532 Colorado College Publication 



Aiken has carefully examined large series of such birds to 

 observe the range of individual variation and to discover if 

 extralimital forms occur. January 30, 1898, with 120 speci- 

 mens in hand he writes: "I detect only one form, lenco- 

 hema, and the differences are doubtless due to age and indi- 

 vidual variation. The majority of males measure 7.25 inches 

 in length, wing 4.23. The brightest colored are nearly as 

 bright as breeding birds and are assumed to be oldest, though 

 some with pale throats appear full adults. The yellowest 

 throated birds have this color suffusing the entire chin, throat, 

 and sides of neck, and tinging the frontal and superciliary 

 stripes. No males are found with immaculate white throats, 

 but many have a narrow whitish streak from chin to breast- 

 collar. 



Streaked upper parts are taken to characterize immaturity, 

 but some marked thus have yellow throats and some with paler 

 backs have pale throats. It appears, therefore, that intensity 

 of yellow is not due to age, but to individual variation. The 

 same variation exists among breeding birds. An undoubted 

 immature plumage is seen with duller pinkish colors and un- 

 developed black loral and breast markings like females. 



Females average considerably smaller. The brightest 

 have the yellow suffusion nearly as intense as in the brightest 

 males, but many females have white throats with no trace 

 of yellow." 



Aiken has also ascertained that breeding birds at high 

 altitudes in the mountains do not differ from those breeding 

 on the lower plains. Only one specimen has been detected 

 that approaches the Mississippi Valley form ; this has been 

 pronounced by Mr. Oberholser as intermediate between leu- 

 ■colx:ma and praticola. 



Pica pica hudsonia. Magpie. 

 Resident; common. 



