Predatory Functional Morphology in Raptors

To: "'L&L Knight'" <>, "'Birding Aus'" <>
Subject: Predatory Functional Morphology in Raptors
From: "Tony Russell" <>
Date: Thu, 26 Nov 2009 08:09:02 +1030
Cor !

-----Original Message-----
 On Behalf Of L&L Knight
Sent: Wednesday, November 25, 2009 8:19 PM
To: Birding Aus
Subject: Predatory Functional Morphology in Raptors

Predatory Functional Morphology in Raptors: Interdigital Variation in  
Talon Size Is Related to Prey Restraint and Immobilisation Technique
Denver W. Fowler*, Elizabeth A. Freedman, John B. Scannella PLoS ONE
4(11): e7999. doi:10.1371/journal.pone.0007999 Despite the ubiquity of
raptors in terrestrial ecosystems, many  
aspects of their predatory behaviour remain poorly understood.  
Surprisingly little is known about the morphology of raptor talons and  
how they are employed during feeding behaviour. Talon size variation  
among digits can be used to distinguish families of raptors and is  
related to different techniques of prey restraint and immobilisation.  
The hypertrophied talons on digits (D) I and II in Accipitridae have  
evolved primarily to restrain large struggling prey while they are  
immobilised by dismemberment. Falconidae have only modest talons on  
each digit and only slightly enlarged D-I and II. For immobilisation,  
Falconini rely more strongly on strike impact and breaking the necks  
of their prey, having evolved a 'tooth' on the beak to aid in doing  
so. Pandionidae have enlarged, highly recurved talons on each digit,  
an adaptation for piscivory, convergently seen to a lesser extent in  
fishing eagles. Strigiformes bear enlarged talons with comparatively  
low curvature on each digit, part of a suite of adaptations to  
increase constriction efficiency by maximising grip strength,  
indicative of specialisation on small prey. Restraint and  
immobilisation strategy change as prey increase in size. Small prey  
are restrained by containment within the foot and immobilised by  
constriction and beak attacks. Large prey are restrained by pinning  
under the bodyweight of the raptor, maintaining grip with the talons,  
and immobilised by dismemberment (Accipitridae), or severing the  
spinal cord (Falconini). Within all raptors, physical attributes of  
the feet trade off against each other to attain great strength, but it  
is the variable means by which this is achieved that distinguishes  
them ecologically. Our findings show that interdigital talon  
morphology varies consistently among raptor families, and that this is  
directly correlative with variation in their typical prey capture and  
restraint strategy.

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