November 3, 1905.] 



SCIENCE. 



549 



less olive on the back and the brown streaks 

 on the sides narrower. This form is found 

 in the Sonoran region, and, as along the 

 Rio Grande, it intergrades with the first; 

 it is called a subspecies, Dendroica cestiva 

 sonorana. Further south, in central 

 Mexico, this form runs larger in size and 

 is recorded as Dendroica cestiva dugesi. 

 Northward, through to Alaska, we have an 

 ally of the parent bird, .but smaller and 

 still more greenish. This is Dendroica 

 cestiva riibiginosa. 



In the West Indies the golden warblers 

 migrate not from south to north, but from 

 the shore to the mountains, and possibly 

 in consequence of the less demand of flight, 

 the wing is shorter and more rounded, while 

 the tail is longer. As these forms do not 

 clearly intergrade with those of the main- 

 land, and, for the most part, not with each 

 other, they are held to represent a number 

 of distinct species, although doubtless de- 

 rived from the parent stock of Dendroica 

 cestiva. Some of these "West Indian forms 

 are relatively large, the wing more than five 

 inches long, and the longest known of these, 

 the type of the species for this reason, 

 found in Jamaica, is called Dendroica pe- 

 techia. On the island of Grand Cayman 

 is a similar bird, a little smaller, Dendroica 

 auricapilla. Of a deeper yellow than pe- 

 techia, and equally large, is the golden 

 warbler of the Lesser Antilles ranging from 

 island to island, from Porto Rico to An- 

 tigua. This form, first known from St. 

 Bartholomew, is Deiidroica petechia har- 

 tholemica. A smaller bird, a little differ- 

 ent in color, takes its place in the Bahamas. 

 This is Dendroica petechia flaviceps. 



In Cuba the golden warbler is darker 

 and more olive, with other minor differ- 

 ences from the form called hartholemica, 

 of which it may be the parent. This is 

 Dendroica petechia gundlachi. A similar 

 bird, but with the crown distinctly chest- 

 nut, is Dendroica petechia aureola, the 



golden warbler of the Galapagos and Cocos 

 Islands, off the coast of Ecuador and Peru. 

 Scattered over other islands are smaller 

 golden warblers with the wing less than 

 five inches long, and with the crown tawny 

 red, as in aureola. These are known col- 

 lectively as Dendroica ruficapilla, the type 

 being from Guadeloupe and Dominica. 

 More heavily streaked, with the crown 

 darker in color, is the golden warbler of 

 Cozumel, Dendroica ruficapilla flavivertex, 

 and with very similar but with darker 

 crown is Dendroica ruficapilla flavida, of 

 the island of St. Andrews. Always the 

 nearest form lies across the barrier, and 

 among these forms the chief barrier is the 

 sea. With a darker chestnut crown is 

 Dendroica ruficapilla rufopileata, of the 

 island of Curacao, and still darker bay is 

 the crown of Dendroica ruficapilla capitalis, 

 the golden warbler of the Barbadoes. 



Still other golden warblers exist, with 

 the chin and throat chestnut as well as the 

 crown. One of these, olive green on the 

 back, is Dendroica rufigida, of Martinique. 

 The others are more yellow. One of these, 

 with the sides heavily streaked, inhabits 

 the isthmus region, Dendroica erythacho- 

 ides, called a distinct species, because no 

 intergradations have been made out. An- 

 other more faintly streaked replaces it on 

 the Atlantic coast from Yucatan to Costa* 

 Rica, Dendroica tryanti, while the Pacific 

 coast, from Sinaloa to Costa Rica, has an- 

 other form, with still fainter markings, 

 Dendroica bryanti castaniceps. An ex- 

 treme of this form with the throat and 

 breast tawny, but not the crown, is found 

 in Jamaica again and is known as Den- 

 droica eoa. In this case, which is one 

 typical of most groups of small birds, the 

 relation of the species to the barriers of 

 geography is so plain as to admit of no 

 doubt or question. Given the facts of in- 

 dividual fluctuation and of heredity, it is 

 manifest that while natural selection may 



