COURTENS W, FIJN RC & RINGGROEP DELTA (2020) Site fidelity of Sandwich Terns Thalasseus sandvicensis in the northern Delta area, Southwest-Netherlands . LIMOSA 93 (4): 173-179.
To gain more insight in survival, migration and breeding
dispersal of Sandwich Terns, a colour-ringing project was
started in the Dutch Delta area in 2010. About 2500 juvenile
and 220 adult birds have been ringed over the last decade,
leading to 14 500 resightings up to May 2020. During the
breeding season of 2019, a special effort was made to read as
many colour-rings as possible in the breeding colony of the
Scheelhoek Nature Reserve (where most of the Sandwich
Terns were ringed). 263 different birds were seen, of which
84% was ringed in the Delta area itself. 11% was ringed in
the Dutch Wadden Sea and the rest originated from colonies
in Scotland and Ireland or were ringed during migration.
22-34% (with a mean of 27%) of the juveniles born between
2012 and 2016 (and still alive) was seen in the Scheelhoek
colony in the breeding season of 2019. As most 2nd and 3rd
year birds stay in Africa, almost no juveniles from the 2017
and 2018-year cohort were seen during the breeding season
of 2019. Adults were more faithful to the colony where they
were ringed during an earlier breeding season than juveniles.
Between 17-67% (with a mean of 42%) of adult birds still alive
from each year cohort (2012-18) was seen in their colony of
origin in 2019.
[pdf only for members] [dutch summary]