Tree Swallows are occasional but regular migrants and breeders in Arizona, especially in the northern and higher-elevation parts of the state. These small, iridescent blue-green swallows with clean white underparts are among the earliest swallows to arrive in spring migration, often appearing in March as they move northward. They are most commonly seen around lakes, ponds, rivers, and marshes where flying insects are abundant. In Arizona, they can be observed in places such as Lake Mary near Flagstaff, the San Rafael Grasslands, and other wetland habitats where suitable nest cavities are available.
Although Tachycineta bicolor is not as widespread a breeder in Arizona as Violet-green Swallow (Tachycineta thalassina), it does nest locally in the state. Nesting usually occurs in tree cavities or artificial nest boxes, particularly in areas near water. Their breeding distribution in Arizona is scattered and somewhat limited, with more reliable nesting reports from the northern plateau region and select riparian zones. During fall migration, large flocks sometimes gather, feeding in flight over water before continuing south to wintering grounds in Mexico and Central America.
