Long-term Movement Patterns for Seven Species of Wading Birds

We obtained banding and recovery records from 1914 through 1994 for seven species of wading birds from the Bird Banding Laboratory, United States Geological Survey, Patuxent Wildlife Research Center. We analyzed these data to evaluate differences in dispersal distance and frequency of dispersal movement among species. All records were from birds banded as juveniles and recovered at least five months later between March and July, which is the breeding season in most regions of North America. Focusing on recoveries during the breeding season reduced the chance that movements were related to migration rather than dispersal. When an individual was banded and recovered in the same ten-minute block of latitude and longitude, a movement distance of zero km was recorded. The frequency of zero-distance records provides an indication of breeding site fidelity for each species at a spatial resolution of ten minutes. Our results showed that mean dispersal distance was greatest for the Little Blue Heron (Egretta caerulea; 1148 km) followed by Glossy Ibis (Plegadis falcinellus; 1142 km), Tricolored Heron (Egretta tricolor 1019 km), Great Egret (Casmerodius albus; 909 km), Snowy Egret (Egretta thula; 837 km), Great Blue Heron (Ardea herodias; 758 km), and White Ibis (Eudocimus albus; 545 km). Species which dispersed large distances also exhibited fewer zero-distance records, indicating greater movement frequency. The White Ibis has been classified as a nomad, at one end of a continuum defined by low breeding site-fidelity and several life history traits associated with unpredictable foraging habitat. We found that White Ibises were indeed recovered at new locations the majority (76%) of the time but that the other six species of wading birds we examined were even more likely to move to different sites during subsequent breeding seasons. Movement distance and site fidelity will both likely affect whether a response to habitat restoration is due to immigration or local reproduction. Although an increase in total birds using a restored habitat may be an indication of increased habitat quality, caution should be used in inferring population changes without understanding reproduction, mortality, and movement of individuals using restored habitats.