Reflective Questions -

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Biomechanics of Flight

Jewell Schock Museum of Natural History

Bird Name (Lesser Yellowlegs)

There are three main forces that act on flying animals, namely drag, lift and thrust. Birds use a combination of strategies while moving in the air such that they are able to manipulate the forces acting on them to their advantage. The strategies, mostly used are flight, soaring, gliding and parachuting.

Flight

Birds have streamlined bodies to minimize drag forces for fast flight. This force is relative to the flight speed increasing when the speed is high therefore limits the bird’s motion. However the force is helpful when a flying animal tries to slow down. Additionally, lift is an important force that helps an animal in flight because it keeps them airborne. Birds and other flying animals normally have low weight and have the ability to flap wings quickly and move quickly to maximize lift (Hutchinson, 2005). Finally, thrust is a critical force in flight; birds have large flight muscles to produce thrust which opposes drag.

Soaring:

This is a strategy used by large animals to overcome drag forces and high weight. These animals have large wings overcome these forces. Another problem these animals face is that of thrust which increases slower than weight and drag, thus there is a limitation in the size of a flyer. Therefore, soaring is best for these animals which have a low wing loading, since it is energetically efficient and involves very little wing flapping.

Parachuting and Gliding

These are modes, mostly used by vertebrates as modes of aerial locomotion with most parachuting when airborne and using other means of locomotion when they are on the ground. Gliding is partly a form of parachuting whereby animals produce lift forces by an airfoil-type membrane. Most of the gliders are now extinct with only bats known to have evolved from its gliding vertebrate ancestors (Hutchinson, 2005).

General Description

  The Lesser Yellowlegs (Tringa flavipes) is a medium-sized, slender, long-legged shorebird measuring 27 cm similar in appearance to the Greater Yellowlegs, which is relatively larger. The bird derives its name from its brightly colored legs. Tringa flavipes has a long neck and a straight, sharp-pointed slightly upturned bill. The bird’s tail and rump are white (Dewey, 2009).

Habitat

Tringa flavipes breed in the open in boreal forest region between Alaska and Quebec in the far north. They build nests on the ground in clearings near ponds. The species is found on coasts, lakeshores, mudflats and in the marshes during migration and winter. In comparison to the closely related, Greater Yellowlegs, which are typically found on extensive mudflats, Tringa flavipes are normally found in more secure areas, in smaller ponds. Additionally, they nest in drier protected areas in comparison with their larger counterparts.

Diet

The bird’s main diet consist of insects during the breeding season, and small fish and crustaceans during the rest of the rest of the year.

Adaptations to Flight

Tringa flavipes has a number of adaptations to flight. The bird has a slender streamlined body to help overcome wind resistance. Also the bird has a hollow skeleton and a lightweight beak to reduce body weight (McCready & Behm, 2012). Large and Strong muscles are attached to a large keel on the bird’s lower body. The barbules present on the vanes of each of its feathers zip them together to give the feathers strength to hold air foil. Additionally the barbules maintain the shape and the function of the feathers (Moorpark College, 2014). Tringa flavipes feather anatomy, during flapping and flight, causes the feathers to rotate in their follicles. The rotations occur during upstroke with the greater side pointing down to allow air to slip through the wing, thus breaking the wings integrity to allow for an easier upward motion. Reestablishment of the wing integrity gives the bird the necessary lift. The bird applies this strategy when “taking off” or when achieving lift at very slow speeds (Moorpark College, 2014). By flying fast the bird is able to get the lift needed to remain in flight.

In comparison to a vulture, the former has wings with slotting, alulas and pronounced camber to produce high lift at low speed. The vulture’s wings have an aspect ratio intermediate between elliptical wings and high aspect ratio wings. Unlike the Tringa flavipes, which is a flyer, vultures are land soarers with broad and slotted wings to allow sensitive response for static soaring (Moorpark College, 2014).

When landing the bird extends its wide tail feathers to create enough pressure between the ground and its body so that it can land gently on its legs. The bird is adapted as an active feeder by its long legs, which enables it to run through shallow water to chase its prey.

Application of Tringa flavipes Biomechanics in Robotics

Based on the bird’s flight mechanism the flapping wing form, power scheme, transmission framework and the total structure of a robot can be designed. A reliable flapping wing mechanism can be designed to incorporate the bird’s mechanism to produce lift and thrust by the down stroke and upstroke of the wings. In The robot design and fabrication all the dynamic characteristics of the flapping mechanism of the bird should be considered. The robot should consist a simple and compact structure, highly efficient and reliable transmission of a small DC motor, and be of a minimal weight (McMasters & Cummmings, 2004). The bionic design of the bird will guide the choice of the parameters such as gear ratio, wingspan, wing area and rod length of the linkage mechanism (Xiong, Huang, & Xiong, 2008).

For an almost perfect mimic of the bird’s mechanism the wing diameter and thickness of the robot or an airfoil should reduce gradually from wing base to the tip. This design will reduce energy consumption and skeleton stress. An aerodynamic analysis is vital to calculate the lift and thrust during the actual flying of the robot. Furthermore, the shape deformation of flexible wing and adaptive system should be considered in the design (Xiong, Huang, & Xiong, 2008). This can be achieved by dividing the wing into many wing elements along the wingspan direction and its airfoil. To further increase the efficiency of the robot in flight operation an active articulated torsional drive unit can be incorporated into its design to enable the twisting of its wings at specific angles (Festo, 2010).

Bibliography Dewey. (2009, October 14). Tringa Flavipes. Retrieved from Animal Diversity Web: http://animaldiversity.ummz.umich.edu/accounts/Tringa_flavipes/ Festo. (2010, May 16). SmartBird – bird flight deciphered. Retrieved from Festo: http://www.festo.com/cms/en_corp/11369.htm Hutchinson, J. (2005). Vertebrate Flight. Berkeley. McCready, S., & Behm, D. (2012, May 13). Lesser Yellowlegs. Retrieved from All About Birds: http://www.allaboutbirds.org/guide/Lesser_Yellowlegs/id#similar McMasters, J., & Cummmings, R. (2004). Airplane Design and the Biomechanics of Flight-A More Completely Multi-disciplinary Perspective. Seattle: American Institute of Aeronautics and Astronautics, Inc. Moorpark College. (2014, August 23). Birds: Adaptations Focused on Flight. Retrieved from Moorpark College: http://sunny.moorparkcollege.edu/~econnolly/F09BirdL24.htm Xiong, C., Huang, Y., & Xiong, Y. (2008). Intelligent Robotics and Applications. Wuhan: Springer Science & Business Media.