EFFECTS OF FLUSHING NESTING GREATER PRAIRIE-CHICKENS IN ILLINOIS

Important reasons for evaluating researcher impact in nest studies inc lude the possibility of increased abandonment, depredation, embryonic mortality, or bias of other parameters. From a 29-year data set of 110 1 Greater Prairie-Chicken (Tympanuchus cupido pinnatus) nests in Illin ois, we assessed the performance of 115 nests that were visited by inv estigators during egg laying or incubation. The minimum return rate fo r 107 hens hushed up to 5 times was 88% and apparently decreased (G = 9.76, df = 4, P = 0.042) with increased frequency of hushing 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 undistu rbed nests (53%) whose fates were determined prior to discovery. No de sertions could be attributed to investigators activities: Embryonic mo rtality in disturbed nests appeared 3.7 X 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 n est success was related to number of flushes during incubation. Nearly half of embryonic deaths that we could age in disturbed nests occurre d before hen hushes, and most other losses, including whole clutches, were not clearly caused by investigator disturbance.