Swift - 2003-07

Swifts nest in cavities in buildings and in Pembrokeshire in the cliffs of the south coast.

Those nesting in cliffs apart, Swifts in Pembrokeshire are entirely reliant on buildings for nest sites. The amount of renovation that has taken place since the 1980’s has made an increasing number of buildings no longer accessible to Swifts and new constructions have also proved to be unsuitable. It could reasonably be expected, therefore, that the breeding population has decreased over the past 20 years. Comparing the confirmed and probable breeding registrations combined, indicates a 48% decrease between 1984-88 and 2003-07.  This is consistent with the BBS index showing a 47% decrease in Wales as a whole between 1994 and 2007. The possible breeding category was ignored when interpreting the results of both local surveys,

Swifts being such mobile birds when feeding, they can be seen almost anywhere without this providing any clue to their nest site. Although no good method of assessing population has been evolved on a county scale, an estimate was made at the end of the 1984-88 survey by noting how many were entering buildings at some reasonably well-watched colonies and using this as guidance. The result was a rough estimate of about 2,000 pairs. Applying the distribution decrease to this figure suggests there may have been less than 1,000 pairs by the end of 2007. However this assessment makes no allowance for any decrease occurring within the surviving distribution, something which has not been quantified. It could well be that the number breeding in Pembrokeshire has dipped below 1,000 pairs.

 Graham Rees

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 39

Orange = breeding probable = 13

Yellow = breeding possible = not included

Total tetrads in which registered = 52 (10.6%)

Short-eared Owl - 2003-07

Short-eared Owls are very much birds of open rough grassland and heath, nesting on the ground usually under the shelter of heather, bracken or tall grasses. They will also breed in young forestry plantations. Areas with high populations of small mammal prey and a lack of disturbance, including disturbance from ground predators are key to their success.

Given these requirements, it is perhaps not really surprising that Short-eared Owls are a scarce breeding bird in Pembrokeshire and within Wales. Such “optimal” breeding habitat occurs mainly on the offshore islands.

Skomer is a long-established and regionally important breeding site for them, supporting up to five pairs between 1984 and 88, about 20% of the entire Welsh population at that time. In 1993 an unprecedented 12 pairs nested on the island. They also used to breed regularly on the commons of the St David’s peninsula where there are good stands of rough grassland and wet heath. The population appears to be fairly stable, compared with the 1984-88 period, though it fluctuates, probably depending on the density of vole populations.

During the 2003-07 atlas period between one and four pairs bred on Skomer and a single pair nested on Ramsey in 2005 for the first time since 1971. Breeding may also have occurred on Dowrog, where one was recorded carrying food in late May 2004 but breeding was not proven. Further sightings included a pair appearing to hold a territory on Dowrog in May 2006, but breeding did not occur.

Pellets analysed on Skomer have shown that although Short-eared Owls largely feed on young Rabbits and Skomer Voles, they may also take significant numbers of Storm Petrels, like the Little Owls breeding there.  Fifty-five pellets examined in 2007 produced 18 Storm Petrels, whilst Storm Petrels formed 31% of prey recorded in 13 pellets in 2004.

Bob Haycock

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 2

Yellow = breeding possible = 1

Total tetrads in which registered = 3 (0.6%)

Tawny Owl - 2003-07

Examination of the tetrad map suggests that the Tawny Owl breeding population distribution has thinned out in places over the last 20 years, especially across the more intensively farmed landscape with smaller amounts of woodland in the south of the county. However, there was evidence of higher tetrad occupancy in the east, and also on the St David’s peninsula where they were absent in the 1984-88 atlas period.

Overall there was a 21% decline in the number of tetrads in which they were found. The number of tetrads where presence only was recorded was down by 50% but the number of tetrads where probable and confirmed breeding was recorded was probably not significantly different between the two atlas periods.

The population stronghold currently appears to be in the more wooded Eastern Cleddau area and tributary valleys. There is a reasonably strong presence in the Gwaun and Cych valleys and also near the town of Pembroke. These apparent changes in distribution need to be treated with some caution. Being mainly nocturnal, they are a difficult species to record and so their distribution may be affected by observer effort bias. Added to the problem is the fact that both males and females will call from different parts of their territory and this could inflate the population estimate.

Donovan and Rees (1994) postulated that there were 4 – 5 pairs of Tawny Owls per occupied tetrad in Pembrokeshire during the 1984-88 atlas period. This produced an estimate of between 800 and 1,000 pairs across the county.

