6. Cliff Swallow

Nests - Can occur as soon as birds begin visiting colony sites and coincides with the establishment of nest ownership or the beginning of nest-building. Nest building follows shortly after pair formation; some males begin nest-building before securing a mate. The nest site within a colony often is not chosen until 3–5 d after the colony site is selected. When constructing new nests, birds first cling to the substrate in several places, gradually confining their activity to 1 spot where the nest is to be built. Nests are placed on vertical cliff faces, entrances to caves, under the branches of large tree limbs (rarely), under the eaves of buildings, under bridges, in highway culverts, and under overhangs on dams.
Birds gather mud in their bills along the bank of a stream, lake, or temporary puddle (e.g., ruts in road), usually at a site within 0.5 km of the colony but sometimes several kilometers distant. A bird brings a mud pellet back to the colony and molds it into the nest with a shaking motion of the bill. The shaking causes a partial liquefaction of the mud, disperses moisture, and allows fresh mud to overrun small air spaces, resulting in a stronger structure when dry.

Eggs - ovate to elliptical-ovate, ground color white, creamy white, or pinkish white. Speckling of various shades of light and dark browns. Clutch size is 3 to 4 eggs.

Incubation - 11 to 15 days by both males and females

Fledging - altricial at hatching with fledging occuring at 20 to 21 days