Birdwatch at Arundel Wildfowl and Wetlands Trust

Some migratory birds need to eat a vast quantity of food in order to undertake their autumnal migration. Many warblers, for example, will adapt their diet in the period preceding their journey and weigh twice their normal weight as they set off. Some warblers feed on aphids as they contain a higher concentration of sugar than most other insects; others ignore insects altogether in favour of nectar!

One drawback of this gluttony is that heavier birds are not as agile as their 'svelte-like' friends who can eat on the wing; such as swallows. Fat little birds are not only easier prey for predators but also provide a decent meal! However, this preparation is not a question of choice. It is in fact another of nature's amazing adaptations.

Before setting off, the metabolism of the bird changes, this subtle alteration is triggered by hormones which allow the bird to utilise the food more efficiently and store the energy it needs for a long flight.

For full feature see West Sussex Gazette October 25