The appearance of house martins in late April is almost as welcome as that of their relative, the swallows, Unlike most migrant songbirds which only reveal their presence by singing lustily from the depths of foliage, these are supremely visible as they hunt insects over our fields and gardens.
They are also extremely popular, probably because they choose to live in such close proximity to man. Both almost invariably choose our buildings as a nest site. The swallow (see www. ) chooses the shelter and security inside a barn or garage, but the marten chooses to rear its brood on the exterior – almost always under the eaves. Naturally this begs the question of what they did before man began to build vertical walls with stone (it is hard to see where they could have nested on an iron age roundhouse).
The answer is that they must once have sought out cliffs both along the coast and inland. Indeed across Southern Europe, a relative, the crag martin, still nests almost exclusively on precipices and in caves. Both martins site their nests below an overhang for shelter from the elements and protection from predators. But natural sites such as this are in short supply across most of Northern Europe, so the birds must have learned to tolerate the close proximity of neighbours – and they remain sociable nesters to this day. All the same, there must have been huge pressure on available sites, so when man began to build big stone structures, the birds readily switched preferences.
Most of these early artificial cliffs would have been military – castles or bridges – which might explain the name martin which originally came from Mars, the god of war. And they are mentioned in Macbeth as nesting on Cawdor Castle just before Duncan’s murder.
Today the familiar globed nests are usually tucked under the eaves of houses in towns and villages. These small cups need no description, each made of 1,000 mouthfuls of mud and spit. As they work hard over a week or so to complete their nest, they chatter excitedly: which only adds to their appeal.
Despite the familiarity we have with these little birds which are quite happy to nest within inches of open windows and within feet of constant human activity, we know remarkably little about half their lives. No one knows where they go in winter. Despite millions of birds having been rung over the past century, only two rings have ever been recovered from Africa. The experts’ best guess is that they probably spend our colder months hunting insects high over the vast rainforests – and quite possibly never landing but instead sleeping on the wing high above the Congo.