Directions of arrivals of Great Blue Herons (Ardea herodias) at nests with large chicks near Montréal, Quebec

Abstract

We studied the arrivals of Great Blue Herons (Ardea herodias) breeding at the Ile Saint-Bernard heronry near Montréal, Quebec. A total of 42 nests were monitored during the daytime. Overall (i.e., for all flight directions), the distance separating the colony from the potential feeding areas seems to have been the single most important factor in the herons' choice of feeding sectors. Date, wind direction, and water level had a slight influence on the use of feeding areas in this riverine system. Flight directions varied slightly according to these variables during the sampling period. Other variables such as wind speed, time of day, cloud cover, and rain had less influence on the distribution of flight directions. Many breeding pairs used only one or two sectors in particular while feeding their brood. We suggest that in natural environment contamination studies, the faithfulness of certain pairs to specific feeding sectors could help to identify the origin of the contaminants found in the tissues of sampled birds.