Guillemot - 2003-07

Guillemots nest in dense, noisy colonies with many birds crowding together.  Mainly nesting on ledges on near vertical cliffs, they are also present on the top of sea stacks in a few sites.

Guillemots are found in very large numbers on the south coast at Castlemartin, especially at Elegug Stacks, where the well known colonies provide a thrilling and easily observed wildlife spectacle. Skomer has the largest island colony, but there are quite significant colonies on St Margaret’s Island, on Skokholm, and on Ramsey.  A small number breed on Grassholm and on the north coast of the county there are scattered colonies of a few hundred birds.

The overall population has been increasing steadily for 40 years and although there have been minor “blips” in the rate of increase this trend is echoed at all colonies.  The main study colonies and the detailed whole island counts on Skomer, suggest an average annual rate of increase of 5.7%, the colony increasing from 2,400 birds in 1970 to 17,700 in 2008.  In the period between the two atlases of 1984–88 and 2003-07, the overall county population grew from around 16,000 to over 30,000 birds.

The number of Guillemots is currently at its highest level since counting seabirds became a regular  annual priority for conservationists and ornithologists, but there is some evidence from comments made by Lockley et al (1949) that pre war populations were higher, perhaps much higher, on the basis of some photographs of colonies. It was surmised that during the war years the high level of marine pollution caused the deaths of many thousands of Guillemots.

Guillemots are very vulnerable to marine pollution incidents as they spend most of their time "rafting" (floating on the surface) and shallow-diving. The Sea Empress incident at the entrance to Milford Haven in February 1996, followed by the Erika incident off the French coast in January 2000, killed many birds from the Pembrokeshire colonies. The Sea Empress spill killed mainly adults and there was a subsequent 60% decline in breeding numbers on St Margaret’s Island. The effects at other coastal and the major island colonies was less clear but subsequent research has shown that such incidents do manifest themselves in reduced survival rates in the years following the incident.  However, because there are so many immature birds trying to establish themselves in the colonies the effect has been masked.  (Votier et al 2005). The Erika incident mainly affected immature birds less than 6 years old and there was no discernable subsequent effect on numbers at any of the colonies.

Steve Sutcliffe

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 17

Yellow = breeding possible = not included

Total tetrads in which registered = 17 (3.5%

Great Black-backed Gull - 2003-07

Great black-backs are top predators on the seabird islands, taking eggs and chicks of other species, and are regular predators of Puffins, Manx Shearwaters and Rabbits. They nest in single pairs or loose colonies, the former preferring prominent places on the top of rocky outcrops, while those in colonies will select dense vegetation on the top of the islands. Over 90% of the Pembrokeshire pairs breed on the offshore islands with rest as scattered individual pairs around most of the county coastline.

Numbers of these gulls have fluctuated widely.  Apparently very small numbers were present in the county in the late 19th Century (Harrison & Hurrell, 1933) but by 1949 they could be found all around the coastline and especially on the islands, where Lockley et al (1949) found 310 pairs on Skomer, Middleholm, Skokholm, Grassholm and St Margaret’s combined. Davis (1958) reported between 490 and 520 pairs in the county following an all Wales survey and they continued to increase with 542 pairs recorded in 1969’s Operation Seafarer (Cramp et al 1974). 

Control measures in the 1960s and 1970s on Skomer and Skokholm, followed by a botulism outbreak in the early 1980’s, reduced numbers to a low of about 140 pairs in the mid-1980s.  There has been a steady but slow recovery since then and the population had risen to around 300 pairs in 2000 but has subsequently remained stable, except on Skomer where it has declined by about a third. The mean breeding success recorded on the Pembrokeshire islands in the ten years to 2005 was 1.15 to 1.29 chicks per pair, by far the highest success rate in the UK during this period. In consequence there has been a steady recovery since the 1980’s and the population in the county had risen to around 300 pairs in 2000 and has subsequently remained stable at around this number.

