BI-160 LAB REPORT #2 NAME ___________

EXERCISE 2 Avian Muscles & Flight Dynamics

Introduction To investigate the major avian muscles, their uses, and the dynamics of flight of a bird, you will complete a variety of exercises. While you are completing these exercises, keep track of the amount of time you spend on each. You will be asked at the end of this lab to estimate the total amount of time it took you to complete this lab.

EXERCISE 2.1 The Avian Skeleton

Due to the modifications of the birds body for flight, many muscles in birds that are homologous (the same) in origin to our human muscles have changed in their shape and functions. In addition, many of the muscles are small and difficult to dissect. Therefore, we will confine our investigation of avian musculature to the major superficial muscles of the wing, trunk, and leg. Muscles accounts for a significant percentage of a bird’s total mass – anywhere from 30% to 60%. The relative distribution of these muscles is correlated with the lifestyle of the species. Strong flyers such as pigeons, doves, and hummingbirds have relatively heavy flight muscles and light leg muscles, while birds that rely more on legs, such as ostriches, have considerable heavier leg muscles and lighter flight muscles.

1. Using the diagram on the following page of a pigeon’s musculature, compare the wing, trunk, and leg regions of a bird.

2. Humans often eat birds like chicken and turkey for a protein source. How would you expect the leg muscles to compare to the wing muscles in these types of birds?

Lab Topic 2: Avian Muscles & Flight

3. The largest muscle in the bird’s body provides the powerful downward thrust of the wing and averages 15% of the total body mass is the _______________________.

Leg musculature is concentrated toward the upper (proximal) portion of the leg to keep weight closer to the center of the body. A secondary benefit of this placement is that leg muscles can be adequately insulated by feathers, rather than lying exposed on the naked ends of the legs. Almost all of the actions of the foot and toes are controlled by muscles located in the proximal portion of the leg through a complex series of tendons which stretch along the tibiotarsus and tarsometatarsus. In perching birds, bending of the ankle joint automatically causes flexion (contraction) of the toes, allowing a secure grip without the exertion of continuous muscular force. That would fatigue the leg muscles!

4. What is the largest muscle in the leg?

Lab Topic 2: Avian Muscles & Flight

5. Compare some of the muscles labeled on the pigeon diagram with your own body. What muscles do you know of that are the same?

EXERCISE 2.2 Flight Dynamics

Birds are defined by their possessions of feathers and their ability to fly. Indeed, adaptation to flight is the singular theme in bird evolution, anatomy, physiology, and behavior. Almost everything about a bird is, in some fashion, related to flight. Although not all birds fly, the overwhelming majority do, and those that don’t, apparently once did. To fly, three things are required: lift, thrust, and elimination of friction. Lift is the term given to the process of getting off the ground. You cannot fly if you are landlocked. However, getting off the ground itself doesn’t result in flight. To be a truly flying animal, you must be able to propel yourself forward. In fact, the definition of true flight (as opposed to gliding or soaring) is self-sustained forward motion. To fly, birds must provide the power or thrust for this forward motion. Finally, to maximize flight, a moving object must eliminate as much drag (friction) as possible. Therefore, all flying animals are streamlined in design to minimize the friction. These three requirements must be met in order to fly, and birds show considerable adaptations to each. Below is a list of adaptations. Beside each, indicate whether the adaptation is helpful in Lift (L), Thrust (T), or Streamlining (S). Remember that Lift centers around weight-reduction, Thrust centers on power-promotion, and Streamlining centers on reducing drag. _____ fusiform (tapered at both ends) _____ pneumatic (hollow) bones _____ energy-rich diet _____ teeth replaced by lightweight beak _____ forelimbs modified into wings _____ reduction of many organs _____ no external ears (ear lobes) _____ center of gravity beneath wings _____ heat-conserving plumage (feathers) _____ legs lightened by using tendons _____ efficient circulatory system to deliver oxygen and nutrients _____ body covered by lightweight feathers _____ no skin glands _____ egg laying, adults don’t carry heavy embryos

Lab Topic 2: Avian Muscles & Flight WING DESIGN The typical wing shape for a bird is in the shape of an airfoil. The leading edge (toward the wind) is thicker while the trailing edge (down wind) is much thinner. The upper surface of the wing is convex shaped while the under surface is concave shaped. These differences in shapes lead to the basic properties of flight: differential pressures created on the opposite surfaces of an airfoil. As air moves hits the leading edge and splits to flow cross the wing, the upper and lower air currents move at different speeds and create lift. The upper air current moves faster since it must travel further to reach the trailing edge of the wing at the same time as the lower current which results in lower pressure. This generates a net upward force (almost like a pulling upward force). The slower under-wing currents results in the opposite effect: higher pressure generating a “pushing-up” effect upward. This difference in pressures exhibited by the split air currents is known as the Bernoulli’s Effect. Birds can split the primary feathers at the tip of the wing to allow air flow over each primary separately and create several airfoils at the wing tips and thereby create even more lift. This is known as Slotting. The wing of a bird is designed to fit its lifestyle, be it a speed demon like a swift, a land-soaring sailplane like a condor, or a ground dweller like a pheasant. There are four basic wing types to fit these different lifestyles. Read the description for each wing type then choose the wing letter that best represents this type.

Lab Topic 2: Avian Muscles & Flight

1. Elliptical Wing – birds that live in the forest and on the ground, such as doves and pheasants, have short, wide wings with many slots (spaces between the primary feathers). This wing shapes confers high maneuverability and rapid take-offs.

2. High-speed Wing – long, relatively slim wings without slots are found in birds that

feed in the air, like swifts and swallows, or make long migrations, like terns. This wind is better suited to fast, level flight than to fast take-offs and manuevereability in close quarters.

3. High-aspect Wing – soaring sea birds, like the albatrosses and shearwaters, have

very long, slim wings designed for high-speed gliding in strong steady winds.

4. Slotted High-Lift Wing – birds that soar over land, such as condors and hawks, have long, wide wings with many slots. The design combines maneuverability with efficient gliding, enabling the birds to circle the small updrafts of warm air that occur over land.

Lab Topic 2: Avian Muscles & Flight

Compare the flight of a duck to a hummingbird by studying the wing strokes in the following diagram.

1. What differences can you see in the pattern of their wing strokes?

EXERCISE 2.3 Mastery of Flight Video (VHS #5895b)

In this exercise, you will need to view the video “Mastery of Flight” (VHS #5895b) from the Life of Birds series. We will watch this video in class on the third week, but if you miss it, this video will be available for viewing in the Dye Learning Center on campus only. Take notes as you watch. Hand in your notes along with the answers the following questions.

1. How are birds streamilined to reduce drag? 2. How does flying in formation aid in flight? 3. What is the most economically efficient form of flight? 4. According to the video, why do birds spend so much time cleaning and preening their

feathers? 5. Who is the fastest bird in the air? 6. Who is the slowest bird in the air? 7. How do birds fuel their energetically costly activity of flight?