Swifts, swallows and house martins are amongst the most endearing of British breeding birds. They are not resident, escaping to warmer climes to over-winter, but substantial numbers arrive in Britain in the spring to breed.

Cornwall Council has produced guidance for developers, builders, surveyors, architects and householders.

This link takes you to the guidance document providing much more useful information - Accommodating swallows, swifts and house martins.