SWAL­LOW NEST­ING

BBC Wildlife Magazine - - Our Wild World -

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

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