Long-tailed Tit - 2003-07

Suffering high mortality during severe winters, the breeding population during the 1984-88 survey was considered to be below optimum because of the effects of the cold winter of 1979. Numbers showed signs of recovery during the period of the survey and by 1988 it was estimated that between 1,100 and 1,600 pairs were breeding in the county, based on there being an average of six to eight pairs per occupied tetrad. The 2003-07 survey took place following a long period of mild winters and showed a 16% spread in distribution. The BBS findings suggested there was a 58% increase in Wales between 1994 and 2007, which if applied to the 2003-07 distribution gives an estimate of 2,500 breeding pairs in Pembrokeshire by the end of 2007.

Graham Rees

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 134

Orange = breeding probable = 53

Yellow = breeding possible = 39

Total tetrads in which registered = 226 (46.1%)

Pied Flycatcher - 2003-07

Pied Flycatchers were first proved to breed in Pembrokeshire, at Ffynone, in 1978 but they may have bred at Llancych in 1936. Colonisation of Pembrokeshire took place in the late 1970’s and 1980’s and the 1984-88 survey estimated the county population was about 100 pairs by 1988. Since then the population has undergone a decrease, so by the time of the 2003-07 survey there had been a 39% contraction in its county distribution. Even during the course of the survey there was known contraction, those breeding at Blackpool Mill Leat in 2003 having disappeared by 2004. It is estimated that 30 pairs were nesting in Pembrokeshire by the end of 2007. Pied Flycatchers decreased in the UK by 49% between 1996 and 2006 according to the BTO, early indications being because they have not adapted to peak food availability being advanced as a result of the trend towards earlier springs. Consequently the Pied Flycatcher has been amber-listed under the Birds of Conservation Concern 3 (Eaton et al., 2009). 

Graham Rees

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 4

Orange = breeding probable = 15

Total tetrads in which registered = 19 (3.9%)

Spotted Flycatcher - 2003-07

This is a species that has been declining in the UK since at least the 1960’s. The BBS calculated a decrease in excess of 50% by 2007. The Pembrokeshire survey of 1984-88 estimated a total of 900 pairs breeding in the county, based on an average of four pairs per occupied tetrad. The 2003-07 survey found there had only been a contraction of 7% in distribution. The Pembrokeshire BAP Breeding Bird Survey of 2003 found numbers were still high in old woodland, albeit the survey scope was small. It would seem that Spotted Flycatcher numbers in the county may have decreased to a lesser degree than the 37% calculated by the BBS for the UK as a whole between 1995 and 2006. Applying the BBS value to the 2003-07 distribution for Pembrokeshire suggests that about 500 pairs were breeding during the 2003-07 survey.

Graham Rees

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 66

Orange = breeding probable = 107

Yellow = breeding possible = 35

Total tetrads in which registered = 208 (42.5%)

Goldcrest - 2003-07

The Goldcrest suffers high mortality during severe winter weather. This was experienced in 1979, affecting the breeding population during the 1984-88 survey, when it was estimated that there were about 5,000 pairs by 1988. There were no severe winters thereafter up to and including the time of the 2003-07 survey. During this survey a 33% increase in distribution was detected, despite clear felling of some conifer plantations, probably because most had been surveyed before felling took place. The BBS found there had been a 14% increase in numbers in Wales in 2006–07, which if applied to Pembrokeshire suggests the population had risen to about 6,000 pairs during the survey of 2007 but this is likely to decrease following the loss of so many conifer plantations.

Graham Rees

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 72

Orange = breeding probable = 249

Yellow = breeding possible = 11

Total tetrads in which registered = 332 (67.8%)

Willow Warbler - 2003-07

This leaf warbler is familiar to many by virtue of its liquid, cascading song. A summer visitor to Britain, wintering in southern Africa, it is normally present in Pembrokeshire from April to September. Scrub, woodland edge and recently planted woodland are its prime habitat, where nests are placed on the ground concealed by vegetation. Willow warblers are normally absent as a breeding bird from the offshore islands, except for the partially wooded Caldey and are not usually found breeding in gardens.

The population estimate which accompanied the 1984-88 survey is now considered to be unsound. Census results from Dyfed Wildlife Trust reserves were applied across the whole county without taking habitat into account, and resulted in an inflated value. Had the findings of the 1988-91 National Atlas been available, a national average value could have been applied and would have resulted in a more realistic estimate of 13,500 pairs nesting in the county.

