I think that we often try to look too hard and try too hard to justify
things. There is a lot of randomness in evolutionary process and an even
greater amount of compromise. The white face on a heron could be a social or
sexual signal, to indicate adulthood, it could be a reproductive isolating
mechanism from other species of heron that don't have it. It could be
counter shading or any other sort of thing. Maybe we shouldn't be
questioning the white face but the blue-grey body. After all, most (all?)
egrets that hunt in similar ways are all white.
-----Original Message-----
From: Jill Dening <>
To: James Davis <>; Birding-aus
<>
Date: Friday, 23 April 1999 12:22
Subject: Re: birding-aus Neck-swaying White-faced Hero
> BTW,
>>would you like to venture a guess why the heron's face is white?
>
>Jim,
>
>Sorry, I have been out of computer reach these past days. Like Anne Green,
>I first favoured the notion that the broken colours of the face make it
>hard for prey to discern a predator from below the waterline. However, I
>can also come up with counter-arguments to this:
>
>For instance, if this is in fact a plausible theory,
>1. why do more birds, which hunt in this manner, not have broken
>colours? e.g. the Jabiru must pose a clearly discernible outline from
>within the water.
>2. why is the neck coloured in unbroken grey, when the bird would be
>better off with total camoflage? Why camoflage one part, when the neck -
>and body - would be so obvious?
>
>Already I can think of counter-arguments to my counter arguments (like some
>species becoming more successful food gatherers than others, as a result of
>their camoflage, leading to greater breeding success). However, I sometimes
>have my doubts about reasons attributed to why birds have certain features.
>
>What do YOU think?
>
>Cheers,
>
>jill
>
>Jill Dening
>Sunshine Coast, Qld
>
>26º 51' 152º 56'
>
>
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