Did you know that of all the swallow species that occur in Portugal, the House Martin (Delichon urbicum) is the species that forms the largest breeding colonies?
This martin builds its nests, closed mud bowls with a narrow circular entrance, on the eaves of buildings or viaducts. The nests of this species can be found from small villages to large urban centres.
As well as being an urban species, this martin is also a gregarious species, so it can form large nesting colonies, often overlapping several nests.
The largest colony recorded in the andorin campaign is made up of more than 560 nests. If you too know of an isolated nest or colony, register it on our website!