Steve Sutcliffe

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 21

Orange = breeding probable = 9

Yellow = breeding possible = not included

Total tetrads in which found = 30 (6.1%)

Herring Gull - 2003-07

Only 40 years ago Herring Gulls could be found breeding in almost every cove and on every cliff around the Pembrokeshire coastline but in the early 2000s they are predominantly confined to the offshore islands. Unfortunately we know rather little about their historic numbers, perhaps because they appeared so common they were never counted.  Indeed the eggs were widely collected for human consumption at least up to the 1960’s.

Herring gulls feed along the coastline, in the fields and formerly at rubbish tips and around the docks. They will readily take any food offered to them.  Their ability to adapt to available food sources enabled them to increase in numbers dramatically, around 10% per year, between the 1950’s and the early 1970’s, when there was abundant waste available on rubbish tips and in the docks at Milford Haven.

The subsequent dramatic decline of c.80% in the early 1980’s was almost totally caused by a botulism outbreak which killed many hundreds of adult birds (Sutcliffe 1986).

It is clear from the map that Herring Gulls still breed all around the coastline of the county, but today mostly in small numbers and often on isolated offshore rocks.  The main concentrations are on the islands and in particular on Caldey, where numbers have recovered from a low of 675 pairs in 1998 to just over 2,000 in 2008, making it one of the largest colonies in the UK.  On the other islands the populations have not recovered: on Skomer and Skokholm it has been relatively stable at just under c. 450 to 600 pairs and 250 to 350 pairs respectively during the last decade.  The islands of Ramsey and the Bishops hold around 300 pairs and there are small colonies of 50 to 200 pairs on St Margaret’s and Grassholm Islands, Dinas Head and along the Castlemartin coastline. The whole county population in 2003-07 was probably in the order of 4,000 pairs, compared with the peak 1969 counts of 12,700.

Steve Sutcliffe

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 69

Orange = breeding probable = 5

Yellow = breeding possible = not included

Total tetrads in which registered = 74 (15.1%)

Lesser Black-backed Gull - 2003-07

Formerly the main colonies were confined to the islands of Skomer and Skokholm with a few on Caldey, St Margaret’s and Ramsey and occasionally on the mainland cliffs. Mathew (1894) knew of colonies of 20 – 30 pairs but there were around 2,000 by the middle of the century (Lockley et al 1949). The population increased dramatically from the early 1950’s, to peak at around 20,000 pairs on Skomer and 5,000 on Skokholm in the mid-1980’s. 

This increase was fuelled largely by a ready source of food in the form small fish that were a discarded by-catch of the scampi fishery in the nearby Smalls grounds.  New legislation introduced in the mid-1980’s changed the mesh size of the nets so that fewer small fish were caught and this food supply was lost to the gulls in a very short period. The result has been almost very low breeding success, including total failure in some years, from 1989 to the present day and a resultant steady decline in the number of gulls. Numbers of Lesser Black-backed Gulls breeding on the mainland coast have increased in several places in the last 20 years, with a gradual spread in distribution during this time, but the population here is small.

Over 95% of Lesser Black-backed Gulls in the county breed on Skomer, Skokholm and Caldey Islands.  They are found in large colonies wherever there is good cover for chicks and prefer a bracken/gorse/thick grass habitat.  In 2007 the county population was around half of the peak at c. 13,000 pairs and continuing to decline because there are so few immature birds entering the breeding population.  

Steve Sutcliffe

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 30

Orange = breeding probable = 6

Yellow = breeding possible = not included

Total tetrads in which registered = 36 (7.3%)

Kittiwake - 2003-07

Kittiwakes nest in dense colonies on ledges of vertical cliffs.  Although now almost totally confined to the islands of Skomer, St Margaret’s, Grassholm and Ramsey, they were formerly very common coastal breeding gulls, especially along the Castlemartin coastline to Stackpole Head. Kittiwakes have never nested on Skokholm.

These changes in the breeding colony sizes and distribution have been dramatic and largely remain unexplained, for whilst the Skomer population has remained relatively stable at around 2,200 pairs, other colonies have disappeared completely. In the period following the Seabird survey of 1985-87  the thriving colony on St Margaret’s Island reduced from well over 300 pairs to just 6 in 2000, and then increased again to over 300 in 2009.  This quite rapid change must include some birds which have moved from other breeding sites. Along the Castlemartin peninsula a population of around 700 pairs during 1984-88 had declined to about 30 pairs by 2007.

