While Purple Martins (Progne subis) will often tolerate other birds nesting in adjacent nest boxes, these are usually not closely related species. The House Sparrow (Passer domesticus), Starling (Sturnus vulgaris), and the Eastern Bluebird (Sialia sialis) are mentioned by Bent as common competitors for nesting sites in active martin colonies. On 22 June 1962, a female Tree Swallow (Iridoprocne bicolor) was perched on the lower railing of one of the martin houses at UMBS, Cheboygan County, Michigan. Investigation revealed a nest containing four small Tree Swallows in a lower corner box. Two pairs of Purple Martins nesting in the same house were incubating and two other males frequented the same house. The entire colony was composed of 24 birds in three houses along the shore of Douglas Lake. During three afternoons of observation, no interspecific conflicts were noted at this house. A photograph was made showing that the Tree Swallows occupied the side of the house nearest the trees. None of the martins was seen on this side, but preferred the more open approach afforded elsewhere. I banded the young Tree Swallows on 23 June, and they had fledged by 28 June. The martins had young by this time, which did not fledge until early in July.