Weaver nests are well constructed, and are thus sometimes taken over by other birds or animals for roosting or breeding, see examples.
Sociable Weaver nests have been used more than the nest of any other weaver species, see examples.
Weaver nests may be used as a platform for the nests of other species, eg Verreaux's Eagle.
The PHOWN database can be searched for individual species that are known to take over weaver nests, eg. Red-headed Finch.
List of weavers whose nests are often used by other birds or animals (in desc order of No. of records)