Hi Tweeter Heron Watchers,

My favorite GBH "bible" is The Great Blue Heron by Robert W. Butler. Everything in the book is referenced and cross-referenced where indicated. The measured differences between male and females stated in Butler's book include size, most males are 5-15% larger and males have longer bills through culmen length examination. Male culmen length averages 129-146mm vs 122-131mm. From all the time I have spent observing the herons at Medina Park it is not too hard to see the bill length difference at the nest when the male and female are together.

Of course it really helps when mating is observed, this eliminates all doubt.

I highly recommend this book to anyone who wants to learn more about Great Blue Herons.

Kathy
Roosting in Kent, near Lake Meridian
(chukarbird at yahoo dot com)
Any driving directions contained within this message are given as a courtesy, beware, author is directionally challenged and will not vouch for them.


--- On Sat, 3/7/09, Scott Downes <downess at charter.net> wrote:

> From: Scott Downes <downess at charter.net>
> Subject: [Tweeters] re: Great Blue Heron male/female distinction
> To: tweeters at u.washington.edu
> Date: Saturday, March 7, 2009, 8:39 PM
> >From field observations there is basically no way to
> tell sexes by plumage without having a bird in the hand. If
> you were lucky enough to have a bird in the hand, its still
> difficult. I'm quoting a section from Pyle's
> Identification of North American Birds Part II section on
> Great-blue Heron. This is typically a reference for banders
> and biologists, not a typical field guide, though some
> birders do own it if interested in plumage details.
>
> Pyle: Male=female by plumage aspect. If you know the
> subspecies you can use measurements of the ornamental plumes
> for sexing . Males average longer than females for these
> plumes during January-May but extensive variation, age and
> individual overlap precludes reliable sexing.
>
> So in the field, no ability to tell by plumage. In hand
> some indication but can be difficult and overlap exists.
>
> Hope this helps.
>
> Scott Downes
> downess at charter.net
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