Separated in all plumages and ages from all other North American swallows except Cave Swallow by a square tail and orange rump. In all populations, exhibits a chestnut-colored throat. Most subspecies show a cream- or white-colored, triangular-shaped forehead patch, characters that separate the species from Cave Swallow. Head and neck are noticeably thicker than other North American swallows (Brown and Brown 1995).
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see Marks et al. 2016, Birds of Montana.
Western Hemisphere Range
In the Bozeman area, normal migration periods are May 5 to June 1 and August 25 to September 10.
Historically inhabited open canyons, foothills, escarpments, and river valleys that offered a vertical cliff face with a horizontal overhang for nest attachment. Now found in a wide variety of habitats because of use of artificial nesting structures such as bridges and buildings. Avoids heavy forest, desert and alpine areas. Most colony sites are located near open fields or pastures where the birds forage and a water source is often nearby. Proximity to mud source is often cited as a breeding-habitat requirement (Brown and Brown 1995).
Flying insects at all times of the year. Insects taken reflect local availability. Occasional pieces of seeds are found in stomachs but these represent either accidental ingestion or use as grit (Brown and Brown 1995).
Typically nest in large colonies; a single site may contain up to 3,500 active nests. Nests are made of mud on vertical substrates. Cliff swallows are distinguished by their enclosed, gourd-shaped nests and the larger colonies. Single brood. Clutch size ranges 1 to 6 eggs. Eggs are ground color white, creamy white or pinkish white. Ovate to elliptical-ovate in shape (Brown and Brown 1995). Egg dates near Fortine are from June 9 to July 17. Statewide, nesting occurs from mid-May to mid-July.