Voorkomen van Bronskopeend in Nederland en het West-Palearctische gebied

In dit artikel wordt het voorkomen van Bronskopeend Anas falcata in Nederland en de overige landen van het West-Palearctische gebied (WP) en ook in Noord-Amerika beschreven. In de meeste landen van de WP (en oostelijk Noord-Amerika) wordt deze Siberische soort als \'escape\' behandeld; Nederland is hierop (met westelijk Noord-Amerika) een uitzondering omdat de soort hier wel op de nationale avifaunistische lijst is geplaatst. Er zijn in totaal negen gevallen, waarvan enkele betrekking hebben op vogels die enkele jaren achtereen terugkeerden naar dezelfde locaties(s). Alle gevallen betreffen mannetjes. Voor aanvaarding is cruciaal dat met zekerheid is vastgesteld en gedocumenteerd dat de vogel ongeringd was en onbeschadigde vleugels had. Waarnemingen waarbij dit niet is vastgesteld komen niet voor aanvaarding in aanmerking (\'omgekeerde bewijslast\'). Naast degelijke \'onbesliste\' exemplaren zijn er in Nederland meerdere waarnemingen van (vrijwel) zekere \'escapes\'; hiervan wordt een aantal recente voorbeelden besproken.

De determinatie van deze soort kent bij adulte mannetjes weinig problemen en er zijn geen waarnemingen afgewezen op basis van een onzekere determinatie. Wel is er een geval in Limburg van een vermoedelijke hybride Bronskopeend (mogelijk met Krakeend A strepera) die veel kenmerken van Bronskopeend vertoonde, maar met name wat koppatroon betreft afwijkend was, en werd in mei 2007 een mogelijke hybride gemeld bij het Nuldernauw, Gelderland. Er zijn geen gevallen van vrouwtjes, waarschijnlijk doordat deze veel lastiger te herkennen zijn dan mannetjes. Wel zijn er enkele vrouwtjes als \'escape\' vastgesteld of gemeld. In het artikel wordt ingegaan op het verspreidingsgebied in Oost-Azië en het trekgedrag en wordt aangegeven dat de soort tegenwoordig als \'bijna bedreigd\' (\'near threatened\') wordt beschouwd, met een wereldpopulatie van nog maar 35 000 exemplaren (geschat 100 000 in het begin van de jaren 1990).

Een overzicht wordt gegeven van alle bekende waarnemingen in de WP buiten Nederland, van 1839 tot en met 2007; het gaat om 61 exemplaren (60 gevallen), op drie na alle van mannetjes en het merendeel adulte. Omdat de soort in de meeste landen niet wordt beschouwd als potentiële dwaalgast en dus niet wordt beoordeeld is het overzicht van gevallen waarschijnlijk niet compleet en is ook niet duidelijk of in alle gevallen de determinatie correct is (al zal dat laatste vanwege de eenvoudige herkenning meestal wel het geval zijn). In dit overzicht zijn geen waarnemingen opgenomen van exemplaren die duidelijk van niet-wilde herkomst waren (op basis van ringen en/of vleugelbeschadigingen). Vrijwel alle waarnemingen in de WP vallen in de periode oktober-juni. In 1992 en in de winter van 2003/04 was sprake van hogere aantallen dan normaal. In Noord-Amerika wordt de soort ook af en toe waargenomen, met name in Alaska, VS, en verder zuidelijk langs de westkust en worden eveneens discussies gevoerd over de status. In recente jaren zijn in Noord-Amerika zeven gevallen aanvaard als vermoedelijk wilde vogels.
Op basis van een aantal aspecten wordt geconcludeerd dat een wilde herkomst van (een deel van) de vogels in de WP goed denkbaar is dat er op basis van het verspreidingsgebied en trekgedrag geen reden is om deze soort niet als potentiële dwaalgast te beschouwen. Het feit dat een aanzienlijk deel van de gevallen in de WP op zekere of vermoedelijke \'escapes\' betrekking heeft doet aan die conclusie niets af maar zorgt wel voor een \'vertroebeld\' beeld van het werkelijke voorkomen.

Max Berlijn, Wilhelminastraat 9, 6285 AS Epen, Netherlands (max.berlijn@nn.nl)

Marbled Duck near Doornenburg and Pannerden in August 2004

On 14-16 August 2004, a Marbled Duck Marmaronetta angustirostris stayed near Doornenburg and Pannerden, Gelderland, the Netherlands. The bird was aged as a juvenile based on, among others, poorly contrasting pale markings on the upperparts, absence of obvious spotting on breast and flanks, and weakly developed crest. Because the bird had no signs suggesting a captive origin it was accepted by the Dutch rarities committee (CDNA) as the first record of this species for the Netherlands. There has been a handful of previous reports in the Netherlands, including some of presumed or proven captive origin, but none was fully documented and/or submitted.

