Larus cachinnans in the Netherlands

(last update: December 24, 2021)

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Nests at De Kreupel 2021
nest r-02P4 20
nest w-201U 21
nest g-XLHD 21
nest r-KA 21
nest r-KB 21
nest r-KC 21
nest r-KD 21
nest r-KE 21
nest r-KF 21
nest r-KH 21
nest r-KJ 21
nest r-KK 21
nest A01 21
nest C03 21
nest C04 21
nest C06 21
nest D01 21
nest D03 21
nest D05 21
nest D06 21
nest D07 21
nest D08 21
nest E01 21
nest H01 21
nest L01 21
nest L02 21
nest L05 21
nest L06 21
nest L07 21
nest M01 21
nest M04 21
nest M06 21
nest Q01 21

Lelystad:
nest y-PNED
nest y-PESV
nest y-PLDP
nest y-PHSV
nest y-P:A02
nest y-P:U60
nest zy-MT
nest r-FB
nest r-FC
nest 001
nest 003
nest 006
nest 009
nest 011
nest 012
nest 013
nest 014
nest 015
nest 016
nest 016B
nest 017
nest 018
nest 019
nest 021
nest 025
nest 027
nest 028
nest 029
nest 031
nest 032
nest 033
nest 034
nest 035
nest 036
nest 037
nest 038
nest 039
nest 040
nest 041
nest 042
nest 044
nest 045
nest 046
nest 047
nest 048
nest 053
nest 055
nest 056
nest 058
nest 060
nest 062
nest 063
nest 065
nest 066
nest 067
nest 072
pair A
pair B

Cachinnans breeding in the Netherlands - population trends

Caspian Gull Larus cachinnans - new breeding bird in The Netherlands (in prep.)
Albert J de Jong, Mars J M Muusse, Leon Kelder, Roland-Jan Buijs & Merijn Loeve

Settlement started with some single pairs scattered at inland freshwaters. The first record was a ringed fifth calendar year male Caspian Gull paired with a Herring Gull near Amerongen, Utrecht in a colony of Lesser Black-backed Gulls and Herring Gulls. Unfortunately, the metal ring of the Caspian Gull was not read but ring type suggested east European origin (Boele et al 2015). The nest with 3 eggs was controlled on May 16th and 25th, 2012 and at least one hybrid young fledged early July. (Buijs & Gelderblom 2013).

In 2013, presumably the same pair was present at the same location. It raised two chicks which  fledged around July 22nd. In 2014, a nest on island De Kreupel in IJsselmeer, Noord-Holland was most likely the first pure pair of Caspian Gulls breeding in the Netherlands. The pair was first observed in May and by August one juvenile was seen begging to an adult here (unfortunately no courtship nor nesting was observed, hence this breeding record was categorized “most likely” (Boele et al 2016).

The first certain pure pair of Caspian Gulls was found in 2015 at a sandy bank along a small river arm in Aerdt, Gelderland. The nest with two eggs failed (Boele et al 2017). Already, in 2014 and 2015, some late summer observations of pairs with begging fledglings near Lelystad, Flevoland indicated something might have been going on in Ijsselmeer area  (www.waarneming.nl), however, we could not eliminate the possibility these were families from eastern Europe ‘early on the move’ . Also in 2015, an adult bird was observed at island De Kreupel again, but no breeding behavior was observed.

