the most important specimens Charles Darwin brought back

from the Galapagos were finches.

Initially he wasn't sure how they were related

but when back in England,

they were examined by the ornithologist John Gould

he reported that in fact Darwin had brought back

13 different species of finch,

all of which were unique to the Galapagos.

This realisation played a significant role

in Darwin's formulation of his theory of evolution.

The most important differences between the finches

came in their beaks.

Some were large, some were small.

Each one was suited

to the availability of particular foodstuffs.

Eventually Darwin theorised that different species of finch

had evolved on different islands,

their distinctive beaks being an adaptation

to distinct natural habitats or environmental niches.

In the years since Darwin's visit,

many other scientists and ornithologists

have come to the Galapagos to study its finches.

In this experiment researchers are observing the woodpecker finch,

using this wooden box to stand in for a tree.

The woodpecker finch

is one of the only birds to use tools to help it find food.

A stick or small twig enables it to dig deeper into tree bark

for insect larvae.

This skill enables it to survive

in conditions which other birds would find difficult.

In the dry season it can gather up to 50% of its food in this way.

Woodpecker finches are hungry birds

which in the wild need to eat every three hours,

so they never turn down the chance of a free meal.