After twenty days the chick cracks its shell and breathes for the first time. Three days earlier, an older sibling had done the same so there is already a wobbling, hissing presence in the nest. There may be one more egg that is a further three days from hatching. If food is scarce, the new chick and its younger sibling will die as the parent birds focus on feeding the eldest, strongest bird, its head start in growth favouring it in the race to adulthood and thus making it most likely to survive. Fortunately, this season food is plentiful. The parents feed the chick pieces of a wadded mass of spiders and flying insects that they have caught in the air and stored in a hollow in their throats. (Later, the chick will consume the whole ball in one swallow.) The parents collect any faecal sacks that the chicks have produced. Mostly these are dropped away from the nest as they fly off to gather more food. Sometimes, for reasons unknown, they are swallowed, perhaps to appease for a moment the parent birds’ own hunger, which must be frequently tormenting through the long weeks of rearing chicks.
After a few weeks of growth, the chick begins moving purposefully about the nest, exercising its flight muscles, the pectorals that power the downstroke and the supracoracoideus muscles that raise the wings again. There isn’t room for the chick to open its wingspan so it performs a sort of press-up on its wing tips and vibrates its chest.
After several more weeks, the chick spends long periods sitting at the entrance to the nest, staring out at the world, learning in some way, calculating, calibrating. It does this for a few days, then flies out.
Fledging is not a graduated process for swifts. There is no hopping from branch to branch in short, bumbling flights that increase in height and distance. The swift leaves the odorous, parasite-infested darkness of the nest all at once and takes to the air where it may fly, may live, without touching another solid surface, for the next three years.
Swifts eat, sleep and mate in the air. They drink by catching in their mouths raindrops or the ice crystals of cloud vapour, the same way they catch the tiny airborne spiders that make up the greater part of their diet. Landing only in order to breed, adult birds fly continuously for ten months of the year, firstly in the skies of sub-Saharan Africa, then heading north across the desert on migration to their breeding sites across Europe.
Swifts come closer than any other creature to living in the sky and having air and ceaseless movement as their home. They reach great heights and great speeds. They can fly horizontally at nearly seventy miles per hour. Only the peregrine falcon flies faster than this, and then only in its brief vertical stoop, the arrowing free fall it uses to catch its prey. Swifts are small animals, about six and a half inches long with a wingspan of about two and a half times that. They typically breed after three years and die after seven or eight, though some have been known to live for more than twenty.