DO OTHER BIRDS TAKE OVER SWALLOW NESTS?
Yes. Though swallows can be very aggressive towards other birds that approach and threaten their nests, they often lose out to larger and more dominant species. House sparrows can be a particular problem, destroying eggs and chicks and sometimes taking over a dwelling altogether. An evicted pair can make another nesting attempt, but the failure may cause the partners to opt for a ‘divorce’ instead.
DO PAIRS USE THE SAME NEST FOR THEIR SECOND BROOD?
Yes, a second brood is usually reared in the same nest as the first. It takes seven weeks for swallows to bring up their chicks, so time is tight. Re-using an existing nest can save 5–12 days, and obviously makes sense unless the dwelling has a high parasite load, in which case it is better to start again elsewhere. Swallows may make two or more breeding attempts each season, particularly if they are early arrivals.
IF A SWALLOW RE-PAIRS WHILE ON MIGRATION, WHOSE NEST DOES IT USE?
Successful swallow pairs often return to the same nest, though this will depend on whether another couple is present and the condition of the nest itself. However, many birds die on migration, so pairs frequently reform. The first swallows to return are the older males, so while a widower is likely to re-use his old nest, a widow will be more likely to end up using a different one. Mike Toms