The occurrence of Marbled Ducks in north-western Europe is analyzed to shed some light on the probable origin of the bird. A total of 61 reports (72 individuals) of which 51 (60 individuals) since 1980 were gathered from European countries east to Austria, Finland, Italy and Poland. The most northerly report is from southern Denmark and, apparently, the species is lacking from any list (A through E) of Finland, Ireland, Norway and Sweden. The reports show a strong peak in August-October and this coincides with the peak occurrence of the species in north-eastern Spain. The latter is thought to be the result of a northward dispersion of birds fleeing from drought in the breeding areas. This was probably also the driving force behind the movements of a Spanish ringed bird that was shot north-east of Lyon, France, in September 1992 (at c 1800 km distance from the ringing site). The occurrence of the species in western central Europe shows strong similarities to the occurrence in France and is compatible with a wild origin. It is concluded that vagrancy to western and central Europe is likely but only with low frequency because of the small size of the Spanish breeding population, where such vagrants are supposed to come from, although an eastern origin is also possible.
Numbers of Marbled Duck in captivity in Belgium and the Netherlands seem to have decreased strongly since 1991. Furthermore, all these birds legally have to be ringed since 1995 and, in addition, almost all are pinioned. The total number of unringed and not-pinioned individuals in captivity is believed not to exceed a few 10s of birds in these countries. According to consulted wildfowl breeders, Marbled Ducks kept in captivity show a reduced shyness. Wild birds captured as ducklings, reared to adulthood in captivity and then released into their natal areas also showed a notably reduced shyness. The species is very rare or absent in parks and similar \'open collections\', presumably because it lacks an attractive plumage. In conclusion, the chances of an escaped individual to be unringed, shy and well flying like the Dutch bird in August 2004 seem to be small.

Rik Winters, Aquamarijnstraat 60, 9743 RB Groningen, Nederland (groenebijeneterhome.nl)

Eastern Imperial Eagle at Kamperhoek in April 2005

On 3 April 2005, a third calendar-year Eastern Imperial Eagle Aquila heliaca was observed at Kamperhoek, Flevoland, the Netherlands. Kamperhoek is situated in the north of Oost-Flevoland and is a good spot for observing high numbers of migrating birds. The bird was discovered during counts of diurnal migration and was seen by seven observers. It stayed in the area for a short while (in flight) before moving on in a north-easterly direction. It was identified by the combination of the pale, yellowish-brown ground colour of the underparts and underwing coverts with the dark streaked chest, pale head and trousers, conspicuous pale \'window\' in the remiges and the lack of a light wing-bar on the underwing. Several characters point to a third calendar-year bird. In particular on the photographs showing the upperparts, the difference between moulted and retained remiges can be seen. The inner four to five upper primary coverts have broad white tips and must have been replaced shortly before. This is the first record of Eastern Imperial Eagle for the Netherlands and as such long awaited, since the species occurs as a regular vagrant in countries north-east of the Netherlands, notably in Denmark. Most records in north-western Europe concern young birds in spring or autumn, often at well-known (raptor) migration hotspots.

Ruud F J van Beusekom, Noordwal 56, 1274 AG Huizen, Nederland
(tjiftjaf@wanadoo.nl)

Eurasian Pygmy Owl at Sumarreheide in October 2002

On 4 October 2002, a small owl was picked up alive after colliding with a window at Sumarreheide, Friesland, the Netherlands. The residents took c 30 sec of video footage of the owl, after which it escaped and flew off. It was tentatively identified as Little Owl Athene noctua (the only small owl species regularly occurring in the area). In February 2004, a few video-stills were shown to a local owl expert, who re-identified the bird as Eurasian Pygmy Owl Glaucidium passerinum. The observation was submitted and the bird was accepted as the first Eurasian Pygmy Owl for the Netherlands. It was identified by its very small size, facial pattern, spotted crown and brown-streaked underparts. Some North American Glaudicidium species (which could theoretically occur as escapes) can be very similar in morphology but the Nearctic taxa always show \'swollen\' nostrils, which Eurasian Pygmy Owl lacks.

The bird may have originated from Germany, where the species is spreading north-west and where the closest breeding areas are c 110 km from the Dutch border; one of the northerly strongholds (Lüneburger Heide, Niedersachsen) is situated at c 230 km from Sumarreheide. Dispersal of (especially first-year) birds is well known and ringed birds have been recorded up to 300 km from the breeding site. A Scandinavian origin is also a possibility (during invasion years, birds regularly come as far south as northern Denmark) but, since there were no notable southward movements in Scandinavia in autumn 2002 (contrary to autumn 2003, when there was a small invasion with three to four birds reaching Denmark), this is less likely.

