House Martins and Swifts

[Guinnessman1974]

It is well know that House Martins and Swifts build nests close to man, in the eves of buildings, on bridges etc.

Where would they have nested otherwise? I guess cliff edges etc.

There is often talk about humans causing declines in populations of species, however since urbanisation had we originally helped the increase in numbers of House Martins and Swifts through provision of nest sites in buildings?

worth a thought?

[aeshna5]

As you suggest they would have been much more limited in the past- natural cliffs + Swifts may have used some large tree cavities.