lis THE WILSON BU LLETIN— September, 1921 



gee and Tulsa counties. The main dill'ei-ence between tliese 

 regions is one of Imniidity, the eastern counties having an 

 annual rainfall of o5 to 40 inches and tlie southwestern 

 about 30. Probably tlie bird life is more abundant at all 

 times in the more luxuriant vegetation of the east tlian the 

 west. So our July tigiires doubtless represent the etfects 

 of two causes of abundance — more favorable environuieut 

 than the region visite<l in June as well as the actually 

 greater number of birds to be seen in -Inly. Although we 

 cannot rely on the proportions as they stand, it is un- 

 doubtedly true that more birds are to be seen on a Koad- 

 side Census when the males are in full song and after the 

 young are raised than while the young are in the nest. 



The greatest number of birds seen per mile was 18 and 

 the least 1.6 with the exception of the rainy (\'dj. The 

 former record occurred on July 15tii and was swelled by 

 great numbers of young Mourning Doves and Horned 

 Larks. The very small number of the other census must 

 have been due to the unusual heat for it was taken at noon 

 on the day when the temperature reached 99° F. The four 

 largest and smallest censuses taken in pleasant weather 

 are shown in Table III. 



TABLE III. 

 The Largest and Smallest Censuses Taken in Pleasant Weather 



Average Num- 

 Datc Tim.- nf Day Di?lan<p Plare her of birds 



Seen per Mile 



Julj^ 15 6 - 7 P. M. 11 miles Prairie, Tulsa Co. 18 



May 30 4 - 5 P. M. 10 miles Prairie, Kingfisher Co. 13 



June 9 11 - 2 P. M. 35 miles Prairie, Grady Co. 2 



July 3 12 - 2 P. M. 10 miles Woods, Pushmataha Co. l.G 



We saw 72 different species in tlie 41 censuses. The 

 average number of species seen in an average run of 20 

 miles was 17, while the shorter tri])s, averaging 7 miles, 

 gave us 12. The effect of weather and character of coun- 

 try on the innidx'i- of species seen is sliown in Table IV. 



