A Cetti’s Warbler, but not as we know it…

Leucistic Cetti's Warbler, RSPB Conwy (Marc Hughes)

Spring weather, rudely interrupted from Monday, brought Chiffchaffs and Blackcaps to almost every lowland parish in North Wales, it seems. Wheatears also arrived in number, while a handful of other early summer migrants included Ring Ouzel on territory above the Conwy Valley, the region’s first Swallow on Bardsey and Willow Warbler at Penmon Point. Elen, Glaslyn’s female Osprey, returned to the nest site early on Friday, with several others in Wales last week. Black Redstarts stopped at South Stack and Rhoscolyn on passage.

The explosive songs of seven Cetti’s Warblers greet visitors to RSPB Conwy, though one since last September has not the usual chestnut plumage but an almost white body with black wings. Unlike most warblers, these are resident in the UK and most movements are relatively short. Since first nesting in southern England in 1973, they have spread north facilitated by climate change. The first breeding in Wales – at Oxwich Marsh, Gower – was in 1985 and in North Wales in 1997, although curiously, the first Welsh record was on Bardsey over 50 years ago.

The unusually marked bird at Conwy is not albinism, but leucism, a condition where the cells responsible for the production of melanin are absent, so it lacks darker colours. This individual may be the first leucistic Cetti’s Warbler in Wales; I am unable to find records of others in the UK. Readers may recall a leucistic Blue Tit that visited an Anglesey garden for several months over winter 2023/24.
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A Surf Scoter and Red-necked Grebe swim in Conwy Bay, viewed from Penmaenmawr, and another Red-necked Grebe was in Caernarfon Bay, where two dozen Great Northern Divers gather before flying farther north. Bitterns’ booming calls carry across reedbeds at RSPB Cors Ddyga, but one calling at a mainland site was more unusual. There is no historic evidence that Bitterns have bred in mainland Northwest Wales; it is more likely that this is a winter migrant late to return to its nesting area. Anglesey’s wintering flock of Cattle Egrets increased to eight near Porth Tywyn Mawr, a Lesser Yellowlegs remains on the Clwyd estuary, Smew on Llyn Alaw and a Crane visited RSPB Burton Mere Wetlands.