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P. A. Buckley, Michael Gochfeld, Francine G. Buckley, Efficacy and Timing of Helicopter Censuses of Black Skimmers and Common Terns on Long Island, N.Y.: A Preliminary Analysis, Proceedings of the Colonial Waterbird Group, Vol. 1 (1978), pp. 48-61
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Buckley et al. (1978) studied this question.
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