I examined images of over 6,300 individual hummingbirds from the Cornell Lab of Ornithology's Macaulay Library to clarify conflicting reports on molt and plumage strategies in 8 species that breed or have bred primarily in the southwestern United States. Fixed replacement sequences from 2 nodes among primaries and 2 nodes among secondaries were found without exception, conforming to the findings of previous studies. I concluded that the preformative molt varied from limited to partial in 3 species, partial to incomplete in 3 species, partial to complete in 1 species, and complete in 1 species. Results of this study clarify molt terminology in Trochilidae as based on evolutionary homologies, and they establish new criteria for age determinations. The Macaulay Library clearly provides an important resource for the investigation of avian molts and plumages. I present a road map for such studies and suggest many other questions on avian molt that can also be investigated. I encourage contributors to the Macaulay Library to take and upload images of birds in molt or in worn plumages.

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