36 
THE CONDOR 
| Voe. VII 
riatn and Mr. Chapman were diligently counting 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. 
Ithaca , N. Y. 
Do Birds Migrate along their Ancient Immigration Routes? 
BY EEONHARD STEJNEGER 
UNITED STATES NATIONAL MUSEUM 
N THE last number 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 
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 refutation of this 
untenable theory and error ? The negative exam- 
ple of Protonotaria citrea which, it is claimed, can- 
not have immigrated into its present breeding 
home by a portion of its migration route, viz., that 
part which lies between southern Mexico and the 
mouth of the Mississippi River! 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 
Palmen’s theory, the latter was never meant or never said to include all and every 
kind of migration 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 Palmen’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 Palmen’s theory 
