Nest & Reproduction

What do Cliff Swallow nests look like?

Cliff Swallow nests are built entirely of mud the birds collect in their beaks. The nest is an enclosed, gourd-shaped structure about the size of a melon (15-20 cm in diameter). It takes about 1-2 weeks for a new nest to be built; both males and females build the nest. The nest is lined with a small cup of grass to hold the eggs. The birds begin nesting activities in late April-early May by building new or repairing old nests.

Cliff Swallow Nest

What are the details of Cliff Swallow reproduction?

Cliff Swallows Feeding

Both male and female Cliff Swallows are able to breed when they are 1 year old and are able to breed every year of their life (on average 4-6 years, but can be up to 13 years). They are socially monogamous—1 male and 1 female per nest, but are genetically polygamous—both males and females mate with multiple individuals (extra-pair copulations and fertilizations are frequent). The typical clutch size is 4 eggs per nest and the typical brood size is 3 eggs. Both females and males incubate the eggs, females do the majority of the incubation, for about 2 weeks and the eggs all hatch on the same day. Both females and males feed the chicks; each chick is fed approximate once per hour. The chicks fledge (leave the nest) at 23-26 days of age and are fed by their parents for 3-5 days until they are capable of foraging for themselves. During this time the fledglings are ‘parked’ in crèches or nurseries of hundreds to thousands of chicks near the colony; parents are able to identify their own offspring in the crèche by voice and facial recognition and only feed them. Cliff Swallows are nearly always single-brooded, but may lay replacement clutches if eggs are lost early in incubation. Adults are philopatric, which means they often returning to nest at colonies where they reproduced successfully in the past. Yearling Cliff Swallows often return to the same general area where they were chicks to nest, but very rarely to the same colony.