Validating the use of artificial nests in predation experiments

Artificial nests with Japanese quail (Coturnix coturnix) eggs have often been used in experiments to compare patterns of predation with different ecological and nest-site attributes. Many investigators assume that predators respond to artificial nests as they would to natural nests; however, this assumption has rarely been tested. In 1996, in La Plata County, Colorado, we investigated differences in predator response to quail eggs in natural American robin (Turdus migratorius) nests in their original location, and artificial wicker-basket nests placed both in a 6 x 8 grid pattern at 30-m intervals and in a natural pattern 30 m in a random direction from each natural nest. Over the 15-day trial, predators responded differently to quail eggs in natural and artificial nests. By the first (5-day) check, predators had depredated 44.4% (n = 27) of natural nests, 11.1% (n = 27) of artificial nests 30 m from natural nests, and 14.6% of artificial nests in the grid (n = 48; P < 0.01). By the second (10-day) check, they had depredated similar proportions in all trial types (P > 0.10). However, by the final (15-day) check, more artificial nests in the grid had been depredated (91.7%) than either artificial nests located 30 m from natural nests (66.7%) or natural nests (70.4%; P < 0.02). We found no difference in predation patterns among nests placed less than or equal to 2 m and those >2 m aboveground. We suggest that because predators respond differently to natural and artificial nests, caution should be exercised in making management decisions based upon results of artificial nest experiments.