Overall the Kittiwake population has declined significantly in the county in recent times.  Between 1969-1970 and 1985-1987 surveys the county population increased from 3,037 to 3,935 pairs but had subsequently declined to around 3,100 pairs in 2000 and had probably a similar population total in the period 2003 to 2007.

The breeding success on Skomer is variable with productivity ranging between 0.30 and 1.01 chicks per pair but generally near to 0.5.  It is a low level of success and there is a “feeling” that, as at many other colonies around Britain in the first decade of the 2000’s, Pembrokeshire colonies have suffered breeding failure and a rapidly declining population is just about “hanging on”.

Steve Sutcliffe

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 6 (1.2%)

Curlew - 2003-07

By the 1980s it was estimated that only about 20 pairs were still breeding in Pembrokeshire.  Of these, the majority (13 pairs) were on Skomer, with the rest in the boggy areas of the Preseli Hills. Between 2003 and 2007 the number of tetrads in which they were found had shrunk to just two from 12 recorded during the 1984-88 period, a decline of 83%.

They were only confirmed breeding on Skomer where six to nine pairs nested during the 2003-7 atlas period. The breeding population in Wales is also in trouble - BBS records indicate a 33% decline in the population between 1994 and 2007 across Wales as a whole, based on 37 sample sites.

Further research is needed to determine if former mainland haunts in Pembrokeshire are capable of supporting breeding curlews again.

Bob Haycock

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 1

Orange = breeding probable = 0

Yellow = breeding possible = 1

Total tetrads in which registered = 2 (0.4%)

Snipe - 2003-07

Within Pembrokeshire, Snipe were considered to be fairly widespread as a breeding species until about 50-60 years ago. During the 1984-88 atlas period they were recorded from nine tetrads, mainly in the Preseli Hills and in the catchment area of the Eastern Cleddau. Only a handful of pairs were recorded, and whilst breeding may have occurred in three separate tetrads, there was no certainty of this. It was thought that extensive land drainage and reduced grazing of the commons had caused the decline, with an increase in predators placing further pressure on the remaining population.

Some 20 years later, Snipe were recorded from 5 tetrads during 2003-07 but only three of these were inland within areas of potentially suitable breeding habitat. The other two locations being near the coast were almost certainly records of transient birds. Even at the inland locations, it is likely that Snipe recorded here were also migrants. No “classic” display flights were recorded and their former haunts currently seem unable to support a breeding population.

Bob Haycock

Fieldwork 2003-07 (based on 490 tetrads)

Yellow = breeding possible = 5

Total tetrads in which registered = 5 (1%)

Lapwing - 2003-07

In winter they can appear in flocks of several hundred to a few thousand and occur widely across farmland and coastal habitats. The number of pairs attempting to breed in Pembrokeshire has continued to decline over the last 20 years, continuing a trend noted in Donovan and Rees (1994).

Lapwing distribution, as indicated by the number of tetrads in which they were found, fell by a massive 86%, between 1984-88 and 2003-07, reflecting the significance of the overall decline in the breeding population. All atlas categories declined by large amounts. Breeding numbers are also declining in many other parts of Britain, and they are red-listed in the Birds of Conservation Concern 3 (Eaton et al., 2009).

The BBS index indicated a UK-wide decline of 18% between 1994 and 2007, but there were insufficient 1km squares sampled to give a Wales index for the species.  

It was estimated that there were around 70 pairs in Pembrokeshire during 1984-88. During 2003 – 2007 the maximum recorded breeding population in any one year was only 14 pairs, in 2003, with between about nine and 12 breeding pairs recorded each year subsequently, a decline of between 80 and 87%.

One or two pairs have attempted to breed on the Castlemartin peninsula, but recently the entire population has been more or less split between two key breeding centres at Ramsey Island and the old dismantled BP oil tank farm at Kilpaison. Ringing of nestlings by the Pembrokeshire Ringing Group at the latter site is showing that some young are surviving and returning in later years, possibly to breed in the same area.

