In the midst of the bushes on the bank stood a tree. It was not tall
compared to the other trees of the Dingle, but standing alone as it did
amongst the undergrowth it attracted the eye at once. Barrett, looking
at it, saw something which made him forget water-wagtails for the
moment. In a fork in one of the upper branches was a nest, an enormous
nest, roughly constructed of sticks. It was a very jerry-built
residence, evidently run up for the season by some prudent bird who
knew by experience that no nest could last through the winter, and so
had declined to waste his time in useless decorative work. But what
bird was it? No doubt there are experts to whom a wood-pigeon's nest is
something apart and distinct from the nest of the magpie, but to your
unsophisticated amateur a nest that is large may be anything--rook's,
magpie's, pigeon's, or great auk's. To such an one the only true test
lies in the eggs. _Solvitur ambulando_. Barrett laid the pill-boxes,
containing the precious specimens he had found in the nest at the top
of the hill, at the foot of the tree, and began to climb.

It was to be a day of surprises for him. When he had got half way up he
found himself on a kind of ledge, which appeared to be a kind of
junction at which the tree branched off into two parts. To the left was
the nest, high up in its fork. To the right was another shoot. He
realized at once, with keen disappointment, that it would be useless to
go further. The branches were obviously not strong enough to bear his
weight. He looked down, preparatory to commencing the descent, and to
his astonishment found himself looking into a black cavern. In his
eagerness to reach the nest he had not noticed before that the tree was
hollow.

This made up for a great many things. His disappointment became less
keen. Few things are more interesting than a hollow tree.