and by the first week in June they reappear at their breeding grounds in the frozen North. What a journey! Eight thousand miles of latitude separates the extremes of their elliptical course, and 3,000 miles of longitude constitutes the shorter diameter, and all for the sake of spending ten weeks on an Arctic coast!
ARE BIRDS EXHAUSTED BY A LONG FLIGHT?
During the spring migration of 1903 two skilled ornithologists spent the entire season near the coast of northwestern Florida, visiting every sort of bird haunt. They were eminently successful in the long list of species identified, but their enumeration is still more remarkable for what it does not contain. About twenty-five species of the smaller land birds of the eastern part of the United States, including a dozen common species, were not seen. Among these were the chat, the red- start, and the indigo bunting, three species that are abundant throughout the whole region to the northward. The explanation of this seems to be that these birds, on crossing the Gulf of Mexico, flew far inland before alighting, and thus passed over the observers. It would thus seem that the popular idea that birds find the ocean flight excessively wearisome, and that after laboring with tired pinions across the seemingly endless wastes they sink exhausted on reaching terra firma, is not in accordance with the facts. The truth seems to lie in almost the opposite direction. Endowed by nature with wonderful powers of aerial locomotion, under normal conditions many birds not only cross the Gulf of Mexico at its widest point, but may even pass without pause over the low, swampy coastal plain to the higher territory beyond. So little averse are birds to an ocean voyage that many fly from eastern Texas to the coast of southern Mexico, though this 400 miles of water journey hardly shortens the distance of travel by an hour's flight. Thus, the birds avoid the hot, treeless plains and scant provender of southern Texas by a direct flight from the moist, insect-teeming forests of northern Texas to similar country in southern Mexico. Under favorable conditions, birds can fly practically where, when, and how they please; consequently their choice of route and the distance covered at a single flight are principally governed by the food supply.
RELATIVE POSITION DURING MIGRATION.
The relative position of the northern and southern groups of individuals as a species during the two yearly migrations is one of the doubtful points that late investigations help to elucidate. The supposition is that in the case of species which adopt what might be called normal fall migration, birds which nest farthest south migrate first and proceed to the southern end of the winter range; those that breed in the middle districts migrate next and occupy the middle of the winter range; and finally, those of the northern part of the breeding range migrate last, and remain the farthest north for the winter. In other words, the migration is a synchronous southward movement of the whole species, the different groups of individuals or colonies retaining in general their relative positions. This has been generally believed, but only of late has it been clearly proved as to any particular species.
An example or two will make this clear. The black and white creeper breeds from South Carolina to New Brunswick. In the southern part of its range it nests in April. New Brunswick, however, is scarcely reached by the earliest birds before the middle of May, as the species occupies about fifty days in crossing the breeding range. If sixty days are considered the shortest possible time in which such a bird can build a nest, rear the young, molt, and be ready for the return journey, then no New Brunswick black and white creeper is ready to start south
