Why do birds migrate? | Rye Harbour Nature Reserve

Why do birds migrate?

Sunday, 12th November 2023

Why do birds migrate?
Wheatear © Tom Lee

Paul Tinsley-Marshall

Site Manager, Rye Harbour Nature Reserve

I’ve always thought that it’s an extraordinary thing that it is possible to see a bird, and with a little knowledge about what species it is and the place in which you are seeing it, to know that that bird is on an epic journey. 

It only takes a little more curiosity to enable you to discover whether you bird is likely to be near the beginning, middle, or end of its journey. If you see a Wheatear on the beach at Rye Harbour Nature Reserve in the early spring, or early autumn, you can be pretty sure it’s at some point on an amazing journey.

Redshank © Barry Yates
Redshank © Barry Yates

The reasons why birds migrate, and the risks they take in doing so, are fascinating too. The journeys they make can be extremely long and dangerous, and are one of the main causes of death in some species.

What makes it all worthwhile? The resources birds need to live and breed vary in availability at different times of year, and in different places. Food, a mate, or somewhere to build a nest, are things that birds might need all of the time, or just some of the time, and finding them all in the same location, or somewhere without too much competition from others isn’t always possible. To get around this, some birds have evolved migration strategies to ensure they are in the right place at the right time in their life cycle.

Ringed Plover with eggs © Barry Yates
Ringed Plover with eggs © Barry Yates

Migration can be a particularly effective strategy for ground-nesting birds, such as the Ringed Plover, which in the UK have the run the gauntlet of mammalian predators such as Foxes, Badgers, Weasels, Rats, Pine Martens and Hedgehogs.

Many of the birds that we see in the UK either on migration or overwintering breed in the far north of our hemisphere, where the extensive tundra, boreal forests and taiga offer a comparatively predator-free environment. At this northerly extreme, daylight is constant in the summer, which means more time for feeding, which can mean better body condition, the ability to lay more eggs, the chance of raising more chicks and more chance of your young making it to adulthood. The abundance of sunlight means that vegetation is very productive, providing plentiful food for herbivorous birds such as geese, and habitats that support many insects, benefitting insectivorous birds.

This post is also available on Sussex Wildlife Trust website

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