Comparing the results of the two local surveys indicate a retraction in distribution. The BBS suggests a 20% decrease in Wales between 1994 and 2007, which if applied to Pembrokeshire results in a population estimate of approaching 10,000 pairs nesting by 2007. This accords with the subjective opinion, that Willow Warblers were less numerous during 2003-07 survey than they were during the 1984-88 survey.

Evidence is emerging that this marked decrease is probably due to unfavourable conditions prevailing in the Willow Warblers’ tropical African wintering area.

Graham Rees

 

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 47

Orange = breeding probable = 307

Yellow = breeding possible = 15

Total tetrads in which registered = 369 (75.3%)

Chiffchaff - 2003-07

The repetitive song which gives the Chiffchaff its name is a familiar sound in the summer time. It favours deciduous rather than coniferous trees but is widespread in the county. The domed nest is usually well concealed and placed low down in the available vegetation.

Chiffchaff numbers have been increasing across Europe since about 1980. The first estimate of the Pembrokeshire breeding population was made following the results of the 1984-88 survey. At an average density of 15 pairs per occupied tetrad, a total of 6,000 pairs was suggested.

By the end of the 2003-07 survey a 13% spread in distribution had been plotted in Pembrokeshire and the BBS noted a 42% increase in Wales between 1994 and 2007. Using these figures an estimate of 8,500 pairs breeding in the county by 2007 emerged.

Graham Rees

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 101

Orange = breeding probable = 319

Yellow = breeding possible = 8

Total tetrads in which registered = 428 (87.3%)

Wood Warbler - 2003-07

This summer visitor is the largest and most colourful of the British leaf warblers, its green upperparts contrasting with its bright yellow breast and silky white belly. Seeing the male trembling while it delivers its trilling song is a fulfilling experience. Closed canopy woodland with little understory is the favoured habitat, where the nest is concealed on the ground among rank vegetation.

About a third of the UK population is found in Wales, where ideal habitat of deciduous woodland grazed by sheep has very little understory growth. Those breeding in Pembrokeshire are at the periphery of their distribution and have been found to be less abundant than in the main area. This may in part reflect the fact that the majority of county’s woodlands are not grazed and the understory and shrub layers are too dense for this species.

The UK population was estimated at 17,200 singing males in 1984–85 and the Pembrokeshire total at 250 singing males in 1988. A subsequent steady decline has been detected across northern and western Europe, the UK total being estimated at 9,000 -10,500 by the year 2000. The 2003-07 Pembrokeshire survey found that distribution had decreased by 50% compared with 1984-88, the remaining total being no more than 100 singing males, perhaps fewer.

Graham Rees

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 3

Orange = breeding probable = 19

Yellow = breeding possible = 3

Total tetrads in which registered = 25 (5.1%)

Dartford Warbler - 2003-07

The dark, long-tailed, vinous-breasted, resident Dartford Warbler is a rare breeding bird in Britain, with a population of less than 2,000 pairs. It inhabits heathland with gorse and heather. Although skulking within such habitat it does occasionally sing from the tops of gorse sprays. The nest is concealed within deep cover.

Historically Dartford Warblers have been confined to southern England, mostly found in Hampshire and Dorset, where numbers were reduced during severe cold winters but recovered in milder following years. The successive “Arctic” winters of 1961–62 and 1962–63 drastically reduced the population, with only 11 pairs known to have survived. The mild winters which have since prevailed enabled them not only to steadily increase but also to expand their range, principally to the west.

In Wales they were breeding in Gwent by 1998, in Glamorgan by 2000 and in the first year of the Pembrokeshire Breeding Birds Survey of 2003-07 up to six pairs were confirmed to be breeding at one locality. By the end of 2007 they had been found in eight tetrads, with a total population of 13 – 15 pairs. All were in lowland areas, none having yet been found in uplands as has been the case in Somerset, Devon and the Brecon Beacons.

Graham Rees

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed

Orange = breeding probable

Whitethroat - 2003-07

Whitethroats are perky, largely brown warblers are widespread in the county during the summer. They are particularly evident during their frequently performed song flights, when their disjointed, scratchy song draws attention to their presence. They inhabit heathlands, scrub, hedgerows, woodland edge and very young tree plantations. Nests are placed in low bushes, nettles, brambles and tall grass.

