Hi Mike and others,
Thanks for your comments, Mike.
I am an over-night expert on black-backed gulls so it is good to have my own
thoughts backed-up.
I read the entry for Pacific Gull in HANZAB (well....the important bits) and had reasoned that these
were "1st immature birds".
But I was not sure if they were also breeding birds.
I checked the Wingspan article you mentioned (well......the important bits) and there is mention of
the change in eye colour.
In that article David James suggests that the eye colour changes from dark in a "first-year plumage
non-breeding" (which I presume is the same as "1st immature non-breeding" in HANZAB) to pale in a
"first-year plumage breeding".
HANZAB suggests that this eye colour change occurs with the onset of the first
post-breeding moult.
(These two explanations may really mean the same thing depending on the
interpretations.)
As the irises of these birds are dark it seems to me that these are non-breeding "first-year plumage
birds", considering the time of the year.
As breeding is said to occur in Sept-Nov that would sound reasonable would it
not?
One of the birds was still there near the boat-ramp today (Sun 10th July) in spite of the very
strong westerly winds buffeting the area.
The light was much better this time and the bird was very approachable. I got to within 10 metres
for some good photos.
Mike said:
"I'm confident that the darker bird is in its first year. Strictly speaking
not a juvenile because that plumage persists only until about April. At this
time of year I'd consider it to be in 1st non-breeding plumage. The other
bird may be one year older because of the bill pattern but I think more
likely just a more advanced 1st year bird. They are similar in plumage and
both have mainly dark eyes. My observations suggest eyes start to pale when
about 8 months old, July/August. By mid-year, a second year bird should have
a predominently pale eye (HANZAB). Another good reference is David James'
'Bird Identification' article in Wingspan vol. 5 No. 2, June 1995, 'Picking
a Gull-Friend, Identification and ageing of black-backed gulls', but this
doesn't discuss iris colour (unless I overlooked that in a quick glance this
morning)."
Cheers
Bob Inglis
Woody Point
Qld Australia
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