Larus cachinnans in the Netherlands
(last update: December 24, 2021)
Albert de Jong
Cachinnans breeding in the Netherlands - species composition
ARE THOSE CASPIAN GULLS REALLY CASPIAN GULLS?
As mentioned in the section international trend, Caspian Gull, in their westwards expansion, are known for mixed pairing in areas where they meet Herring Gull, sometimes Yellow-legged Gull, and even Lesser Black-backed Gull. Offspring of such mixed couples may look similar to one of the parents, may show a combination of the parental features, or may in fact resemble a third species. And even more, those hybrid birds will eventually start breeding when adult, and may raise backcrosses, so-called 'F2 hybrids'. What to call birds in such a mixed population?
When ringing chicks in mixed colonies in Poland, it is impossible to ID each and every individual. Therefore, the Polish ringing scheme introduced a new category "Larus
cachinnans kolonia", for ringed chicks from colonies with Caspian Gull dominance, and those chicks which proved to have at least one Caspian Gull parent.
In analogy, "Larus argentatus kolonia" is used for ringed chicks from colonies with Herring Gull dominance, or when its known at least one parent is Herring Gull.
We have to accept we are dealing with birds from a contact zone. And with time, hybrids will raise F2, F3, etc backcrosses which eventually are impossible to tell from 'pure' birds, unless we know a birds complete pedigree.
In the Netherlands we call these head-scratching birds 'river' gulls, referring to the situation along the main inland river systems where four gull species meet and breed.
Jeroen Nagtegaal, ringer in southern Netherlands, has collected data on such birds, see HERE. As the project continues, he documented all weird kind of combinations, e.g.
Lesser Black-backed Gull (Larus fuscus graellsii aka "Dutch intergrades")
Yellow-legged Gull (Larus michahellis)
Herring Gull (Larus argentatus argenteus)
Caspian Gull (Larus cachinnans)
"River" Gull - hybrids / Gibbins BB
POPULATION SIZE AT DE KREUPEL
POPULATION SIZE AT LELYSTAD
From the kayak, at approx 40 meters distance, we observed guarding birds on the breakwaters. We then landed, searched for the eggs and placed code flags on a bamboo stick near the nest.
We monitored 41 coded nests in 2020. Several nests appeared to belong to either Herring Gull or Lesser Black-backed Gull, and were subsequently skipped from the research.
For most nests, the substantial distance to neighbouring nests made countings easy. However, for some location we found clusters of nests, and especially in these clusters we may have missed breeding pairs.
WHICH NESTS AT DE KREUPEL & LELYSTAD ARE CASPIAN GULL?
How to be sure a nest at De Kreupel or Lelystad belongs to Caspian Gull? We use the following steps.
Ad point 4: in 2020 we collected data for all nests that were classified 'potential Caspian Gull nest'. We photographed the birds as much as possible, and examined each individual. The full table is HERE. Results for 2020 are summarised below.
species composition Lelystad of selected nests (table above)
pair composition Lelystad of selected nests (table above)
general notes & remarks
|Caspian Gull cachinnans P:U60 4CY, May 15 2021, Lelystad, the Netherlands. Parent of nest P:U60.
This image illustrates the situation in colony Lelystad: Caspian Gull breeding together with Herring and Lesser Black-backed Gulls.
|Mixed flock of gulls at artificial breakwaters, Lelystad, the Netherlands.
In this particular section at 'dam 1' all four species are breeding together: Herring, Lesser Black-backed, Yellow-legged and Caspian Gull.
|By far the dominant species in colony Lelystad: Lesser Black-backed Gull. In future, we plan to monitor long term trends and the interaction between Herring, Lesser Black-backed and Caspian Gulls in this mixed colony.|
|Lesser Black-backed Gull graellsii 1.T 12CY, March 24 2021, Lelystad, the Netherlands.
Ringed as pullus on July 01 2011 at Maasvlakte, the Netherlands, now breeding at Lelystad.
|Lesser Black-backed Gull graellsii S.11 9CY, April 26 2021, Lelystad, the Netherlands.
Ringed as pullus on June 18 2014 at Maasvlakte, the Netherlands, now breeding at Lelystad.
|Lesser Black-backed Gull graellsii Y.BSN 9CY, March 24 2021, Lelystad, the Netherlands.
Ringed as pullus on July 07 2014 at Forteiland - IJmuiden,Maasvlakte, the Netherlands.
Like the two Maasvlakte birds above, originally a bird from a coastal colony, now breeding at this rapidly growing inland location.
|Lesser Black-backed Gull graellsii adult, March 30 2021, Lelystad, the Netherlands.
Identification should be no problem.
|Lesser Black-backed Gull graellsii adult, June 08 2021, Lelystad, the Netherlands.
