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R. Kent Johnson, Roland R. Roth, John T. Paul, Mass Variation in Breeding Wood Thrushes, The Condor: Ornithological Applications, Volume 92, Issue 1, 1 February 1990, Pages 89–96, https://doi.org/10.2307/1368386
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Abstract
Data from a 15-year study of breeding Wood Thrushes (Hylocichla mustelina) indicate that body mass varies with sex, year, time of day, and breeding stage. The pattern of mass variation with breeding stage differs for the two sexes. Mean female mass is low during the prebreeding stage (50.3 g), but increases rapidly, reaching its highest level in the laying stage (57.4 g). It is reduced during the incubation (54.2 g) and feeding stages (51.1 g), rises again in the break between broods (53.6 g), but declines in the postbreeding period (50.7 g). Male mass is lowest in the prebreeding stage (46.5 g), but slightly higher in the laying period (48.0 g). It increases in the incubation period (49.4 g), then declines in the feeding (48.3 g) and break stages (47.2 g), but reaches its greatest level in the postbreeding period (49.9 g). Both sexes may be physiologically stressed during the feeding stage, but male stress is probably greater in the prebreeding and break stages.
