Larus cachinnans in the Netherlands

(last update: December 24, 2021)

Coordinators:
Albert de Jong
Leon Kelder
Roland-Jan Buijs
Merijn Loeve
Mars Muusse

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Cachinnans breeding in the Netherlands - nonbreeding season

you can participate in this project too!
please send in your observations of colour ringed birds to: ring@buijsecoconsult.nl

In colony de Kreupel and in colony Lelystad we have ringed both Caspian and Herring Gulls. Some notes:

  • For the after season dispersal we only use data for Caspian Gull or hybrid Caspian Gull birds, no other species.
  • In the plots, we do not include observation of juveniles within the colony or within the very near vicinity of the colony, as this is no dispersal.
  • We do include all observations of immature birds (2CY, 3CY) within the colony or within the very near vicinity of the colony.

DISPERSAL OF RINGED CHICKS

Below complete set of observations plotted (criteria, see above).
Period: up to November 2021.
Most southern bird - Caspian Gull cachinnans FV, November 07-11 2021, Caleta de Vélez (Harbourt), Málaga, Spain.
Recoveries east of colonies = 0 birds.
Observations abroad, U.K. = 10 birds, 50% of them at Cromer - Cley coastline.
Observations abroad, Belgium = 2 birds.
Observations abroad, France = 2 birds.
Observations abroad, Spain = 5 birds.
Observations abroad, Portugal = 3 birds.

Below: observations outside the colony, of ringed juveniles within the first 2 months (July - August).
Strong concentration of observations at Cromer - Cley, U.K., which is an almost direct line westwards from the colonies.

Below: observations outside the colony, of ringed juveniles in the period September - October.
This period still regarded as 'migrating months'.
Long distance birds already at Iberian coastline, including Caspian Gull cachinnans F|5 which reached Praia do Molhe Leste - Peniche, Portugal already by September 3rd, 2020.

Below: observations of ringed birds in the 1st winter period 1CY November - 2CY March.
This period regarded as 'first winter'.
Observations within 50 km range from colony = 7 birds.

Below: observations of ringed birds in the 1st summer period 2CY April - 2CY August.
This period regarded as 'first summer', birds in complete moult.
Observations within 50 km range from colony = 7 birds (100% of the observations).
No observations from abroad.

Below: observations of ringed birds in the period 2CY September - 2CY October.
Migration period, nonetheless most observations close to colonies.
Observations = 6 birds, of which 1 bird in NW France (is Caspian Gull cachinnans F9 which was still near the colony 3 weeks earlier).

Below: observations of ringed birds in the period 2CY November - adult December.
All observations of birds older than 2CY November, since we hardly have ringed pulli which have reached that age. have
Observations = 7 birds, of which 3 birds ringed at the nest as breeding adults. All 3 birds rather close near the colonies.

FOOD RESOURCES IN WINTER

Many observations along coastlines, which may indicate food trips by following fishing vessels.

FOOD COMPETITION IN WINTER

In summer in the North Sea region, fishing vessels often followed by Lesser Black-backed Gulls, a species that migrate south in winter and maybe leaving open a position for Caspian Gulls?