BIRDWATCH AT ARUNDEL WILDLIFE AND WETLANDS TRUST

The reason there are so many around at the moment is that numbers are building up pre-migration.

They will build in suitable sites along the south coast as they prepare for their sea crossing south over the continent. So, what are they up to?

After their young have fledged, around mid-August, the adults will hang around the nest site and begin their moult. They will replace body feathers and sometimes a few flight feathers as well.

Moulting requires energy, both because the feathers being lost may result in a reduction in flight performance and insulation against bad weather but obviously will also require energy in the production of new feathers.

The swallow's life story is a series of trade-offs, each with a cost and a benefit, and the timing, or prioritisation, is crucial.

The key events in a swallow's life, such as breeding, will be so costly as to take energy from other vital functions, such as immune response and growth.

So, having invested a huge amount of time and energy in the 'kids', our adult swallow now enjoys a bit of 'me time', investing in a new set of feathers that will need to see the bird through the winter in southern Africa.

For full feature see West Sussex Gazette October 3