glaucescens Glaucous-winged Gull & Western Gull occidentalis

(last update: 22-12-2016 )

Coordinators:
Alvaro Jaramillo
John Cant
Mars Muusse

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1cy June
1cy July
1cy Aug
1cy Sept
1cy Oct
1cy Nov
1cy Dec

2cy Jan
2cy Feb
2cy March
2cy April
2cy May
2cy June
2cy July
2cy Aug
2cy Sept
2cy Oct
2cy Nov
2cy Dec

3cy Jan
3cy Feb
3cy March
3cy April
3cy May
3cy June
3cy July
3cy Aug
3cy Sept
3cy Oct
3cy Nov
3cy Dec

4cy / sub-ad Jan
4cy / sub-ad Feb
4cy / sub-ad March
4cy / sub-ad April
4cy / sub-ad May
4cy / sub-ad June
4cy / sub-ad July
4cy / sub-ad Aug
4cy / sub-ad Sept
4cy / sub-ad Oct
4cy / sub-ad Nov
4cy / sub-ad Dec

adult Jan
adult Feb
adult March
adult April
adult May
adult June
adult July
adult Aug
adult Sept
adult Oct
adult Nov
adult Dec

Western Gull occidentalis pre-basic moult (4CY), August 09 2017, Pacific Grove, California USA. Picture: John Cant.

P5/P8. No spot on P4, full band on P5, P6 almost reaching to tip of P5. Note brown old outer greater primary coverts. No mirror on old P10.
Outer primaries much resembling old 2nd gen feathers: faded brown and no mirror on P10. However, adult-type old secondaries and 3rd gen type rectrices age this bird as 4CY (unless in the coming years it will appear that occidentalis commonly replace tail and secondaries in a winter moult - like Lesser Black-backed Gulls do, hence unlike a Herring Gull strategy).