We also measured the wind vector consisting of the wind speed and the direction from which the wind was blowing, and then obtained the air speed vector (air speed and heading direction) by vector subtraction of the wind vector from the ground speed vector [1]. Being from the same family (Anatidae), the Mute Swan and Greylag Goose are quite close to geometrical similarity, so the differences between the two power curves deviate only a little from those that would result from simply scaling up the goose by linear factor of 1.44. The body drag coefficients are central to range calculations. Search for more papers by this author , Susanne Åkesson. for the air speed (14.5 ± 0.953 m s−1). Figure 2. As these were selected runs in which the bird was flying steadily along, a mean speed could be calculated, which was reasonably representative of the run. He estimated that values around k = 0.8 would be typical for this kind of wing. Practical measurement procedures are given by Pennycuick [1]. If this represents a trend, it is in the opposite direction from that expected. During later analysis, the wind speed and direction were interpolated between the balloon ascents before and after each observation, to obtain an estimate of the wind speed and direction at the bird's height and the time of the observation. School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK . Now the solid circle for the White-tailed Eagle is above the line, but that for the Mute Swan is still below. First, we measured the ground speed vector, consisting of the bird's speed relative to the observer's position on the shore and its track direction, i.e. Listen online to Rusted Root - Send Me On My Way and see which albums it appears on. Revising the value used for the body drag coefficient (Cdb) in (equation 4.1) upwards would raise the high-speed end of the power curve, so decreasing the estimate of Vmp. Table 2.Means and standard deviations of measurements of Mute Swans of known sex from winter swan catches at the Wildfowl and Wetlands Trust, Caerlaverock. The maximum chemical power available depends on the aerobic capacity of the heart and lungs, which is unknown, but is likely to provide a wider margin above minimum power in smaller birds, and very little margin in swans. )Download figureOpen in new tabDownload powerPoint, Figure 3. The waterfowl and waders often flew in compact flocks, often with more than one species in the flock. We wrote custom software in Visual Basic .NET, developed from a previous Vector ornithodolite project in which the earlier Vector 1500 was used [7]. Additional taxes may apply. Air speed is the mean of run means, and n is the number of runs. The solid circles in figure 6 are species averages, and we did not expect any of them to fall below this line. The filled circles are not expected to fall below the dotted line, nor open circles above it.Download figureOpen in new tabDownload powerPoint. Hedenström & Alerstam [9] have argued that cruising speeds above Vmr may be optimal in some circumstances, even though this requires increased aerobic capacity, and this may be the explanation for the four small waders (Dunlin, Ringed Plover, Ruff and Red Knot) that show average air speeds above Vmr in figure 6 (open circles above the dotted line). An estimate of the air density at the bird's measured flying height was recorded as part of the data for each observation, according to the height correction in [1]. Prime members enjoy FREE Delivery and exclusive access to music, movies, TV shows, original audio series, and Kindle books. It also analyzes reviews to verify trustworthiness. It begins by calculating the rate at which the muscles have to do mechanical work (i.e. Double-logarithmic plot of equivalent air speed (mean of run means) versus body mass. Your recently viewed items and featured recommendations, Select the department you want to search in. Our estimate of Vmr is 12 per cent faster in the swan than in the goose and would be the speed at which each species covers the greatest air distance per unit fuel energy consumed, if it had sufficient power to fly at that speed. Air speeds of migrating birds observed by ornithodolite and compared with predictions from flight theory, List of study species, their measurements, and mean equivalent air speeds. By adjusting the default value of the induced power factor in the Flight program to k = 0.9, and leaving the default body drag coefficient at Cdb = 0.10, we recognize that slotted wing tips with separated, upturned primary feathers effectively increase the wing span, and that species whose body shapes resemble classical streamlined bodies are likely to have lower body drag coefficients than those with prominent heads, big feet or long tails. Figure 3. They cover a mass range of over 400 : 1 and a wing span range of nearly 9 : 1. http://creativecommons.org/licenses/by/3.0/, which permits unrestricted use, provided the original author and source are credited. The results are always anomalously high, in the region of 0.2–0.4, which is associated with bluff bodies rather than streamlined bodies. The Mute Swans in our study also held their feet in the same position when flying, below the tail. If k = 0.9, the Mute Swan's body drag coefficient has to be increased from 0.10 to 0.12, to bring the estimate of Vmp below its observed mean air speed. Figure 1. The value assumed (0.23) for the efficiency with which the muscles convert fuel energy into work comes from two classical experiments on wind tunnel birds [2,3], and this value affects the estimated chemical power but, perhaps counterintuitively, it has no effect on estimates of Vmp or Vmr.