IJmuiden Project - Fred Cottaar, José Verbeek, Maarten van Kleinwee & Mars Muusse

(last update: January 01, 2023)

Lesser Black-backed Gull (graellsii) F2-hybrid Y.BWP 1CY-5CY, June 2015 - October 2018, the Netherlands. Picture: Mars Muusse & Maarten van Kleinwee.

Ringed as pullus in season 2015 at Forteiland, IJmuiden. Ringed by Fred Cottaar ringing team.

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 YBWN. Both appeasred gentle birds, assumed females (F0), but YBWP turned out to be male. 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:
- Dutch Birding 2004-1 "Yellow-legged Gulls and hybrids breeding at IJmuiden", by Fred Cottaar.
- Dutch Birding 1994-6 "Geelpootmeeuw gepaard met Kleine Mantelmeeuw broedend te IJmuiden", by Fred Cottaar & Kees Verbeek.

Lesser Black-backed Gull (graellsii) F2-hybrid Y.BWP 5CY, March 29 2019, IJmuiden, the Netherlands. Picture: Maarten van Kleinwee.

Note the sub-adult markings in the upper and lower wing.

Lesser Black-backed Gull (graellsii) F2-hybrid Y.BWP 4CY, October 01 2018, Scheveningen, the Netherlands. Picture: Mars Muusse.

Much like Lesser Black-backed Gulls.

Lesser Black-backed Gull (graellsii) F2-hybrid Y.BWP 4CY, April 16 2018, IJmuiden, the Netherlands. Picture: Maarten van Kleinwee.

Lesser Black-backed Gull (graellsii) F2-hybrid Y.BWP 4CY, April 09 2018, IJmuiden, the Netherlands. Picture: Maarten van Kleinwee.

In 2018, YBWP again returned to the colony but now accompanied by a female Lesser Black-backed Gull. They occupied a territory which was about 15 meters away from the nest where YBWP hatched. Father YAHH also returned to its regular territory (hence, in sight of YBWP), but with a new partner because mother YASC has not been seen since 2015 unfortunately.

Lesser Black-backed Gull (graellsii) F2-hybrid Y.BWP 3CY, April 10 2017, IJmuiden, the Netherlands. Picture: Maarten van Kleinwee.

In 2017, YBWP revisited the colony and was seen close to the location where it hatchedin 2015.

Lesser Black-backed Gull (graellsii) F2-hybrid Y.BWP 2CY, July 20 2016, Utrecht, the Netherlands. Picture: Mars Muusse.

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.

Lesser Black-backed Gull (graellsii) F2-hybrid Y.BWP 1CY, June 29 2015, IJmuiden, the Netherlands. Picture: Maarten van Kleinwee.

In June 2015, we ringed a juvenile gull in the colony of IJmuiden Forteiland, the Netherlands as Green YBWP. Its father was a presumed hybrid Lesser Black-backed Gull x Yellow-legged Gull (ringed as Green YAHH) and its mother a Lesser Black-backed Gull (ringed as green YASC).

parents: Lesser Black-backed Gull (graellsii) hybrid Y.AHH & female Y.ASC May 11 2015, IJmuiden, the Netherlands. Picture: Maarten van Kleinwee.

Mother Lesser Black-backed Gull Green YASC on the nest with father (presumed) hybrid Lesser Black-backed Gull x Yellow-legged Gull Green YAHH on the left.