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 041
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 041 positioned at breakwater 2, close to large code "17" marked on block.
- This pair has a complicated history. Main problem: whole month of April a group of adults were guarding a nest together on blocks, close to each other. Group included Herring Gull 4CY, Caspian Gull with intense yellow legs, and Yellow-legged Gull ( type) adult. April 16th, 2021 nest 17 contained 2 eggs and parentage was unknown, but on April 24th the nest was empty.
- By May, the group had split and May 15th, 2021 the yellow legged female Caspian Gull and male Yellow-legged Gull (hybrid) started their own nest, 6 meters east from old nest 17.
- Herring Gull from the group started also a new nest in May, only 1 meter away from old location (see nest 17 season 2021 data).
- ID 2021 certain, parents are female Caspian Gull cachinnans, and male Yellow-legged Gull michahellis or hybrid bird with michahellis blood.
| location | March 30th, 2021 guarding group. | April 26th, 2021. | Nest May 15th, 2021: 3 eggs clutch. |
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| partner 1 | April 26th, 2021: male michahellis (-type). | April 26th, 2021. | April 26th, 2021. |
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| partner 2 | April 26th, 2021: female yellow legged cachinnans. | June 8th, 2021. | June 8th, 2021. |
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Visits and data.
| date: | ||||||
| 16-4-2021 | 2 eggs in nest 17, size and pattern okay for cachinnans. Several adults present as small group. Parentage of eggs unknown. | |||||
| egg no: | width (mm) | length (mm) | volume (cm3): | water test on April 16th: | ||
| A | 53,5 | 71,5 | 103,04 | 20 - flat on bottom | ||
| B | 52,3 | 68,9 | 94,89 | 25 - flat on bottom | ||
| 26-4-2021 | Nest 17 is empty. | |||||
| Guarding in group: Herring Gull type 4CY, Caspian Gull with intense yellow legs, and Yellow-legged Gull ( type) adult. | ||||||
| 2 meters west of old nest is a nest with 2 eggs: new nest 17 (parents probably Caspian and Herring Gull). For data, see NEST 17 from this date on. | ||||||
| 6 meters east of old nest 17 are two adults: female Caspian Gull cachinnans, and male Yellow-legged Gull michahellis or hybrid bird with michahellis blood. They have no eggs. | ||||||
| 15-5-2021 | Herring Gull is obvious parent of nest NEW 17, other parent remains uncertain. There is always a guarding adult cachinnans at the blocks though. For data, see NEST 17. | |||||
| female Caspian Gull cachinnans and male Yellow-legged Gull michahellis also have nest with 3 eggs. | ||||||
| 3 eggs: | egg no: | width (mm) | length (mm) | volume (cm3): | water test: No | |
| A | 51,4 | 72,0 | 95,78 | -- | ||
| B | 52,5 | 72,6 | 100,75 | -- | ||
| C | 50,9 | 70,1 | 91,44 | -- | ||
| sum nest: | 287,97 | |||||
| 28-5-2021 | 2 eggs. | |||||
| 08-6-2021 | 2 parents at nest. | |||||
| 28-6-2021 | No birds, no activity, no eggs. | |||||