. British birds. Birds. C. B. TICEHURST: DOWN-PLUMAGE. 187 pass backwards, each tract forming, in most species, a line or crescent of down. It will be noticed that the inner supra- orbital tracts are present in every species which I have examined which has down at all. The outer supra-orbital tracts consist of two or three small, short pre-pennse on each side, situated between the edge of the upper eyelid and the inner supra-orbital tract. They are present in the Mistle-Thrush, Meadow and Red-throated Pipits, Chaflfinch, and Brambling. The occipital tracts consist of two or three fairly large,
. British birds. Birds. C. B. TICEHURST: DOWN-PLUMAGE. 187 pass backwards, each tract forming, in most species, a line or crescent of down. It will be noticed that the inner supra- orbital tracts are present in every species which I have examined which has down at all. The outer supra-orbital tracts consist of two or three small, short pre-pennse on each side, situated between the edge of the upper eyelid and the inner supra-orbital tract. They are present in the Mistle-Thrush, Meadow and Red-throated Pipits, Chaflfinch, and Brambling. The occipital tracts consist of two or three fairly large, well-developed, pre-pennse situated on each side of the occiput. Outer supraorbital. tract. Crural tract Ventral tract Crural tract Diagram showing the Down-tracts of Nestling Birds. The two tracts usually form a line, or crescent, of down when well developed. They are present in every species examined which has any down. The humeral tracts are usually well developed, and run obHquely downwards and outwards from the base of the neck across each humerus just in front of the shoulder joint. They are replaced by the " scapular" feathers of the juvenile plumage. They are present in all the birds that I have examined which have down, except the Wren (see note under this species). The spinal tract runs down the centre of the dorsum from about the level of the shoulder joint to the end of the sacrum in those species in which it is well developed. The length. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original London, Witherby & Co
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Keywords: ., bookcentury1900, bookdecade1900, bookpublisherl, booksubjectbirds
