Red-shafted Flicker 241 
with eight and nine fresh eggs on April 30th. Dille 
gives May 29th near Denver, while Scott at Twin Lakes 
notes June Ist as average dates. 
Intermediate forms.—Where the range of the Yellow- 
shafted Flicker meets that of the Red-shafted form— 
from western Texas north along the eastern bases of 
the Rocky Mountains to Montana and Alberta, and 
especially in Wyoming and Montana—most of the Flickers 
are intermediate in character between these two quite 
distinct species. Every gradation between the two 
has been observed. Baird (58, p. 122) first drew attention 
to this remarkable state of affairs, which he characterised 
as “unparalleled in the annals of ornithology.” He 
believed that it was due to interbreeding of the two 
original forms, continued into successive generations. 
Although this view has not been wholly accepted by 
Coues (74, p. 292) and Allen (92), both of whom have 
discussed the matter at considerable length, it appears 
to be the only conclusion possible to account for the 
facts. A series of experiments in interbreeding these 
two birds in captivity on Mendelian lines, would probably 
throw light on the matter. 
In the eastern plains and foothills of Colorado the 
intermediate forms are not at all uncommon, and there 
are a considerable number from the neighbourhood of 
Colorado Springs showing every step between the two 
pure-bred forms in the Aiken collection. Nearly all 
these were taken in April on the spring migration, and 
as a rule they go further north to breed. 
ORDER MACROCHIRES. 
This order. contains the Goatsuckers, Swifts and 
Hummers, three groups of birds of very different external 
appearance, but undoubtedly allied to one another in 
R 
