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 3 6 THE CONDOR [VOL. VII riam and Mr. Chapman were diligently comiting the young pelicans in the rooker- ies. And when, finally, the work was done, and we went back to the boats and our Indians rowed us away from the curious bird cities on the island, it was near- ly night, and long before we had crossed the seven miles of water that lay before us the wonderful evening fell, the almost peacock blue of the water faded and be- came purple, violet, and at last, as the full moon rose over the jagged horizon all settled into the cool gray night of the desert. ]thaca, iV. . Do Birds Migrate along their Ancient Immigration Routes? BY LEONHARD STEJNEGER UNITED STATES NATIONAL MUSEUII N THE last n. umber of THE CONDOR Prof. W. W. Cooke has an article entitled "An Untenable Theory of Bird Migration" intended as a refuta- _.,, tion of Palmen's theory, which in a paper not specially devoted to bird migration I had briefly stated in its generality as follows: "The annual mouth of the Mississippi River! migration route of a species indicates the way by which it originally immigrated into its present breeding home." His laudable aim is to stop this "error" before it makes further headway "in this country." And wherein consists this reftdalfort of this untenable theory and error? The negative exam- pie of Protonotaria cilrea which, it is claimed, can- not have immigrated into its present breeding home by aporlion of its migration route, viz., that part which lies between southern Mexico and the He gives an explanation of how it may have hap- pened that the prothonotary warbler now apparently makes a direct flight across the Gulf of Mexico, and if examined closely it will be found that this explanation, so far from being a refutation is merely a slight modification of the theory. But even if Prof. Cooke's example were shown to be diametrically opposite to Palmn's theory, the latter was never meant or never said to include all and every kind of nfigration route kept by the thousands of species. No doubt many routes have been deeply modified by comparatively recent topographical and hydro- graphical changes. In others the modifications have been less marked, in few per- haps there have been no modifications in details. But that does not affect the truth of Palmn's generalization in its wider applicability, nor make it an "unten- able" theory, much less an "error." To "refute" this hypothesis which has stood the test of nearly forty years, it is not enough to prove that there are some birds which go to their breeding grounds by other routes, but it must be shown that the vast majority do not go by the original immigration route. Even were it demon- strated that the theory holds only for a limited number of species it could not be dismissed as untenable and erroneous. I may also call attention to the fact that when I referred to Palmn's theory