no. 3637 HERMIT THRUSH — ALDRICH 3 



in a variety of habitats ranging from dense coniferous forest to low 

 deciduous shrubs. It is primarily, however, a bird of somewhat open 

 situations in a generally forested area such as brushy thickets along 

 roadsides or forest borders, partly open bogs, and young mixed 

 coniferous-deciduous growth that has sprung up after a forest has 

 been cut or burned. 



In winter the habitat is usually a dense cover of woody growth 

 such as pine forests with brushy undergrowth or brushy swamps in 

 the southeastern United States and chaparral and streamside thickets 

 in the Southwest. 



Trends in Morphological Variation 



Morphological variation of the hermit thrush was determined by 

 comparison of 2039 study specimens. Of these, 524 were adults col- 

 lected during the breeding season in virtually all sections of the 

 breeding range of the species. The other 1515 specimens were adults 

 taken during migration and wintering seasons or were juveniles 

 collected on the breeding grounds. 



The adult plumages of the hermit thrush are derived from a single 

 basic plumage grown after a postju venal or postnuptial (prebasic) 

 molt that takes place in the late summer. The fall plumage, there- 

 fore, consists of freshly grown feathers while the nuptial plumage of 

 late spring and early summer is derived gradually by wear from these 

 same feathers. 



For the study of geographic variation in size and color, I have 

 relied entirely on adult specimens taken during the breeding season. 

 Identification of specimens in fresh autumn plumage was made by 

 using the same relative differences in color determined from more or 

 less worn breeding specimens. I realize that discrimination of both 

 color and length of wing and tail would be more exact if based en- 

 tirely on specimens in fresh postnuptial or postjuvenal plumage. In 

 my opinion, however, individuals that have molted into fresh plumage, 

 particularly young of the year, cannot safely be assumed to be on 

 their breeding grounds. Evidence of postbreeding wandering by many 

 species is coming to light more and more often. A good example has 

 been documented in the white-crowned sparrow (DeWolfe, 1967). A 

 number of apparent cases were noted during the present hermit 

 thrush study. T. D. Burleigh (in litt.) informs me that he has recorded 

 fall migrant hermit thrushes at Moscow, Idaho, as early as September 4. 

 Phillips et al. (1964) record G. g. sequoiensis at San Francisco Peaks, 

 Ariz., on September 1. They also found a specimen of G. g. auduboni 

 away from the breeding grounds at Flagstaff, Ariz., in August and 

 interpreted its presence as representing postfledgling dispersal of 

 young. 



