MUSEUM OF COMPARATIVE ZOOLOGY. 235 



specimens than in New England ones. In Sturnella ludoviciana the 

 yellow of the ventral surface in Florida specimens is far more intense 

 than it is in northern ones ; the slate color of Guleoscopies carulinensis 

 is correspondingly darker, and the ferruginous of Harporhynchus ruf us is 

 much redder. In Centurus carolinus not only are the black transverse 

 bars on the back broader and darker, but the red on the head and 

 abdomen becomes more extended and lustrous. In Picus pubescens 

 the white spots on the wings become smaller and fewer, with a greater 

 tendency to black streaks on the sides of the breast, a variation in the 

 direction of P. Gairdneri and P. Harrisi, as will be noticed at length 

 in the remarks on P. pubescens and P. villosus in Part IV. Similar 

 differences occur between northern and southern specimens of Picus 

 borealis, which are so great as to have led Mr. Cassin to regard the 

 southern type as specifically distinct from the northern. Similar differ- 

 ences to those above described occur between northern and southern 

 specimens of Thryothorus ludovicianus, Troglodytes a'edon, Geotldypis 

 trichas, Colaptes auraius, Buteo lineatus, and various other species, as 

 will be described more in detail in Part IV. 



The climatic variation in respect to the relative size of the white 

 spaces on the rectrices and primary remiges may be illustrated by a 

 single example. In northern specimens of Pipilo erythrophihalmus the 

 terminal white spots of the tail feathers are found on the four outer 

 feathers of each side ; but in Florida-born ones they occur on only the 

 three outer feathers on each side ; and are correspondingly reduced in 

 length. The white area on the tail of Florida specimens hence has 

 only about the extent that would be presented in northern specimens if 

 the outer pair of feathers were removed. The extent of the white 

 space at the base of the primaries is correspondingly reduced in size in 

 the southern type. 



Extending the examination to northern species, it is found that simi- 

 lar color differences with the latitude of the birthplace are of frequent 

 occurrence. In Bernicla brenta and Bernicla canadensis the smaller 

 southern-born birds are, as a general rule, considerably darker than the 

 larger northern-born ones. The same is true of Fulix marila and 

 Bucephala americana, the so-called Bucephala ulandica being the 

 larger northern type of B. americana, in which the white markings on 

 the wings and head occupy a somewhat larger area. It is altogether 

 probable also that the so-called Anser frontalis holds a similar relation 



