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.

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