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Page:Popular Science Monthly Volume 54.djvu/800

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THE POPULAR SCIENCE MONTHLY.

carnival he has only to loiter in the nearest grove to hear the wonderful performance of the catbird. The catbird is the real harbinger of summer. He is familiar throughout the countryside, liked or disliked according to the dispositions of folks, but when he appears amid the May-day throng every one knows that summer has come. As a countryman once said to me: "You can't place any dependence on the robin—it may snow the very day he comes; but a catbird never makes a mistake—it's summer with him for sure."

The passing on of the great warbler waves to the north and the ending of the migration likewise mean the passing of the spring. It is summer any time after the 15th of May, or, to be more accurate, after the last of the migratory warblers, thrushes, and tanagers have passed beyond our woods. To a New-Englander summer will come a little later, nearer the true almanac date of June 1st. To a dweller in Virginia the last of April is the passing of spring and the advent of summer.

Some ten or more years ago several enthusiastic ornithologists living in the neighborhood of Philadelphia began keeping records of the times of arrival of the different species of birds, and at the same time noted the conditions of temperature in relation to the abundance of individuals. After several years of these observations they were able to see clearly that these bird waves were directly related to the waves of rising temperature marking the advent of warm spells of weather. One of the most significant facts deduced from these observations was the remarkable regularity in the first appearance of certain species. For example, the Baltimore oriole in eight years of observation never arrived before the 1st of May, and only twice later than the 4th—viz., once on the fifth and once on the 7th. The list on the opposite page shows the date of first arrivals extending over a period of eight years, from 1885 to 1892.[1]

Another fact of great interest which bears on the south-to-north movement of migrating birds, and which these observations very clearly brought out, was the earlier appearance of individuals of various species at points nearer the river, the first arrival of the same species at points back from the river being, in many instances, several days later. The first report of the arrival of a given species usually came from a low, marshy tract of land immediately bordering the western shore of the Delaware. The second report came from a locality several miles back of the eastern shore of the river, but situated in the low plain of the river valley and within tide-water limits. The third report came from a place some miles back from the river on the uplands, but near the head of a stream emptying into the


  1. The Birds of Eastern Pennsylvania and New Jersey. Prepared under the direction of the Delaware Valley Ornithological Club. By Witmer Stone. Philadelphia, 1894.