Lesser Black-backed Gull (graellsii & intermedius)
(last update: June 25, 2012)
Lesser Black-backed Gull graellsii Y.BWP 2CY, July 20 2016, Utrecht, the Netherlands.
Continental graellsii from this population are also referred to as 'Dutch intergrade', upperparts between medium grey British graellsii and dark grey Scandinavian intermedius.
Green YBWP, together with sister YBWN is an offspring of two ringed adults: Lesser Black-backed Gull graellsii YASC and (presumed) hybrid graellsii x michahellis YAHH. This make YBWP an F2 hybrid (second generation hybrid from michahellis), as is the sister (also F0 code) YBWN. If examined into the smallest details, one may find traits that may indicate this michahellis influences (e.g. inherited may be pale on innerwebs of inner primaries and limited proximal barring or flecking in outer rectrices), but probably this may also be found in pure graellsii populations: phenotypically YBWP is a graellsii in all respects, as was its sister PWN. Both are/were gentle birds, probably females (F0). It will be interesting to measure upperpart grey tone once this bird is in adult plumage. Unfortunately, bird YBWN was found death while migarting south on October 05 2015 along the Atlantic coast of Algarve, Portugal (halfway Quarteira and Portimao). Cause of death unknown.
Two papers have been published on the occurrence of michahellis and its hybrids in this colony:
Complete moult: P1-P5 new fully grown, P6 growing, P7 missing, P8-P10 old juvenile. Tail: R1-R4 missing/growing, R5-R6 old juvenile. Secondaries: at least S1 missing, other juvenile.