No Red-breasted Mergansers were seen during the 2020-21 season. The above averages are for 2014-15 to 2019-20.
The area of Carmarthen Bay viewable from the Amroth/Wiseman’s Bridge area is not part of the Wetland Bird Survey. Nor is it watched on a regular basis. However, virtually all the double-figure counts of red-breasted mergansers are from this site. The counts below are taken from the Pembrokeshire Bird Reports since 1990.
Note from the BTO Waterbirds in the UK report for 2019-20
Species that migrate from the east, including Mergansers, were down compared with the previous winter, likely related to the exceptionally mild weather across Europe. Red-breasted Merganser 10-year trend was -23%, their lowest index value since 1980s, as shown below.
Note from the BTO Waterbirds in the UK report for 2013-14
The decline in the UK’s wintering population of Red-breasted Mergansers, evident since the mid 1990s, has slowed slightly. However, following a spike in numbers in 2010-11 (perhaps associated with the coldest winter across northwest Europe for 35 years), the annual index has resumed its downward trajectory.
Given that numbers wintering to the east of the UK have increased steadily in the last 30-40 years, for example in The Netherlands, the observed trends are suggestive of a range shift perhaps induced by climate change – as has been demonstrated for other waterbirds. However, this hypothesis has not yet been tested for this species, and perhaps pertinently, large decreases have been reported from further east in the Baltic Sea.
Branta bernicla – GWYDD DDU – Winter visitor and passage migrant. Not recorded in June or August
Brent geese were occasional visitors to Pembrokeshire before 1990, and only began to appear regularly on WeBS counts in1993-94 as shown below.
The highest numbers in any season are recorded between December and February
Almost all brent geese are seen on the Cleddau, especially at the Gann or at Angle Bay. Just a handful are counted on the Nevern and Teifi.
As the birds commute – either in a flock, or in small groups – between the Gann and Angle Bay – it is possible that they can be double-counted at times. However, an individual count of 77 at Angle Bay in December 2016, (and other individual counts – 68 at the Gann in 2012 and 62 at Angle Bay in 2017 – on non-WeBS days) that suggest the WeBS totals are reasonable.
Almost all birds are of the light-bellied race (hrota) – with just a handful of dark-bellied birds recorded.
Many ringed birds have been observed, and these prove movements between Ireland (main ringing station), Pembrokeshire and Brittany, and to north-east Canada (breeding grounds) via Iceland and Greenland.