Avocets normally breed for the first time when they are two years old.
Having bred successfully they will be faithful to the site in subsequent years. Pair-bonds are maintained only for the duration of breeding season and break up by the time winter flocks gather.
Avocets nest in loose colonies of up to 150 pairs. Colony size and density are determined by availability of suitable nest sites, distance to water and risk of predation. The nest, built by both sexes, is a shallow scrape on bare mud or in sparse vegetation, even in shallow water, and is composed of short pieces of stems, roots, and leaves of marsh vegetation.
The female lays her clutch of 3-4 pale buff eggs with black markings at 1-2 day intervals any time between mid-April and late June. Incubation begins with the second or third egg. Both sexes incubate for 23-25 days. The young can run about and feed themselves within a few hours of hatching. Both parents care for and brood them.
The young fledge at around 35-42 days, but often remain dependent on their parents for some time afterwards. Avocets are single brooded, but will lay again if the first clutch is lost before hatching.
Chick survival can be poor, and is determined largely by weather and food supply. The average lifespan of those that reach adulthood is thought to be around 7 years. According to the British Trust for Ornithology, the oldest avocet on record was 23 years and 9 months.