Are Peregrines too slow?

To: "'Alan McBride'" <>, "'Birding Aus'" <>
Subject: Are Peregrines too slow?
From: "Stephen Ambrose" <>
Date: Sat, 20 Jun 2009 10:11:27 +1000
The abstract of the scientific paper that the BBC news item cites is shown 

Courtship dives of Anna's hummingbird offer insights into flight performance 
Christopher James Clark*
+Author Affiliations

Museum of Vertebrate Zoology, 3101 VLSB, UC Berkeley, Berkeley, CA 94720, USA

Behavioural displays are a common feature of animal courtship. Just as female 
preferences can generate exaggerated male ornaments, female preferences for 
dynamic behaviours may cause males to perform courtship displays near intrinsic 
performance limits. I provide an example of an extreme display, the courtship 
dive of Anna's hummingbird (Calypte anna). Diving male Anna's hummingbirds were 
filmed with a combination of high-speed and conventional video cameras. After 
powering the initial stage of the dive by flapping, males folded their wings by 
their sides, at which point they reached an average maximum velocity of 385 
body lengths s−1 (27.3 m s−1). This is the highest known length-specific 
velocity attained by any vertebrate. This velocity suggests their body drag 
coefficient is less than 0.3. They then spread their wings to pull up, and 
experienced centripetal accelerations nearly nine times greater than 
gravitational acceleration. This acceleration is the highest reported for any 
vertebrate undergoing a voluntary aerial manoeuvre, except jet fighter pilots. 
Stereotyped courtship behaviours offer several advantages for the study of 
extreme locomotor performance, and can be assessed in a natural context.


Stephen Ambrose
Ryde, NSW

-----Original Message-----
 On Behalf Of Alan McBride
Sent: Friday, 19 June 2009 4:13 PM
To: Birding Aus
Subject: Are Peregrines too slow?

Interesting page on Hummingbirds here:-)


Alan McBride, MBO.

Photojournalist | Traveller |  Writer | Birding Guide +
Member: International Travel Writers & Photographers Alliance
                        American Writers & Artists Inc.

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