FIELD ORNITHOLOGY 



geographical distribution of the species. Any additional specimens 

 to all such are your only " duplicates, " propei'ly speaking. (&) 

 Birds vary so much in their size, form, and colouring, that a " spe- 

 cific character " can only be precisely determined from examination 

 of a large number of specimens, shot at different times, in different 

 places ; still less can the " limits of variation " in these respects be 

 settled without ample materials, (c) The rarity of any bird is an 

 arbitrary and fluctuating consideration, because in the nature of the 

 case there can be no natural unit of comparison, nor standard of 

 appreciation. It may be said, in general terms, no bird is actually 

 " rare." With a few possible exceptions, as in the cases of birds 

 occupying extraordinarily limited areas, like some of the birds-of- 

 paradise, or about to become extinct, like the pied duck,^ enough 

 birds of all kinds exist to overstock every public and private collec- 

 tion in the world, without sensible diminution of their numbers. 

 " Earity " or the reverse is only predicable upon the accidental (so 

 to speak) circumstances that throw, or tend to throw, specimens 

 into naturalists' hands. Accessibility is the variable element in every 

 case. The fulmar petrel "^ is said (on what authority I know not) to 

 exceed any other bird in its aggregate of individuals ; how do the 

 skins of that bird you have handled compare in number with speci- 

 mens you have seen of the " rare " warbler of your own vicinity ? 

 All birds are common somewhere at some season : the point is, have 

 collectors been there at the time ? Moreover, even the arbitrary 

 appreciation of " rarity " is fluctuating, and may change at any 

 time; long- sought and highly-prized birds are liable to appear 

 suddenly in great numbers in places that knew them not before ; 

 a single heavy invoice of a bird from some distant or little- 

 explored region may at once stock the market, and depreciate the 

 current value of the species to almost nothing. For example, 

 Bau'd's bunting^ and Sprague's lark"^ remained for thirty years 

 among special desiderata, only one specimen of the former and two 

 or three of the latter being known. Yet they are two of the most 

 abundant birds of Dakota, where in 1873 I took as many of both 

 as I desired ; and sj)ecimens enough have lately been secured to 

 stock all the leading museums of both Europe and America, (d) 

 Some practical deductions are to be made from these premisses. 

 Your object is to make yourself acquainted with all the birds of 

 your vicinity, and to preserve a complete suite of specimens of 

 -every species. Begin by shooting every bird you can, coupling 

 this sad destruction, however, with the closest observations upon 

 habits. You will very soon fill your series of a few kinds, that 

 you find almost everywhere, almost daily. Then if you are in a 



^ Camptolcemus lahradoriiis. " Fulmarus glacialis. 



^ Passer cuius {Centronyx) bairdi. ^ Anthus {^'eocorys) spraguei. 



