But to return for a moment to the smaller passerines. There are very few of our native species which could be distinguished in the field by their flight alone. For the most part one has to rely on this and clues afforded by characteristic markings: while a further aid is afforded by at least a slight knowledge of the haunts of birds. One would not expect to find a wheatear in a wood, or a wren in a reed-bed. The wagtails are among the easiest of the "undulating" fliers to distinguish, if only because of the great length of the tail. The pied-wagtail, with its black and white plumage--or black, grey, and white in the winter--can be identified at a glance. And so too, may the yellow, and the grey wagtails. The last named has the longest tail of all, and is further marked by his beautiful grey back and bright sulphur abdomen and under tail coverts. All have white feathers in the tail. The pipits and skylark, like the wagtails, have very long inner secondaries, but they can never be confused on this account. They can never be mistaken for wagtails, but on the other hand, the several species can be distinguished, when on the wing, only by long practice. The chaffinch, greenfinch, and goldfinch are with us all the year round, keeping each to his favourite haunts. Most people know them well. But one meets even people living in the heart of the country, who cannot call them by name! The cock chaffinch can be distinguished at once by its white "shoulders," and white bars across the wing, apart from the bright hues of the body, so well shown in the adjoining Plate. The hen has similar wing-marks, but lacks the bright colours of her lord. His cousin, the brambling--who comes to us in the winter--is just as easily identified by his orange-coloured shoulder patch--in place of white--and white rump, which is most conspicuous during flight. The greenfinch is marked, when in flight, by the yellow rump and bright yellow patches at the base of the tail feathers. Who could mistake the goldfinch for any one else but himself? He looks like a butterfly as he flutters about on the tops of tall thistles. The crimson and black bands on his head, the glorious blaze of gold on his black wings, which are further marked with white spots, as also is his tail, make him the most gorgeous of our native finches. The bullfinch, again, is easy to distinguish; though from his habit of haunting thickets and dense hedgerows, he is seldom seen. In flight you may know him by his white rump, rosy breast, and black head. But his mate is more soberly clad: though her black head and white rump, will suffice to make sure of her when, by good fortune, she is encountered.