Dutch Birding volume 28 (2006) no 4

Sykes's Warbler near Almere-Haven in October 1986

On 11 October 1986, a 'Booted Warbler' Acrocephalus caligatus was trapped and ringed near Almere-Haven, Flevoland, the Netherlands. It was studied, photographed and measured by four observers. The Dutch rarities committee (CDNA) accepted the record as the second Booted Warbler for the Netherlands, after one in October 1982. At the time, Sykes's Warbler A rama (then considered a subspecies of caligatus) was briefly considered because a few measurements pointed towards this taxon but not further considered, mainly because little was known about this taxon and because there were no European records.

In 2004, the record was reconsidered by the CDNA as part of a review of all then accepted Booted Warblers to establish if any Sykes's Warblers may have been involved. It showed that the Almere-Haven bird showed characters and measurements consistent with Sykes's Warbler and excluding both Booted Warbler and Eastern Olivaceous Warbler A pallidus elaeicus. The identification was mainly based on the bill length (too long for Booted) and wing to tail ratio (see table 1). Some measurements including tail length were on the short side for Sykes's and several measurements could fit both Booted or Sykes's. The relatively short tail was apparently heavily worn and partly growing and therefore not considered an argument against acceptance as Sykes's (and there is much overlap). In combination with the plumage features, such as rather plain head pattern and plain-coloured tertials, the identification as Sykes's was considered convincing enough for acceptance as the first for the Netherlands.

This is still the only record of Sykes's Warbler for the Netherlands; after 1986, nine more Booted Warblers have been accepted. Sykes's is a rare vagrant in western Europe but seems to be increasing in recent years, probably helped by a better understanding of the identification criteria and more awareness among birders and ringers. In north-western Europe, there are other records from Britain (8; first in 1959, now accepted as the first for Europe), Iceland (1), Ireland (1) and Sweden (2). In Denmark, one bird has been accepted as Sykes's/Booted Warbler and, in Norway, one as Sykes's/Eastern Olivaceous Warbler.

C J (Kees) Breek, Karveel 5866, 8242 WC Lelystad, Nederland
(c.j.breekwanadoo.nl)
Enno B Ebels, Joseph Haydnlaan 4, 3533 AE Utrecht, Nederland
(ebelswxs.nl)
Karel A Mauer, Fluitekruidstraat 63, 1313 KT Almere, Nederland
(kamauertiscali.nl)