Their call is a loud scream in two different tone pitches, the higher of which issues from the female.
They often form 'screaming parties' during summer evenings, when 1 0–20 swifts will gather in flight
around their nesting area, calling out and being answered by nesting swifts. Larger "screaming parties"
are formed at higher altitudes, especially late in the breeding season. The purpose of these parties is
uncertain, but may include ascending to sleep on the wing, while still breeding adults tend to spend the
night in the nest.[citation needed]
Swifts may nest in former woodpecker tree burrows found in ancient forests, such as some 600
reported nesting in the Białowieża Forest of North Eastern Poland, or the small colony found in a
combination of woodpecker holes and tree nestboxes on the RSPB's reserve at the Caledonian
Forest in Abernethy, Scotland. While tree holes and cliffs may have comprised their historic nesting
resource, the almost complete removal of ancient forest from their nesting range has resulted in
adaptation to man-made sites. Swifts build their nests of air-borne material caught in flight, bonded
with their saliva, in suitable buildings hollows, such as under tiles, in gaps beneath window sills, and
most typically under eaves and within gables.
Swifts form pairs that may couple for years, and often return to the same nesting site and partner year
after year, repairing degradation suffered in their 40-week migratory absence. Insects such as clothes
moths, carpet and larder beetles may consume all but the most indigestible nest elements, typically
feather shafts.
Young nesting swifts are able to survive for a few days without food by dropping their body
temperature and metabolic rate, entering a torpid state.
Except when nesting, swifts spend their lives in the air, living on the insects caught in flight; they drink,
feed, and often mate and sleep on the wing.[7] Some individuals go 1 0 months without landing.[3] No
other bird spends as much of its life in flight. Their maximum horizontal flying speed is
111 .6 km/h.[8]Over a lifetime they can cover millions of kilometers.[9]
Feeding parties can be very large in insect-rich areas, such as wetlands. Reports of as many as 2000
swifts feeding over flooded gravel
pits, lakes and marshy river deltas
are not uncommon, and may
represent an ingress of swifts from
within as much as a 1 00 km
(62 mi) radius; swifts nesting in
Western Scotland are thought to
venture to Lough Neagh in
Northern Ireland to feed on the
abundant and nutritious "Lough
Neagh Fly".
Breeding[edit]
Common swifts nest in a wider
variety of sites than any other
species of Apus. Swifts usually
nest in buildings but they can also
be found nesting in holes in trees,
cliffs and crevices, and even in
nestboxes. Swifts usually enter
their nesting holes with direct
flight, and take-off is characterized
by an initial free-fall. Empty
cavities are shallower than those
with nests, and the entry size is
smaller in the former than in the
latter.[1 0]
Migration[edit]