BIOD43H3 Lecture Notes - Lecture 15: Flight Envelope, Mechanical Efficiency, Allometry
Lecture 15: Movement in Fluid Air Part 111
Scaling of Mechanical efficiency
The ability to hover is the most important behavioral feature of hummingbirds, but flight in this taxon,
more generally, involves remarkable abilities to alter flight speed, trajectory and body orientation
(Altshier and Dudley, 2002).
- perceptions that hummingbirds are among the smallest birds. Allometric considerations suggest that,
under isometric size change, translational accelerations should scale as mass–1/3, whereas the magnitude
of rotational accelerations changes in proportion to mass–2/3(Altshier and Dudley, 2002).
• The hovering ability, rapidity of maneuvers and upregulated aerobic capacity of hummingbirds
have long attracted the interest of flight biologists. The range of intra- and interspecific variation
in flight performance among hummingbird, is impressive.
• A dominant theme in hummingbird evolution is progressive invasion of higher-elevation
habitats. Hypobaric (low air pressure) challenge is met through compensatory changes in
wingbeat kinematics, particularly in stroke amplitude.
• Over evolutionary time scales, montane colonization is associated with increases in body mass
and relative wing area. Hovering ability has been well-studied in several North American
hummingbird taxa, yet the broad range of interspecific variation in hummingbird axial and
appendicular anatomy remains to be assessed mechanistically.
- Such varied features as tail length, molt condition and substantial weight change due to
lipidloading can dramatically alter various features of the flight envelope.
• Flight behaviors involved in foraging for insects may also influence the evolution of wing size
and shape.
• Several comparisons of hummingbird communities across elevational gradients suggest that
foraging strategies and competitive interactions within and among species vary systematically
across elevations as the costs of flight change with body size and wing shape.
• Wing beat frequency decreases with larger birds
-Wing beat frequency= NEGATIVE scaling
• Wig elocity/stroke aplitude do’t chage ith ig size
*isometric (muscle length does not change during contraction) scaling of wing area
compensates for bigger mass, and lower wing beat frequency
• Wing velocity must increase with larger birds
-Power output/ per unit body mass = POSITIVE Scaling
• Within species (Intraspecific) larger birds have lower burst reserve capacity
Evolution of Flight
Hovering metabolic rate sales interspecifically
Power required to hovering scales isometrically
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Document Summary
Lecture 15: movement in fluid air part 111. The ability to hover is the most important behavioral feature of hummingbirds, but flight in this taxon, more generally, involves remarkable abilities to alter flight speed, trajectory and body orientation (altshier and dudley, 2002). Perceptions that hummingbirds are among the smallest birds. The range of intra- and interspecific variation in flight performance among hummingbird, is impressive. A dominant theme in hummingbird evolution is progressive invasion of higher-elevation habitats. Hypobaric (low air pressure) challenge is met through compensatory changes in wingbeat kinematics, particularly in stroke amplitude: over evolutionary time scales, montane colonization is associated with increases in body mass and relative wing area. Hovering ability has been well-studied in several north american hummingbird taxa, yet the broad range of interspecific variation in hummingbird axial and appendicular anatomy remains to be assessed mechanistically. Wi(cid:374)g (cid:448)elocity/stroke a(cid:373)plitude do(cid:374)"t cha(cid:374)ge (cid:449)ith (cid:449)i(cid:374)g size.
