Swallows and Swifts - Aerial Feeders

Although swallows and swifts are superficially similar in appearance, and often pose identification problems for beginners, they are actually unrelated. Scientists have not yet determined the closest relatives of the swallows (which include the martins), but they belong to a large assemblage of passerine birds including warblers and larks. Swifts, on the other hand, are related to the New World hummingbirds (with which they share similar wing bone structures) although the ancestry is ancient.

Convergent Evolution

The fact that swallows and swifts have more similar body shapes to one another than they do to their close relatives, is a result of convergent evolution. Both groups of birds are specialized aerial feeders of tiny invertebrates and have long pointed wings which allow them superb maneuverability. Interestingly, the nocturnal nightjars, which are considerably larger but also feed on airborne insects, have a wing to body shape ratio very similar to the swallows and swifts. All these birds catch their prey by keeping their mouths open as they fly through the air.

Harbingers of Spring... or Autumn

In Africa, there are 22 species of swift in 8 genera, and 38 species of swallow and martin in 7 genera. The best known of all the swallows is undoubtedly the Barn Swallow (which was known as the 'European Swallow' until recently). This bird has a vast cosmopolitan range, occurring on every continent except Antarctica. In Africa, these familiar birds are primarily n n-breeding visitors from Europe where - in places such as the England and Holland - they breed mostly on man-made structures and their seasonal return sees them as harbingers of Spring. In sub-Saharan Africa, large flocks of these swallows roost in reedbeds at night where they are vulnerable to capture by people, and this mass-predation is proving to be of increasing conservation concern. Each April, in anticipation of cooler and shorter days in southern Africa, huge numbers of Barn Swallows can be seen aggregating on overhead wires as flocks prepare for their 10 000km journey back to Europe. Like other migratory birds, the effects of global warming are already showing signs of influencing their seasonal movements.

Nests of Mud and Straw

All swallows build cup-shaped nests from mud pellets and straw, and often situate the structure in the shade of a roof awning, bridge or some other sheltered spot. Most species of swallow and martin are gregarious and in Africa, it is not uncommon to see several species foraging together. The South African Cliff Swallow and Grey-rumped Swallow breed colonially, but most of the other species nest alone. Among the more commonly encountered swallows in southern and east Africa are the Wire-tailed Swallow which is always found close to water, and the Lesser Striped Swallow which often nests on houses and other buildings. The Blue Swallow is an endangered species dependent upon high-altitude grasslands which - especially in South Africa - have shrunk in the face of expanding timber plantations.

Living with Mankind

In contrast to the often colorful swallows, the swifts are more difficult to separate. Most are predominantly black in colour, with or without white rumps and throats. Over much of Africa, the Little Swift and White-rumped Swift are the most frequently encountered species, although the Common Swift which is a non-breeding visitor during the southern summer can be locally abundant. These and other species frequently nest under bridges or on the sides of city skyscrapers. With its white belly, the large Alpine Swift is a distinctive species in mountainous regions. The African Palm Swift is pale brown in colour and even more slender and elongated than other swifts; it breeds only among the dry leaves of palm trees and has expanded its range into places like Johannesburg where these trees are commonly cultivated.

Key differeces between Swallows and Swifts

There are several key differences between swallows and swifts. Swifts generally have narrower, sickle-shaped wings and do not perch between foraging flights (in fact, their extremely short legs and toe structure does not allow them to perch at all and they can only cling to rough surfaces!). Not only do swifts capture all their food in flight, but these remarkable birds sometimes even sleep and mate in the air! Swallows tend to fly closer to the ground than swifts and have distinctly broader wings. Many species have long forked tails ending in thin streamers which grow to a maximum length during the breeding season, but the martins typically have shorter squared-off tails.

A Challenge for Bird Watchers

Although swifts and swallows pose an identification challenge for beginner birdwatchers (and are often ignored by experienced ones!), they are fascinating birds whose existence is closely tied to that of mankind.

- Duncan Butchart -

Posted: Birds by CC Africa, Date: 21 November 2006