April 25th -29th 2016, an adult female and a fourth calendar year male Caspian Gull were observed displaying on a newly constructed, sandy island in the Roetwaarden, in river IJssel near Olst, Overijssel. Based on photographs, it was a Caspian Gull male, but identification of the female remained uncertain. Nevertheless, the incubating female showed a slender bill and darkish iris, suggesting a pure bird as well. On May 10th and 12th incubation was observed, but the nest was abandoned on May 17th (Schermerhorn 2017). Also in 2016, checking breakwaters at Lelystad resulted in the discovery of three pairs of Caspian Gulls. On July 1st one pure pair with 3 fledglings, one pure pair without fledglings and a ringed male together with 2 fledglings were seen in the colony of large gulls at this location.  
In April 2017 a new pair of Caspian Gulls was found in the colony of Amerongen, Utrecht. A fifth calendar year male with a German ring (XLDT) and a fourth calendar year male with a Polish ring (02P4) were building a nest and started incubating eggs on April 15th – 19th. Most likely, the nest was disturbed by a goose hunt shortly after. There were no subsequent observations of these birds at this place, but the female was reported on July 9th in the colony of Lelystad, Flevoland. The same date, a pair of Caspians with two chicks was photographed at this location, but the exact number of breeding pairs for colony Lelystad remained unknown that season.
In 2018 a subadult male Caspian Gull successfully bred with a ringed female Herring Gull at Amerongen, Utrecht, raising three chicks, which were ringed May 19th (Buijs & Gelderblom 2019). At Lelystad, two pure pairs (both including one subadult partner) were observed at the breakwaters. Also a hybrid pair of presumed Caspian (male) x Yellow-legged Gull (female) was seen. An alarming pair and a pair with a begging young were seen at isle De Kreupel (Boele et al 2020).

In 2019 Caspian Gulls appeared in fresh water lakes in ‘the Delta’ in the southwest of the country for the first time. One pure pair and one pair Caspian Gull with Herring Gull hybrid bred on Slijkplaat, Haringvliet. Breeding success for these two nests remained unknown. In the colony on the small isle Spuitkop, Markiezaat a Caspian Gull (with unknown partner) was breeding, and the same situation (Caspian with unknown partner) was found in colony Quarles harbor at Vlissingen. Also, several non-breeding Caspian Gulls were reported in other colonies in this region  (Lilipaly et al 2020). On a small island in lake Molengreend, in a former gravel pit near Maasbracht, Limburg one pure pair of two adults had an attempt but failed, but a hybrid pair of a fourth calendar year male Caspian with an adult female Lesser Black-backed Gull succeeded and raised three fledglings which were ringed on June 14th, 2019 (N. Hulsbosch, J. Nagtegaal).

2020
Again, in Haringvliet two nest were found with at least one Caspian Gull. In 2020, we started monitoring colony De Kreupel and colony Lelystad in IJsselmeer; the early stage of a strong increase in breeding Caspians, with ringed birds from Poland and from Germany.

2021
We include some preliminary results for season 2021 here as well. At colony De Kreupel  we located 33 nests, of which 5 nest were pure (both parents Caspian Gull), 5 nests were mixed (Caspian with non-Caspian parents) and 10 nests were uncertain (Caspian Gull with unknown partner). The other 13 nests contained a full clutch of 3 eggs on an early date (indicative for Caspians, together with size and pattern) but none of the parents were documented sufficiently in the next months. We did ring chicks in most these nests, so maybe in future, when these ringed birds will be reported back, we can still categorize the parents. At colony Lelystad we marked  44 nests early in the season, and throughout the breeding season  these were labeled as 18 pure nests, 8 mixed nests, and 15 uncertain nests (one Caspian, but partner remained uncertain).

What is the origin of breeding Dutch Caspian Gulls? Ringed birds.

The very first breeding Caspian Gull, the male at Amerongen, was ringed, but the code was never read and attempts to trap the bird at the nest failed two times. However, the type of ring, a clip-ring, strongly suggests a Polish origin. Up to 2020, we recorded immigrants from Polish, east German and Czech colonies, indicating the on-going process of westward expansion.

Immigrants from Poland

Three colonies have been the source (up to season 2022) for Polish birds breeding at De Kreupel and at Lelystad:
- Paczków origin for most Polish birds in the Netherlands - distance 830 km's.
- Babice for y-PESV - distance 1012 km's.
- Zastów Karczmiski at river Wisła for y-P:U60 - distance 1133 km's.

RED 02P4 - De Kreupel colony
Caspian Gull 02P4, breeding bird at De Kreupel, originally ringed in Poland.
An immigrant from Paczków colony, ringed as pullus on May 15 2014, now breeding in the Netherlands. Trapped as breeding adult in season 2021 and ring replaced, now tibia r-K.G.

