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NREM/ZOOL 4464 – Ornithology Avian morphology: Part 2 – internal anatomy Dr. Tim O’Connell Laboratory information for week of Feb. 25–26, 2015 In lab this week, we will be introducing general avian morphology and comparative morphology, focusing on integument (skin and associated features) and skeletal structure. In addition to your text, background information for this material has been gleaned from the following sources: Hildebrand, M. 1982. Analysis of vertebrate structure. 2nd Ed. John Wiley & Sons, New York. Podulka, S., R. W. Rohrbaugh, Jr., and R. Bonney. (Eds). 2004. Handbook of bird biology. 2nd Ed. Cornell

Lab of Ornithology, Ithaca, NY. For this lab, we will use preserved specimens from the OSU Collection of Vertebrates as well as salvaged birds (window-killed or road-killed). Your first duty with your bird will be to take the following measurements of its outside before you get to eager to take a look inside: Culmen length (all measurements in mm) Wing chord Tail length Tarsus length Weight (g) Fat score (0, 1, 2, 3) Knowing what you now know about skeletal structure, it’s time to look more closely inside birds. Avian musculature is relatively simple, but it is more difficult to visualize for birds than for mammals because birds have been so heavily modified for flight. You do not need to know every muscle in a bird, but you do need to understand some basic principles and important muscle groups. First, check out this basic, ancestral avian body plan: Now let’s modify that a bit and come to understand more about birds. Leg musculature is oven very well developed, especially in flightless birds. In general, the muscle mass of a birds’ leg is concentrated close to its center of gravity. There is no muscle mass (only tendons) on the tarsometatarsus (below the ankle). The gastrocnemius is the “drumstick” of a bird. Flexion of the toes is achieved via tendons pulling from contracting muscles in the drumstick that run down the ankle joint:

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The next big departure among birds concerns the muscles that power flight. In this case, the biceps brachii and the scapulotriceps fold and extend the wing, respectively (they also taste great with Asian Zing seasoning from Buffalo Wild Wings). The power stroke down is provided by the pectoralis, which is often greatly enlarged. Beneath the pectoralis flat up against the keel of the sternum is the muscle that powers the upstroke: the supracoracoideus.

The supracoracoideus gets its name from the fact that it has a tendon that runs from beneath the pectoralis, up and over the top of the coracoid and inserts on the humerus. Thus, when the supracoracoideus contracts, the tendon acts like a pulley to raise the wing. This allows birds to keep their muscle mass for flight contained in one area of the body for maximum stability in flight, rather than have the muscles to raise the wing be located on the bird’s back.

Your mission in lab today is to attempt to see as many of these structures as you can on your own or others’ birds.

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Organ systems The “soft parts” of birds have also been modified for flight. Lacking teeth, birds grind their food within as muscular gizzard, often augmenting its grinding power by swallowing small pebbles and other grit. Birds also need to eat quickly and dash away at the first sign of danger. To accommodate this, birds have a crop in which they store food for later processing. Link to digestive system of chicken: (http://www.ca.uky.edu/poultryprofitability/Production_manual/Chapter3_Anatomy_and_Physiology/Chapter3_digestive.html) Be sure to visit that link to see what you will be looking for on your bird. See if you can identify the following structures for which you will be responsible: (You will need to know their functions as well.) Esophagus Crop Proventriculus Gizzard Duodenum Pancreas Liver Small intenstine Cecum Large intestine Cloaca Respiro-Circulatory systems Birds have a 4-chambered heart. Try to find it on your bird.

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The Respiratory System of birds is unique in that the lungs never deflate so there is never any “waste air” in them. Instead a series of air sacs work to keep the lungs inflated at all times:

Reproductive systems In birds, the reproductive structures are a product of seasonal development and atrophy. If developed, male testes will be located along the back body cavity, and female ovaries (really just one) will adhere to one of the kidneys.