Larus cachinnans in the Netherlands
(last update: August 16, 2020)
Albert de Jong
Merijn Loeve
Roland-Jan Buijs
Leon Kelder
Mars Muusse
Cachinnans - nest Lelystad 017
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 017 positioned at breakwater 2, large code marked on block).
- ID certain in season 2020: parents are Caspian Gull cachinnans.
- Situation in 2021 somewhat more complicated. Main problem: whole month of April a small group of adults were guarding near the nest on top of the dam, 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.
- Same period, late March - April, multiple cachinnans type birds were guarding on the blocks, right below the nest at the waterfront.
- 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, renamed "nest 41".
- Herring Gull from the group started also a new nest in May, only 1 meter away from old location (code remained "nest 17", season 2021 on this page).
- ID uncertain in 2021: one parent certain Herring Gull argenteus, other parent never seen interacting with nest, not even alarming when there were chicks trapped at the nest.
- ID uncertain in 2022: female is cachinnans, male is very likely michahellis-type which eventually move to nest 41 in 2021.
| partner 1 | May 7th, 2020. | . | . |
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| partner 2 | May 7th, 2020. | May 7th, 2020. | May 7th, 2020. |
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| pullus | May 21st, 2020: pullus b[F|C]. | ||
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| location 2021 | March 30th, 2021 multiple cachinnans guarding on blocks. | April 26th, 2021: Herring Gull (left) at new nest. | . |
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| nest 2021 | April 16th, 2021: 2 eggs clutch. | April 16th, 2021: new location, new 2 eggs clutch. | May 15th, 2021: 3 eggs clutch. |
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| partner 1 | April 26th, 2021: Herring Gull sub-adult. | April 26th, 2021: Herring Gull sub-adult. | April 26th, 2021: Herring Gull sub-adult. |
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| partner 2 | April 26th, 2021: Caspian Gull type? Bird in background. | April 24th, 2021: possible partner, but uncertain. | April 24th, 2021: possible partner, but uncertain. |
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| pullus | June 28th, 2021: pullus b[S|Z] Herring Gull type. | June 28th, 2021: pullus b[S|0] Caspian Gull type. | . |
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| nest 2022 | April 29th, 2022: 3 eggs clutch. | April 15th, 2022: nest site. | April 19th, 2022: female at nest site, which is next to 223. |
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| partner 1 | April 11th, 2022: female is cachinnans. | May 4th, 2022: female is cachinnans. | April 11th, 2022: female is cachinnans. |
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| partner 2 | April 29th, 2022: male is michahellis-type. | April 29th, 2022: male is michahellis-type. | |
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| pullus 2022 | May 9th, 2022: pullkus r[C.X]. | . | . |
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Visits and data.
| date: | ||||||
| egg no: | width (mm) | length (mm) | volume (cm3): | water test on April 15th: | ||
| 15-04-2020 | A | 53,3 | 73,1 | 104,56 | 30 - tip on bottom | 3 eggs in the nest. |
| B | 50,7 | 68,3 | 88,40 | 10 - on bottom | ||
| C | 51,2 | 73,7 | 97,28 | 40 - tip on bottom | ||
| sum nest: | 290,23 | |||||
| 21-05-2020 | pullus | Empty nest. One pullus found, ringed b[F|C]. | ||||
| date: | ||||||
| 16-04-2021 | 2 eggs. | Behind block code "17". Red flag placed near nest. | ||||
| 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 | ||
| 24-04-2021 | Nest 17 at flag disappeared? Herring Gull sub-adult started new nest 17 1 meter to the west, it has again 2 eggs. | |||||
| 2 eggs. | Behind bundle of braches and twigs. Flag replaced to this nest. And bundle sprayed red with paint. | |||||
| egg no: | width (mm) | length (mm) | volume (cm3): | water test on April 24th: | ||
| A | 50,9 | 69,3 | 90,4 | 20 - flat on bottom | ||
| B | 50,9 | 70,6 | 92,1 |
20 - flat on bottom | ||
| 26-04-2021 | Herring Gull at new nest 17, at look-out stone 40 cm from nest. Two yellow-legged birds again 6 mtr to the right forming a new pair, will be nest 41. | |||||
| On blocks, 10 meter below nest 17 at waterfront, always a guarding Caspian Gull type (not pure). This will later be nest 45. | ||||||
| 13-05-2021 | On blocks, 10 meter below nest 17 at waterfront, again alert Caspian Gull type. | |||||
| 15-05-2021 | Nest 17 and nerst 41 split now definitely. Nest 17 with Herring Gull sub-adult and 3 eggs. | |||||
| egg no: | width (mm) | length (mm) | volume (cm3): | water test on May 15th: No | Measurements Monika Ballmann. | |
| A | 50,5 | 69,2 | 88,86 | -- | ||
| B | 50,6 | 70 | 90,24 |
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| C | 49,5 | 68,9 | 85 | -- | ||
| 28-05-2021 | metal ring: | tibia ring: | mass (gr): | head + bill: | ||
| pullus | .5559382 | b-S|Z | 123 | 56,5 | ||
| pullus | .5559383 | b-S|0 | 243 | 64,5 | ||
| pullus | .5559384 | b-S|1 | 198 | 63,6 | ||
| 08-06-2021 | Herring Gull sub-adult at nest. | |||||
| On blocks, below nest 17 at waterfront, now 2 Caspian Gull type birds. The guarding Caspian Gull type will now be assigned nest 45, no longer potentially linked to nest 17. | ||||||
| 26-06-2021 | metal ring: | tibia ring: | mass | head + bill | wing | |
| pullus | .5559382 | b-S|Z | 1039 | 113,3 | 287 | |
| pullus | .5559383 | b-S|0 | 947 | 111,3 | 305 | |
| date: | ||||||
| 15-04-2022 | A egg | 77,8 | 50,2 | |||
| B egg | 77,3 | 49,9 | ||||
| C egg | 70,9 | 48,5 | ||||
| 19-04-2022 | adult bird present, same as April 11th. Neighbour is Herring gull and behind 17 is nest with y-X540. | |||||
| 29-04-2022 | A egg | float - 3 mm | ||||
| B egg | float - 2 mm | |||||
| C egg | float - 4 mm | |||||
| 04-05-2022 | both adults: cachinnans female and michahellis (-type) male. | |||||
| 09-05-2022 | A egg | infertile | ||||
| pullus | NLA 5625073 | r-C.X | ||||
| C egg | infertile | |||||