188 BRITISH BIRDS. [vol. vin. 



neither strictly anti-social nor truly social in their 

 breeding-habits ; these include many of the Finches, 

 Pigeons, Plovers, and other Limicoline birds, and 

 other species. In localities where only a few occur 

 they may be marked on a map ; for mstance, I have 

 had no difficulty in mapping Redpolls, Goldfinches, 

 Hawfinches, Lapwings, and Snipe in various parts 

 of the south-eastern counties. But I should not care 

 to map Chaffinches, Linnets, Wood-Pigeons, or (in 

 some places) Lapwings, for they frequently fly long 

 distances during the nesting-season, whilst on the 

 other hand, several nests are sometimes very close 

 together. A census of these birds cannot, perhaps, 

 be very accurate, but a fair estimate may be obtained 

 by means of careful observations. This census, how- 

 ever, will have no real oecological value unless the 

 geology, as well as the topography, of the district is 

 taken into account, and it is still more desirable to 

 note the effect of the geology on the botany, and of the 

 botany on the entomology of the district ; moreover, 

 if the comparison of one year with another is to have 

 a,ny value, the variation of climate from year to year 

 and the effect of such variation on insect and plant-life 

 must be taken into account. 



As soon as the young begin to fly about, however, the 

 difficulty of obtaining an exact idea of the birds inhabiting 

 a district, to say nothing of those passing over or through, 

 increases immensely. In fact, when the breeding- 

 season is over and the birds begin to leave their nesting- 

 places, a totally different method of study is necessary. 

 Among the most important things to observe at this 

 time are the movements of birds and the numbers 

 involved in each movement. I carefully refrain from 

 using the word migration, because I believe great 

 confusion of thought exists among ornithologists as to 

 what is and what is not migration. I believe it is quite 

 impossible to draw any line, except an artificial one, 

 between what is commonly called migration and all 



