And the consensus is...... drum roll.....
These birds are definitely night herons!
Oh, you wanted me to say whether they are Black-crowned or Yellow-crowned.
OK. They are definitely Black-crowned or Yellow-crowned.
I'll be serious now, though now that I'm being serious the answer is not
much different.
So far I have votes from 16 people. There are 10 votes for YCNH and 6
votes for BCNH.
A number of the people said they did not have a lot of field experience
and were mainly using field guides and looking at the pictures to try to
decide.
However, there were a number of experienced birders who indicated that
they had seen immature night herons in the field.
One biologist who has worked extensively in BCNH colonies was pretty
certain that the birds are BCNH. Another birder who has observed
nesting YCNH in the field seemed equally certain that the birds are
YCNH. One interesting vote for YCNH came from an experienced birder
who had just seen an immature BCNH in a park in Reston last week.
Now for the distinguishing marks people used to make their choices.
Bill color was mentioned in many of the comments. The Sibley guide says
the bill of a YCNH will be black, so some people thought the presence of
what seems to be some yellowish color in the bill of these birds means
they are BCNH. I've searched the internet to see what pictures I could
find of both immature night herons and there were quite a number of
pictures identified as YCNH where the birds did not have completely
black bills.
Bill shape was mentioned in a number of the comments. Several
specifically mentioned that the bill shape on the birds in my pictures
was more consistent with YCNH. They said that the bills of BCNH tend to
be a little longer, narrower and more pointed, while YCNH bills are
shorter and stubbier relative to the head. In my searching the internet
for the immature heron pictures, that did seem to be the case.
Length of neck. Many of the people who voted for YCNH noted that the
long thin neck (especially apparent in my heron5 picture) was indicative
of a YCNH. That is one of the features that the Sibley guide identifies
for YCNH.
Large teardrop shaped spots on wings. This is perhaps the field mark
mentioned by the various field guides that seems to cause the most
confusion. Several people identified the birds as BCNH because they
felt the spots on the wings were the large spots expected on a BCNH.
Several other people specifically said these birds were not BCNH because
they lacked the large spots. One person said the white spots on the
wings of a BCNH could be 2 inches in length.
Leg length. Most of the field guides point out that the legs of a YCNH
are longer - though they mostly mention that this will be noted when the
birds are in flight, with the legs of the YCNH extending well beyond
the tail of the bird.
Thin streaking on chest. This is another one that went both ways.
Some people felt the streaking on these birds was thin and so that
supported YCNH, while some others said these birds did not have the thin
streaking one would find on a YCNH.
So the biggest thing I've learned from this is that choosing between
immature BCNH and YCNH ranks right up there as one of the more difficult
bird identification problems.
I hope more of you will continue to send me your evaluations of the bird
pictures I posted. Especially those of you who have field experience
with both species.
By the way I did find an interesting site in my internet searching that
shows comparison pictures of YCNH and BCNH.
http://www.surfbirds.com/Rarities/usstoppress-aug-0201.html
-- allen hart
-- Herndon, VA
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