RE: [SBB] Western Tanager & Spotted Sandpipers

["Alvaro Jaramillo" <[[email protected]]>]

Joe et al. 

    I do think that there is a human prejudice here, but it is mainly due to
our general focus on mammals and higher vertebrates. Larger females than
males are rare in mammals, although it occurs in some bats as I recall. The
cases in birds are more common than generally appreciated (many shorebirds,
owls, diurnal raptors, jaegers/skuas, Moorhens etc). It gets trickier to
apply in other vertebrates, particularly those which keep growing as long as
they are alive (fish, amphibians etc). In many fish, females that become big
will turn into males if the mating male dies (many wrasses, parrotfish etc),
so how do you score those? The largest females are not female any longer!
There are many, many insects and arachnids in which the females are larger
and often this is related to selection for size due to larger egg production
volumes. Having said all that, I do think that species with larger females
than males are clearly rarer in the bird and mammal world.  

Good birding

Al

Alvaro Jaramillo
[[email protected]]
Half Moon Bay, CA

Field Guides - Birding Tours Worldwide
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> -----Original Message-----
> From: Joseph Morlan [mailto:[[email protected]]]
> Sent: Thursday, April 28, 2005 8:18 AM
> To: Alvaro Jaramillo
> Cc: 'Bill Bousman'; [[email protected]]; 'South-Bay-Birds'
> Subject: Re: [SBB] Western Tanager & Spotted Sandpipers
> 
> On Wed, 27 Apr 2005 18:59:10 -0700, "Alvaro Jaramillo"
> <[[email protected]]> wrote:
> 
> >Note that sex role reversed is the standard term in behavioural ecology
> to
> >refer to situations where males are the limiting sex in calculations of
> >reproductive success, a scenario that selects for inter-female
> competition
> >and usually larger size and ornamentation. It implies that this situation
> is
> >somehow incorrect (reversed)
> 
> The situation where females are larger than the males (owls, raptors,
> etc.)
> is often called "reversed sexual size dimorphism" in scientific
> literature.
> Is it really that uncommon for females to be larger than males?  Or is it
> possible that scientists may be assuming inherent human prejudice by using
> such terminology?
> 
> --
> Joseph Morlan, Pacifica, CA 94044  jmorlan (at) ccsf.org
> Birding Classes in SF start Feb.8  http://fog.ccsf.edu/~jmorlan/
> California Bird Records Committee  http://www.wfo-cbrc.org/cbrc/
> 
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