Update April 1, 2003: added
15 more examples of FRGU primary patterns.
These Franklin's Gulls (Larus pipixcan)
were photographed at Village Creek Stirring Tanks in early March
of 2003. NOTE that the apparent difference in mantle color
in the first image is an artifact created by the slightly different
angles of the two birds, in strong, low sunlight:
The left bird looks typical of birds I have previously assumed
to be 3CY birds in Spring:
- but the right bird looked rather odd, causing me to look more
closely:
It too looked less-than-fully-adult, but more obviously-so:
A study of the primaries revealed that both birds seem to have
suspended the Spring primary molt - but at different points:-
The left bird has renewed up to P8, with P9 and P10 of an older
generation (but clearly not juvenile); note on these older feathers
the more-extensive black, browner and more-worn basal edges, and
the missing (worn away) white apical spots (that were clearly
quite large):
The right bird has renewed only up to P6, with P7 to P10 of an
older generation (again clearly not juvenile - note the mirror
on the underside of the opposing P10); note on these older feathers
the more-extensive black, browner and MUCH more-worn basal
edges, and the missing (worn away) white apical spots (that were
clearly quite large); also note that the lower tertials are also
unmolted and extremely worn:
I am now in the process of studying the molt in arriving migrant
FRGUs (currently mid-March 2003); it's early days, but there seem
to be a number of birds with retained older outer primaries.
