Researcher Disturbance in Colonies of Wading Birds: Effects of Frequency of Visit and Egg-Marking on Reproductive Parameters


In two closely matched colonies of Tricolored Herons (Egretta tricolor) we found no differences in reproductive parameters of the one visited frequently (16 times) and the other visited infrequently (7 times). Visits to colonies were standardized and were initiated only after most of the herons had partially completed their clutches. These results suggest that limited colony visitations beginning after courtship and early egg-la-lying do not result in large disturbance effects. We caution, however, that these findings should not be applied without further testing, especially since the colonies we studied were relatively free of aerial and ground predators. We also found that letters marked on the sides of eggs were turned down by parental birds significantly more often than expected due to chance. We suggest researchers label eggs inconspicuously on the ends or not at all.

Colonial Waterbirds