regular species. These belong mostly to the Anatidæ and Charadriidæ.
Next in order is the fourth class—the accidental and occasional visitors. These amount to 169, but owing to the difficulties of observation many of them may undoubtedly be classed as regular spring, autumn, or winter migrants.
In the same way the numbers of the other classes must be modified according to locality, period, and observation.
Of the fifth class, only one species—the Great Auk—is exemplary. One species—the Little Owl—may also be classed as a lately introduced bird, like the Red-legged Partridge of an earlier date.
Thus, then, we see how it is possible for the birds on the British list to amount to 415 species, since considerably over one-third are accidental visitors, and barely half of them remain to breed with us. After all, when we consider the fact in all its bearings, it is not so very surprising if we look at it from a world-wide point of view. Our islands are situated in the temperate regions, where birds that live in the warmer regions migrate to breed. We get, then, birds from the semi-tropical regions, and birds on their way to and from the far north from our own region. In a similar way we are situated only a few miles, in the south, from the Continent. This in itself explains why our own avifauna is largely supplemented in the summer by visitors from all parts. Indeed, when we come to think of it, we must wonder why many species abundant on the Continent are not met with at all in our own country. We find birds, such as the Stork, breeding in Holland, which from its nature might just as well breed in England.
Lastly, it is not surprising that we receive visits from American species, when we consider the long distances travelled by our summer migrants, and the fact that it is only a five days' trip in the liners of the Atlantic to the New World. How comparatively short a distance must it seem, then, to such an untiring creature on the wing as the bird!
