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Measurements
Linear
Males have slightly longer beak, wing, and tail than females (Table 1). Male museum skins in Louisiana (n = 20) and wintering males in Alabama in 1999 (n = 66) had mean wing chord lengths that were indistinguishable from Ontario birds (KJM). See also Systematics for geographic variation in body size.
Mass
Many sources of mass data (e.g., Holcomb 1968, Wiseman 1975, Middleton 1977a, 1986, Carey et al. 1978, Thiel 1980). Mass varies seasonally; males heavier than females from Sep to May, but females heavier during breeding season, Jun–Aug (Appendix). Winter increase in mass primarily consequence of winter fattening (Carey et al. 1978, Middleton 1986).
McGraw, Kevin J. and Alex L. Middleton. 2009. American Goldfinch (Spinus tristis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/080
