Everything you ever wanted to know about the common swift

Swifts are the quintessential birds, surpassing all others in their mastery of the air. Elegant, bewitching and indefatigable, from the moment a young swift takes flight for the first time, they will not touch land again for two years. This article explores how swifts have evolved as a synanthrophic species, making use of buildings and the artificial environment to thrive alongside us and how they may show us the way forward for conserving many other species alongside economic development.

Summer evenings

Swifts visit the UK for a few brief months each year and are the true harbingers of summer. They are unique in their flight capabilities; eating, sleeping and mating on the wing. They only land to lay their eggs and raise their young. Swifts feed on aeroplankton, the insect and spider soup blown up into the air in dense numbers during the summer. They collect a ball of food (bolus) in a pouch at the back of their throats and once they’ve caught around 500 food items, either eat or pass the bolus to their young. Perhaps most impressively, they are one of very few birds capable of mating in the air, tumbling through the sky together for a brief copulation. At night they are able to turn off half of their brains and ascend to a great height to spend the night in a semi sleep, an excellent survival mechanism as birds are highly vulnerable to nocturnal predators whilst roosting in trees.

They have evolved so completely to life in the air that their feet relative to body size are amongst the smallest of all birds, making it almost impossible to take off from the ground. As a result, they are faced with a challenge when it comes to finding places to nest. They need to find somewhere they can fly directly into as they cannot perch or walk like most birds. Equally as tricky is finding a place where they can drop directly out of. They need to plunge a minimum of three metres from their exit point towards the ground so that they are able to start flying before they fatally ground. As a consequence, typical nesting sites, either on the ground or within dense areas of bushes or trees, are not suitable for swifts.

Home sweet home

Present day nesting places include under the eaves of houses, old churches, under roof tiles and in introduced nesting boxes or bricks. This habit can be traced back centuries, though of course it was not their original nesting habitat. In some places they still nest in holes and crevices in trees, caves and cliffs but nearly all European swifts now use artificial nesting places. However, in recent decades, new buildings have been designed as such that they do not allow for entry of swifts, or other creatures, and this has started to reduce good nesting locations.

Swifts undertake mammoth migrations from the UK to Africa each year. They leave the UK in August and return in May, without ever landing, putting in over tens of thousands of miles per year. They return to the UK annually to breed but every year a few more swifts, who remain very loyal to nest sites, come back to find their old nest entrance has been blocked up by homeowners who have renovated the insulation and seal around their homes. In addition many of their traditional nesting sites in run down or older buildings are being knocked down and replaced by new modern houses, often with no convenient nesting holes incorporated. This is thought to be one of the reasons for recent population declines in the UK.

Photo by Alberto Novo / Shutterstock
Photo by Alberto Novo / Shutterstock

The built environment

The links between anthropogenic activity and the environment often tell a story of devastating habitat and biodiversity loss. The human impact on the environment is hugely complex and goes back centuries before industrialisation and presently there is no getting away from the economic development which is happening across our globe. However, the example of swifts gives hope that there are things we can do to ensure economic development can also benefit species.
Fortunately, the decline of urban wildlife has been noted in the UK and it is now becoming more commonplace to incorporate wildlife friendly enhancements to new buildings and refurbishments. Swifts take to artificial nest boxes and a few tricks can help to encourage them in. Playing back their own calls early in the morning can encourage them to investigate new sites and they take well to nest boxes placed under eaves or inside ‘swift bricks’, a normal looking but hollow brick with a small hole in for swifts to enter through

Example of an inbuilt swift brick.
Example of an inbuilt swift brick.

Wildlife enhancement like these can make a crucial difference in the fate of urban species. Scientific research will help to refine specifications for the best refuges and homes for different species as we begin to grasp optimum requirements. In addition, the introduction of green and brown roofs, living walls and simple measures like planters can transform the urban environment from concrete jungle to wildlife friendly. Indeed, without the need for pesticide introduction in these spaces, unlike arable land, it is possible to make these areas thrive with insect life too, which provides food for more charismatic species.

Peregrine falcons, foxes, otters, hedgehogs and swifts have all found a home in British cities, allowing nature starved urban dwellers spectacular encounters with some of the UK’s most well loved species. There is further work to be done in order to encourage a culture of designing for biodiversity in the built environment but if we start with swifts, we can encourage more species to live alongside us. In an ever developing world this will be invaluable, both for wildlife and our own well being.

Visit the Swift Conservation website for news and videos on various swift projects in Europe.