Larus cachinnans in the Netherlands
(last update: August 16, 2020)
Albert de Jong
Leon Kelder
Roland-Jan Buijs
Thijs Horst
Merijn Loeve
Mars Muusse
Cachinnans - nest Lelystad g-M|= (017B-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 17B positioned high on breakwater dam 2, within dense Blackberry vegetation. In 2022: code 17B sprayed again on the block.
- ID certain in 2021, one parent photographed, characteristics match pure Caspian Gull cachinnans.
- ID certain in 2022, both parents are Caspian Gull cachinnans.
- ID certain in 2023, Caspian Gull cachinnans are same as in 2022.
- ID certain in 2024, both Caspian Gull cachinnans are same as in 2022/23.
- ID certain in 2025, both Caspian Gull cachinnans are same as in 2022-24. Male ringed in 2025, now g-M|=.
| location | Nest location April 24th, 2021. | April 29th, 2022: nest (from north). | . |
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| eggs | April 29th, 2022: full clutch, nest with 3 eggs. | April 9th, 2023: full clutch, nest with 3 eggs. | April 21st, 2024: full clutch, nest with 3 eggs. |
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| partner 1 | April 24th, 2021: cachinnans female. | April 19th, 2022: cachinnans female. | April 19th, 2022: cachinnans female. |
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| partner 1 | May 13th, 2023: cachinnans female. | May 13th, 2023: cachinnans female. | April 23rd, 2024: cachinnans female. |
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| partner 1 | May 02 2024: same female cachinnans as 2023. | May 02 2024: same female cachinnans as 2023. | April 23rd, 2024: cachinnans female. |
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| partner 1 | April 25 2025: female Caspian Gull. | April 25 2025: female Caspian Gull. | April 25 2025: female Caspian Gull. |
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| partner 2 | May 1st, 2022: cachinnans male. | April 19th, 2022: cachinnans male. | May 1st, 2022: cachinnans male. |
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| partner 2 | May 13th, 2023: "dark eyed" cachinnans male. | May 13th, 2023: "dark eyed" cachinnans male. | May 02 2024: same male cachinnans as 2023. |
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| partner 2 | May 02 2024: same male cachinnans as 2023. | May 02 2024: same male cachinnans as 2023. | April 28 2025: male cachinnans, now g-M|=. |
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| chicks | May 9th, 2022: pullus r[C.V]. | May 9th, 2022: pullus r[C.W]. | May 11th, 2023: pullus r[8.G]. |
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| chicks | August 2nd, 2023: chick r[8.R]. | June 18th, 2024: g-A|K. | May 31st, 2024: g-A|L. |
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| chicks | July 09 2025: chick g-R|H. Fledged. | July 09 2025: chick g-R|J. Fledged. | . |
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| food: | May 14th, 2024: fish bolus of chick g-A|L. | . | . |
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Visits and data 2021:
| date: | ||||||||
| 24-04-2021 | Patrolling adult and landing at location. We did not climb the dam to search. | |||||||
| 06-05-2021 | No bird present. | |||||||
| 15-05-2021 | No bird present. | |||||||
| 28-05-2021 | No visit. | |||||||
| 26-06-2021 | No visit. | |||||||
| Visits and data 2022: Estimation egg laying: A-egg = April 08 2022. Estimating hatching = May 06 2022. |
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| 15-04-2022 | A egg | 68,1 | 50,4 | tip bottom - 40 | 2 blue eggs. | |||
| B egg | 65,6 | 49,7 | tip bottom - 40 | |||||
| C egg | 68,7 | 50,6 | tip bottom - 40 | |||||
| 19-04-2022 | 2 parents present at nest. | |||||||
| 29-04-2022 | A egg | float - 1 mm | ||||||
| B egg | float - 1 mm | |||||||
| C egg | float - 1 mm | |||||||
| 01-05-2022 | female is cachinnans. | |||||||
| 09-05-2022 | pullus | r-C.V | NLA 5625070 | |||||
| pullus | r-C.W | NLA 5625071 | ||||||
| pullus | -- | NLA 5625072 | pullus too small for plastic. | |||||
| colour | metal | mass | wing | head + bill | bill | |||
| 17-05-2022 | pullus | r-C.V | NLA 5625070 | 257 | ||||
| 30-05-2022 | pullus | r-C.V | NLA 5625070 | 615 | 175 | 95,1 | 39,3 | |
| food: fish is Roach | ||||||||
| 02-06-2022 | male alarming. | |||||||
| 17-06-2022 | No birds near nest, r-CW flying around at north side. | |||||||
| 21-06-2022 | No activities near nest, r-CV & r-CW & 3rd chick (only mmetal?) swimming at north side. If so, then 3x chicks fledged from this nest. | |||||||
| 12-07-2022 | R-CV & r-CW photographed. | |||||||
| 17-05-2022 | R-CW photographed. | |||||||
| egg sizes & volume 2023 | ||||||||||||
| SPECIES | NEST | A_length | A_width | A_volume | B_length | B_width | B_volume | C_length | C_width | C_volume | TOTAL NEST: | known parents? |
