Temporal patterns of predation of duck nests in the Canadian prairies

In 1995 we deployed 800 simulated nests equipped with nest mortality timers to assess temporal patterns of predation of duck nests in the Canadian pra iries. Timers recorded 470 predation events (70% of 672 depredated nests). Predation was nonrandom throughout the day, with a peak occurring between 0 0:00 and 06:00. Coyote (Canis latrans) and red fox (Vulpes vulpes) depredat ed nests at similar times (mean 18:32 and 22:42, respectively), whereas mea n depredation time was significantly later for striped skunks (Mephitis mep hitis, 02:08). We failed to detect a difference in depredation interval for neighboring nests destroyed by striped skunk (median = 62 h 18 min, n = 15 ) vs. pairs of nests depredated by different species (red fox-skunk, skunk- coyote and coyote-red fox, median depredation interval = 123 h 1 min, n = 6 ). Simultaneous observation of radio-marked skunks revealed that skunks spe nt 2-25 min at simulated nests and became inactive after nest destruction i n ca. 50% of cases. Based on observations of striped skunk behavior and nes t-timer data, we suggest that density-dependent nest predation is caused by increased patch use rather than area-restricted search.