Bardskull

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The bird skull is a collection of fused bones that support the brain and sensory organs. It has evolved to be strong but lightweight, which is essential for flight. The various bones of the skull are difficult to differentiate because they fuse almost seamlessly. Nevertheless, we can separate the avian skull into the following components: The bills of many waders have Herbst corpuscles which help them find prey hidden under wet sand, by detecting minute pressure differences in the water. [50] All extant birds can move the parts of the upper jaw relative to the brain case. However, this is more prominent in some birds and can be readily detected in parrots. [51] There are only a few muscles in the trunk and the tail, but they are very strong and are essential for the bird. These include the lateralis caudae and the levator caudae which control movement of the tail and the spreading of rectrices, giving the tail a larger surface area which helps keep the bird in the air as well as aiding in turning. [39] Modern birds evolved from the theropods, a group of two-legged dinosaurs that included well-known examples like Velociraptor and Tyrannosaurus. Some of these extinct dinosaurs developed feathers, lost their teeth, and grew beaks before they took to the air. Due to the high metabolic rate required for flight, birds have a high oxygen demand. Their highly effective respiratory system helps them meet that demand.

Kinsky, FC (1971). "The consistent presence of paired ovaries in the Kiwi(Apteryx) with some discussion of this condition in other birds". Journal of Ornithology. 112 (3): 334–357. doi: 10.1007/BF01640692. S2CID 28261057. Birds have extremely varied diets, which is one of the major causes of the impressive variety of bill shapes. Continue reading to learn about some important feeding strategies and the bill adaptations that make them possible. Filter feeders Birds and mammals are the two groups of large-brained, endothermic (“warm-blooded”) animals on Earth. In this lab you’ll compare bird and mammal skeletons, and you’ll see some clear homologies between these two groups. This shouldn’t be too surprising, since both birds and mammals are descended from the same early vertebrate ancestors. On the other hand, you will also see some distinct differences between bird and mammal skeletons. There are two main kinds of explanations for these differences: ancestry and adaptation. While birds and mammals both came from the same original terrestrial vertebrate ancestors, they came from different branches of the vertebrate tree. If bird skeletons have unique features, it could be because birds inherited those features from their recent ancestors. Therefore, we can't interpret birds' skeletal features without knowing something about their phylogeny. On the other hand, birds do one thing that is dramatically different from mammals: they fly. If bird skeletons have unique features, it could be because birds are adapted to flying. Therefore, we can't interpret birds' skeletal features without considering how the skeleton functions in flying and in other activities. The bursa of fabricius is a circular pouch connected to the superior dorsal side of the cloaca . The bursa is composed of many folds, known as plica, which are lined by more than 10,000 follicles encompassed by connective tissue and surrounded by mesenchyme. Each follicle consists of a cortex that surrounds a medulla. The cortex houses the highly compacted B lymphocytes, whereas the medulla houses lymphocytes loosely. [92] The medulla is separated from the lumen by the epithelium and this aids in the transport of epithelial cells into the lumen of the bursa. There are 150,000 B lymphocytes located around each follicle. [93] See also [ edit ]

Storer, Robert W. (1982). "Fused Thoracic Vertebrae in Birds". Journal of the Yamashina Institute for Ornithology. 14 (2–3): 86–95. doi: 10.3312/jyio1952.14.86. ISSN 1883-3659.

a b c Zaher, Mostafa (2012). "Anatomical, histological and histochemical adaptations of the avian alimentary canal to their food habits: I-Coturnix coturnix". Life Science Journal. 9: 253–275.Natural selection has changed the shape and size of bird beaks in dramatic and fantastic ways. The basic concept of the process is that helpful mutations improve fitness and are likely to be passed on to future generations, causing a slow change in time toward more specialized or effective anatomy. Stryer, Lubert (1995). In: Biochemistry (4thed.). New York: W.H. Freeman. pp.250–1. ISBN 0-7167-2009-4. All species of birds with the exception of the penguin, have a small region of their lungs devoted to "neopulmonic parabronchi". This unorganized network of microscopic tubes branches off from the posterior air sacs, and open haphazardly into both the dorso- and ventrobronchi, as well as directly into the intrapulmonary bronchi. Unlike the parabronchi, in which the air moves unidirectionally, the air flow in the neopulmonic parabronchi is bidirectional. The neopulmonic parabronchi never make up more than 25% of the total gas exchange surface of birds. [56] Vocal Bird anatomy: Birds produce sounds through the air that passes through the Syrinx, which is shown close up in the bottom right. Changes in the hindlimbs did not affect the location of the forelimbs, which in birds remained laterally spaced, and in non-avian dinosaurs they switched to a parasagittal orientation. [36] At the same time, the forelimbs, freed from the support function, had ample opportunities for evolutionary changes. Proponents of the running hypothesis believe that flight was formed through fast running, bouncing, and then gliding. The forelimbs could be used for grasping after a jump or as "insect trapping nets", animals could wave them, helping themselves during the jump. According to the arboreal hypothesis, the ancestors of birds climbed trees with the help of their forelimbs, and from there they planned, after which they proceeded to flight. [38] Muscular system [ edit ] The supracoracoideus works using a pulley-like system to lift the wing while the pectorals provide the powerful downstroke