Effects of egg type on depredation of artificial ground nests

We examined depredation of artificial ground nests containing three egg types (brown chicken, white chicken, or Northern Bobwhite [Colinus virginianus]) in relation to plot age (clearcut vs uncut) and time period (trials 1-5) at the Barrens Grouse Habitat Management Area, Centre County, Pennsylvania, from May-July 1993. One hundred thirteen (38%) of the total nests were disturbed. Fewer nests were disturbed in clearcut (32%) than in uncut plots (43%) (P ≤ 0.05). Clearcut plots had higher densities of brushy vegetation near ground level which better concealed nests and reduced foraging efficiency of predators. Rates of nest disturbance varied with time period (P ≤ 0.005); in general, rates were greater in trials 1- 3 than in trials 4-5, partially because of gypsy moth (Lymantria dispar) defoliation during trials 1-3. Nest fate also differed significantly (P ≤ 0.001) with egg type. Rates of disturbance were lower with nests containing brown chicken eggs (24%) compared to nests containing white chicken eggs (46%) or Northern Bobwhite (43%) eggs Nests with brown chicken eggs were better camoflaged and, hence, less likely to be disturbed. Based on our findings, we recommend that brown chicken eggs be used as an alternative to Japanese Quail (Coturnix coturnix japonica) eggs when simulating nests of Ruffed Grouse (Bonasa umbellus) or Wild Turkey (Meleagris gallopavo) in artificial ground nest studies.