Observations of two areas, based on calling birds heard within 3 tetrads in woodland at Stackpole and within 2 tetrads at Pickle Wood and Minwear, were made during the 2003-07 period by Haycock, (unpublished data). This suggested a maximum breeding density in both areas of two and three pairs per tetrad respectively, about half the estimated total for the earlier period. Both these areas contain what is considered to be optimal breeding and feeding habitat.

1988-91 National Atlas notes the difficulties in estimating the population of this species due to their nocturnal behaviour. They suggest an average density of 10 pairs in each occupied 10-km square for Britain as a whole, based on 1988-91 National Atlas data and a national Tawny Owl survey (Percival, 1990). This provided a lower estimated population for Britain than previous national population estimates but was considered to be the best available at that time. However, it was based mainly on a single year national Tawny Owl survey when small mammal populations were low.

If two or three pairs per tetrad, from a small sample of only five tetrads, is typical of other tetrad densities where they were recorded in 2003-07, then this would provide a Pembrokeshire-wide estimate of between about 320 and 470 pairs.

Whether there has been a considerable reduction in the Tawny Owl breeding population is difficult to determine, for reasons given earlier. An apparent slight distribution increase in the east of the Vice-County may also reflect better recording effort in this area, and so may not represent a real shift. More survey work is required to determine if the 21% decline in the number of tetrads supporting Tawny Owls equates to a real population decline or just re-emphasises difficulties in recording this species. 

Bob Haycock

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 50

Orange = breeding probable = 79

Yellow = breeding possible = 30

Total tetrads in which registered = 159 (32.5%)

Little Owl - 2003-07

Little Owls are found in open lowland country; they often perch in quite prominent positions close to nest sites and so are not quite as difficult to census, compared with the larger owls. According to Donovan and Rees (1994) Little Owls were thought to be increasing again following a gradual decline in the middle part of the 20^th Century.

Recent data suggest that there has clearly been a significant crash in their population during the years between 1984-88 and 2003-07. During the earlier atlas period, Little Owls were recorded in 31 tetrads, but from only six tetrads during 2003-07, an 81% decline. All atlas categories registered fairly large declines.

Donovan and Rees (1994) estimated that there were probably 50 pairs breeding in Pembrokeshire in the 1980s. During the recent atlas period, breeding was confirmed only on Skomer Island and on Ramsey Island. On the Pembrokeshire mainland they were recorded at just a thin scattering of widely distributed locations where breeding was not proven.

Although this is an introduced species to Britain, first recorded in Pembrokeshire at Solva in 1920 (Donovan and Rees, 1994), the Little Owl is now one of our rarest breeding species.  Judging by the latest distribution maps, it would appear to be one we could lose, at least on the Pembrokeshire mainland.

Bob Haycock

Barn Owl - 2003-07

Barn Owls are thinly scattered across the county, mainly associated with farmland, particularly where there are good amounts of rough grazing. River valleys, such as those of the Western and Eastern Cleddau, are good areas for them. They mainly nest in farm buildings, including crevices in natural cliffs and quarries. Old semi-ruined buildings can also be important. Being a Schedule 1 species (under the Wildlife and Countryside Act) they are afforded extra protection measures, such locations need to be considered carefully in development planning applications.

They will readily utilise artificial nest sites provided in appropriate locations, including nest boxes placed in modern farm buildings or in trees. Being mainly nocturnal, Barn Owls can be difficult to locate. However, breeding adults can often be seen out hunting before dark when they are feeding young, gracefully flitting along hedgerows and grassy areas in search of rodents.

Due to recording difficulties, the atlas tetrad maps probably under-estimate their true distribution. Nevertheless, the number of tetrads in which they were recorded was actually very similar in both atlas periods.

With annual fluctuations in breeding success, mainly linked to cycles in vole populations, it is very difficult to estimate Barn Owl population levels without detailed study. It was considered that there were around 100 breeding pairs in Pembrokeshire in 1984-88, based on the number of tetrads where they were found. 

During the first atlas survey a large proportion of the records of Barn Owls came by talking to farmers, something that was also important during 2003-07.

With an absence of more detailed methods of estimating the population, the overall population is considered to be similar to that of the earlier period. The total number of tetrads with confirmed and probable breeding was higher than that of the earlier atlas period, so the actual breeding population may have been higher.

