Page:Blackwood's Magazine volume 002.djvu/665
who saw the sand of the shores of Bœtica transformed by fire into a transparent glass, should have at once foreseen that this new substance would prolong the pleasures of sight to the old; that it would one day assist the astronomer in penetrating the depths of the heavens, and in numbering the stars of the milky way; that it would lay open to the naturalist a miniature world as populous, as rich in wonders, as that which alone seemed to have been granted to his senses and his contemplation; in fine, that the most simple and direct use of it, would enable the inhabitants of the coast of the Baltic Sea to build palaces more magnificent than those of Tyre and Memphis, and to cultivate, almost under the frost of the polar circle, the most delicious fruits of the torrid zone.[1]
Changes in the Plumage of Birds.
The changes in the plumage of birds, more particularly of the gull tribe, may be considered as presenting some of the chief difficulties to be overcome in the study of ornithology; and one of the greatest benefits which could be conferred upon the science, would be an ample collection of observations regarding those changes, formed in the course of an attentive examination of the same individuals during a series of years. From such data, there is little doubt that certain general principles might be deduced, which would tend in a great degree to dispel the confusion which has hitherto pervaded this important department of the study, and, consequently, materially to simplify the labours of the naturalist. This desirable object can only be attained by means of observations on the living birds. The examination of specimens in collections, however useful it may afterwards be found, cannot at present be considered as beneficial in the highest degree, in as far as we are still unprovided with any generally applicable laws, by which to regulate our opinions regarding the variations in the plumage of species. Till such laws are established, each ornithologist will follow his own ideas, or those of the author whose sentiments he has been accustomed to adopt, concerning the specimen submitted to his examination; and as it rarely happens that any number of men draw the same conclusions from a particular fact, so long as it remains unconnected with a series of observations, doubt and error will continue to be handed down in future, as they have been during preceding years. It is therefore of the utmost importance to the advancement of ornithology, that accurate records should be kept of the changes in the plumage of birds, by those who have it in their power to attend to these as exemplified by living instances; and it is of equal importance that, along with the observations themselves, the period of the year at which they are made, and the age of the individuals observed, should also be specified. It is indeed the general want of such requisites, that renders the inspection of uncommon birds in cabinets so much less interesting than it might otherwise be deemed.
The following positions contain some of the fixed principles which appear to us to regulate the changes of plumage in the tribe of gulls.
It may be asserted, that the young of all the species are more or less mottled with brown:
That with the exception of three species, the skua, the arctic, and the black-toed gulls,[2] brown may be considered as a colour which never characterises the perfect state:
That no gull is in the plumage of maturity, in which there is a predominating mixture of brown and pearl gray, or white; and, consequently, that the wagel, the great gray gull, and other similar birds, are the young of certain other species:
That all gulls, in which the upper parts are pure pearl gray, may be considered as matured:
That, with the exception of one species (the ivory gull of the arctic zoology, described in the Fauna Grænlandica under the name of Larus Candidus), no gull has been hitherto discovered with the plumage entirely white:
That, with the exception of the same species, all gulls hitherto described have some parts of the primary quill-feathers marked with black or gray, for the most part with black: