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We see then that, in all probability, a bird which left its winter home in Africa will arrive in the Mediterranean area sometime in the first fortnight of March, and that it will spread thence over Europe at a rate which may vary from about 20 to 60 miles a day, depending on a number of factors, not the least of which is the presence of a suitable food supply. There is thus no sudden rush from winter quarters to breeding area in one tremendous and breathtaking jump. Gone are the days of the romantic birdwatcher who believed that the swallow which he saw to-day was but yesterday hawking for flies over the Congo, having flown here with an average speed of 100 miles an hour. Migration we now know to be—as far as that over land is concerned—a slow but steady drift reckoned in miles per day, rather than miles per hour. |