Since the 1980s, winters have been generally milder so winter survival of Barn Owls may also have improved. More detailed surveys are needed to refine ways of estimating population levels.

Bob Haycock

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 47

Orange = breeding probable = 18

Yellow = breeding possible = 36

Total tetrads in which registered = 101 (20.6%)

Cuckoo - 2003-07

Cuckoos were found in only 80 tetrads between 2003 and 2007 compared with more than 200 tetrads 20 years ago (a decline of about 62%). All atlas categories registered huge declines.

What is most apparent is that the population is now reasonably widespread only in the open country of the Preselis and on the St. David’s peninsula. Their recorded distribution here in 2003-07 was fairly similar to that of the 1984-88 atlas period. Both these areas probably support potentially good populations of ground-nesting host species (such as Meadow Pipit). They have all but disappeared as a regular breeding species in the south of the county and along the Teifi valley bordering Ceredigion. Surprisingly, Cuckoos appear to have declined along the Castlemartin peninsula where there are still good populations of potential host species within the extensive Military Range.

In 1984-88 it was assumed that the Pembrokeshire Cuckoo population was about 210 pairs (approx one pair per occupied tetrad). The most recently available figures from BBS (Wales) indicate that there has been a 52% decline in the Cuckoo population index between 1994 and 2007. According to a BTO Report (Say Goodbye to the Cuckoo), the national Cuckoo population showed a decline of more than 60% across the country during the period 1981-2006. Because of this population fall, Cuckoos have been added to the “red-list” of birds of conservation concern. The decline in the number of tetrads in which they were found in Pembrokeshire (62%) very much mirrors the national picture over the same period.

If the decline in Pembrokeshire is between 52% (based on the Welsh BBS results, albeit from only 56 sample sites across of Wales) and about 62% (based on the decline in tetrad distribution) – this would suggest a current estimated population of no more than 80-109 pairs, now largely confined to optimal habitat in the north of the County. Because Cuckoos calling in early spring may still be on migration, it is probably better to consider only those tetrads with probable or confirmed breeding evidence; this suggests a population of no more than 70 pairs in the recent atlas period.

The Cuckoo may be the victim of a variety of factors. They may be struggling to find enough food during the breeding season here in the UK and also suffering a similar fate on their wintering grounds in Africa. Declining habitat quality may also be affecting host species such as Meadow Pipit and Dunnock (species also showing signs of decline nationally) and thus affecting the ability for Cuckoos to rear a sufficient number of young each year needed to maintain a stable population.

Bob Haycock

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 1

Orange = breeding probable = 69

Yellow = breeding possible = 10

Total tetrads in which registered = 80 (16.3%)

Collared Dove - 2003-07

Most people, whether they live in town or village, will be familiar with this pale buff dove with its striking dark collar and monotonous cooing song. Originally a bird of the Orient, it has expanded its range to eventually colonise Britain. It first nested in Pembrokeshire in 1961 and was widespread by the time of the 1984-88 survey. It has been found to have a close association with human habitation, occurring around farmsteads, small holdings and gardens but to be absent from more open countryside. Its flimsy nest is placed in trees, particularly conifers and it is able to breed all year long.

Comparison of the two survey results shows a 15% increase in distribution by the latter period. This compares with an 18% increase in Wales as a whole between 1984 and 2007 noted by the BBS. The estimated Pembrokeshire breeding population of 1,600 – 2,100 which accompanied the survey of 1984-88, was based on a range of six to eight pairs per occupied tetrad, which attempted to cater for higher densities in suburban areas than in isolated homesteads. The same situation prevailed during the 2003-07 survey, so applying the 15% increase to the earlier estimate suggests a breeding population in the range of 1,830 to 2,440 pairs in the county.

Graham Rees

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 69

Orange = breeding probable = 199

Yellow = breeding possible = 41

Total tetrads in which registered = 309 (63.1%)

Woodpigeon - 2003-07

It was estimated that there were about 10,000 pairs breeding in Pembrokeshire at the end of the 1984-88 survey. This was based on an average of 25 pairs per occupied tetrad. The 1988-91 National Atlas used an average of about 40 per tetrad for the UK as a whole. The highest concentrations were found in woodland and areas of arable farming, particularly where these habitats were found adjacent to each other.

