Shamoun-Baranes Judy, van Loon Emiel
Computational Bio- and Physical Geography, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands.
J Exp Biol. 2006 Sep;209(Pt 18):3489-98. doi: 10.1242/jeb.02385.
During non-migratory flight, gulls (Larids) use a wide variety of flight strategies. We investigate the extent to which the energy balance of a bird explains flight strategy selection. We develop a model based on optimal foraging and aerodynamic theories, to calculate the ground speeds and airspeeds at which a gull is expected to flap or soar during foraging flight. The model results are compared with observed flight speeds, directions, and flight strategies of two species of gulls, the black-headed gull Larus ridibundus and the lesser black-backed gull Larus fuscus. The observations were made using a tracking radar over land in The Netherlands. The model suggests that, especially at combinations of low ground speed (approximately 5-10 m s(-1)), high air speed (approximately 20-25 m s(-1)) and low ground and air speed, gulls should favor soaring flight. At intermediate ground and air speeds the predicted net energy gain is similar for soaring and flapping. Hence the ratio of flapping to soaring may be higher than for other air and ground speed combinations. This range of speeds is broadest for black-headed gulls. The model results are supported by the observations. For example, flapping is more prevalent at speeds where the predicted net energy gain is similar for both strategies. Interestingly, combinations of air speed and flight speed that, according to the model, would result in a loss of net energy gain, were not observed. Additional factors that may influence flight strategy selection are also briefly discussed.
在非迁徙飞行期间，鸥类（鸥科）会采用多种飞行策略。我们研究了鸟类的能量平衡在多大程度上能解释飞行策略的选择。我们基于最优觅食和空气动力学理论开发了一个模型，以计算鸥类在觅食飞行中预期振翅或翱翔时的地速和空速。将模型结果与两种鸥类，即黑头鸥（红嘴鸥）和小黑背鸥的观测飞行速度、方向及飞行策略进行了比较。这些观测是在荷兰的陆地上使用跟踪雷达进行的。该模型表明，特别是在低地速（约5 - 10米/秒）、高空速（约20 - 25米/秒）以及低地速和空速的组合情况下，鸥类应更倾向于翱翔飞行。在中等地速和空速时，翱翔和振翅的预测净能量增益相似。因此，振翅与翱翔的比例可能高于其他空速和地速组合的情况。这种速度范围对黑头鸥来说最广。模型结果得到了观测结果的支持。例如，在两种策略预测净能量增益相似的速度下，振翅更为普遍。有趣的是，根据模型，会导致净能量增益损失的空速和飞行速度组合并未被观测到。还简要讨论了可能影响飞行策略选择的其他因素。
