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|5 & g-N|S (014-2025)
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 014 positioned at breakwater 2. Same spot throughout years 2020-2023.
- ID certain in 2020, both parents are Caspian Gull cachinnans.
- ID certain in 2021, both parents are the same as previous year, Caspian Gull cachinnans.
- ID certain in 2022, both parents are the same as previous year, Caspian Gull cachinnans.
- ID certain in 2023, both parents are the same as previous year, Caspian Gull cachinnans.
- In 2024 nest not used.
- In 2025: Caspian Gulls. Male ringed in 2025, now g-M|5. Female ringed in 2025, now g-N|S.
| location | Nest location on April 15th, 2020. | April 16th, 2021. | April 26th, 2021: female on block. |
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| location | April 9th, 2023: location. | April 23 2025: nest 14, aka "Red Rope". | July 09 2025: nest 14 with g-M|5 & g-N|S. |
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| nest | April 15th, 2020: 3 egg clutch. | April 15th, 2022: 3 egg clutch. | April 9th, 2023: first egg. |
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| nest | April 23 2025: 3 eggs (full clutch). | . | . |
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| partner 1 | April 27th, 2020: cachinnans. | April 27th, 2020: cachinnans. | April 16th, 2021: P9 with thin band. |
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| partner 1 | April 16th, 2021. | April 11th, 2022: male is cachinnans. | April 11th, 2022: male is cachinnans. |
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| partner 1 | April 12th, 2022: male is cachinnans. | April 27th, 2022: male is cachinnans. | April 26 2024: Caspian Gull male. |
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| partner 1 | April 26 2024: Caspian Gull male guarding. | April 25 2025: Caspian male, now g-M|5. Mirror on P8. | May 08 2025: Caspian Gull male g-M|5. |
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| partner 2 | May 7th, 2020: cachinnans. | May 7th, 2020: cachinnans. | April 26th, 2021: female cachinnans. |
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| partner 2 | April 26th, 2021: female cachinnans. | April 26th, 2021: P9 with broad band. | April 29th, 2022: female cachinnans. |
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| partner 2 | April 29th, 2022: female cachinnans. | April 29th, 2022: female cachinnans. | April 27th, 2023: female cachinnans. |
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| partner 2 | May 13th, 2023: female cachinnans. | April 26 2024: Caspian Gull female. | April 26 2024: Caspian Gull female. |
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| partner 2 | April 26 2024: Caspian Gull female. | May 01 2025: female ringed, now g-N|S. | May 05 2025: Caspian Gull female g-N|S. |
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| pullus | May 21st, 2020 pullus n[F|=]. | May 21st, 2020 pullus n[F|+]. | June 8th, 2021: female with chick. |
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| pullus | June 26th, 2021: pullus r[F.L] | June 26th, 2021: pullus r[F.M] | June 26th, 2021: pullus r[F.N] |
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| pullus | May 9th, 2022: pullus r[C.T]. | May 9th, 2022: pullus r[C.U]. | May 17th, 2022: pullus r[5.2]. |
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| pullus | May 11th, 2023: pullus r[7.=]. | May 11th, 2023: pullus r[8.U]. | May 11th, 2023: pullus r[8.X]. |
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| pullus | May 13 2025: chick g-T|R. | May 13 2025: chick g-T|S. | . |
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Visits and data 2020.
Estimation egg laying: A-egg = April 09 2022. Estimating hatching = May 07 2022.
| datum: | egg no: | width (mm) | length (mm) | volume (cm3): | water test on April 27th: | |
| 15-04-2020 | A | 50,5 | 76,9 | 98,74 | 35 - tip on bottom | 3 eggs in nest. |
| B | 50,4 | 77,2 | 98,74 | 25 - tip on bottom | ||
| C | 50,4 | 71,8 | 91,83 | 15 - tip on bottom | ||
| sum nest: | 289,31 | |||||
| 27-04-2020 | Certainty about parents, cachinnans. | |||||
| 21-05-2020 | pullus | Nest empty, with fish. 2 chicks ringed. n[F|=]. | ||||
| pullus | Nest empty, with fish. 2 chicks ringed. n[F|+]. | |||||
| 02-06-2020 | pulli | n[F|=] together with large juvenile, so nest with 3 juveniles fledged? | ||||
| Visits and data 2021. | ||||||
| egg no: | width (mm) | length (mm) | volume (cm3): | water test on April 27th: | ||
| 16-04-2021 | A egg | 52,2 | 73,9 | 101,39 | 40 - tip on bottom | 3 eggs. |
| B egg | 51,2 | 73,7 | 97,28 | 40 - tip on bottom | ||
| C egg | 50,2 | 68,7 | 87,17 | 30 - tip on bottom | ||
| 26-04-2021 | Partner 1 at blocks in front of nest. Seemingly same parents as last year. | |||||
| 15-05-2021 | 3 eggs. (in retrospect: we should have checked for presence of letters on the eggs. Was this the still the same brood as on April 26th?) | |||||
| 28-05-2021 | 2 eggs + 1 chick (1 day old). What has been the breeding period for these eggs??? Was there a rapid 2nd attempt in late April??? | |||||
