Because little tufts of hair, produced from one common bulb, are the rudiment of the future feather. In a few days a black cylinder appears, which opens at the extremity, and gives passage to the feather. The opposite end receives those blood-vessels, which supply the vessel-like substance in the barrel of the feather; when the stalk of the feather has received its complete growth, this vessel-like body is dried up, and presents the well known appearance called pith, in the barrel of quills.
Because one extremity of their bodies is occupied with the bill, and the other with a sort of oar or rudder. The anterior appendices (or wings) are organs of mere locomotion ; and the remaining portion of the body, or the extremities of the posterior appendices, serve to give them a firm position on their two legs. We find, however, that in these animals the toes are more articulated than in mammalia; that they are in a great degree capable of being separated from each other ; and the nerves with which they are furnished considerable. It may be inferred, therefore, that the feet of birds would be tolerably perfect organs of touch, if they were not used as organs of locomotion; and that, the less they are used for the latter purpose, the more perfect is the sense of touch. Accordingly, we find that parrots take up their food with their feet, and convey it to their mouths. In birds of prey the sense is probably more acute, as their feet are little used for progression. In the gallinaceous birds, (as fowls) whose feet are constantly on the ground, and in the ostrich and cassowary, which do not fly, the epidermis (or outer skin) is thickened, and its sensibility consequently diminished. - Lawrence's Notes to Blumenbach's Comparative Anatomy.
Because it is not the buds, but the insects frequenting them, of which the birds are in search.
Because the birds there are unrivalled in beauty, the birds of Cayenne excepted. Thus, in passing up the river, every now and then, the maam, or tinamou, sends forth one long plaintive whistle, from the depths of the forest, and then stops ; whilst the yelping of the toucan, and the shrill voice of the bird called pi-pi-yo, are heard during the interval. The campanero never fails to attract the attention of the passenger; at a distance of nearly three miles, you may hear this snow-white bird tolling every four or five minutes, like the distant convent-bell. From six to nine in the morning, the forests resound with the mingled cries and strains of the feathered race ; after this they gradually die away. From eleven to three all nature is hushed, as in a midnight silence, and scarce a note is heard, save that of the campanero and pi-pi-yo ; it is then that, oppressed by the solar heat, the birds retire to the thickest shade, and wait for the refreshing cool of evening. At sundown, goatsuckers skim along the trees on the river's bank, and, with owls, lament and mourn all night long. The houtou, a solitary bird, and only found in the thickest recesses of the forest, distinctly articulates " houtou, houtou," in a low and plaintive voice, an hour before sunrise ; the maam whistles about the same hour ; the hannaquoi, pataca, and maroudi, announce the sun's near approach to the eastern horizon ; and the parrots and paroquets confirm his arrival there. - Abridged from Waterton's Wanderings.