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 - nest Lelystad 053
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 053 positioned on artificial breakwater dam 1, nest between large blocks. Many Lesser Black-backed Gulls here, and all nests hidden between blocks, invisible from the canoe.
Nest is 25 meters east of T-split, approx position of michahellis-outlook. Nest flagged with '053' in 2021-2023. - Full clutch at early date in 2021 + pattern on eggs were indication for cachinnans. Both pulli photographed as juveniles raising suspicion towards hybrid ID.
- ID in 2021 uncertain: probably 2 parents are cachinnans.
- ID in 2022 uncertain: one parent is same cachinnans as in 2021.
- ID in 2023 uncertain: one parent is same cachinnans as in 2021.
| location: | April 16th, 2021: nest between blocks. | April 16 2021: Albert plotting nest. | April 26 2021: michahellis at look-out. |
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| April 15th, 2022: nest between blocks, 3 eggs. | April 15th, 2022: which are the parents??? | April 15th, 2022: temporarily coded "110". | |
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| nest: | May 15 2021: cachinnans-like 2 eggs. | May 15 2021: fuscus-like 3 eggs. | May 15 2021: confusing nests at close range. |
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| partner 1: | May 15 2021: cachinnans is one of the parents? | May 15 2021: fuscus-breeder next to 53 flag. | April 19th, 2022: cachinnans is one of the parents? |
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| pullus | May 28th, 2021 pullus r[F.A]. | May 28th, 2021 pullus b[F|=]. | . |
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| May 17th, 2022 pullus r[5.N]. | May 17th, 2022 pullus r[5.P]. | May 30th, 2022 pullus r[7.D]. | |
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| juvenile | August 22nd, 2021 juvenile r[F.A]. | December 19th, 2021 pullus b[F|=]. | July 12th, 2022: 3 juveniles fledged in 2022. |
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Visits and data.
| date: | ||||||
| 16-04-2021 | Nest checked. 3 eggs. | |||||
| egg no: | width (mm): | length (mm): | volume (cm3): | water test on April 24th: | laying date: | |
| A | 49,2 | 70 | 85,32 | 30 - tip bottom | ||
| B | 50,6 | 67,1 | 86,50 | 15 - tip bottom | ||
| C | 50,3 | 70,1 | 89,30 | 35 - tip bottom | ||
| sum nest: | 261,12 | |||||
| 24-04-2021 | Michahellis present. | |||||
| 26-04-2021 | Michahellis present, but is this the exact location of nest 53? Flag has fallen down. | |||||
| 06-05-2021 | 2 cachinnans at this location, but flag has fallen down, no exact position determined from water. | |||||
| 13-05-2021 | No visit, Camilla is trapping a Spoonbill. | |||||
| 15-05-2021 | 3 eggs in nest near flag, with brownish pattern, resembling LBBG-eggs. Was this measured on May 6th? 1,5 meters east another nest, 2 bluish eggs, more like cachinnans. | |||||
| Landing adult cachinnans at this nest photographed; LBBG near flag 53 photographed. | ||||||
| 28-05-2021 | Two pulli ringed. | |||||
| metal ring | darvic ring | head + bill | age | |||
| pullus | .5559425 | b-F|= | 52,8 | age: 2 / 3 days old | ||
| pullus | .5559426 | r-F.A | 50,8 | age: 2 / 3 days old | ||
| egg: just hatching. | ||||||
| 8-6-2021 | No visit. | |||||
Visits and data 2022 for nest 53 (coded 110 in 2022):
Estimation egg laying: A-egg = April 9 2022. Estimating hatching = May 7 2022.
| length (mm) | width (mm) | volume (cm3): | water test on April 15th: | ||||
| 15-04-2022 | A egg | 67,8 | 50,3 | -- | 20 gr - tip bottom | ||
| B egg | 68,8 | 49 | -- | 20 gr - tip bottom | |||
| C egg | 69,8 | 50,9 | -- | 30 gr - tip bottom | |||
| Code "110" sprayed on block. Within 10 minutes afetr leaving, 4 (!) cachinnans at this spot. | |||||||
| length (mm) | width (mm) | volume (cm3): | water test on April 27th: | ||||
| 27-04-2022 | A egg | -- | -- | -- | 3 mm - floating | ||
| B egg | -- | -- | -- | 3 mm - floating | |||
| C egg | -- | -- | -- | 1 mm - floating | |||
| 17-05-2022 | Ringing chicks (chicks are approx 8 days old): sub-adult cachinnans attacks us. Is this parent 2? Adult cachinnans present too. | ||||||
| metal | darvic | mass | |||||
| pullus | NLA 5625112 | r-5P | 180 | ||||
| pullus | NLA 5625113 | r-5N | 219 | ||||
| metal | darvic | mass | wing | H+B | bill | ||
| 30-05-2002 | pullus | NLA 5625187 | r-7D | 734 | 175 | 97,8 | 39,9 |
| Check: really pullus from this nest? | |||||||
| One adult cachinnans is guarding near chicks = parent 1. But 3 more cachinnans present; likely nest 110 and 113 combined. | |||||||
| 21-06-2022 | r-7D and r-5P and one unringed chick (sibling?) swim near nest 109. Also stand on blocks. | ||||||
| 28-06-2022 | r-7D and r-5N picture. | ||||||
| 28-06-2022 | r-7D and r-5P picture. All 3 ringed chicks have fledged. | ||||||
| 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 | 53-2023 | 73,4 | 48,7 | 87,65 | 68,6 | 48,5 | 81,25 | 68,3 | 47,7 | 78,25 | 247,14 | same as 2022 |
| ring pulli: -- | laying A egg: -- | hatch A egg: -- | ||||||||||
| 53-2023 | ||
| dam: | dam 1 blocks | |
| location: | is nest 53/110, same as 2021/2022 | |
| 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 nest 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. |