Hi Jenny,
Sure nature is full of curious questions and trying really hard can give
some answers, some of which are supportable. Of course there are also surely
many more birds that have dark or black markings around the eyes, supposedly
for the same reason as you mention ("In the sporting world"). I can't think
of any reason for what you ask other than social signalling. It is sort of
like someone asking a few years ago why does a White-faced Heron have a
white face, to which I asked why does a White-faced Heron have grey body. It
is after all like an egret, most of which are white. I don't know which came
first.
It would appear that birds (and most other animals) devote a lot of energy
and genetic input into producing colours and colour arrangements, when logic
suggests just being all white would be simpler. Clearly the disadvantage of
being all white (presumably from attracting predators and not being pretty
enough to attract partners or having more difficulty signalling what species
you are) outweighs this. My only hint would be that small patches of white
on the face and maybe near the eye are ways of achieving benefit of reducing
the amount of colour needing to be produced in bits of the bird small enough
and intimate enough to not be a disadvantage in terms of attracting
predators. Yet still achieve social connections with partners at close range
maybe by highlighting the eye to partners, which may well be an effective
cosmetic predilection for white eyeliner (seems like a good benefit to me).
So is my suggestion correct? I have no idea and wouldn't know how to prove
it anyway.
Philip
-----Original Message-----
From:
On Behalf Of jenny spry
Sent: Sunday, 13 May 2012 11:06 AM
To: birding-aus
Subject: White eye lines
Hi all,
I have a curiosity question. In the sporting world, baseball for example,
players are known to paint a black strip on their cheekbone. It is meant to
stop the glare of the sun reflecting off the cheek and interrupting their
view of the ball, target, whatever. As I look through my photos and the
field guides I am noticing a reverse strategy. Lots of bird species have
either a row of white dots or a white line on or near the bottom eyelid. As
it appears on many birds across many families I don't imagine that it is
just a cosmetic predilection for white eyeliner.
Birds I have noticed it on include Aus Spotted Crake, White-browed
Scrubwren, Black Noddy, Common Noddy, Southern Emu-wren, Shy Heathwren, Male
Magpie-lark (but not the female) etc etc. Does anyone know if there is a
reason for these small white lines near the bottom eyelid on some but not
all dark-headed species? Oh, and I don't include birds with large white
patches on the cheek or around or near the eye, just the ones with a small,
discrete, white mark or row of white dots on or near the bottom eyelid.
cheers
Jenny
http://jenniferspryausbirding.blogspot.com.au/
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