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Flight speeds and energetics of seven bird species Kolotylo, Rebecca Ann


Flight speeds of seven bird species, the Tree Swallow (Tachycineta bicolor), Mountain Bluebird (Sialia currucoides), White-throated Swift (Aeronautes saxatalis), European Starling (Siurnis vulgaris), Black Tern (Chlidonias nigra), Pigeon Guillemot (Ceppkus columba), and Red-necked Grebe (Podiceps grisegna), were recorded using a Doppler radar handgun. Velocities were measured of adult birds flying to and from foraging areas while rearing young, and totalled 1178 records. Morphological measurements were also made on some of the species and were used, along with literature values, to construct curves of estimated total power required for flight versus flight velocity for each species. The mean observed flight speed, V[sub obs], for each species was then compared to the minimum power speed, V[sub mp], and the maximum range speed, V[sub mr], on the power curve. For five of the seven study species, the V0be was significantly greater than V[sub mr], and thus appeared to be independent of morphology, foraging methods and habitats. The V0bs of the other two species was found to be between V[sub mp] and V[sub mr]for the Pigeon Guillemot and less than V[sub mp] for the Red-necked Grebe. In a more detailed study of the Tree Swallow and the Mountain Bluebird, V[sub obs] was determined to be fairly constant over the recording period. Individual power curves were constructed for five female Mountain Bluebirds and three female Tree Swallows, since both morphological measurements and flight speeds were recorded for these individuals. In each case, V[sub obs]was significantly greater than V[sub mr]. For the bluebird, it was also found that the number of visits to the nest per hour per nestling did not appear to increase with the age of the nestling. The rate of feedings, however, was quite variable for both the Tree Swallow and Mountain Bluebird. By setting the observed flight speed, V0be, equal to. a predicted optimal speed, V[sub obt], the net rate of energy gain during foraging by the parents could be determined. Comparing this energy gain with estimates of nestling energy requirements for both species resulted in the conclusion that the observed speed could not be the same as the optimal speed, and that in order to meet nestling requirements, the parents may increase their feeding rate during other parts of the day not under observation.

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