Atlantic Salmon
Copyright Mike Brown

Ireland’s biodiversity waxes and wanes as migrant species enter and leave the country. Most of these are birds but some fish, such as salmon and thwaite shad, can be described as migratory, as can several species of butterfly and moth. Red admiral, painted lady and clouded yellow butterflies and the hummingbird hawk moth are all insects that visit us in summer from continental Europe and North Africa. 

What springs to most people’s mind when you mention migrants are such familiar species as swallows and cuckoos and the once-familiar corncrake. They are accompanied by dozens of lesser-known bird species. Most of them come to us from Africa. It’s believed that what tempts them to make the long and dangerous journey is the length of our summer days. They are all birds that need daylight to gather food and when they have the extra burden of feeding their young as well as themselves they need extra daylight. Of course, this elegant explanation doesn’t work so well when you consider the cuckoo, which never feeds its own young.

Many of our summer migrants seem to be declining in numbers, some of them, like the ring ouzel and the corncrake, quite dramatically. There are a variety of reasons for this but most birds that come to us from Africa have to cross the Sahara Desert twice a year. Due to climate change, the Sahara is getting bigger and becoming a greater obstacle to migrating birds.

Winter Migrants

There is an even larger and more important migration of birds that spend the winter here. Between roughly March and October they live in the arctic and sub-arctic. They come here because we are the most northerly country in the world where the soil and the water does not freeze in winter, at least not for very long periods of time. Some of these are land birds like the short-eared owl, the fieldfare and the woodcock, but more of them are wetland birds. They come to the coast and they come to inland rivers, lakes, bogs and callows. Unfortunately as bogs are harvested and wetlands are drained the amount of suitable habitat available to them is declining.

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