id	3648
datum	7 februari t/m 9 april 2007: 62 dagen
gemeente	De Bilt (UT)
locatie	De Bilt
coördinaten	N 52.11845  O 5.1741
aantal, kleed	1
soort waarneming	veldwaarneming
status	Aanvaard, gepubliceerd in jaarverslag CDNA
waarnemer(s)	W. Reinboud, R.F.J. van Beusekom et al
opmerkingen	7 February to 9 April, De Bilt, Utrecht, photographed, sound-recorded (W Reinboud, R F J van Beusekom et al; Dutch Birding 29: 126, plate 167, 193, plate 263, 2007). Considering tristis claims is a hard job for the committee, as is illustrated by the well-observed and extensively documented bird that stayed at De Bilt, Utrecht, from 19 January to 9 April (Dutch Birding 29: 126, plate 167, 193, plate 263, 2007), which is still under consideration. It has provoked a lot of discussion because it called like a 'normal' tristis but showed more green in the plumage and more pale in the bare parts than may be expected for a 'normal' tristis and the report has not been accepted after three rounds. However, new data from the regular wintering areas (eg, Kazakhstan) may prove that these characters fall within the normal variation of tristis and the CDNA has therefore postponed its final judgement, which will be published in the next report - or later...[Annual Report 2007]. 'Classic' individuals, cold brownish birds lacking yellow and green tones in their plumage and with black bare parts, can be easily identified, especially when heard calling. The bird seen and frequently heard at De Bilt in 2007 was, on the other hand, a more difficult individual with more greyish plumage and paler bare-parts coloration. However, it called frequently and constantly as Siberian. It is argued that these types of birds are best regarded as Siberian (van den Berg & The Sound Approach 2009) and, hence, it was accepted as such, albeit after extensive debate [Annual Report 2009].

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Dick Groenendijk · Siberische Tjiftjaf

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