Outdoors: Nature note

One unmistakable sound of early spring is the territorial drumming of greater and lesser spotted woodpeckers. The curiously mechanical noise - brrrrrrrp, brrrrrrrp, like short bursts of machine-gun fire - is caused by male birds hammering their beaks on dead branches to warn off other males and advertise to females that a desirable customer is in occupation of the tree. The beak-strokes are incredibly rapid - a lesser spotted woodpecker has been timed putting in 33 hits in 1.3 seconds - and both species have an in-built cushion at the base of the bill to stop the shock of the impacts being transmitted to the brain.

When it comes to hacking out a nest-hole, the birds adopt different tactics. By experimental tapping they find points at which trunks or branches are rotten and, therefore, suitable for excavation; then they bore and chip away as quietly as possible, so that they do not attract the attention of predators.

Spotted woodpeckers are small, slim birds, mottled black and white, and males have small crimson caps. Greater spotteds are only about 9in long, lesser spotteds less than 6in long. Green woodpeckers, their large cousins - both sexes of which are red-capped - do not drum territorially; but all three species share the same looping, undulating flight.