Gedachten bij terugmeldingen van Nederlandse roofvogels op de Evenaar

The Dutch Ringing Scheme (Vogeltrekstation Arnhem) offers an online form for members of the general public to report a ringed bird. These reports are automatically added to the databank and are immediately visible on the species maps on www. griel.nl/pages/staticmaps.aspx. The maps contain quite a few unusual records, as summarised in this paper (information on the maps as per late March 2012). Maps of various species of raptors show one or more ring recoveries on the Equator with coordinate 00°00'; 00°00'. Several such records provided ‘in my garden’ or ‘?’ as site of ring recovery. Other maps show one or more ring recoveries in The Netherlands of species without a single record in the Western Palearctic, of species without a single record in The Netherlands, or of extremely rare visitors (Table 1). Odd records are present on maps of other species as well, and on maps of species groups like falcons, raptors and geese. Many of these odd records had been reported by members of the public through the online form. The analysis revealed that members of the public often make errors when filling in ring number. Many of these ‘wrong ring numbers’ can not be linked to an existing ring number, meaning that the ringer will not get a report, and that the finder will not be notified of the recovery. Quite a few of these unusual ring recoveries have been online for several months or more, and some for more than two years. This indicates that there is no check on the reliability of online ring recoveries reported by members of the public. Furthermore, scientists may take it for granted that the information on the maps is reliable, as the Dutch Ringing Scheme is part of the Royal Netherlands Academy of Arts and Sciences. The method of adding online reports of members of the public to the maps needs improvement. I propose: (1) new ring recoveries reported online by the general public must be controlled before they appear on the maps. This must be carried out daily, so members of the public can be asked immediately for feedback or more details when necessary; (2) all ring recoveries already reported by the general public through www.griel.nl must be checked; (3) all ring recoveries by the general public must be stored with name and address of the reporter (including e-mail address), as records without an observer’s name have less scientific value compared to traceable records.