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 035 / w-327:U (2023)
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 035 positioned at breakwater 1 east of nest 28 (5 meters). Code added to lookout block of parent.
- ID certain in 2020, both parents are Caspian Gull cachinnans.
- ID certain in 2021, same two parents, Caspian Gull cachinnans.
- 2022: only late in the season a nest was found at this location, with a bulky adult male Caspian Gull. Exact spot of nest 35-2020 / 35-2021. Caspian is partner 2 (male) of 2020 and 2021.
Temporarily, we labeled the nest "141", although we suspected it to be the same male as 35-2021, but now it is a mixed pair with Herring Gull female.
Late in the season (June 21st, 2022) we saw hybrid offsprings (2 juveniles), which were not ringed (Avian flu H5N1 kept us from ringing after May 30th). - 2023: same male Caspian Gull as previous years. Early in season suspected to be paired with Herring Gull, but more likely with w-327:U.
| location | April 16th, 2021: partners near nest. | April 16th, 2021: partners near nest. | May 4th, 2022: Caspian male is breeding. |
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| May 4th, 2022: nest markings is 141. | May 4th, 2022: nest markings. | April 9th, 2023: nest markings. | |
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| eggs | April 27th, 2020: 3 eggs clutch. | April 16th, 2021: 2 eggs clutch. | May 4th, 2022: 3 eggs clutch. |
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| April 9th, 2023: 3 eggs clutch, early nest. | April 9th, 2023: adult male Caspian Gull. | . | |
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| partner 1 | May 7th, 2020: cachinnans female. | May 7th, 2020: cachinnans female. | May 7th, 2020: cachinnans female. |
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| April 16th, 2021: cachinnans female. | April 16th, 2021: cachinnans female. | April 26th, 2021: cachinnans male. | |
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| partner 1 | May 30th, 2022: female Herring Gull argenteus. | May 30th, 2022: female Herring Gull argenteus. | May 30th, 2022: female Herring Gull argenteus. |
| 2022: Herring |  |
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| June 21st, 2022: female Herring Gull argenteus. | June 21st, 2022: female Herring Gull argenteus. | June 21st, 2022: female Herring Gull argenteus. | |
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| 2023: w-327:U | May 13th, 2023: w-327:U at the nest. | May 13th, 2023: w-327:U at the nest. | May 13th, 2023: w-327:U at the nest. |
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| partner 2 | May 7th, 2020: cachinnans male. | May 7th, 2020: cachinnans male. | May 7th, 2020: cachinnans male. |
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| 2021: cachinnans male. | May 4th, 2022: cachinnans male. | May 4th, 2022: cachinnans male. | |
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| May 17th, 2022: cachinnans male. | May 17th, 2022: cachinnans male. | May 17th, 2022: cachinnans male. | |
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| May 13th, 2023: male Caspian Gull. | May 13th, 2023: male Caspian Gull. | May 13th, 2023: male Caspian Gull. | |
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| pulli | May 21st, 2020: pullus n[F|V]. | May 21st, 2020: pullus n[F|W]. | September 26th, 2020: juvenile n[F|W]. |
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| pulli | June 8th, 2021: 2 large unringed chicks. | June 21st, 2022: hybrid pulli nest 141-2022. | July 12th, 2022: hybrid pullus nest 141-2022. |
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| July 8th, 2023: juvenile g[7|L]. | May 18th, 2023: juvenile g[7|M]. | . | |
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Visits and data.
