id	67218
datum	8 t/m 11 november 2016: 4 dagen
gemeente	Groningen (GR)
locatie	Beijum, Groningen
coördinaten	N 53.24911  O 6.5851
aantal, kleed	1, eerste-kalenderjaar mannetje
soort waarneming	veldwaarneming
status	Aanvaard, gepubliceerd in jaarverslag CDNA
waarnemer(s)	J. Welbedacht et al
opmerkingen	8-9 November, 1cy male, photographed, found dead on 11 November, collected; skin retained at Naturalis Biodiversity Center, Leiden, Zuid-Holland (J Welbedacht et al; Dutch Birding 38: 487, plate 742-743, 2016) Despite many observers searching for the bird, it was not seen after the morning of 9 November. Two days later, it was found dead in a garden. It was obvious from the start that a rare, Asian thrush with (a lot of) Dusky Thrush genes was involved but several features did not perfectly match a ‘classic’ bird – whatever that may be within this species complex. In Asia, hybridisation or introgression with Naumann’s Thrush T naumanni occurs on a large scale and, to a lesser extent, also with the two ‘dark-throated’ thrushes (Red-throated Thrush T ruficollis and Black-throated Thrush T atrogularis). It was therefore a tough record to assess, and it circulated for a long time. The bird was included in the collection of Naturalis Biodiversity Center, where autopsy revealed it to be a male. The CDNA studied the specimen and found that the underparts were poorly marked for its gender (in the field it was even identified as a female by many). Furthermore, eg, a few orange breast-feathers were found and the shape of the dark cheek patch did not match most ‘undisputed’ young birds. The CDNA tried to get a clearer image of where plumage variation of this taxon ends and where introgression begins. For every presumed aberrant feature, we found examples on images of otherwise undisputed birds from Asia. Although we failed to find a bird that combined all of these ‘aberrant’ features, the CDNA decided that, based on current knowledge, this individual falls within the variation for Dusky and the record was therefore accepted. However, the committee remains interested in new insights in the complex situation of the Asian thrushes. Annual Report 2018.

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Bruine Lijster in Groningen - Update [dutchbirding.nl]

DB 38:486 Bruine Lijster in Groningen – veel discussie en een tragisch einde

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