Limosa lapponica – RHOSTOG GYNFFONFRTH – Passage migrant
Black-tailed Godwits were regular autumn migrants through the county, with up to 10 being recorded (though not always on WeBS counts) in most years. One or two, and occasionally larger numbers, were sometimes seen in mid-winter on the upper reaches of the estuary.
Since the early 2000s, larger numbers were being seen on the Pembroke Upper Millpond. During subsequent winters, this flock was sometimes recorded on the Millponds, sometimes at Pembroke River, and sometimes at Cosheston Pill. There have been additional observations of larger numbers at Angle Harbour in recent years.
The great change in numbers can be seen from the maximum seasonal counts (any month) on the Cleddau Estuary, above. The relatively large counts in 1996-97 winter seemed, at the time, to be a one-off, but subsequent winters suggest that was just the beginning.
Average monthly counts (all Pembrokeshire WeBS sites) for the five-winter periods from 2010-15 and 2015-20 above, show that the changes are not limited to numbers, but affect the the pattern of occurrence too.
Counts at migration time depend on how many are passing through on that particular day, and with only one count day a month, they can be difficult to interpret. The above graph shows the maximum autumn (September-October), mid-winter (November – February) and Spring (March) counts for each season since 2000-01. Clearly there are increasing numbers staying throughout the winter.
A clue to the reasons for the changes come from several birds that were carrying colour-rings or flags. These indicated that they came from the Icelandic breeding population.
Research on this Icelandic population has shown that considerable changes have taken place in the birds’ behaviour. Basically, climate change has meant there is a greater area of Iceland available to breeding birds early in the season. The Icelandic population has therefore been able to increase. The original small Icelandic population wintered in southern Portugal, with few birds stopping in the UK. As the population has expanded into new areas, these new sub-populations are wintering closer to home. This means more birds wintering in the UK, particularly in the south-west, and in Ireland. You can read a lot more about this here
WeBS counts from sites across Wales show a dramatic increase in numbers from the late 1980s onwards, believed to be linked to these increases in the Icelandic breeding population.
Annie Haycock (BBS & WeBS local organiser)
References:
British Trust for Ornithology Wetland Bird Survey online results
Appleton G, Wader Tales
HAYCOCK A, 2019. Wetland Birds on the Cleddau Estuary. A report to the Milford Haven Waterway Environmental Steering Group.
Pembrokeshire Avifauna 