Article Figures & Tables
Figures
- Fig.1.
Wingbeat frequency showed a significant curvilinear relationship (quadratic function) with air speed for both bird 1 (A) and bird 2 (B) (General Linear Model, GLM; bird 1: F1,8=126.88, P<0.0001; bird 2: F1,8=84.83, P<0.0001). The equations for the fitted curves are given in Table2. The proportion of variance (r2) explained by the statistical model was extremely high for both birds (96.9% and 96.1%, respectively). Values are means ± s.e.m. (N=5 flight sequences).
- Fig.2.
The downstroke fraction of the wingbeat cycle period versus air speed for bird 1 (A) and bird 2 (B). Horizontal lines represent the fraction of 0.5 where the downstroke and upstroke fractions are equal. For both birds, the relationship between downstroke fraction and air speed was best represented by a quadratic function (GLM; bird 1: F1,8=176.08, P<0.0001; bird 2: F1,7=21.45, P<0.01). Values are means ± s.e.m. (N=5 flight sequences).
- Fig.3.
(A,B) Wingbeat amplitude (wrist amplitude, filled circles; wingtip amplitude, open squares) increased with air speed (wrist amplitude; GLM; bird 1: F1,9=276.05, P<0.0001, r2=96.5%; bird 2: F1,8=241.85, P<0.0001, r2=96.4%). The duration of the downstroke (C,D) decreased, and the downstroke angular velocity (E,F) increased with air speeds exceeding 7ms−1. A,C,E, bird 1; B,D,F, bird 2. Values are means ± s.e.m. N=4 at air speeds 11 and 13ms−1 (bird 2, D,F); all other N=5 flight sequences.
- Fig.4.
Mid-downstroke (maximum) wingspan (A,B) decreased with increasing air speed, although for bird 1 (A) this relationship was best represented by a quadratic function and for bird 2 (B), a linear function (GLM; bird 1: F1,8=12.54, P<0.01, r2=85.9%; bird 2: F1,8=63.42, P<0.0001, r2=88.8%). (C,D) Mid-upstroke (minimum) wingspan (GLM; C, bird 1: F1,9=73.37, P<0.0001, r2=89.1%; D, bird 2: F1,8=91.09, P<0.0001, r2=91.9%) and (E,F) wingspan ratio (GLM; E, bird 1: F1,9=67.61, P<0.0001, r2=88.3%; F, bird 2: F1,8 =86.72, P<0.0001, r2=91.6%) also decreased with increasing air speed. Values are means ± s.e.m. At airspeeds 11ms−1 (bird 1, A,C,E) and 10ms−1 (bird 2, B,D,F) N=4. All other N=5 flight sequences.
- Fig.5.
Upstroke pause duration for bird 1 (A) and bird 2 (B). The average length of these pauses at each air speed was calculated using only those wingbeats containing the pauses (i.e. does not include pauses of zero length). The duration of these pauses reached maximal levels between 10 and 12ms−1. Values are means ± s.e.m. (N=5).
- Fig.6.
Wingtip path of a characteristic wingbeat in lateral view (A) and rear view (B) at 4ms−1, 8ms−1 and 12ms−1. Arrows indicate the direction of movement and filled circles indicate the position of the wingtip on each frame, with 8ms between the nearest circles. The silhouettes illustrate the body posture at the upstroke/downstroke transition.
- Fig.7.
Body tilt averaged across the upstroke, downstroke and mid-stroke portions of the wingbeat cycle. For both bird 1 (A) and bird 2 (B), body-tilt angle showed a significant quadratic relationship with air speed, and decreased with increasing air speed (GLM; bird 1: F1,8=5.92, P<0.05; bird 2: F1,7=41.78, P<0.0001). Values are means ± s.e.m. (N=5).
- Fig.8.
Tail spread (A,B) decreased with increasing air speed, although for bird 1 (A) this relationship was best represented by a cubic function, and for bird 2 (B) a quartic function (GLM; bird 1: F1,7=17.61, P<0.01; bird 2: F1,5=13.05, P<0.05). Tail-angle of attack (C,D) also decreased with increasing air speed, and for both birds this relationship was best represented by a cubic function (GLM; C, bird 1: F1,7=8.36, P<0.05; D, bird 2: F1,6=6.42, P<0.05). The angle of tail spread in some of the flight sequences for bird 1 (A) was obscured: the number of flight sequences for which tail-spread angle data were obtained, therefore, varies between 1 and 5. All other N=5. Values are means ± s.e.m.
Tables
Article navigation
Related articles
Cited by...
More in this TOC section
Similar articles
Other journals from The Company of Biologists
Editorial – The changing of the guard
In his Editorial, Hans Hoppeler announces that he will be stepping down as Editor-in-Chief of JEB in July 2020. He reflects on the history of JEB, why he has enjoyed his tenure as JEB’s Editor-in-Chief and the recent developments in the publishing world.
Big Biology podcast
JEB is partnering with the Big Biology podcast and in this sponsored episode, JEB Editor Michael Dickinson talks to the Big Biology team about the aerodynamic mechanisms of insect flight, how insects control flight with their tiny 100k neuron brain and his recent JEB paper showing how fruit flies navigate using the sun and polarized light as a compass.
Editors’ choice – An appetite for invasion: digestive physiology, thermal performance and food intake in lionfish (Pterois spp.)
Invasive lionfish are a colossal problem in the Mediterranean Sea and western Atlantic Ocean. Now it turns out that they are successful invaders because they invest more energy in digestion than moving about.
Travelling Fellowship – Anti-ageing in the Greenland Shark
Find out how Pierre Delaroche’s Travelling Fellowship grant from the Journal of Experimental Biology took him to Greenland, where he gathered data to further understand the ageing process in the longest-living vertebrate known to science. Don’t miss the next application deadline for 2020 travel, coming up on 29 November. Where will your research take you?
Commentary – Yank: the time derivative of force is an important biomechanical variable in sensorimotor systems
The derivative of force with respect to time does not have a standard term in physics. In their new Commentary, David C. Lin and his colleagues propose that the term ‘yank’ should be used to denote the time derivative of force.
Runners waste energy every time their legs stop swinging, but now a team of scientists from the US and Canada have shown that a springy ankle tether can reduce runners’ energy costs by 6.4%, which is nearly the entire cost of swinging the limbs. Read the full research article here.
Journal of Experimental Biology is pleased to announce a new partnership with Publons! This allows reviewers to easily track and verify every review by choosing to add the review to their Publons profile when completing the review submission form. Publons also makes it simple for reviewers to showcase their peer review contributions in a format that can be included in job and funding applications (without breaking reviewer anonymity). Read the official announcement here!
preLights – Oxygenation properties of hemoglobin and the evolutionary origins of isoform multiplicity in an amphibious air-breathing fish, the blue-spotted mudskipper (Boleophthalmus pectinirostris)
Charlotte Nelson highlights work in mudskippers suggesting that a diversity in expressed hemoglobin isoforms is not required for the switch between aquatic and aerial respiration.