FEEDING FLIGHTS OF CATTLE EGRETS NESTING IN AN AGRICULTURAL ECOSYSTEM

I examined feeding flights of breeding cattle egrets (Bubulcus ibis) i n the Mexicali Valley, Baja California, Mexico, to determine patterns of arrivals and departures and if flights from the colony were random or were directed towards selected parts of the Valley. Nearly 90% of t he cattle egrets departed from or arrived at the heronry in flocks of two to 35 individuals, but groups of two to four individuals were pred ominant (75%). Numbers of departures in groups of two and three indivi duals were significantly greater than numbers of arrivals in groups of similar size, while numbers of departures and numbers of arrivals in groups greater than three were similar. The feeding flight patterns we re non-random and were significantly oriented towards the northeast si de of the valley where there was perhaps more food available because o f facilitation by surface irrigation of crops. Feeding flight departur es were concordant in direction within consecutive days, which suggest s preference for previous feeding patches. Previous experience and loc al enhancement seem to be two mechanisms by which cattle egrets locate d good foraging patches.