In July evening flights of swifts wheeling high over our garden are a regular feature. Wonderfully wild screaming reveals their whereabouts although the visitors are often scarcely visible to the eye. On other occasions up to a dozen will hurtle just above the rooftops. Yet it is remarkable how infrequently one hears of aerial collisions.
During cold and windy weather parent swifts can spend long periods sitting on nests close together, or on top of each other with bodies hunched and feathers ruffled. In abnormally cold weather swifts may throw out complete clutches of eggs before themselves congregating in clusters on walls. Swifts will take shelter in their nests in heavy rain, even staying in for much of the day.
I have watched them flying in front of and away from an approaching heavy thunderstorm. Local storms are regularly dodged in this way.
A spectacular form of aerial display is when individual swifts fly up to the nest entrance holes of other swifts and brush or bang against them apparently with their wings before continuing their flight. Single swifts may fly up in this way to a number of nests in succession. This type of display is restricted to fine weather with little or no wind and is particularly noticeable on the first fine day after a spell of bad weather.
Swifts use the same nest year after year, merely adding fresh material. This is caught in the air. As a result, building is erratic being most frequent when there is sufficient wind to sweep suitable material into the air.
Dry grasses, straw, dead and green leaves, flower petals, winged seeds, feathers and scraps of paper have all been found in nests. Fresh poppy petals are sometimes used. The material is stuck to the nest with saliva.
Intruding swifts which attempt occupying a nest-site cause frequent and, on occasions, lengthy fights. These struggles are accompanied with violent screaming.
In early August when the first swifts are migrating south, strangers may be found roosting within a colony. None stay longer than a single night and it appears these strangers merely join resident swifts to pass the night. Migrating swifts have also been reported settling at dusk on telegraph poles.
Like flying anchors, these symbols of high summer have greater mastery of the air than any other bird. Swifts drink, bathe, preen, collect food and nesting material all without alighting. The night is spent on the wing and they are the only bird known to mate on the wing.
The swift's stay here is short, extending from early May to early August the period coinciding with high insect populations and long hours of daylight. Once their young can fly swifts have no reason to linger here. Indeed, there seems no need for young birds to strengthen wings in practice flights.
Parent swifts returning with food for their young reveal a large bulge below the beak due to a mass of insects packed into the throat pouch glued together in saliva. Detailed observations have shown that a swift may bring 40 meals a day to the young. One rapidly appreciates the remarkable numbers of insects and airborne spiders consumed by a single family.
Leaving their nest fledgling swifts instantly take up an independent airborne life and are apparently ignored by their parents. For their size they are long-lived and individuals known to be 19 and even 21 years are on record.
These died, not of old age, but from accidental causes including a collision at speed with another swift. Swifts recovered outside the breeding range and off migration routes are probably non breeders undertaking weather movements involving thousands of birds. These long distance flights around depressions are to avoid heavy rainfall and may well involve journeys of between 600 and 1200 miles.
Ringing evidence confirms that a young swift can be hundreds of miles southwards on its first trip to central African winter quarters within 48 hours of leaving the nest.
Although the swift's stay here is so short, it is a familiar bird. At dusk bunches of these tireless birds rise so high that they become mere crescentic specks in the darkening sky. They hang in the heavens, balancing on warm air currents with scarcely a wing movement.
Voices remain faintly audible even when the birds have become invisible for they are content to play away the night, drifting under the summer stars.
Passage migrant swifts continue passing through East Anglia until mid September. October occurrences are distinctly uncommon and November sightings even more so.
very warm southerly winds during early November 1984 swifts reappeared
at several localities along the Norfolk coast. Their surprise appearance
coincided with deposits here of Sahara dust
By Michael J. Seago