The map shows a similar distribution between the two local surveys at the tetrad level. Some minor changes were noted at a more local level, where young plantations had grown to the point where they became untenable for Whitethroats. Assessing population levels at any given time has been complicated by periodic collapses in numbers. In 1969 the British population was reduced by about 77%. This was associated with drought conditions in the African area where Whitethroats winter. Subsequent recovery has been interrupted by further population crashes of varying magnitude. By 1974 the breeding population had stabilized at approaching half the pre 1969 level but the subsequent recovery was interrupted by another crash in 1984. The 1984-88 Pembrokeshire survey took place in a period of recovery and by 1988 it was estimated to have reached an average density of 20 pairs per tetrad, giving a county total of 8,000 pairs. The similar returns for the 2003-07 survey would seem to indicate no change in the county population but in the meantime the BBS calculated a 10% increase between 1994 and 2007 but a decrease of 18% between 2000 and 2005. It seems that the estimate of 8,000 pairs in Pembrokeshire by 2007 is realistic, despite fluctuations during the time between the two local surveys.

Graham Rees

 

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 115

Orange = breeding probable = 289

Yellow = breeding possible = 12

Total tetrads in which registered = 416 (84.9%)

Lesser Whitethroat - 2003-07

The Lesser Whitethroat, a summer visitor, is an inconspicuous warbler which favours deep cover. Its most notable feature when seen well is its black patch through the eye. Its monotone rattling song often reveals its presence in the scrubby areas it frequents and where it nests.

No way has been found to separate possible passage birds from the records when evaluating the results of the 1984-88 survey. A minimal density of one pair per tetrad was used to estimate a county breeding population of 70 pairs. The 1988-91 National Atlas shows an abundance distribution where the Pembrokeshire density was much lower than the UK average of just over two per tetrad, suggesting that the local estimate was realistic. The same situation existed when assessing the returns from the 2003-07 survey, so the county estimate remains the same. Nonetheless the uncertainty of the impact of migrants being involved, means it should be regarded as a maximum and the true level might have been smaller, for the BTO considered that the UK population dropped to about 64,000 pairs by the year 2000 from an estimated 80,000 in 1991.

Graham Rees

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 4

Orange = breeding probable = 66

Yellow = breeding possible = 9

Total tetrads in which registered = 79 (16.1%)

Garden Warbler 2003-07

Surely it was this summer visitor that inspired the acronym LBJ (little brown job). It does however possess a pleasant mellow warbling song, though its critics often refer to this as being like a “garbled Blackcap”. It nests low down in shrubs and trees around woodland edge, rides and glades.

The 2003-07 survey found a marked absence in the extreme south compared to the 1984-88 presence. Nonetheless the totals registered for each of the two surveys was identical. The abundance map in the 1988-91 National Atlas indicates near maximum density in Pembrokeshire, which suggests the 1988 county estimate of 2,000 pairs was realistic. Since then the BTO has used a number of survey methods to conclude that although there have been short term fluctuations in the population, there has been a shallow long term decline. The BBS quantifies this as a 25% decrease in Wales between 1994 and 2007, which suggests the Pembrokeshire population had dropped to about 1,500 pairs by 2007.

Graham Rees

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 14

Orange = breeding probable = 163

Yellow = breeding possible = 16

Total tetrads in which registered = 193 (39.4%)

Blackcap - 2003-07

A predominantly grey warbler, the male with a distinctive black cap, the female’s cap ginger, the Blackcap inhabits the cover of trees and scrub, where it nests. It is found in all bar the barest parts of the county. Its melodic, fluty, song draws attention to its presence but it can be difficult to locate. Most Blackcaps are summer visitors to Pembrokeshire.

A variety of monitoring schemes have concluded that Blackcaps have been consistently increasing since at least the 1970’s. Despite much conjecture, no convincing explanation has been suggested as to why this has been so. The 2003-07 county survey found that there had been a 17% increase in distribution compared with that found in 1984-88.  The BBS has calculated an increase of 87% in Wales between 1994 and 2007. Applying these increases locally suggests approaching 13,000 pairs were breeding in Pembrokeshire at the end of 2007, compared to 7,000 pairs estimated in 1988. 

Graham Rees

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 71

Orange = breeding probable = 317

Yellow = breeding possible = 9

Total tetrads in which registered = 397 (81%)