Larus cachinnans in the Netherlands
(last update: August 16, 2020)
Albert de Jong
Merijn Loeve
Roland-Jan Buijs
Thijs Horst
Leon Kelder
Mars Muusse
Cachinnans - Lelystad g-N|C & g-N|E (163-2025)
General remarks:
- Eggs: Volume measured by Stonehouse (1964) and Spaans & Spaans (1975), which make comparison possible with data from Texel (Camphuysen pers comm 16.04.2020).
- Nest 163 positioned on section "dam 1 blocks", in NW part, below (north) of nest 53. Confusion in 2023 about which parents belong to which nest.
- Nest 163-2024 next to Elderberry, called "nest Vliertje". In 2025 same location.
- ID uncertain in 2023: one parent is sub-adult Caspian Gull cachinnans. Finally, agreed upon chicks r-87 and r-88 belowng to nest 53.
- ID certain in 2024: male Caspian / Yellow-legged Gull michahellis type; female Caspian Gull cachinnans.
- ID certain in 2025, same birds as 2024. Male Caspian Gull cachinnans (type), now g-N|E; female Caspian Gull cachinnans, now g-N|C.
| nest | April 12th, 2024: 3 eggs clutch. | April 21st, 2024: 3 eggs clutch. | April 21st, 2024: red spot on boulder. |
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| nest | April 23 2025: 3 eggs (full clutch). | April 23 2025: 3 eggs (full clutch). | |
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| nest | May 13th, 2023: both parents are cachinnans. | April 21st, 2024: Caspian Gull incubating at "Vliertje". | . |
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| partner 1 | May 13th, 2023: adult cachinnans. | May 13th, 2023: adult cachinnans. | May 13th, 2023: adult cachinnans. |
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| partner 1 | May 02 2024: female Caspian Gull. | May 02 2024: female Caspian Gull. | May 02 2024: female Caspian Gull. |
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| partner 1 | April 28 2025: female Caspian Gull g-N|C. | April 28 2025: female Caspian Gull g-N|C. | April 28 2025: female Caspian Gull g-N|C. |
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| partner 2 | May 13th, 2023: sub-adult cachinnans. | May 13th, 2023: sub-adult cachinnans. | April 23rd, 2024: michahellis-type. |
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| partner 2 | May 02 2024: michahellis-type. | May 02 2024: michahellis-type. | May 02 2024: michahellis-type. |
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| partner 2 | April 28 2025: male Caspian Gull g-N|E. | April 28 2025: male Caspian Gull g-N|E. | April 28 2025: male Caspian Gull g-N|E. Broad black band. |
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| pullus | July 8th, 2023: weak juvenile r[8.7]. | July 15th, 2023: juvenile r[8.8]. | . |
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| pullus | June 18th, 2024: chick g-A|8. | June 18th, 2024: chick g-A|9. | May 7th, 2024: chick g-A|+. |
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| pullus | August 10 2025: chick g-R|S. | August 23 2025: chick g-T|P. | . |
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Visits and data 2023:
| egg sizes & volume 2023 | |
| SPECIES | NEST |
| cach x cach type | 163-2023 |
| 163-2023 | uncertainty about chicks: decision = nest 053. | |||
| dam: | dam 1 | |||
| location: | Blocks dam 1 - west section, under (north of) nest 53. | |||
| breeders: | cach x cach type | |||
| OBSERVATIONS: | ||||
| 11-05-2023 | pull | 2 chicks ringed. | ||
| 18-05-2023 | puli | R-87 was present | ||
| 27-05-2023 | pull | Low on N-side, found again r-87 & r-88 from nest 163 (or from 53)? See notes on tab 53. | ||
| 18-06-2023 | pull | r88 might be hybrid? Op blokken dam 1, west stuk, laag, op noord (dus wrschl niet van nest 53?), maar klimt omhoog. | ||
| 25-06-2023 | pull | r-88 and r-87 both present | ||
| 53-2023 / 163-2023 (likely 2 nests, but maybe all data for 1 pair only). | ||
| dam: | dam 1 blocks | |
| location: | is nest 53/110, same as 2021/2022. Later in season chicks ringed little north of this spot, but then no Caspians higher on dam. Same couple? | |
| breeders: | cach x cach | |
| OBSERVATIONS: | ||
| 26-4-2023 | nest: | Refreshed red stripe on block, nest is 1,5 m south of red stripe. |
| eggs: | 3x egg, measured. No water test. | |
| 11-5-2023 | nest: | 1 egg hatching, other 2 still complete, but many nests here. If this is the wrong nest, then maybe R-87 & R-88 from nest 163? In retrospect: yes, likely of 163. |
| 18-5-2023 | nest: | Empty, no chicks found. |
| 27-5-2023 | nest: | No shit at nest, no traces of chicks. Low on N-side, found again R-87 & R-88 from new nest number 163 (and likely not from 53)? |
| 18-6-2023 | pull: | R-88 might be hybrid? See nest 163 (which is north of 53), for details on R-8.7 and R-8.8. Present on N-side, but walks up to location nest 53! |
Visits and data 2024.
