Identification of Dark-breasted Barn Owl in Britain

A BBRC review of the identification criteria of ‘Dark-breasted Barn Owls’ Tyto alba guttata concluded that only those birds with completely buff underparts were safely identifiable as guttata. Many British claims of guttata show varying amounts of white below, and are thought to originate from the wide intergrade zone between guttata and nominate alba, although variation within alba may also account for some darker-breasted birds. This paper forms the basis for assessing future claims of guttata. Observers and county records committees are encouraged to apply these criteria to previous records where possible. taxa thought to be sufficiently rare in Britain to be considered by BBRC. Following that report, BBRC set out to establish whether guttata was identifiable out of range and to come up with a set of criteria against which future records could be assessed, and this paper presents a summary of the findings. A review of past records of guttata is beyond the scope of this paper, but observers and county recorders are encouraged to submit past records to BBRC that are thought to meet the acceptance criteria. Identification White-breasted Barn Owl The first step towards identifying guttata in Britain is to become fully familiar with the resident population of nominate alba. The majority of alba should be easily separable from guttata. Nonetheless, it should be borne in mind that there is considerable variation within alba, and that the sexes may also differ markedly. On average, males are paler than females, and many individuals have unmarked silky white underparts, yellowish-toned upperparts, pale sides to the neck and pale remiges and rectrices. Females can look similar to males, but are usually slightly darker above with more grey markings, have more extensive black spotting below and show darker and more barred remiges and rectrices. They also usually show a buff wash to the upper breast. The ratio of grey to buff on the upperparts is approximately equal for the darkest females. Dark spots can extend from the neck sides down onto the breast, belly and flanks, and even onto the thighs and feathered tarsi. The underwing-coverts may also be spotted. The buff wash to the upper breast varies in extent, but is usually not as dark as on guttata. The belly is invariably white, as are the thighs on the vast majority of birds (perhaps all). Importantly, the facial disc is always predominantly white, with darker markings restricted to the area immediately in front of the eye. Dark-breasted Barn Owl A ‘classic’ guttata is extremely distinctive, and should cause no real identification problems. The base colour to the upperparts is a deep, rich buff. This may be strongest on the scapulars, wing495 British Birds 102 • September 2009 • 494–503 Identification of Dark-breasted Barn Owl in Britain 320. White-breasted Barn Owl Tyto alba alba, Lincolnshire, July 2009. A classic alba: note the mostly unmarked, silky white underparts, particularly the belly and thighs, and the largely white facial disc, darker markings being restricted to the area immediately in front of the eye. N ei l S m ith 321. White-breasted Barn Owls Tyto alba alba, one ringed as a chick in 2004 in Yorkshire (left), one collected in Co. Meath. Note the extensive buff wash to the breast of the Yorkshire bird, and the faint buff wash and extensive spotting of the Irish bird. Birds similar to these in Britain have been thought to be guttata in the past. Pa ul F re nc h © N H M ,T ri ng coverts and remiges and contrasts with the more yellowish hues of many alba. Dark grey marbling covers more than half of the upperparts of guttata, typically two-thirds or more. The grey is especially dense and prominent on the crown, where it may be the only colour (rarely the case in all but the darkest alba). Individual variation is marked, and some birds show almost solidly grey mantle, scapulars and coverts. Dark buff wraps around the sides of the head and onto the breast, extending down across the entire underparts, including the belly, feathered tarsi, undertailand underwing-coverts. It may be darkest on the breast, but is generally fairly uniform in intensity over the underparts. Any bird showing an obvious contrast between dark breast and pale belly is not guttata. The underparts of both sexes are liberally spotted, unlike those of most alba. The size and intensity of spotting does vary, but should at least be present. The two races differ consistently in facial pattern. In particular, guttata shows a prominent dark surround to the eye; this can be almost purplish in colour, and radiates outwards from the eyes to cover varying amounts of the facial disc. This seems to be present on all guttata to some degree, but appears less prominent among individuals from the western parts of the range. The edge of the facial disc is also darker in guttata, on average. 496 British Birds 102 • September 2009 • 494–503 Identification of Dark-breasted Barn Owl in Britain 322. Dark-breasted Barn Owl Tyto alba guttata, Bavaria, Germany, March 2002.This is a classic guttata with the deep buff of the underparts extending onto the feathered tarsi. In addition, note the liberal spotting across the breast, the predominantly grey scapulars, the dark markings around the eyes radiating across the facial disc and the dark grey tips to the primaries. G ün te r Ba ch m ei er 323. Dark-breasted Barn Owl Tyto alba guttata, Gelderland, the Netherlands, July 2005. This brood of four juveniles illustrates that there is some variation among guttata. Note that the bird on the far right has more extensive dark markings around the eyes compared with the other three. This may be primarily sex-related, as females are on average slightly darker and more heavily spotted. M ic hi el S ch aa p (w w w .m ic hi el sc ha ap .n l)