| cach x cach | 17B-2023 | 67,8 | 50,4 | 86,71 | 69,2 | 48,5 | 81,96 | 68 | 51,3 | 90,10 | 258,78 | same as 2022 |
| ring pulli: 10-mei | laying A egg: 5-apr | hatch A egg: 3-mei | ||||||||||
| catch: | date: | metal: | darvic: | mass: | wing: | head+bill: | ||||||
| Pullus | 11-5-2023 | NLA 5556462 | r-8.G | -- | -- | -- | ||||||
| Pullus | 11-5-2023 | NLA 5556463 | r-8.R | -- | -- | -- | ||||||
| Pullus | 27-5-2023 | NLA 5556462 | r-8.G | dead >7 days ago | ||||||||
| Pullus | 18-6-2023 | NLA 5556463 | r-8.R | 1133 | 356 | 131,9 | ||||||
| 17B-2023 | ||
| dam: | dam 2 central | |
| location: | on S-side "17B" coded on block, path to top of dam, in Blackberry complex. | |
| breeders: | cach x cach | |
| OBSERVATIONS: | ||
| 04-04-2023 | adult: | 2 cach present. |
| 09-04-2023 | adult: | 2 cach present. |
| nest: | Nest with 3 eggs. No watertest, ring chicks in 1st session. | |
| 26-04-2023 | adult: | 1 cach present. |
| nest: | 3 eggs. Not measured. | |
| 11-05-2023 | pulli: | 2 chicks ringed, is there a 3rd chick? |
| 13-05-2023 | adult: | pair present, same as 2022. Female spot on P10. Male dark eye. |
| 18-05-2023 | nest: | nest empty, no chicks found. |
| 27-05-2023 | pulli: | dead chick near nest: r-8G. |
| 18-06-2023 | nest: | no birds present. R-8R trapped in water with net & measured. Fledged: 1 chick. |
| 25-06-2023 | pulli: | r-8R present. |
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 | cach | 69,4 | 50,6 | 89,47 | 65,9 | 51 | 86,30 | 65 | 49 | 78,58 | 254,35 | ||
| 017B-2024 | # eggs | A-egg | hatch | # ringed chicks | # all chicks | # fledged chicks | comments | ||||||
| 3 | 17-4-2024 | 15-5-2024 | |||||||||||
| dam: | dam 2 central | ||||||||||||
| location: | 17B-2021, 2022, 2023 | ||||||||||||
| parents? | Same birds | ||||||||||||
| ring pulli: | 21-May | ||||||||||||
| date | darvic | metal | location / nest# | species | sexe | age | wing | mass | head+ bill | bill | tarsus | gonys | greyscale |
| 02-05-2024 | g-A|K | .5631214 | nest 17B | PONT | 1CY | 63 | |||||||
| 02-05-2024 | g-A|L | .5631214 | nest 17B | PONT | 1CY | 63 | |||||||
| 14-05-2024 | g-A|L | .5631215 | nest 17B | PONT | 1CY | 409 | CONTROLL | ||||||
| OBSERVATIONS: | |||||||||||||
| 21-04-2024 | eggs: | 3 eggs, measured. | |||||||||||
| 02-05-2024 | eggs: | 1x blue egg. | |||||||||||
| chicks: | 2x chick ringed: g-A|K & g-A|L. | ||||||||||||
| 05-05-2024 | chicks: | blue egg gone, but only 2x ringed chicks found in vegetation. | |||||||||||
| 14-05-2024 | chicks: | g-A|L is 409 gr. CONTROLL. | |||||||||||
| food: | Bolus: fish. | ||||||||||||
| 31-05-2024 | chick: | g-A|L at nest. | |||||||||||
| 04-06-2024 | nest: | no chick found. | |||||||||||
| 18-06-2024 | chicks: | g-A|K & g-A|L at water, and maybe the 3rd chick as well. Fledged: "at least" 2 chicks, likely 3 chicks. | |||||||||||
Visits and data 2025 g-M|= (17B).
| 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-M|= (17B) | cach | cach | 68 | 50 | 65 | 50 | 63 | 50,6 | 3 | |||||
| dam: | dam 2 central
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| location: | 17B, same nest as in 2021-2024
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| parents: | this season managed to trap male, now g-M|=. | |||||||||||||
| ringed: | ||||||||||||||
| date | darvic | metal | location / nest# | species | sexe | age | wing | mass | head+ bill | bill | tarsus | gonys | greyscale | |
| 28-04-2025 | g-M|= | 6254498 | 17B | PONT | M | >4CY | 454 | 1107 | 140 | 62 | 74,1 | 21 | 6 | |
| 31-05-2025 | G-R|H | 5641899 | on water | PONT | pullus | 704 | 116 | |||||||
| 31-05-2025 | G-R|J | 5641900 | on water | PONT | pullus | 837 | 113,9 | |||||||
OBSERVATIONS:
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| 16-03-2025 | nest | 2x cach at nest location 2021-2024. | ||||||||||||
| 20-03 | nest | 2x cach present.
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| 01-04 | nest | 2x cach present.
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| 21-04 | eggs | 3x eggs measured.
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| adult | attempt to trap breeding adult, failed.
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| 28-04 | nest | 2x eggs hatching.
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| adult | male cachinnans trapped on nest, now g-M|=.
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| 08-05 | adult | both partners present.
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| 31-05 | chicks | g-R|H & g-R|J trapped on water around X60J in a group of juveniles; X60J and g-A|B alarming above (but X60J alarming a lot). | ||||||||||||
| 09-07-2025 | chick | g-R|H caught on water, but was resting at nest 17B with ringed brother (likely g-R|J but uncertain) and unringed mother.
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