248 



Palmer, Our Small Eastern Shrikes. iJulv 



universal ignorance of the real excubitoroides being sufficient to 

 determine the issue. Also, identifications of excubitoroides from east 

 of the Plains have been based on breeding birds, usually, some- 

 times on winter specimens taken at the most northern part of their 

 winter habitat. In no instance do these seem to have been com- 

 pared with typical specimens of the form whose name they took. 



Taxonomic Differences. 



Lanius ludovicianus ludovicianus Linn. 



Loggerhead Shrike. 



Subsfecific characters. — Adult $ : Above dark slaty; beneath almost 

 immaculate white; bill large and stout, swollen toward tip; hook large 

 and coarse, gently curved downwards; tail longer than wing. 



Adult $: Similar, but smaller. Type locality, " Louisiana." 



Lanius ludovicianus migrans, siibsp. nov. 



Migrant Shrike. 



Subsfecific characters. — Adult $ : Above bluish gray; beneath pale 

 slaty; throat white; bill smaller, i-egularly tapering; hook delicate and 

 sharply bent downwards; tail shorter than wing. Type, No. 163077, 

 $, Kingston, Ontario, April 4, 1S98; Dr. C. K. Clarke. 



Adult $ : Duller, especially beneath, and smaller. 



Distribution. 



From middle Louisiana eastward along the Gulf Coast and its indenta- 

 tions ; throughout Florida, and eastward into North Carolina. Extending 

 from this range to an indeterminate distance up the vallej's, though gen- 

 erally confined below the lOO-foot contour line.' Non-migratory except 

 at its more northern and its higher habitat .... ludovicianus. 



^ It would seem desirable that the life distribution of forms should be con- 

 sidered in relation to contour unes, altitude and the influences of the various 

 kinds of forest distribution being the principal factors affecting them. The 

 relative quiescent humidity of swamps and dense forests with their very slight 

 interactions resulting from rapid general climate changes, plus the minimum 

 amount of sunlight, produces results different from the dryer and more exposed 

 elevations or depressions. The amount of sunlight, the character of the food, 

 and the influences of a limited habitat seem more important in their results 

 than degrees of temperature. Increase or decrease of the radiating powers of 

 the ground surface destroys or drives out forms and necessarily influence 

 those that remain, or replace them, and this radiating power is determined by 

 influences other than mere temperature. 



