Wren – 2019 BBS

Troglodytes troglodytes – DRYW – Breeding resident

The wren is a pretty ubiquitous species across Pembrokeshire, it having been recorded in almost every tetrad in the 2003-07 atlas.  More than that, the BTO Atlas 2007-11 shows that Pembrokeshire is one of the most densely populated areas of the UK as far as wrens are concerned.

While it is basically a bird  of deciduous woodland, it is an adaptable species also common in scrub, pastoral farmland, villages, towns, and even coniferous woodland.  So, not surprisingly it is recorded in virtually every square covered by the Breeding Bird Survey in the county.

With less than 15 squares surveyed before 2002, the results could be expected to be a little erratic, while the apparent dip in the population in 2001 was the result of only two squares being surveyed during the foot-and-mouth outbreak.  Nevertheless, the population density seems to be increasing overall.

Like many small, but warm-blooded, creatures, the wren is susceptible to cold weather, so it should be expected that breeding populations will be reduced after severe winters.  The graph shows the short-term effects of cold conditions in 1995/96, 2009/10, 2010/11 and 2017/18.  These are evident on the Breeding Bird Survey index for both Britain and for Wales, yet in Pembrokeshire there is an unexplained dip in the summer before the 2017-18 winter and an increase afterwards. 

In the longer term, the population in Wales has increased by 9% between 1995-2018 (Harris et al. 2020), and in Pembrokeshire it is showing a similar trend.

Skokholm

While Skokholm isn’t part of the BBS network, all the breeding birds there are monitored intensively each year.

Wrens first bred on the island in 1988, and numbers have been increasing ever since.  In 2018, 63 territorial males were mapped.  Perhaps surprisingly, given the snow and freezing conditions prevalent during February and March that year, the total was five up on that of previous year and two up on the 2016 Skokholm record.  The reason for this substantial increase in the number of territorial males is unclear.

Annie Haycock (BBS & WeBS local organiser)

References:

BALMER D, GILLINGS S, CAFFREY B, SWANN B, DOWNIE I, FULLER R. 2014. Bird Atlas 2007-11: The Breeding and Wintering Birds of Britain and Ireland.  HarperCollins.  UK

BROWN R & EAGLE G, 2018 Skokholm Annual Report. Wildlife Trust for South and West Wales.

HARRIS S J, MASSIMIMINO D, EASTON M A, GILLINGS S, NOBLE D G, BALMER D E, PEARCE-HIGGINS J W & WOODCOCK P. 2019. The Breeding Bird Survey 2018. BTO Research Report 717. British Trust for Ornithology, Thetford.

More about the Wren in Pembrokeshire