Swifts, Apus apus, and How to Help Them.

by Judith John.

Swifts arrive in the UK in late April or May to breed, usually at traditional nest sites, and leave in July or August for South Africa. Whilst in Britain their chief requirements are food for themselves and developing young and safe breeding sites. Swifts feed on flying insects and spiderlings high up on air currents, bringing from 300 to 1000 insects in each bolus of food they bring back for their chicks. The number of swifts arriving in the UK declined by 47% between 1995-2014 and more recent RSPB figures show a 51% decrease in their breeding numbers between 1995 and 2015.

In Bromley numbers recorded are now very low. The pilot study carried out this year returned only three definite records of breeding, in Mottingham, the Hillcrest Road area of Orpington and in the Petts Wood area. They have been seen flying at rooftop level near Orpington Station, which suggests they may have bred close by, but this needs further investigation. Swifts are also known to have bred in the Bromley South area in the past, but their numbers here have declined over the last 15 years from 12 in 2002 to 2 in 2014, and none have been seen since then in this area.

Records were also received of swifts flying above the Goddington Park area, Oakhill Road near Orpington Station, Friar Road & Robin Hood Green Poverest, Downe and High Elms, Leaves Green, Pickhurst Rise West Wickham and Hayes Road Bromley.

The swift survey was repeated in 2018, Bromley Biodiversity Partnership working closely with Bromley RSPB. 122 volunteers surveyed 228 500m x 500m squares once a month between May 12th and July 26th. In total an area of 57 square kilometres was surveyed, representing about 75% of the area suitable for swifts in LBB. There were few records after mid July. Swifts flying at roof height or entering nest holes were seen in 162 10m squares and there were 49 nests recorded. Most of the swift nests were seen in the north of the borough. The greatest number of nests was in Derrick Road, Beckenham, where residents said they had been nesting for 40 years, with others clustering in the Anerley Park/Crystal Palace area and in Orpington.

Meanwhile, although there may be many reasons why swift numbers have been dropping which we cannot influence because they live overseas for much of the year, there are 2 problems which it may be possible to address in Bromley borough: reduced nesting sites and reduced availability of insect prey.

Loss of nesting sites

Swifts generally nest within holes and cavities in the roofs of older buildings in larger villages, towns and cities. With the increased drive for better insulation, buildings are better sealed than in the past, so swifts are returning to discover their nest site has gone or access is blocked. This situation could be remedied by the installation of swift bricks in new buildings or when houses are re-roofed or renovated so, especially in areas where swifts have been seen, when planning application is applied for new builds or renovations it is worth asking for swift bricks to be incorporated as a condition of permission being granted.

They can also be put up by individuals. Swift bricks cost from £15 and are readily available on the internet. Ideally at least 2 should be put in since swifts tend to nest colonially and it is a good idea to purchase a CD of swift calls to attract them - these cost about £2. There is lots of advice about where and how to site them at www.swift-conservation.org. Swift boxes can also be bought or made but these do not last as long.

Loss of Insect Prey - Native Shrub & Tree Planting

A study in 63 German nature reserves carried out between 1989-2016 (Hallmann et al., 2017) reported a 75&percent; decline in flying insect biomass during this time. In the UK the picture is likely to be very similar. If you can look back 30 years you may be able to remember how, on long motorway journeys, it was necessary to stop to clean car windscreens and headlamps, sometimes more than once, before you reached your destination. Flying insects are eaten by bats and some birds, and their young grubs (larvae) are fed by many birds to their chicks.

The aim of planting more native shrubs and small trees is to improve declining invertebrate numbers since native invertebrates are adapted to eat native plants. The invertebrates are food for other declining species including birds, bats and other animals and the native plants also provide food such as berries. The shrubs and trees will also provide increased habitat for nesting and roosting. The Bromley Biodiversity Partnership (of which OFC is an active member) is therefore asking people to plant at least one native shrub or small tree in their garden, or even a native hedgerow or ask if it might be possible to plant some in local school or sports grounds, allotments or parks.

In this way it should be possible to provide more food for birds, bats and other animals and also to improve links between green spaces, including via gardens so animals can more easily move between green areas. A file of native hedge plants, shrubs or small trees suitable for gardens or other areas, with details of flowering, fruiting, soil requirements and importance for invertebrates is available and can be downloaded here: Native Hedge Plants for Gardens and a poster is here: Native Shrubs and Trees Poster.

We hope that this initiative will, over time, improve links between existing green spaces and therefore make it easier for some declining species to move and spread to more areas.

Reference: Hallmann CA, Sorg M, Jongejans E, Siepel H, Hofland N, Schwan H, et al. (2017) More than 75 percent decline over 27 years in total flying insect biomass in protected areas. PLoS ONE 12(10): e0185809.
https://doi.org/10.1371/journal.pone.0185809

Swift Survey Poster

To see or download a poster about this year's swift survey, please click here:

Downloadable Swifts Poster