[obol] Re: Peregrine Feeding
- From: Wayne Hoffman <whoffman@xxxxxxxx>
- To: Range Bayer <range.bayer@xxxxxxxxx>
- Date: Thu, 3 Apr 2014 08:53:52 -0700
Thanks, Range -
I'll reply directly to Michael
Wayne
On Wed, Apr 2, 2014 at 9:44 PM, Range Bayer <range.bayer@xxxxxxxxx> wrote:
> Passing this on for Michael McMann
>
> ---------- Forwarded message ----------
> From: Mike McMann <mdmcmann99@xxxxxxxxx>
> Date: Sun, Mar 30, 2014 at 4:52 PM
> Subject: peregrine feeding
> To: Range Bayer <range.bayer@xxxxxxxxx>
>
> Hi Range, Checking back through some of the OBOL postings to catch up
> and found Wayne's great observations on the peregrine that hauled a
> male Surf Scoter up to the Yaquina Head cliffs. Don't have my
> vacation sign-on completely figured out yet but was hoping you could
> pass this on.
>
> I'm a former falconer and have observed many Peregrine Falcons at
> their eyries. This subject intrigues me and I thought others might be
> interested in some observations and subsequent reading:
>
> 1) The 1/3 Guide Line: Brown and Amadon, 'Eagles, Hawks and Falcons of
> the World' 1968, and others, use the 33% rule. That a raptor can
> navigate comfortably with prey weighing 1/3rd of it's body weight in
> most wind conditions. Wayne was surprised to find that the male Surf
> Scoter weighed more than the Peregrine. I can only assume that he was
> using Sibley's weights: Surf Scoter = 2.1lb. and Peregrine = 1.6lb.
> Sibley apparently averages the weights for birds if there is a male
> female difference. But there is as much as a 30-40% difference between
> male and female raptors and between subspecies. John K. Terres, 'The
> Encyclopedia of North American Birds,' 1995; site female Peale's
> Peregrines (subspecies on Pacific Coast) as large as 3.5lb- largest
> subspecies in the world.
>
> 2) Who's Doing the Hunting? Since there is such a difference in
> weights between male and female Peregrines the prey weight will depend
> on which is doing the hunting. Observers know that the female
> peregrine does most of the incubation and feeding during early
> nesting. That means the male is doing most, if not all, the hunting
> and gathering during this period. With their weights varying between
> 1.8 and 2.33lb that means the prey normally has to weigh in between .6
> and .8lb. Note: I led excursions where we assumed Rhinocerous Auklets
> (1.1lb) were the main prey in one area. We never saw a single
> Peregrine until we moved into a zone that featured an abundance of
> Cassin's Auklets (6 oz.- .4lb.)
>
> 3) Wayne's Big Haul: This was undoubtedly an above average haul for
> this Peregrine. Even if the Yaquina bird is one of the largest
> Peale's Peregrines, a male Surf Scoter would have been 2/3 of it's
> body weight. This is pretty far south for the Peale's subspecies so
> if it is actually the smaller F. p. anatum subspecies it ups the ante
> even more. I suspect Alan Jenkins is right (a USAF pilot would know a
> lot about this) that the prevailing winds were favorable for this
> female. It implies that the falcons can adjust their prey selection
> if the wind is right...? Wondering also if this impressive kill was
> part of a mating prenuptial given Wayne's further observations? Could
> be the germ for a couple academic papers on the horizon...
>
> Michael McMann
>
>
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