Sand martin

The sand martin (Riparia riparia) is related to the swallow and the house martin in the hirundinidae family, but is only a distant cousin of species such as the purple martin which are more familiar in North America. Sand martins are about twelve centimetres (less than five inches) in length, so they are the smallest of the European martins/swallows.

The sand martin is a migratory bird, spending its winters in Africa (south of the Sahara) and flying north any time from mid-March to June. The early arrivals are among the earliest migrant birds to reach Britain. It is found on rivers and other bodies of water throughout the United Kingdom in summer, apart from the extreme north and west of Scotland.

Appearance

The plumage of the sand martin, which is similar as between males and females, is brown above and white below, with a prominent brown bar across the chest. The wings are also brown, both above and below. It is therefore lighter in colouring than the similarly shaped house martin, and it also has a less prominent fork in the tail.

Behaviour

The sand martin flies with erratic, flitting movements, mainly over water as it takes insects on the wing. It perches on wires and branches, often in large numbers.

It has a harsh chirruping call and a twittering song that can be very noisy when a large number of birds are in voice at the same time.

Breeding

As its name suggests, the sand martin makes its nest in sandy or muddy river banks, and also in inland soft cliffs next to quarries and gravel pits. They may also use railway embankments or sea cliffs, or even holes in brickwork. Sand martins are colonial nesters, with up to a hundred pairs nesting together.

The sand martin has no special “equipment” as a burrowing bird, and the excavation of a nesting hole, performed by both members of a pair, is a tiring business. The bird begins by pecking with its beak and then uses its feet to remove the mud or sand, eventually digging a horizontal tunnel up to a metre long. Due to the effort required to dig a nesting tunnel, old tunnels are likely to be reused, sometimes for several years until a tunnel collapses or otherwise becomes unusable, when other birds such as starlings or sparrows may take them over.

At the end of the tunnel the sand martin excavates a cavity around ten centimetres in diameter that is lined with bits of vegetation and feathers. Anything between three and seven eggs are laid, which are incubated by both partners in turn for up to 14 days. Incubation only begins after the last egg has been laid, so the chicks therefore hatch together and are the same size as they grow. The nestlings stay in the nest for up to 23 days and continue to be fed by their parents for another two weeks after they have fledged. A second brood is common.

Sand martins return to Africa in August or September.

Conservation

Sand martin numbers are healthy in the United Kingdom, although populations can fall dramatically if there are harsh winter conditions in Africa, such as drought. The sand martin has amber status and is a protected species, which can cause problems if nesting tunnels are built in active sand quarries.

© John Welford