15 June 2009

Diving Anna's hummingbirds

Courtship dives of Anna's hummingbird offer insights into flight performance limits, by Christopher James Clark, Berkley.

In this new paper the dice speeds of displaying hummingbirds was found to be 27.3 m/s, representing 385 body lengths per second. It is claimed to be the highest size-specific dives measured this far, and it should represent a body drag coefficient of less than 0.3. This resembles me of a paper on diving birds recorded by radar in Spain, as they reached southern Spain after the crossing of Sahara in spring. In that study, Felix and I recorded terminal velocities in barn swallows at about 50 m/s, i.e. nearly double that in the hummingbird. However, due to the more than twice longer body length in the swallows they will not quite reach the 385 body lengths per second as the hummingbird. What is interesting here is that the hummingbird appears to reach 27 m/s with flapping wings, and hence some significant profile drag in addition to the drag of the body. As we are currently concerned with drag of bodies and various random additions, this paper may be quite relevant.

1 comment:

  1. Also:

    Anna's hummingbirds are cool birds, from an ornithological perspective as well. I remember this beatiful hummingbird species from our garden in California where it was breeding.