Oberprieler, Ulrich; Cillie, Burger (2002). Raptor Identification Guide for Southern Africa. Parklands: Random House. p.8. ISBN 978-0-9584195-7-4. LAUDER, GEORGE V. (1982-05-01). "Patterns of Evolution in the Feeding Mechanism of Actinopterygian Fishes". American Zoologist. 22 (2): 275–285. doi: 10.1093/icb/22.2.275. ISSN 1540-7063. Scientists have been trying to decipher the intricacies of this process for centuries. A research team in the Museum, led by Prof Anjali Goswami, is working to find out more about how and why we evolved the way that we have.

The partially digested and pulverized gizzard contents, now called a bolus, are passed into the intestine, where pancreatic and intestinal enzymes complete the digestion of the digestible food. The digestion products are then absorbed through the intestinal mucosa into the blood. The intestine ends via the large intestine in the vent or cloaca which serves as the common exit for renal and intestinal excrements as well as for the laying of eggs. [69] However, unlike mammals, many birds do not excrete the bulky portions (roughage) of their undigested food (e.g. feathers, fur, bone fragments, and seed husks) via the cloaca, but regurgitate them as food pellets. [70] [71] Drinking behaviour [ edit ] The development of the skull is a particularly complex process, where hard bony tissues have to interact with many other organs, such as the eyes and brain. Birds’ skulls appear to remain proportionally much larger and rounder than those of other reptiles through development, retaining their embryonic characteristics. Evolutionary advantageAll 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. Louchart, Antoine; Viriot, Laurent (2011). "From snout to beak: the loss of teeth in birds". Trends in Ecology & Evolution. 26 (12): 663–673. doi: 10.1016/j.tree.2011.09.004. PMID 21978465. a b Ornithology, The Cornell Lab of. "All About Bird Anatomy from Bird Academy". academy.allaboutbirds.org . Retrieved 2018-05-11. Eberhard, W (2010). "Evolution of genitalia: theories, evidence, and new directions". Genetica. 138 (1): 5–18. doi: 10.1007/s10709-009-9358-y. PMID 19308664. S2CID 1409845. These characteristics might seem to be unique to birds, but the surprising thing is that all of them have been found in nonflying fossil dinosaurs. While it's been clear for many years that birds descended from dinosaurs, researchers have only recently learned how much those prehistoric dinosaurs resembled birds. Some of these characteristics have traditionally been explained as adaptations to flight, but if the characteristics first appeared in dinosaurs long before the evolution of flight, then they weren't adaptations to flying.

Osborne, June (1998). The Ruby-Throated Hummingbird. University of Texas Press. p. 14. ISBN 978-0-292-76047-9. 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. 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.Article text (excluding photos or graphics) available under an Attribution-NonCommercial-ShareAlike Creative Commons license. In birds, the last 5 to 6 caudal vertebrae are fused to form the pygostyle. [14] Some sources note that up to 10 caudal vertebrae may make up this fused structure. This structure provides an attachment point for tail feathers that aid in control of flight. [7] Highlighted in red is an intact keeled sternum of a dissected pigeon. In flying birds the sternum is enlarged for increased muscle attachment. Scapular girdle [ edit ] In addition, specialized nectar feeders like sunbirds ( Nectariniidae) and hummingbirds ( Trochilidae) drink Svihus, Birger (2014). "Function of the digestive system". The Journal of Applied Poultry Research. 23 (2): 306–314. doi: 10.3382/japr.2014-00937.