YELLOW PESV - Lelystad colony
Caspian Gull PESV. In season 2019 (9CY) and 2020 (10CY), this was a bird breeding at Lelystad. It is an immigrant from Babice colony, Poland where it was ringed as pullus in 2011. Several records since, at waste recycling plant in Oss, and 27 records in the Lelystad area, both in the Netherlands. Interestingly, after fledging, this bird was never observed in Poland again. This bird was not recorded in colony Lelystad or anywhere else after breeding season 2020 and may be dead now.

YELLOW PLDP - Lelystad colony
Caspian Gull PLDP, a bird breeding at Lelystad in season 2020 (9CY) and in 2021 (10CY), immigrant from Paczków colony, Poland. Like the previous bird PESV, after fledging, this bird too was never observed in Poland again. In 2022 the bird did not breed at Lelystad again, but is still alive, and was photographed in nearby Amsterdam on May 24 2022. It may now breed at one of the 'less frequently monitored' dams or small islands between Lelystad and Amsterdam.

YELLOW PNED - Lelystad colony
Caspian Gull PNED, breeding at Lelystad in seasons 2019 (7CY) - 2022 (10CY). A female immigrant from Paczków colony, Poland. An observation in the database for Czechia in May 2020 is very much unlikely.

YELLOW PHSV - Lelystad colony
Caspian Gull PHSV, breeding at Lelystad in seasons 2020 (10CY) - 2022 (12CY). A female immigrant from Paczków colony, Poland. trapped and with new rings in 2022, now tibia r-C.G. Currently uncertain situation whether it survived the 2022 Avian Flu outbreak.

YELLOW P:A02 - Lelystad colony
Caspian Gull P:A02, breeding at Lelystad in season 2021 (5CY). A male immigrant from Paczków colony, Poland. Ringed as pullus on May 25 2017, now breeding in the Netherlands. No observations after summer 2021 in the database. Hence, bird did not return to breed in 2022.

YELLOW P:U60 - Lelystad colony
Caspian Gull P:U60, breeding female at Lelystad in seasons 2021 (4CY) and 2022 (5CY). Ringed as pullus on June 09 2018 in a mixed Caspian Gull colony "Larus cachinnans kolonia" with cachinnans dominance at river Wisla, Poland, by ringer Lukasz Bednarz. In all respects, y[P:U60] is cachinnans, no indication for hybrid.

Immigrants from Germany

One colony is the source (up to season 2022) for all German birds breeding in the Netherlands: Gräbendorfer See colony at Lausitz, Brandenburg, Germany (51°42'00"N 14°06'00"E). Distance 605 km's.

GREEN XLDT - Lelystad colony & De Kreupel colony
Caspian Gull XLDT, in season 2020 a 8CY bird breeding at Lelystad and in 2022 breeding as 10CY bird at De Kreupel. This bird was ringed DEH EA-183800 and g-XLDT, ringed as pullus Caspian Gull (Larus cachinnans) on June 07 2013 at Gräbendorfer See - Lausitz, Brandenburg, Germany (51°42'00"N 14°06'00"E).

GREEN XLHD - De Kreupel colony
Caspian Gull XLHD, breeding at De Kreupel in season 2020 as 5CY bird and in 2021 as 6CY bird. Ringed as pullus Caspian Gull (Larus cachinnans) DEH EA-137968 and g-XLHD, on May 29 2016 at Gräbendorfer See - Lausitz, Brandenburg, Germany (51°42'00"N 14°06'00"E).

YELLOW - X311 - De Kreupel colony
Yellow ringed bird from east Germany, now successfully breeding at De Kreupel.
In season 2021 a 6CY bird, immigrant from Germany. This bird was ringed DEH EA-204311 and y-X311, ringed as pullus Caspian Gull (Larus cachinnans) on June 06 2016 at Gräbendorfer See - Lausitz, Brandenburg, Germany (51°42'00"N 14°06'00"E).

YELLOW - X540 - Lelystad colony
Yellow ringed bird from east Germany, now successfully breeding at Lelystad.
5CY bird in season 2022, ringed as pullus Caspian Gull (Larus cachinnans) rings DEH EA-204540 and y-X540, ringed on June 03 2018 at Gräbendorfer See - Lausitz, Brandenburg, Germany (51°42'00"N 14°06'00"E). In 2020 this bird shortly returned to the native colony in Germany, but decided to breed in the Netherlands.

