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Repeated Sampling Affects Tree Swallow Semen Characteristics, Michael Lombardo, M.L. Green, P.A. Thorpe, M.R. Czarnowski, H.W. Power

Michael P Lombardo

Male Tree Swallows (Tachycineta bicolor) face intense sperm competition because mated pairs copulate frequently, extra-pair copulations are common, and females store sperm. We examined the effects of repeated sampling on the characteristics of Tree Swallow semen by manually expressing semen from 15 males immediately after capture (T₀) and then hourly for 4 h (T₁-T₄). The semen characteristics of individual males varied in response to repeated sampling. The total number of sperm cells we obtained from each male over the 4-h sampling period varied from 10⁴-10⁷. Semen samples lacking …