During summer, first basic Tree Swallows with light dusky “bibs” are flying about, often intermingling with other swallows, such as Bank Swallows. At first glance, both of these species have brownish uppersides, and both can show a breast band. However, a juvenile Tree Swallow’s breast band differs from that of a Bank Swallow’s by being grayish rather than brown. The band fades in intensity towards the centre and lacking sharp edges and the central downward spike (Wilds 1985). Tree Swallows are hefty with broad-based wings, often held straight out, leading to a sharply triangular shape overall; their wingbeats are noticeably less rapid and less shallow than those of Bank Swallows. With Bank, the wings are quite tapered and often held at an angled orientation (exacerbating the tapered look, such as seen in the Bank at right in the photo); the body is short and conical.; overall, a dainty bird, and one that is dwarfed by a close-flying Tree Swallow.
When availed a back-on view, keep an eye on the upperparts: with Bank, the darker wings and tail contrast with the slightly paler rump; with Tree, look for the even brownish wash throughout and a whitish spur to the sides of the rump.