YELLOW - X804 - De Kreupel colony
Yellow ringed bird from east Germany, now successfully breeding at De Kreupel.
In season 2020 a 4CY bird, immigrant from Germany. This bird was ringed DEH EA-204804 and y-X804, ringed as pullus Caspian Gull (Larus cachinnans) on May 31 2017 at Gräbendorfer See - Lausitz, Brandenburg, Germany (51°42'00"N 14°06'00"E).

YELLOW - X56A - Lelystad colony
Yellow ringed bird from east Germany, now breeding at Lelystad.
History much like y-X540. Ringed as pullus Caspian Gull (Larus cachinnans) DEH EA-202456 and y-X56A, on June 03 2018 at Gräbendorfer See - Lausitz, Brandenburg, Germany (51°42'00"N 14°06'00"E). In season 2022 a 5CY bird.

YELLOW - X71A - Lelystad colony
Yellow ringed bird from east Germany, now breeding at Lelystad.
Ringed as pullus Caspian Gull (Larus cachinnans) but suspected to be a hybrid, rings DEH EA-202471 and y-X71A, on June 03 2018 at Gräbendorfer See - Lausitz, Brandenburg, Germany (51°42'00"N 14°06'00"E). In season 2022 a 5CY bird.

YELLOW - XCHP - Lelystad colony
Yellow ringed bird from east Germany, now successfully breeding at Lelystad.
In season 2022 a 5CY bird, immigrant from Germany. This bird was ringed DEH EA-211894 and y-XCHP, ringed as pullus Caspian Gull (Larus cachinnans) on June 06 2018 at Gräbendorfer See - Lausitz, Brandenburg, Germany (51°42'00"N 14°06'00"E). For sure this is a hybrid Caspian x Herring Gull.

Immigrants from Czech Republic

Two Czech birds have been recorded breeding in the Netherlands, both from:
Pasohlávky, Jihomoravský kraj, Czechia (48°53'47.83"N 16°35'56.72"E). Distance 905 km's.

WHITE - 201:U - De Kreupel colony
Ringed as pullus Larus cachinnans at Pasohlávky, Jihomoravský kraj, Czechia (48°53'47.83"N 16°35'56.72"E), by ringer Frantisek Zicha. Now breeding bird at colony De Kreupel in season 2021.

WHITE - 327:U - Lelystad colony
Ringed as pullus Larus cachinnans 327:U and metal ring CZP CX1388, on May 24 2018 at Pasohlávky, Jihomoravský kraj, Czechia (48°53'47.83"N 16°35'56.72"E). Present in Lleystad colony during mst of the breeding time in 2021 and in 2022, but both times failed to make a nest.

Immigrants from Belarus

Caspian Gull r-KY27 was recorded in the breeding colony at Lelystad. Ringed on the rooftop colony in Minsk, Belarus. Distance 1485 km's.

RED KY27 - Lelystad colony
Caspian Gull KY27. For a week, Caspian Gull (Larus cachinnans) r-KY27 bonded with Czech female w-327:U at colony Lelystad in April 2022. However, the attempt failed and r-KY27 was reported back in Belarus later in season 2022. R-KY27 and metal BYM D01997 was ringed as breeding adult male Caspian Gull (Larus cachinnans) on May 10 2021 at sector VIII in Gatovo colony, Minsk, Belarus ( 53°46'29.13" N 27°39'1.93" E), by the Irina Samusenko ringing team.

RETURNING RINGED BIRDS AT LELYSTAD

As the ring project on juveniles started as recently as season 2019, we wait for those local birds to mature. Already, a few birds returned in their second year (or were just lingering around).

Code: n[F|G].
Code: n[F|L].
Code: n[F|N].
Code: n[F.C].
metal ring De Kreupel.

WHAT IS THE DISPERSAL OF DUTCH JUVENILES

Already, several birds that were ringed at Lelystad and De Kreupel, were recorded outside the colonies. Some birds remained in the near vicinity of the colony (e.g. a bird recorded multiple times within 30 km's from Lelystad), but some birds proved to be more adventurous, flying to the U.K. and to Portugal.

To follow: a map showing arrows to recovery sites, of birds hatched in the Netherlands.