disappear from the throat in both sexes, and the dorsal plumage becomes of a lighter colour in each; the back of the male assuming the grey of the female during the breeding season, while that of the female and the young of the year in both sexes changes to a very light grey. Indeed, between the two latter, there is no external difference of appearance.
About the middle of August the pied wagtails commence their return towards the sea-coast, and now first appear to be gregarious in their habits. At this season I have noticed them in considerable numbers on village commons, and similar localities in the interior of the county, where they remain but a few days, and then proceed to the south. At the latter end of the month, or the beginning of September, they may be seen near the sea, in flocks of from thirty to forty, flying invariably from west to east, parallel with the shore, and following each other in constant succession. These flights continue from daylight until about ten o'clock in the forenoon; and it is a remarkable fact, that so steadily do they pursue this course, and so pertinacious are they in adhering to it, that even a shot, fired at an advancing party, and the death of more than one individual, cannot induce the remainder to fly in a different direction; for after opening to the right and left, their ranks again close, and the progress towards the east is resumed as before.
I have observed that their proximity to the shore, during this transit from west to east, seems to depend in some degree upon the character and extent of the country intervening between the downs and the sea. For instance, in the more western parts of the county, between Chichester and Worthing, where a flat, maritime district, of considerable extent, and in a high state of cultivation, lies between the hills and the sea, the flocks appear to be less numerous, or rather more scattered, and occur at greater distances from the coast than in the neighbourhood of Brighton, where the downs approach closely to the shore, and where the flocks appear to become more concentrated. I am acquainted with a good practical observer, who informs me that in the neighbourhood of Brighton, he has seen upwards of a thousand pass in a single morning. The same person has witnessed, as well as myself, the arrival of these birds from the continent in March, on the open coast near Hove, between Brighton and Shoreham.
I think there can be but little doubt that these flocks, the greatest proportion of which consists of the young birds of the year, at this time but a few months old, in thus pursuing their course along the shore in an easterly direction, are impelled by a wonderful instinct to