Management of their breeding habitat is being carried out by the RSPB on Ramsey; this includes minimising potential disturbance from visitors to the island. Recent attempts by the RSPB to help create suitable arable conditions in the Castlemartin Corse/Broomhill Burrows area have, so far, failed to attract the birds to stay and breed successfully here.  

Bob Haycock

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 3

Orange = breeding probable = 0

Yellow = breeding possible = 1

Total tetrads in which registered = 4 (0.8%)

Ringed Plover - 2003-07

Within Pembrokeshire, the status of Ringed Plovers and their distribution has remained pretty well unchanged over the last c. 20 years. The table suggests a decline in the number of tetrads in which Ringed Plovers were found, but during the 1984-88 period two tetrads included birds that were most likely to have been migrants as there was no confirmed or probable breeding reported.

A single pair bred in each of the five years 2003-07 on the Castlemartin Range. The nest site is on the cliff-top above Wind Bay near Linney Head. In 2007 a second pair held territory for a short time in May and early June above Berryslade, a little way west of Wind Bay, but were not proven to have nested. Several other Ringed Plovers stayed into early June on nearby Frainslake Beach but no breeding occurred here, or in dune hollows in Brownslade Burrows where they have bred in the last decade, but outside the atlas period. The Castlemartin site was not known to be occupied in 1984, but has been in regular occupancy since around 1990.

The main nesting habitat at Castlemartin is open, exposed stony limestone terrain directly above c. 30 metre high sea cliffs, contiguous with short herb-rich and invertebrate-rich maritime grassland turf where the birds often feed. Here a small area of limestone clitter provides suitable bare ground for a nest scrape, sufficient to hide cryptically marked eggs. There are numerous boulders and crevices for chicks to hide from predators and to shelter under. Sometimes two clutches are laid over a breeding season which extends from May to August.

Despite being within a busy army training range, and with a metalled road running along-side the breeding site, the plovers are afforded reasonable levels of protection. The breeding location is identified as a “sensitive area” on estate management maps, and there is usually very little military activity close to the nest site.

Because it is an active military range, relatively few people currently visit the area, unless they are briefed and are undertaking approved activities. Guided walking groups and climbers are briefed annually about seasonal bird nesting restrictions, which covers the plover nesting zone, to minimise disturbance to cliff-nesting birds. The plovers are also monitored each year to help ensure appropriate protection measures are adequate and up to date.

Tetrads in which registered (based on 490 tetrads) = 2 (0.4%)

Bob Haycock

Oystercatcher - 2003-07

In Pembrokeshire oystercatchers are largely restricted to the coast, breeding on rocky shores, sea-cliffs and tops of small islets and larger offshore islands. On the mainland they have a fairly regular, if thinly spread, linear distribution along the coast. However, on the larger islands, Skomer and Skokholm for example, they can form loose colonies at a higher concentration.

Oystercatchers are long-lived birds and it is possible that some of the same birds observed in the 1980s were still breeding in the recent survey period.

Comparing the total number of tetrads in which they were found suggests a small and probably insignificant decline in breeding population distribution between 1984-88 and 2003-07, down by about 13%.  Although there was a large decline in the number of tetrads where confirmed breeding was reported, this was more or less balanced by the number of tetrads that registered probable and possible breeding evidence.

Scrutiny of the tetrad distribution map suggests that, although there are fewer tetrads with confirmed breeding, overall there was generally very little change in their distribution on the mainland coast and offshore islands north of Milford Haven. A close look at the map suggests that their distribution has thinned out a little along parts of the south coast.

In 1984-88, it was estimated that there were about 300 pairs of breeding Oystercatchers. At least 50% of these were on the offshore islands, where more regular monitoring is conducted. In 2003-07, the island populations again recorded in the region of 140-160 pairs. This suggests that the Pembrokeshire population is probably reasonably stable, at least in optimal habitat locations.

Monitoring of a small Oystercatcher population along the Castlemartin peninsula, between 2003 and 2007, has provided evidence of 7 – 8 regularly nesting pairs along a 20 km length of limestone coast, covering seven coastal tetrads. Nesting density was quite low and nests were patchily distributed, ranging from one – three per tetrad, but they were absent from some tetrads. Three of these pairs regularly breed at Stackpole each year in one tetrad, in some years with limited success. They are monitored annually and this number has not changed much over the last 20 years.

