Effects of flushing nesting greater prairie-chickens in Illinois

Important masons for evaluating researcher impact in nest studies include the possibility of increased abandonment, depredation, embryonic mortality, or bias of other parameters. From a 29-year data set of 1101 Greater Prairie-Chicken (Tympanuchus cupido pinnatus) nests in Illinois, we assessed the performance of 115 nests that were visited by investigators during egg laying or incubation. The minimum return rate for 107 hens flushed up to 5 times was 88% and apparently decreased (G = 9.76, df = 4, P = 0.042) with increased frequency of flushing caused by investigators. The success of 105 nests from which hens were flushed (68%) was higher (G = 7.55, df = 1, P < 0.01) than that of 840 undisturbed nests (53%) whose fates were determined prior to discovery. No desertions could be attributed to investigators activities. Embryonic mortality in disturbed nests appeared 3.7X higher (Z = 4.59, P = 0.001) than in undisturbed nests, but some egg removal by predators prior to our inspections may have biased results. Neither embryonic loss nor nest success was related to number of flushes during incubation. Nearly half of embryonic deaths that we could age in disturbed nests occurred before hen flushes, and most other losses, including whole clutches, were not clearly caused by investigator disturbance.