SUGGESTIONS AND DIBECTIONS FOli FIELD-WORK. 13 



medium of exchange among oruithologists the world over; they represent value, — money value 

 and scientific value. If you have more of one kind than you can use, exchange with some 

 one for species you lack ; both parties to the transaction are equally benefited. Let me bring 

 this matter under several heads, (a.) Your own " series" of skins of any species is incomplete 

 until it contains at least one example of each sex, of every normal state of plumage, and every 

 normal transition stage of plumage, and further illustrates at least the principal abnormal 

 variations in size, form, and color to whicli the species may be subject ; I will even add that 

 every difierent faunal area the bird is known to inhabit should be represented by a specimen, 

 particularly if there be anything exceptional in the geographical distribution of the species. 

 Any additional specimens to all such are joai only "duplicates," properly speaking. (6.) Birds 

 vary so much in their size, form, and coloring, that a " specific character" can only be pre- 

 cisely 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.) Tlie rarity of any bu'd is necessarily an arbitrary and fluctuating con- 

 sideration, 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 collection in the world, 

 without sensible diminution of their numbers. " Rarity " or the reverse is only predicable 

 upon the accidental (so to speak) circumstances that throw, or tend to throw, spechnens into 

 naturalists' hands. Accessihilitij 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 specimens you have 

 seen of the " rare " warbler of your own vicinity? AH birds are common somewhere at some 

 season; the point is, have collectors been there at tlic time? Moreover, even the arbitrary 

 appreciation of " rarity " is fluctuating, and may cliange 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 fi'om 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, Baird's bunting and Sprague's larlv remained tVir thirty years among our special 

 desiderata, only one specimen of tlie former and two or three of the latter being known. Yet 

 they are two of the most abundant birds of Dakota, wliere in 1873 I took as many of both as 

 I desired ; and specimens enough have lately been secured to stock all the leading museums 

 of tills country and Europe. (d.) Some practical deductions are to be made from these 

 premises. 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, «dtli tlie closest observations upon habits. You 

 wiU very soon fill your series of a few Icinds, that you find almost everywhere, almost daily. 

 Then if you are in a region the ornithology of which is well known to the profession, at once 

 stop killing these common birds — they are in every collection. You should not, as a rule, 

 destroy any more robins, bluebirds, song-sparro'ws, and the like, than j'ou want for yourself. 

 Keep an eye on them, studying tlrem always, but turn your actual pursuit into otlier channels, 

 until in this way, gradually eliminating tlie undesirables, you exhaust the bird fauna as far as 

 possible (you will not quite exhaust it — at least for many years). But if you are in a new 

 or little-known locality, I had almost said the very reverse course is the best. The chances 

 are that the most abundant and characteristic birds are " rare " in collections. Many a bird's 

 range is quite restricted : you may happen to be just at its metropolis ; seize the opportunity, 

 and get good store, — yes, up to fifty or a huudi-ed ; aU you can spare will be thankfully 

 received by those who have none. Quite as likely, birds that are scarce just where you happen 



