Ilitsheva, V.D. & Mikheyeva, A.V. (1986): Apodiformes. In Zhizn zhivotnikh vol. 06, p. 314-321
(APUSlist No. 4440)
by IGOR FEFELOV
Common (Black) Swift
Within most of its range the Common Swift (Apus apus) nests in urban environments. But in Transbaikal it nests solely within forests while A. pacificus nests within the cities. In Finland, the Common Swift nests within both cities and forests.
The Common Swift arrives late in small groups, often 1 to2 or even more days apart, during warm weather, usually coinciding with the start of a cyclone. The arrival is prolonged and lasts 14 to 27 days. Then within a few days Common Swift begins nest building, which lasts 8 days. Usually 2, more rarely 3 eggs are laid. There is only one clutch per season. Incubation time is 11-16 days, depending on the weather. If the weather and/or feeding situation become bad for a long period of time, then the Common Swift may even expel eggs from the nests.
Chicks leave the nests usually at 38 to 39 days old, sometimes even 33 to35. But in
unfavourable seasons, they wait until the 56th day.
In bad weather the chicks will stay hungry because of the shortage of food, and their body temperature falls to 20 °C. In this state of torpor the chicks may will have to wait up to 9 or even 12 days until better weather supports more insect availability. In such situations adult swifts may move to areas with more favourable weather and better insect availability.
Birds catch the flying insect food items in flight, stuffing their buccal cavity with the items until they have a "food ball". They then bring it to the nest.
Maximum feeding activity has been recorded in Leningrad as a total of 34 visits to the nest in one 19 hour period. Towards the time of fledging, feeding visits decrease to 4 to 6 times per day.
Interestingly, chicks get the maximal
body mass at roughly the 20th day of their life and then they lose some of that
weight before they fly away.
Chicks begin flying and feeding
immediately after leaving the nest. Sometimes chicks
leave the nest place when their parents are still present there, but sometimes the opposite happens, parents (but usually only one of them), leave the nest area first and
then the fledglings depart.
Usually in migrant bird species more
northern individuals leave nest areas earlier than the
southern ones do. But the BS does the opposite. For example, it was found swifts start their migration from Finland later than from Switzerland; in Switzerland they finish breeding earlier. This holds true right across their range.
Swifts living near sea coasts often fly out over the open sea at sunset, returning at sunrise. Their absence may last from 4 or 5 to 7 or 8 hours, depending on the season of the year.
I am thankful to Edward Mayer, who edited the English text.
© APUSlife 2009, No. 4441