Why roost at the same place? Exploring short-term fidelity in staging Snow geese

Abstract

When a communal roost is large relative to foraging distances, variance in foraging success may affect the positioning of the birds within the roost and we should expect fidelity to positions that improve foraging success. We explored fidelity of Snow geese (Chen caerulescens) to three sections of a 5-km 2 roost in flooded lowlands during their spring stopover in Quebec. From 1998 to 2000, we located 166 radio-tagged geese on 1077 occasions. Fidelity rates were higher than expected by chance in all sections in 1998, in two in 2000, but in none in 1999. Fidelity increased with the number of birds using a section, suggesting a positive effect of conspecific attraction. We tracked 292 foraging trips of 108 radio-tagged geese; birds from different sections tended to forage in specific directions. Average distance to foraging sites saved by appropriate choice of a section varied between 7 and 17%, depending on the section. however, distance traveled over 2 successive days did not decrease when geese switched from roosting in one section to another, suggesting that minimization of foraging-trip distance may stem simply from the spatial organization of foraging trips in order to reduce travel distance to food patches. higher fidelity rates were associated with shorter travel distance in only one section of the roost, and dominant birds arriving early in the season tended to be more faithful to this section. We conclude that conspecific attraction, reduction in travel costs to foraging sites, and individual variation in dominance determine roost positioning and fidelity concurrently. © The Cooper Ornithological Society 2010.