Western jackdaws become sexually mature in their second year. Genetic analysis of pairs and offspring shows no evidence of extra-pair copulation and there is little evidence for couple separation even after multiple instances of reproductive failure. Some pairs do separate in the first few months, but almost all pairings of over six months' duration are lifelong, ending only when a partner dies. Widowed or separated birds fare badly, often being ousted from nests or territories and unable to rear broods alone.