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 015
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 015 positioned at breakwater 2, just west of nest 017 (which has a huge mark on a block), hidden behind small prunus (avium?).
- ID uncertain in 2020, on April 27th, a bird took off the nest with much black on P10 and broad band on P5. This is partner 1 (female). Partner 2 is cachinnans.
- ID 2021: male 2021 is same male 2020. Also female 2021 is same as female 2020.
- ID 2022: male cachinnans is the same bird as previous years. Female is Herring Gull argenteus.
- ID 2023: male cachinnans is the same bird as previous years. Female is Herring Gull argenteus.
| location | Nest on May 7th, 2020. | Eggs April 15th, 2020: 3 egg clutch. | May 13th, 2021 guarding cachinnans and michahellis (nest45). |
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| location | April 16th, 2021. | Eggs April 16th, 2021: 3 egg clutch. | May 15th, 2021: 1 cold egg & Roach (or Rudd hybrid). |
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| May 30th, 2022: again nest behind prunus. | May 30th, 2022: 3 eggs. | ||
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| partner 1 | May 7th, 2020: P9-P10 pattern diagnostic. | May 7th, 2020: Caspian Gull type. | May 13th, 2021: Caspian Gull type. |
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| partner 1 | May 13th, 2021: Caspian Gull type. | May 13th, 2021: P9-P10 pattern diagnostic. | April 4th, 2023: mixed pair present. |
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| partner 2 | May 7th, 2020. | May 7th, 2020. | . |
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| partner 2 | April 26th, 2021: guarding female and male has a look too. | April 26th, 2021. | April 26th, 2021. |
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| partner 2 | May 30th, 2022: male cachinnans. | May 30th, 2022: male cachinnans. | . |
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| pullus | May 28th, 2021: b[F|M]. | May 28th, 2021: b[F|N]. | June 21st, 2022: 2 unringed chicks (but H5N1 restrictions). |
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| July 15th, 2023: unringed hybrid juvenile. | . | . | |
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Visits and data.
| date: | ||||||
| egg no: | width (mm) | length (mm) | volume (cm3): | water test on April 27th: | ||
| 15-04-2020 | A | 51,5 | 70,6 | 94,28 | 90 - floating, 3mm above surface | |
| B | 51,8 | 72,1 | 97,41 | 90 - floating, 3mm above surface | ||
| C | 50,7 | 70,2 | 90,86 | 90 - floating, 3mm above surface | ||
| sum nest: | 282,54 | |||||
| 27-04-2020 | One parent with much black on P10 and broad band on P5. | |||||
| 21-05-2020 | pullus | Failed nest. No pulli, no shit, no food left-overs. | ||||
| 16-04-2021 | egg no: | width (mm) | length (mm) | volume (cm3): | water test on April 16th: | red flag 15 placed near nest. |
| A egg | 52,6 | 70,6 | 98,35 | 50 - tip bottom | ||
| B egg | 51 | 72 | 94,29 | 40 - tip bottom | ||
| C egg | 50,5 | 74,5 | 95,66 | 35 - tip bottom | ||
| sum nest: | 288,30 | |||||
| 24-04-2021 | 2 eggs. | 1 adult at blocks, guarding from look-out. | ||||
| 26-04-2021 | Herring Gull tolerated on block in front of nest. Probably Herring from nest 15B. | |||||
| Also, female on look-out and male leaves the nest for a short break or to check everything is okay. | ||||||
| 13-05-2021 | Female often on look-out block close to block 17, raising confusion if this is the partner of nest 17. | |||||
| 15-05-2021 | 1 egg cold, unfertile. Measurements Monika Ballmann: 73.2x50.4 (probably labeled C-egg in April) | |||||
| 2 chicks present in nest: Mass = 232 gr & Mass = 193 gr. | ||||||
| Food in nest: Roach (this is often a fishermen's by-catch from traps 200 meters from the nest). | ||||||
| 28-05-2021 | metal | tibia | mass | head + bill | 2 chicks ringed. | |
| pullus | .5559385 | b-F|M | 707 | 86,3 | ||
| pullus | .5559386 | b-F|N | 730 | 93,7 | ||
| 08-06-2021 | Both pulli swimming 100 meters from waterfront, right between dams with large bulkships approaching. Protected by 1 parent, made their way back to dam 2. | |||||
| 26-06-2021 | Nest abandoned. | |||||
Visits and data 2022:
Estimation egg laying: A-egg = ?. Estimating hatching = June 07 2022.
| date: | ||||||
| egg no: | width (mm) | length (mm) | volume (cm3): | water test on April 27th: | ||
| 30-05-2022 | A | 47,6 | 67 | 90 - floating, 3mm above surface | ||
| B | 47,5 | 64 | 90 - floating, 3mm above surface | |||
| C | 47,8 | 65,9 | 90 - floating, 3mm above surface | |||
| sum nest: | -- | |||||
| 30-05-2022 | Adults: Herring Gull female and Caspian Gull male. | |||||
| 17-06-2022 | Adult Caspian Gull male present. | |||||
| 21-06-2022 | At least 2x unringed chicks present at nest site. No ringing anymore (H5N1 restrictions this year). | |||||
| 17-07-2022 | At bread near nest (from the boat) several unringed birds in a flock, including rings from nest 14. No doubt, some are the offspring of nest 15. | |||||
| 17-07-2022 | Adult Caspian Gull male is defending. | |||||
| 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 teus | 15-2023 | 67,3 | 49,2 | 82,02 | 68,3 | 47,2 | 76,61 | 65,4 | 47,4 | 73,98 | 232,62 | same as 2022 |
| ring pulli: 12-jun | laying A egg: 8-mei | hatch A egg: 5-jun | ||||||||||
| 15-2023 | ||
| dam: | dam 2 central | |
| location: | Between prunus trees, between 48 and 17. Near waterfront. | |
| breeders: | cach x teus | |
| OBSERVATIONS: | ||
| 09-04-2023 | nest: | no eggs, nest is ready. Male cachinnans with broken P5 band. |
| 26-04-2023 | nest: | empty. |
| 30-04-2023 | nest: | empty. |
| 11-05-2023 | nest: | 3 eggs, measured. |
| 18-05-2023 | nest: | 3 eggs. |
| 27-05-203 | nest: | 3 eggs. Late nest, (this year again) the hybrid chicks will not be ringed probably. |
| 25-06-2023 | Pulli: | 1 large chick present, at least 1 nearly fledged (not classified as fledged yet). |