1094 U.S. NATIONAL MUSEUM BULLETIN 237 part 2 



JUNCO INSULARIS Ridgway 



Guadalupe Junco 

 Contributed by Thomas Raymond Howell 



Habits 



This junco is a permanent resident on Guadalupe Island, Baja Cal- 

 ifornia, Mexico. The island lies about 135 miles due west of the Baja 

 California coast and about 250 miles south southwest of San Diego, 

 Calif., at lat. 29°10'N. and long. 118°18'W. It is a true oceanic is- 

 land, volcanic in origin, that has never been connected with the main- 

 land. Its dimensions are approximately as follows: length, 22 miles; 

 width, 4 to 7 miles, broadest at north central portion; maximum ele- 

 vation, at north central portion, 4,500 feet. The junco is one of a 

 number of endemic land birds found presently or formerly on Guada- 

 lupe Island, and Uke most of the others its ancestors probably reached 

 the island from the mainland to the northeast. A. H. Miller (1941b) 

 discusses the possible origin and relationships of insularis in consider- 

 able detail in his famous monograph of the genus Junco. He con- 

 cludes that the affinities of insularis are with the Junco oreganus group. 

 Although some authors consider the Guadalupe junco to be a sub- 

 species of oreganus, Miller retains specific status for insularis and 

 suggests that this form was derived from vagrants of a migratory 

 junco population inhabiting the California coast in Pleistocene or 

 pre-Pleistocene times. 



The Guadalupe junco is distinguished principally by its relatively 

 long bill and short wing and tail, the reduced size of the sternum 

 (F. A. Lucas, 1891), and a virtual absence of sexual dimorphism in 

 color. Both sexes of insularis resemble somewhat the females of 

 Junco oreganus pinosus. The streaked juvenal plumage of insularis 

 also resembles that of oreganus juveniles. 



The flora and fauna of Guadalupe Island have a sad history of de- 

 struction by introduced house mice, house cats, goats, and overzealous 

 collectors. Successive stages of change in the avifauna may be traced 

 through the papers of R. Ridgway (1876), W. E. Bryant (1887), J. E. 

 Thayer and O. Bangs (1908), and T. R. Howell and T. J. Cade (1954). 

 The first biologist to visit Guadalupe Island was the botanist Edward 

 Palmer, and he collected specimens of birds in the spring of 1875 that 

 were subsequently described as new by Ridgway (1876). Palmer's 

 notes on the junco, as quoted by Ridgway, are as follows: 



These are the most abundant birds of the island, and are so tame that they may 

 be killed with a stick or captured in a butterfly-net. While I was looking for in- 

 sects under stones and logs, these birds would sometimes join in the search, and 

 hop almost into my hands. They gathered chiefly ants and their eggs. At 



