Great Blue Heron (Ardea herodias) Science Article 7
A comparison of the accuracy of different techniques for counting Great Blue Heron (Ardea herodias) nests suggests that aerial-visual estimates and aerial photographic counts provide reliable measures of colony size while minimizing disturbance to nesting herons. Additionally, post-nesting season ground counts of nests provide a suitable, less disruptive alternative to mid-nesting season ground counts at colony sites.
JAMES P. GIBBS et al., J. Field Ornithol., 59(2):130-134