Water takeoff in a pelican (part 2 with reference to pterosaur water takeoffs)
Mike Habib, famous for his pterosaur forelimb take-off scenario, sent a short note recently for which my reply here is aided with illustrations.
M. Habib wrote, “Incidentally, pelicans do not launch using wing power. The launch using a series of pushes from the hindlimbs, which are essentially leaps. Their launch is basically saltatorial. Most of the power is provided by the final leap, as evidenced by the fact that the last “splash” is the largest – they displace more water, not less, as the feet push, so the wings are not picking up more power as they go. Animals do not launch like airplanes.”
Earlier I posted a pelican take-off composite photo that stitched together several scenes from a video from YouTube here (redux in figure 1) in which a Sea of Cortez pelican became airborne from a floating configuration.
Figure 1. Pelican take-off sequence from the Sea of Cortez. Click to enlarge. Full video linked above in text.
Thankfully there’s another YouTube video newly posted in slow-motion here that is even more instructive.
In both videos, you’ll note that the pelican slowly unfolds its wings (as in figure 1) preparing for flight. With one mighty downstroke it becomes airborne (#4 and #5 in figure 1, note the belly is clear of the water). Beneath the waves no doubt the feet have provided some thrust, as we can see by their position as they rise above the waves in the first (slow-motion) 7 seconds (#5 in figure 1) fully extended posteriorly. The wings continue to beat in sync with the feet cycling back, pulling the water backward, using every limb in its power to achieve greater airspeed. But note from the start (#4 in figure 1), the pelican is airborne and flying. Wings are dry. Feet are too, except for occasional dips (leaps? or simply gaining traction?). To my eye the foot motion looks more like a pull (swimming stroke, paddling, thrust from the entire interaction of foot and water), than a push (as in leaping, thrust only from the moment of last contact with the substrate).
Not sure, given the relative sizes of the feet and wings, how M. Habib can say, “pelicans do not launch using wing power.” Looks to me like they use everything they have, with the majority contribution from the enormous wings (and who knows how much added headwind from the breeze). Certainly it takes five and a half foot contacts with the water before the pelican has enough airspeed to rise above the “ground (in this case water) effect” in which the wings benefit from more lift in closer association with the ground (water). And the last splash was the least, not the greatest in both videos.
The key seems to be: one downstroke and everything but the feet leave the water.
All of these musings on pelican water takeoff refer back to my thoughts on convergent water take off in pterosaurs first mentioned earlier and duplicated below (figure 2).
Figure 2. Ornithocheirid pterosaur water launch sequence in the pattern of a pelican launch. LIke ducks, geese and pelicans, pterosaur probably floated high in the water. Here the wings rise first and unfold in an unhurried fashion, keeping dry and unencumbered by swirling waters. Then the legs run furiously, like a Jesus lizard, but with such tiny feet, they were not much help in generating forward motion. The huge wings, however, did create great drafts of air, thrusting the pterosaur forward until sufficient airspeed was attained, as in the pelican. Considering the pelican’s abilities, perhaps the relatively lighter pterosaur could have arisen free of the water on the first downstroke, without much fuss from the hind limbs, especially aided by a light marine headwind.
Another video of a skimming pelican here brings to mind Nyctosaurus and Pteranodon feeding activity over the Niobrara Sea.
And yet another video of an origami Pteranodon here. Amazing. I better stop there. YouTube can be fascinating and distracting.
2012-12-15 18:19:14
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