A bird in the paler end of the spectrum, still obviously darker than Yellow-legged Gull michahellis.
|"River" Gull Larus spec. adult, March 30 2021, Lelystad, the Netherlands.
River Gull captures all kind of hybrids of which parental identity is merely a guess, as in this bird. Here no black on P5 therefore one parent is probably Herring Gull, while pale-slate upperparts and much black on P9-P10 suggest the other parent to be Lesser Black-backed Gull (or maybe Yellow-legged Gull).
| Yellow-legged Gull michahellis male from nest 41-2021, March 30 2021, Lelystad, the Netherlands.
Partner is female Caspian Gull cachinnans with yellow legs too. In 2021 the nest failed.
|Yellow-legged Gull michahellis has been known breeding in the Netherlands for decades. However, the strong increase in Europe in the 1990's never really materialised in our country. Still, it's not rare to find the species in colonies, especially along the major water systems, and often in mixed breeding. Here at Lelystad, a male Yellow-legged Gull bonded to 8CY Herring Gull 97.|
|Yellow-legged Gull michahellis hybrid Z.M 9CY, March 30 2021, Lelystad, the Netherlands.
Breeder at nest 54-2021, this is a female hybrid zy-MT (HY=2013), pullus from Wijk bij Duurstede colony, offspring from Herring x Yellow-legged Gull.
In lelystad, partner is Herring Gull. Offspring from nest 054 are "Herring Gull backcross F2-hybrids".
|Yellow-legged Gull michahellis -- / HM adult, May 11 2021, Stevol eiland, the Netherlands. Picture: Jeroen Nagtegaal ringing team.
Partner is B/Y-HF michahellis
|F1 hybrid michahellis x argentatus -- / AL 4CY, May 11 2021, Stevol eiland, the Netherlands. Picture: Jeroen Nagtegaal ringing team.|
|F1 hybrid michahellis x argentatus -- / CY adult, May 2019 & May 2021, Stevol eiland, the Netherlands. Picture: Jeroen Nagtegaal ringing team.
Partner is B/Y-HH michahellis
|F1 hybrid michahellis x argentatus L||9 5CY, May 11 2021, Stevol eiland, the Netherlands. Picture: Jeroen Nagtegaal ringing team.|
|probably F2 hybrid michahellis x argentatus X argentatus -- / HJ adult, May 11 2021, Stevol eiland, the Netherlands. Picture: Jeroen Nagtegaal ringing team.
Partner is B/Y-HL probably F2 hybrid michahellis x argentatus X michahellis
|probably F2 hybrid michahellis x argentatus X michahellis -- / HL adult, May 11 2021, Stevol eiland, the Netherlands. Picture: Jeroen Nagtegaal ringing team.
Partner is B/Y-HJ probably F2 hybrid michahellis x argentatus X argentatus
|Herring Gull argenteus, May 29 2019, Lelystad, the Netherlands.
Classic bird sporting silvery grey upperparts, fleshy pink legs, pale iris, much black on P10 and reduced black on P5.
|Herring Gull argenteus, March 24 2021, Lelystad, the Netherlands.
Combination of features should pinch ID:
- stubby bill, staring yellow eye, orange-yellow orbital ring,
- pale silvery grey upperparts,
- much black on P10,
- (commonly) reduced black on P5,
- resting birds with compact body and short-winged impression.
| Caspian Gull cachinnans of nest 53-2021, May 15 2021, Lelystad, the Netherlands.
| Caspian Gull cachinnans male 'albatrossing' to an adult female Herring Gull argenteus, March 24 2021, Lelystad, the Netherlands.
Note pale long tongue on P10 and dark iris.
|Caspian Gull cachinnans 201:U 6CY, May 20 2021, De Kreupel - D, the Netherlands. Picture: Leon Kelder.
Ringed as pullus on May 27 2016 at Nové Mlýny II reservoir, Czech Republic; breeder in the Netherlands now.
|Caspian Gull cachinnans K.A adult, April 23 2021, De Kreupel - M, the Netherlands. Pictures: Merijn Loeve.|
|Caspian Gull cachinnans K.G (was 02P4) 8CY, April 23 2021, De Kreupel - B, the Netherlands. Pictures: Merijn Loeve.|
|Caspian Gull cachinnans PLDP 9CY, May 07 2020, Lelystad, the Netherlands.
Parent of "nest 005" in season 2019 and 2020. Originally, ringed as pullus in Poland.
|Caspian Gull cachinnans 327:U 4CY, May 28 2021, Lelystad, the Netherlands. Picture: Albert de Jong.
Inspecting the colony, or a breeder that has settled unnoticed? Originally, ringed as pullus in Czech Republic.