We recorded Bushtit (Psaltriparus minimus) flock size on the Seattle University campus across multiple seasons in order to characterize the timing of pair formation prior to nest building in Washington state and compare it to that of California and Arizona. We also collected autumn and winter foraging locations, specifically vegetation types and foraging heights. We found the disbanding of large flocks (15–20 birds) into nest-building pairs occurred 1–2 months later in the northern part of the Bushtit's range than what is reported in more southern states. Bushtits spent a similar percentage of time foraging in deciduous trees, evergreen trees, and mixed shrubs in fall and winter, often moving along garden strips at heights of 3–4.5 m off the ground. Contrary to published reports, groups of Bushtits repeatedly visited fixed food sources, specifically the yellow flowers of the exotic leatherleaf mahonia (Mahonia bealei) for over 2 weeks on early winter mornings.

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