18 CLELAXD, Takhuj a Bird Census. ["^isffuTy" 



A Method of Taking a Bird Census 



By Professor J. BURTOX CLELAND, M.D., University, 

 Adelaide. 



For some years I have had in view the possibiHty of obtain- 

 ing some crude idea of the actual and relative numbers of the 

 individuals of various species of Australian birds by recording 

 those met with during progressive journeys made by various 

 means of locomotion. The idea was that if, whilst walking, 

 driving, or motoring through the country, a score was kept, as 

 one keeps the runs at cricket, on a sheet of paper or the back 

 of an envelope, of the numbers of each species seen, eventually 

 where sufiicient ground had been covered results of some value 

 might be expected. 



At Easter time in 1917, this scheme took concrete shape at 

 Broken Hill, whilst on a motor run in the country with Dr. W. 

 MacGillivray, R.A.O.U. This journey is recorded as Al in my 

 series. The desired results were easily and accurately tabulated, 

 and 84 individuals of eight species recorded over a distance of 

 15 miles traversed in 1:^ hours. The country was mostly open 

 saltbush plain, and the view for small birds estimated at about 

 100 yards or less, and for large birds about 400 yards. Thirty- 

 three individuals of Epthianura aurifrons (the Yellow-fronted 

 Bush-Chat) were counted over the 15 miles with a lateral view 

 of the disturbed birds of cbout 100 yards on each side — i.e., 

 over an area of roughly a little less than two square miles. 

 One may say, therefore, from the birds actually seen that the 

 density of the population of this species was at least 17 per 

 square mile. Using this as a basis and on the assumption that 

 the rest of the saltbush country of this district was on an aver- 

 age similarly populated, one could by ascertaining the extent of 

 this type of vegetation from the Survey Department, obtain if 

 such was desired a very conservative estimate of the numbers 

 in the district. The figure obtained would evidently be, in this 

 case, surprisingly high. 



In an article on "The Birds of the Pilliga Scrub" (Emu, vol. 

 xviii., p. 272), I gave details of the method adopted when mak- 

 ing a bird-survey of this area. By September, 1919, I had been 

 collecting data for 2| years, had notes of about 90 "journeys," 

 in which I had traversed over 1200 miles, and it seemed an 

 opportune time to bring the subject under notice at the Annual 

 Conference of the Royal Australian Ornithologists' Union at 

 Brisbane, with the objects of explaining the scheme, of obtaining 

 views as to its reliability and value, of receiving suggestions as 

 to improvements, and of inducing others to co-operate. As the 

 idea seemed to meet with acceptance and some interest, and 

 those who employed the method during the excursions seemed 

 satisfied as to its relative reliability, I have in this papei summa- 



