Effects of nest visits on predator activity and predation rate in a Greater Snow Goose colony

We assessed the effect of nest visits by researchers oil the activity of ne st predators and predation rate of eggs in a High Arctic Greater Snow Goose (Chen caerulescens atlantica) colony. The study was conducted in years of moderate (1996) and low (1997) overall nest predation rate, We first compar ed activity late (number of presences per It) and behavior of nest predator s in the colony with and without investigator disturbance. In one year out of two, activity rate and time spent in the colony were higher during nest visits than under undisturbed conditions for Glaucous Gulls (Larus hyperbor eus) and Parasitic Jaegers (Stercorarius parasiticus). Moreover, presence o f investigators significantly increased (4.8 times) the probability of nest attack by predators in one Year. Nevertheless, the immediate revisit techn ique showed that the percentage of goose eggs robbed by predators in monito red nests was low (<0.7%) during a nest visit. In addition, we found no sig nificant difference in mean Clutch size at the end Of incubation or nesting success between nests that were visited repeatedly (8 visits) and those le ss disturbed (<3 visits), Although some predators can be attracted by and L ake advantage of the presence of investigators, our results indicate that n esting parameters estimated for this snow goose colony are not biased by ne st visits. However, the effect of investigator disturbance could be more im portant in other arctic nesting bird species that are unable to successfull y defend their nest against predators or when predation pressure is very hi gh.