The swallow (Hirundo rustica) is a small bird which is just 17-19cm in length. These birds boast dark blue backs, red throats, creamy underparts and tails with two streamers visible in flight. Swallows are incredibly agile in the air and spend a high proportion of their time on the wing.
Males and females are identical in appearance. Swallows are migratory birds that spend the summer months in the Northern Hemisphere and then fly south for the winter. The number of swallows seen in the UK has been prone to fluctuations and there have been regional variations in population trends.
What is the swallow’s population and distribution?
British swallows spend the winter months in sub-Saharan Africa. They migrate by day and at low altitude. These birds are vulnerable to both starvation and exhaustion during their journeys. They can cover up to 200 miles per day and arrive in the UK during April and May. Swallows return to Africa during September and October.
When in this country, they are found in areas where there is a good supply of insects, particularly in places close to water courses and farm buildings. Swallows need rain to promote an abundance of insects and to soften the mud they use to build their nests. However, cold snaps and prolonged rain can reduce the number of insects, leading to the starvation of chicks.
Swallow numbers have declined since 1970. The reasons for the fall in population are not clear but climate change could be to blame. Cold springs, late frosts and hot summers can all be serious issues for swallows. The expansion of the Sahara dessert is creating a significant barrier that swallows struggle to cross during their migration. In addition, farming practices are reducing the number of nesting sites in Europe.
There are thought to be 860,000 swallow territories in the UK. These birds are not yet of conservation concern, but this situation could change soon.
What do swallows eat?
Swallows feed on flies and aphids, which they catch on the wing. They drink by skimming low over lakes or rivers and then gathering up water with their open beaks.
Where do swallows nest?
Females swallow are choosey about their mates and are attracted to the males with the most symmetrical trail streamers as this is indicative of good health and robust genes. Both parents build their nest from mud and grasses and they make up to 1,200 journeys to collect materials. The nests are constructed on ledges and beams in sheds, barns and other open fronted outbuildings. Only the females line the nests. Swallows produce two or three clutches each year and lay around four eggs each time. The eggs are incubated for 14 to 16 days and the chicks will fledge after 18 to 23 days.
Did you know?
Swallows would probably have been much rarer before man started farming.
These birds will adopt artificial nests if they resemble their own mud-built constructions.