The second record for the Netherlands concerns a bird seen and heard by a single observer on 10 December 2005 at Bakkeveen, Friesland; this site is only c 15 km from Sumarreheide.

Enno B Ebels, Joseph Haydnlaan 4, 3533 AE Utrecht, Nederland
(ebels@wxs.nl)
Jan Deinum, Bosweg 15, 9262 SX Sumar, Nederland
(jandeinum@planet.nl)

Yellow-headed Blackbird on Terschelling in July 1982

On 2-3 July 1982, an adult male Yellow-head Blackbird Xanthocephalus xanthocephalus was seen by four observers on Terschelling, Friesland, the Netherlands. The description fits only this species and safely excludes similar species, especially Yellow-hooded Blackbird Chrysomus icterocephalus (which has been recorded as escape in Europe). The bird had been regarded as a presumed escape for many years but has recently been reconsidered by the Dutch rarities committee (CDNA) and has been admitted to the Dutch list as a bird of possibly wild origin. Probably, the same bird was seen on Texel, Noord-Holland, on 20 May and 14 June 1982 but the description contained some incorrect details for this species regarding the head coloration and these sightings were, therefore, not accepted.

Enno B Ebels, Joseph Haydnlaan 4, 3533 AE Utrecht, Nederland (ebels@wxs.nl)
Leo M J van den Bergh, Bieskamp 74, 6651 JN Druten, Nederland (leo.vandenbergh@gmail.com)

Unidentified nuthatch in Siberian Altay in July 2006

In the summer of 2006, Esther van den Heuvel, Bas Roels, John Smit and Theo Zeegers participated in an entomological expedition to the Altay mountains in southern Siberia, more or less on the crossing of China, Kazakhstan, Mongolia and Russia. At one of our campsites, at an altitude of c 2000 m up in the Aktru valley in the central Chuiskiy range, we saw a small nuthatch Sitta which resembled, in our frame of reference, Corsican Nuthatch S whiteheadi. Of course, we knew that this was impossible but with nothing more than a European field guide (Heinzel et al 1996) at hand, we were not able to identify it properly.

The place where we observed the nuthatch was: Aktru, south of Karay, at 2000 m above sea level (50°05\'12.2\'\' N, 87°46\'59.4\'\' E), Kosh-Arachskiy Rajon, Respublika Altay, southern Siberia, Russia. This site is a valley at the end of two glaciers, and more or less at the timberline, c 100 km from the Mongolian border. The forest was a pure stand of larch Larix.
Because it turned out that a pair of this nuthatch was breeding in a larch, we saw the species repeatedly. The two were sexually dimorphic: the male had a black cap, whereas the female had no black cap; both had a distinct dark eye-stripe and a white supercilium. These are exactly the features of Chinese Nuthatch S villosa (cf Harrap & Quinn 1996). The underparts, however, showed relatively little buff coloration, as compared with typical villosa.

The only nuthatch species with a distribution that is known to include southern Siberia is Eurasian Nuthatch S europaea (Harrap & Quinn 1996). However, the clear black cap in the male as well as the white supercilium in both sexes and the small size exclude Eurasian.

According to Nazarenko (2006), the distributional area of Chinese Nuthatch is situated somewhere between 33-45° N and 100-133° E. Its breeding range is quite patchy. If the nuthatch we observed was indeed Chinese, then this would be a breeding record far outside its known breeding range. Another possibility is that our nuthatch could represent a new, undescribed Sitta species. At this moment, based on our field observation, this remains an open question. Either way, the discovery of a breeding pair of Sitta (cf) villosa in the Russian part of the Altay mountains remains a surprising discovery and requires further investigations.

Interestingly, nuthatches have something of a reputation when it comes to remaining undiscovered for a long time; the two most recently described new species for the Western Palearctic were both nuthatches: Corsican Nuthatch (described in 1883) and Algerian Nuthatch S ledanti (described in 1976).

John T Smit, Wolvenstraat 62, 3512 CH Utrecht, Netherlands
(jtsmit@planet.nl)
Theo Zeegers, Eikenlaan 24, 3768 EV Soest, Netherlands
(th.zeegers@xs4all.nl)
Esther van den Heuvel, Eikenlaan 24, 3768 EV Soest, Netherlands
(e.vdheuvel@xs4all.nl)
Bas Roels, Rembrandtkade 57-1, 3583 TR Utrecht, Netherlands
(broels@xs4all.nl)