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May 2013

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From:
Ned Keller <[log in to unmask]>
Reply To:
Ned Keller <[log in to unmask]>
Date:
Wed, 1 May 2013 17:48:34 -0400
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The two Ibis from Fernald Preserve near Cincinnati were seen until
yesterday evening, but were not seen today (or at least, the only report
was negative).

There has been continuing discussion about their identity; but before I get
to that, I have a question: Does anyone have a link to an image of ANY
hybrid that is actually known to be such? I don't mean just a bird that
looks intermediate, but a bird from a hybrid nest that was banded as a
chick, an adult identified by DNA, or any other source of actual positive
knowledge of its identity.

Ruhikant Meetei has posted a link to a stunning image of one bird:
http://ruhikant.smugmug.com/Birds/Spring-2013/28947899_bqnHq9#!i=2487927209&k=XHTbRDx&lb=1&s=O

And here's a post from the Cincinnatibirds message board from Jack Stenger,
reposted by permission:

[quote begins]

There has been discussion in other forums about the identification of the
Fernald ibis. At least one knowledgeable birder thinks that the photos
clearly show a Glossy x White-faced hybrid based off the dark eye and
purplish facial skin. This is an interesting possibility, but I think it’s
hasty to conclusively identify this ibis as a hybrid. (For the record, I
have not seen this bird in the wild.)

The golden rule in documenting rare birds is that extraordinary claims
require extraordinary evidence. Although we birders tend to overlook it,
hybrids are way more extraordinary than non-hybrids.

Our knowledge of dark ibis hybridization seems hardly more than anecdotal –
interbreeding has only been documented in one location in Wyoming (Faulkner
2005), assumed in Oklahoma (Arterburn and Grzybowski 2003), and "apparent
hybrids" are reported widely in the east and west. Even the publications
documenting hybrids frequently use the word “apparent”. Interestingly, in
the area where their ranges overlap, the Gulf Coast, there are no reports
of hybridization (Ryder 1967, Duncan and Johnson 1977, Ryder and Manry
1994). If anybody knows of any other mixed-species breeding attempts I’d be
eager to hear them.

For this to be a hybrid, it means that the following probably occurred: an
individual Glossy Ibis would wander far out of range where there were no
other Glossy Ibis to breed with, mate with a White-faced Ibis, successfully
raise an offspring, which then shows up well out of range itself. Could it
happen? Sure. Did it happen? That would take extraordinary documentation.

Maybe this bird is a hybrid. But assuming that’s the case because of soft
part coloration is a large leap. A bird with duller eyes and skin than
expected (from a photo) does not seem enough to prove a hybrid, especially
considering that young ibises have duller eye/bare part coloration that
deepen in color as they age. Could this bird just be a “late bloomer” and
not yet in breeding condition? If a second year junco retained it’s hatch
year eye color, would we assume it is a hybrid? No, we would use the term
“aberrent”. Why is this same evidence conclusive proof of hybridization in
an ibis?

All references highlight how little we know about the phenotypic
variability, gene flow, and hybridization of Plegadis ibis. If there is one
thing we shouldn’t be, it’s sure. I encourage observers to keep an open
mind about the bird and document it as well as possible. A "hybrid"
identification should not be a default identification for unusual
individuals.

Anyway, I hope more people get to see these awesome birds.



References:

Arterburn, J. W. and J. A. Grzybowski. 2003. Hybridization between Glossy
and White-faced Ibises. North American Birds 57:136-139.

Faulkner, D. 2005. Hybridization and nesting of Glossy
Ibis(Plegadisfalcinellus)in Wyoming. North American Birds 59:382-384.

Ryder, R.A. 1967. Distribution, migration and mortality of the White-faced
Ibis (Plegadis chihi) in North America. Bird Banding 38: 257-277.

Ryder, R.A., and D.E. Manry. 1994. Whitefaced Ibis (Plegadis chihi). In The
Birds of North America, No. 130. (A. Poole and F. Gill, Eds.).
Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The
American Ornithologists’ Union.

[quote ends]


-- 
Ned Keller

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