Portal de Periódicos da CAPES

Probability in Subspecific Identification of Single Specimens

1948; Oxford University Press; Volume: 65; Issue: 3 Linguagem: Inglês

10.2307/4080491

1938-4254

Austin Loomer Rand,

Machine Learning and Data Classification

The second possible explanation of a non-conforming spedmen is that it is an extreme variant of the local population.This is well known, but it is less widely accepted, and should be more often considered in making or evaluating any identifications.The differences between subspecies often are only average ones.It is a currently accepted convention that if seventy-five per cent of the individuals of a sex or age class are identifiable by means of 'characters,' the subspecies be considered valid.It is not necessary that the unidentifiable twenty-five per cent be intermediates; individually their characters may overlap widely and approach the average characters or even the extremes of some other subspecies.Unusually plumaged birds are not at all uncommon.Excessive paling or darkening of plumage is perhaps the most common, but other variations •iving unusual patterns for the species have been recorded, and it sometimes happens that such a mutant may resemble, to a •reater or lesser extent, the condition in another species; thus Wetmore (1931: 33) mentions Black-capped Chickadees (Parus and Carolina Chickadees {P.½arolinensis), both normally with a wholly black crown, that had white feathers on the side of the crown, in the areas where a related species, the Mountain Chickadee lambeli), always has a white stripe.Glover Allen {1914: $$$) calls attention to various sparrows such as the Song and the Lincoln Sparrow (Melospiza melodia) and (M.lincolnii) that normally do not have white outer tail feathers, as having them, recalling the normal condition in some other sparrows such as the Junco (Junco byemalls) and Vesper Sparrow (Pooecetes gramineus).Swarth (1913: 22) has shown the extreme variation in the white collar and the black throat bar in the Canada Goose (Branta canadensis).Also inthe National Museum of Canada is a Canada Goose head that dosely follows the color and pattern of that of the Barnacle Goose ( Branta leucopsis ).Harrison (1946: 69) reports on two aberrant spedmens of the Robin (Erithacus rubecula), taken in England, that show a character in color distribution very similar to that of the related Japanese Robin (Luscinia akahige).Mayr (1942: 81) has shown that a chestnut belly may appear in an island race of the flycatcher, Monarcha castaneoventris, which is usually all black, while another, distant island race of the same species, that usually has a chestnut belly, occasionally may have entirely black individuals.