| NEST code | parent 1 | parent 2 | A_length | A_width | A_volume | B_length | B_width | B_volume | C_length | C_width | C_volume | TOTAL NEST: | |
| cach | 69,2 | 49,1 | 84,00 | 68,9 | 49,4 | 84,66 | 66,5 | 48,3 | 78,11 | 246,77 | |||
| 163-2024 | # eggs | A-egg | hatch | # ringed chicks | # all chicks | # fledged chicks | comments | ||||||
| 3 | 8-4-2024 | 3-5-2024 | |||||||||||
| dam: | dam 1 blocks | ||||||||||||
| location: | Blocks dam 1 - west section, under (north of) nest 53, near (east of) Elderberry near waterfront. | ||||||||||||
| parents? | same as 2023? | ||||||||||||
| ring pulli: | 09-May | ||||||||||||
| date | darvic | metal | location / nest# | species | sexe | age | wing | mass | head+ bill | bill | tarsus | gonys | greyscale |
| 07-05-2024 | g-A|8 | .5631241 | 163 | PONT | 1CY | 121 | |||||||
| 07-05-2024 | g-A|9 | .5631242 | 163 | PONT | 1CY | 75 | |||||||
| 07-05-2024 | g-A|+ | .5631243 | 163 | PONT | 1CY | 116 | |||||||
| OBSERVATIONS: | |||||||||||||
| 12-04-2024 | eggs: | 3 eggs, measured. Small eggs. | |||||||||||
| 21-04-2024 | eggs: | 3 eggs, not measured. | |||||||||||
| adult: | Caspian Gull incubating. | ||||||||||||
| 02-05-2024 | eggs: | 3 eggs. | |||||||||||
| adult: | female Caspian Gull. Male much black on P10 and P8, broad band on P5, with dark iris, red orbital and gape. | ||||||||||||
| 07-05-2024 | chicks: | 3x ringed. | |||||||||||
| 18-06-2024 | chicks: | 3x present: g-A|8, gA|9 & g-A|+. | |||||||||||
Visits and data 2025 for nest g-N|C & g-N|E (163).
| 2025 | parent 1 | parent 2 | A_length | A_width | A_volume | B_length | B_width | B_volume | C_length | C_width | C_volume | TOTAL NEST:
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# eggs | |
| g-N|C & g-N|E | cach | cach | 70,6 | 47,8 | 70 | 49,6 | 69,8 | 49 | 3 | |||||
| (163) | ||||||||||||||
| dam: | dam 1 blocks | |||||||||||||
| location: | nest 163 "Vliertje", at blocks west part, close to waterfront, next to Elderberry. | |||||||||||||
| parents: | same as 2024, this year both parents ringed, now g-N|C and g-N|E.
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| ringed: | ||||||||||||||
| date | darvic | metal | location / nest# | species | sexe | age | wing | mass | head+ bill | bill | tarsus | gonys | greyscale | |
| 28-04-2025 | g-N|C | 5641012 | 163, vliertje | PONT | F | >4CY | 439 | 859 | 124,6 | 55,1 | 67,8 | 18 | 5,5 | |
| 28-04-2025 | g-N|E | 6254554 | 163, vliertje | PONT | M | >4CY | 465 | 1128 | 128,7 | 61,4 | 70,3 | 20,1 | 5 | |
| 13-05 | g-T|N | 5641083 | 163 | PONT | pullus | 537 | ||||||||
| 13-05 | g-T|P | 5641084 | 163 | PONT | pullus | 453 | ||||||||
| 31-05 | g-T|P | g-N|C & g-N|E | PONT | 819 | ||||||||||
| 31-05 | g-R|S | 5641913 | g-N|C & g-N|E | PONT | pullus | 787 | Herring Gull?
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| 09-06-2025 | g-R|S | 5641913 | g-N|C & g-N|E | PONT | pullus | 758 | CONTROL | |||||||
OBSERVATIONS:
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| 23-04-2025 | eggs | 3 eggs, measured.
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| adult | female cachinnans.
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| 28-04-2025 | eggs | 2x eggs hatching.
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| adult | 2x cachinnans trapped on nest now g-N|C and g-N|E.
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| 01-05 | adult | g-N|E present.
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| 13-05 | chicks | 2x chicks ringed, 3rd not found.
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| 31-05 | chicks | retrapped g-T|P.
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| 09-06-2025 | chicks | g-R|S found and measured, g-T|P near nest 139 on blocks.
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| Conlusion: g-T|P & g-R|S fledged, g-T|N not seen after ringing.
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