It is a baking hot summer day in a recently logged forest. Your ears pick up the sound of screeching birds. Well, what do you know! That is the well-known call of the common swift. With its beak full of bugs, the mother birds pop into the hollows of the snags left standing in the clearing. This familiar city bird has found a home for its nestlings in the snag hollow.
That hollow is, in fact, a very natural nesting place for a common swift. This bird is always ready to make good use of the holes burrowed by woodpeckers. A snag left standing in the clearing is an ideal home for the common swift, which soars at the speed of 150 kilometres per hour and tends to steer clear of dense forests. Traditionally, the forest-dwelling common swifts have been referred to as wild or forest swifts.
The snag hollow provides well-needed shelter for the swift nestlings during their first weeks, but after that the birds spend most of their life on the wing. When a swift leaves the nest, it might not touch land until it is two or three years old and ready to breed. So, for the first few years, this bird is constantly aflight. It does not land even to sleep. The common swift has a long life span and may well spend a total of ten years in the air.
Reasons for leaving a snag standing
A snag refers to a standing dead tree, which not only looks beautiful in a forest but is also useful to the environment. While all trees can become snags, pine snags are the most common. You can find snags in all Finnish forests, but as you go farther north, they can be encountered more frequently and they are older. It is beneficial to leave the snags standing during felling, because they contribute to the forest’s diversity. In forest certification systems, snags are trees earmarked for retention. Felled snags are useful only as firewood. They do not pose a threat to the forest as, for example, bark beetles do not feed on them. Whilst pest insects avoid snags, many beneficial insects, birds and small mammals find themselves at home in them.
Photo: Iikka Eklund / Vastavalo.fi
Expert: Juha-Matti Valonen, Environmental Specialist at UPM Forest