| date: | egg no: | width (mm) | length (mm) | volume (cm3): | water test: | |
| 07-05-2020 | A | 50,3 | 70,4 | 89,68 | floating - 7mm | 3 eggs in the nest. |
| B | 50 | 77,8 | 97,93 | floating - 5mm | ||
| C | 50,6 | 74,9 | 96,56 | floating - 6mm | ||
| sum nest: | 284,17 | |||||
| 21-05-2020 | pulli | 1 egg intact, but embryo dead. Two chicks here, ringed n[F|V] & n[F|W]. | ||||
| date: | ||||||
| 16-04-2021 | Both adults at the nest, with 2 eggs. One partner sneeks from the nest, other partner guarding at blocks. | |||||
| egg no: | width (mm): | length (mm): | volume (cm3): | water test: | ||
| A egg | 50,9 | 71,1 | 92,75 | 0 - flat on bottom | ||
| B egg | 51,2 | 72,9 | 96,22 | 20 - flat on bottom | ||
| 26-04-2021 | Both adults at the nest. | |||||
| 06-05-2021 | Only C-egg measured. | |||||
| egg no: | width (mm): | length (mm): | volume (cm3): | water test: | ||
| A egg | 5 mm - floating | |||||
| B egg | 7 mm - floating | |||||
| C egg | 49,4 | 72,2 | 88,71 | 3 mm - floating | ||
| sum nest: | 277,68 | |||||
| 13-05-2021 | No visit. Camilla is trapping a Spoonbill here. | |||||
| 15-05-2021 | No visit. | |||||
| 28-05-2021 | 1 old egg in nest (rotten). 2 chicks not found in dense vegetation. | |||||
| 08-06-2021 | Pictures of 2 large chicks. Attacking parents. | |||||
| 26-06-2021 | 2 large chicks fly away, to open water. | |||||
| Visits and data 2022 for nest 35/141: Estimation egg laying: A-egg = April 30 2022. Estimating hatching = May 28 2022. |
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| 04-05-2022 | Dam 1 north side, exact spot of nest 35. Temporarily coded 141 for this season 2022. Sprayed this on block. Location: the Herring fighting Caspians of 2020/2021. | |||||
| Adult male Caspian is breeding. Is partner 2. Could be bird nest 35 previous years? | ||||||
| 04-05-2022 | 3 eggs. | |||||
| egg no: | width (mm): | length (mm): | volume (cm3): | water test: | ||
| A egg | 50,1 | 72,6 | -- | 15 - tip bottom | ||
| B egg | 49,6 | 73,4 | -- | 15 - tip bottom | ||
| C egg | 50,2 | 72,7 | -- | 15 - tip bottom | ||
| 17-05-2022 | Partner 2 = adult Caspian at nest site. | |||||
| 22-05-2022 | Partner 2 = adult Caspian at nest site. | |||||
| 30-05-2022 | Nest empty, no chicks found in Blackberry vegetation. Herring Gull near nest site = partner 1. | |||||
| 02-06-2022 | Partner 2 = adult Caspian attacks the boat. Should have chicks, he is defending. | |||||
| 17-06-2022 | Partner 2 = adult Caspian attacks the boat. Should have chicks, he is defending. | |||||
| 21-06-2022 | Partner 2 = adult Caspian attacks the boat. Should have chicks, he is defending. At spot 141 is an adult Herring Gull (partner 1) with 2 large chicks. Apparently a mixed pair here. | |||||
| 12-07-2022 | 1 large chick (hybrid) of the mixed pair present. No birds ringed at this nest this season (H5N1 restrictions), unfortunately. | |||||
| 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 or cach x cach (327U??) |
141-2023 | 75,1 | 53,3 | 107,42 | 73,8 | 51,5 | 98,55 | 71,9 | 50 | 90,50 | 296,48 | same male as 2022 |
| ring pulli: May 10th. | laying A egg: Apr 5th. | hatch A egg: May 3rd. | ||||||||||
| catch: | date: | metal: | darvic: | mass: | wing: | head+bill: | ||||||
| Pullus | 18-5-2023 | 5556403 | G-7|L | 475 | 92 | |||||||
| Pullus | 18-5-2023 | 5556404 | G-7|M | 490 | 90 | |||||||
| 141-2023 (formerly 035) | |||
| dam: | dam 1 east | ||
| location: | on block at N-side, east of PNED. Code 141 on block. "the Caspian of nest 035 always fighting the Herring". | ||
| breeders: | cach x teus or cach x cach (327U??) | ||
| OBSERVATIONS: | |||
| 9-4-2023 | nest: | 3 eggs measured. No watertest, ring chicks in 1st session. | |
| adult: | female is teus, male is huge aggressive cachinnans | ||
| 13-5-2023 | adult: | male = cach. Female = cach w-327:U? Unless there is a nest right beneath 035? | |
| 18-5-2023 | pulli: | 2 chicks ringed, 3rd not found | |
| 27-5-2023 | pulli: | dense vegetation, nothing found. | |
| 25-6-2023 | pulli: | g-7|L present, guarded by w-327:U, twice today. | |