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 1st 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 IMACROCHIRES. 



This order contains the Goatsuckers, Swifts and 

 Hummers, three groups of birds of very different external 

 appearance, but undoubtedly allied to one another in 



B 



