Golden-crowned Kinglets breed further south and winter further north than Ruby-crowneds. Golden-crowneds, however, are hardier and migrate later than Ruby-crowneds. Wintering birds here in Minnesota can withstand nighttime temperatures below −40 degrees C. In such conditions, small groups of kinglets may huddle together to keep warm (Swanson et al. 2012).
DNA studies indicate that kinglets are closely related to titmice and Old World warblers. Golden-crowned Kinglets are closely related to European Goldcrests. Ruby-crowned Kinglets, on the other hand, are only distantly related to Golden-crowned Kinglets (Swanson et al. 2012).

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