| Female at nest, but P10 slightly ackward for pure cachinnans? (probably wrong bird?) | ||||||
| 08-06-2021 | Male is cachinnans. | |||||
| Female appears at blocks with one chick. | ||||||
| metal | tibia | mass | head + bill | wing | ||
| 26-06-2021 | .5550684 | r-F.L | 859 | 111,7 | 264 | cachinnans |
| .5550685 | r-F.M | 948 | 112,8 | 252 | cachinnans | |
| .5550686 | r-F.N | 912 | 112,2 | 228 | cachinnans | |
| Visits and data 2022. | ||||||
| 11-04-2022 | adult near nest. | |||||
| egg no: | width (mm) | length (mm) | volume (cm3): | water test on April 27th: | ||
| 15-04-2022 | A egg | 51,7 | 70 | -- | 10 - tip on bottom | 3 eggs. |
| B egg | 51,7 | 76,7 | -- | 30 - tip on bottom | ||
| C egg | 51,7 | 72,1 | -- | 20 - tip on bottom | ||
| 19-04-2022 | guarding adult on block. | |||||
| 29-04-2022 | A egg | float - 1 mm | ||||
| B egg | float - 2 mm | |||||
| C egg | float - 1 mm | |||||
| metal | tibia | mass | head + bill | wing | ||
| 09-05-2022 | 5625068 | r-C.T | cachinnans | |||
| 5625069 | r-C.U | cachinnans | ||||
| 1 egg, hatching soon (A-egg). | ||||||
| metal | tibia | mass | head + bill | wing | ||
| 17-05-2022 | 5625069 | r-C.U | 363 | -- | cachinnans | |
| 5625136 | r-5.2 | 206 | 69,7 | cachinnans | ||
| 30-05-2022 | from the boat one ringed chick visible, not found back later between blocks. | |||||
| 17-06-2022 | two ringed chicks present, possibly 3rd as well, but not seen. | |||||
| 21-06-2022 | r-52 swimming, together with r-54 (from nest y-X56A). R-CU & r-CT not seen. | |||||
| 21-06-2022 | Later this day: now r-52 swimming in creche with another 3 juveniles, including r-CU. Not all legs visible, to check for rings. | |||||
| 17-07-2022 | r-52 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 | 14-2023 | 73,9 | 50,7 | 95,64 | 75,8 | 51 | 99,27 | 68 | 50,2 | 86,28 | 281,19 | same as 2022 |
| ring pulli: 14-mei | laying A egg: 9-apr | hatch A egg: 7-mei | ||||||||||
| catch: | date: | metal: | darvic: | |||||||||
| Pullus | 11-05-2023 | NLA5556459 | r-7.= | |||||||||
| Pullus | 11-05-2023 | NLA5556460 | r-8.U | |||||||||
| Pullus | 11-05-2023 | NLA5556461 | r-8.X | |||||||||
| 14-2023 | |||||||
| dam: | dam 2 central | ||||||
| location: | "14" code strayed on stone. Is nest 14-2020/2022 | ||||||
| breeders: | cach x cach | ||||||
| OBSERVATIONS: | |||||||
| 09-04-2023 | nest: | 1 egg measured. No watertest. | |||||
| 26-04-2023 | nest: | 3 eggs measured, and water test | A: floating - 1 mm | ||||
| adult: | alarming parent | B: floating - halfway | |||||
| 27-04-2023 | adult: | Male cach at nest. Female guarding | C: floating - 0 mm | ||||
| 11-05-2023 | pulli: | 3 chicks ringed | |||||
| 13-05-2023 | adult: | male dark eye, no black P4. Female pale eye, black on P4. | |||||
| 27-05-2023 | nest: | no alarming adults, no chicks found. Nest failed apparently. | |||||
Visits and data 2024.
| 014-2024 | |||||||||||||
| dam: | dam 2 central, code on block. | ||||||||||||
| location: | all in the open, obvious spot for years | ||||||||||||
| parents? | Not settled yet. | ||||||||||||
| OBSERVATIONS: | |||||||||||||
| 21-04-2024 | eggs: | nest empty. Location used by r-6L to rest. Sometimes adult cach present. | |||||||||||
| 26-04-2024 | adults: | 2x adult Caspian Gull at nest site. | |||||||||||
| 07-05-2024 | nest: | empty. | |||||||||||
Visits and data 2025 nest g-M|5 & g-N|S (014).
| 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:
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| g-M|5 & g-N|S (14) | cach | cach | 72,2 | 48,7 | 70,1 | 49,7 | 68,8 | 48 | 3 | |||||
| dam: | dam 2 central
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| location: | nest 14 2020-2024
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| ouders: | new, both Caspian Gulls trapped this season and ringed. | |||||||||||||
| ringed: | ||||||||||||||
| date | darvic | metal | location / nest# | species | sexe | age | wing | mass | head+ bill | bill | tarsus | gonys | greyscale | |
| 25-04-2025 | g-M|5 | 5641006 | 14 | PONT | M | >4CY | 459 | 1249 | 143,2 | 65,6 | 73,1 | 20,4 | ||
| 01-05-2025 | g-N|S | 5641022 | 14 red rope | PONT | F | >4CY | 440 | 906 | 122,1 | 77,7 | 65,7 | 17,4 | 6 | 25B00658
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| 13-05-2025 | g-T|R | 5641090 | 14 red rope | PONT | pullus | 115 | ||||||||
| 13-05-2025 | g-T|S | 5641091 | 14 red rope | PONT | pullus | 210 | ||||||||
OBSERVATIONS:
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| 23-04-2025 | nest | 3 eggs, measured.
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| 25-04 | adult | male cachinnans trapped on nest, now g-M|5.
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| 01-05 | adult | female cachinnans trapped in nest, now g-N|S.
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| 08-05 | adult | both partners present.
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| 13-05 | chicks | 2x chicks ringed, 3rd not found.
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| food | both chicks, vomit is fish bolus. Eventually, chicks not fledged. Failed season.
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