In 2006, it was reported that in one fairly remote nest, on the shore of Carew River, 8 eggs had been laid which was almost certainly a result of egg dumping involving two females.

Based on 76 tetrads where Oystercatchers were found along the mainland coast of Pembrokeshire, an average of two pairs per occupied tetrad would seem to be a reasonable assumption. This would suggest at least 150 pairs which, when combined with the most recent Islands totals, is similar to the 300 pairs in Pembrokeshire as a whole, estimated in the mid 1980s.

If the decline in distribution and confirmed breeding status along parts of the south coast is real and not due to observer bias, then perhaps parts of the coast are sub-optimal for this species. However, it is also worth considering other possible reasons why they could have thinned out, or their breeding success may have been affected here.

Oystercatchers breeding on the rocky coast are dependent for food on good populations of molluscs and other marine prey in the inter-tidal zone. Perhaps their apparent thinning out, and lack of confirmed breeding, along parts of the south coast is a legacy of the Sea Empress oil spill that affected this coastline in winter/spring 1996.

Surveys have shown that the coastal habitats have recovered well since, but perhaps the density and range of age structures of molluscs, limpets, whelks, mussels, and other marine prey have not yet fully recovered in some locations. Perhaps there are still insufficient food resources to fully support them throughout the breeding season?

Another possible issue that needs consideration is the increase being made of the coastal inter-tidal zone by people undertaking “coasteering”. This activity (involving combinations of rock-clambering and swimming along a linear course at the base of the cliffs, usually by groups of people) has become extremely popular along parts of the south coast and along other sections of the Pembrokeshire coastline during the last 20 years.

Whilst the routes used may not cause too much lasting damage to marine food sources in an already harsh, wave-lashed environment; breeding birds on the lower ledges and cliff-crevices may now be more frequently disturbed in areas used for recreation than was the case in the past.

The Pembrokeshire Outdoor Charter Group, involving Activity Centres and conservation bodies, are attempting to improve knowledge of the range and sensitivities of species and habitats on the coast. Hopefully this will ensure that the small number of breeding and roosting birds specialising in the harsh rocky inter-tidal zone will be afforded sympathetic protection. There is still a need to identify the areas used by wildlife and for more detailed monitoring.

Bob Haycock

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 25

Orange = breeding probable = 25

Yellow = breeding possible = 26

Total tetrads in which registered = 76 (15.5%)

Moorhen - 2003-07

Normally retiring in nature, moorhens can become quite confiding in public areas, such as Pembroke Mill Ponds. Moorhens inhabit lowland fresh water places with well vegetated margins, which are essential for nesting. They sometimes use old nests of other birds, even when they are in trees.

A comparison of the two surveys indicates a 13% increase in distribution by the latter period. If this is applied to the estimate of 300 pairs accompanying the earlier survey, then there were probably about 340 pairs in 2007. The increase was probably due to irrigation reservoirs which were new and bare during the 1980’s now acquiring vegetation.

Graham Rees

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 86

Orange = breeding probable = 52

Yellow = breeding possible = 32

Total tetrads in which registered = 170 (34.7%)

Water Rail - 2003-07

This slender, long-billed crake with its cryptic brown and grey plumage broken by dark streaks, is more often heard than seen. It inhabits mainly fresh water lowland, boggy places with dense plant growth, making it difficult to see and providing concealment for its nest.

Bearing in mind how difficult detection of this species is, the survey results must be regarded as representing a minimum presence. The most striking difference in distribution change is the absence in the St David’s area indicated by the latter survey. There has been no obvious visible change, or loss or fragmentation, in the relevant habitat during the interval between surveys, suggesting apparent absence may not have been real. In that case it could be concluded that there has been no change in the county population level of about 20 pairs. A specialist census concentrating on this species might well be revealing and could lead to a reassessment of its breeding status in Pembrokeshire.

Graham Rees

  

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 1

Orange = breeding probable = 5

Yellow = breeding possible = 10

Total tetrads in which registered = 16 (3.3%)