This is an interesting record and good to have it so well documented.
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).
Now how about nailing the gull at the mouth of the Maroochy River reported
via Jill Denning?
Mike Carter
30 Canadian Bay Road
Mt Eliza VIC 3930
Ph: (03) 9787 7136
Email:
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