Vol. X.] MAILLIARD— BIRDS, MAMMALS OF SISKIYOU COUNTY 89 



While a comparison of the number of species noted by dif- 

 ferent field parties is usually of interest to the student of the 

 geographic distribution of birds, such comparison loses value 

 when the dates of observation are not similar. Although the 

 records given in the reports of the Merriam and the Alexander 

 expeditions to this region or its vicinity do not quite correspond 

 to those given in this paper, many of those of the first two 

 being either of an earlier or later date than the Academy expe- 

 dition, for the benefit of future observers it seems worth while 

 to call attention to the differences in these recorded lists. 



The Merriam report includes 136 species of birds against our 

 109. This expedition covered a greater variation of territory 

 than did ours, with larger range of elevation, and remained in 

 the field from the middle of July until the beginning of October. 

 This list includes a number of water birds and raptores that 

 we did not find, as well as some birds of higher altitudes than 

 those we visited. Among those not mentioned by Merriam are 

 the following : Band-tailed Pigeon, American Osprey, North- 

 ern Spotted Owl, Nuttall's Woodpecker, Ash-throated Fly- 

 catcher, Traill's Flycatcher, Gray Flycatcher, California Purple 

 Finch, Western Vesper Sparrow, Brewer's Sparrow, Cedar 

 Waxwing, Black-throated Gray Warbler, Pallid Wren-tit, Rus- 

 set-backed Thrush, and the Olive-backed Thrush, a total of 



17 species. 



Without further information it is useless to comment on 

 these differences further than to say that some of them are due 

 to differences in actual localities visited, even where these were 

 not far separated from each other, and others may be due to 

 difference in date of observations, which may account for the 

 failure of the Merriam party to find the Russet-backed Thrush 

 which we found widely distributed, although the first date of 

 observation of the Merriam expedition, July 15, seems very 

 early for all the individuals of this species to have departed for 

 the south, especially as the Alexander party found it at Grizzly 

 Creek in the Salmon Mountains as late as July 23. 



Comparing ours with the Alexander expedition list of 95 

 species of birds, the same causes for differences can be assumed. 

 The following is our list of species not therein noted : Mallard, 

 California Great Blue Heron, Anthony's Green Heron, Wil- 



