrans), American badg ers (Taxidea taxus), striped skunks (Mephitis mephitis), and Franklin's gro und squirrels (Spermophilus franklinii), and related these variables to hab itat patch size, The effect of patch size (small vs. large) on estimated an nual mean DSR was dependent on date of nest initiation (early vs. late) and year. Examination of within-year comparisons for early and late nests sugg ested that DSR was generally greater in larger habitat patches. Activity in dices for the 5 mammalian nest predators were influenced differently by yea r, location, and patch size. Activity indices of the red fox were greatest in small patches. Coyote indices were the most inconsistent, demonstrating a year x location x patch size interaction. Activity indices of the striped skunk and American badger varied only among years. Franklin's ground squir rel indices were affected by study area location, with higher indices in th e southeast than the northwest. Red fox activity was weakly correlated with that of the striped skunk and coyote. Although a positive relationship bet ween habitat patch size and nest success probably exists, we believe the ex periment to fully test this hypothesis will continue to be elusive.