Woodland and arable farmland makes up only a small proportion of Pembrokeshire which is largely a pastoral county. Considering also that many of the fields are bounded by hedgebanks with few suitable trees for nesting, makes it likely that Woodpigeon density is lower than the UK average. It is notable too that only a 4% increase in distribution was found between the two local surveys, 1984-88 and 2003 – 2007, compared to a 35% increase in Wales as a whole between 1994 and 2007 noted by the BBS. Using an estimated average of 26 pairs per tetrad it is thought that about 11,000 pairs were nesting in the county at the end of 2007.

Graham Rees

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 160

Orange = breeding probable = 235

Yellow = breeding possible = 40

Total tetrads in which registered = 435 (88.8%)

Stock Dove - 2003-07

The Stock Dove population of the UK was considered to be stable in the 1980’s, having recovered from a decline in the 1950’s and 1960’s caused by the effects of organo-chlorine seed dressings, used in arable farming, which were subsequently withdrawn. It is unlikely this had a big impact in Pembrokeshire which has long been dominated by pasture land. The chemicals did have an effect on Peregrines, the local population crashing in the 1950’s. Peregrines prey on many mobile birds, such as racing pigeons, which would have arrived in the county already affected, and the falcons being at the head of the food chain accumulated the chemicals with detrimental consequences. While the Peregrine population was low, Stock Doves expanded their range in the county, colonising the offshore islands from about 1975. However, as Peregrine numbers recovered, fewer Stock Doves nested on the islands and by the time of the 1984-88 survey had almost disappeared. They continued to nest on some of the mainland cliffs but the majority were thinly spread inland.

It was estimated that on average there were no more than two or three pairs per occupied tetrad, suggesting a county population of 300 – 500 pairs. The 2003-07 survey revealed a marked decrease in Stock Dove numbers, distribution contracting by 38%. This suggests that the Pembrokeshire breeding population lay in the range 180 -300 pairs by the end of 2007.

Graham Rees

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 11

Orange = breeding probable = 49

Yellow = breeding possible = 38

Total tetrads in which registered = 98 (20%)

Feral Pigeon - 2003-07

Feral Pigeons are domesticated birds that have escaped from captivity to breed in a wild state, as well as their descendents. Such domestic birds are derivatives from Rock Doves which have been selectively bred as racers, or to breed throughout the year when they were relied upon as a food resource. Selective breeding has resulted in a great variety of plumage patterns, including some which approximate to their Rock Dove ancestors. It is unlikely that any pure bred Rock Doves have survived in Pembrokeshire because of inter breeding with the numerically preponderant feral varieties. Feral Pigeons in Pembrokeshire nest on ledges in buildings, quarries and sea cliffs.

Comparing the distribution in 1984-88 with that of 2003-07 shows a 63% increase by the latter period. The number of registrations diminished along parts of the coast in the west and north but showed an increase inland, albeit with a considerable adjustment in localities. The increase accords with the findings of the BBS, which assessed a 69% increase in Wales as a whole between 1994 and 2007. The estimate made at the end of 1988 of 3,000 pairs in Pembrokeshire, attempted to allow for larger concentrations in towns than elsewhere. Assuming the estimate was realistic and applying a 63% increase, suggests that approaching 5,000 pairs were nesting in 2007. The reasons for the increase are not known but a diminished interest in maintaining lofts by pigeon racers, with a consequent release of birds, may have been a contributory factor.

Graham Rees

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 119

Orange = breeding probable = 74

Yellow = breeding possible = 40

Total tetrads in which registered = 233 (47.6%)

Puffin - 2003-07

Common offshore around western Pembrokeshire between late March and late July each year, but rarely seen outside this period, they congregate in large rafts close inshore near their breeding colonies in the spring and early summer months and socialise around their breeding colonies each evening.

Puffins are mostly confined to offshore islands free of predators, particularly rats. They nest in burrows on steep slopes in sometimes very dense colonies.  The principal colonies are on Skomer Island, including Middleholm, and Skokholm with small populations on the Bishops near Ramsey, on St Margaret’s Island and at Stackpole Head where they nest in sheer cliff sites.

Numbers in the past were clearly very much higher than they are now and for example it was estimated that 500,000 to 700,000 pairs nested on Grassholm in the  1890’s,  a figure disputed by modern analysis which suggested that around 200,000 pairs would be more realistic.  Whatever the actual figure, the density was clearly much higher than in today’s colonies and on Grassholm there are still remnants of the collapsed burrows testifying to this. This colony was more or less deserted during the 1920’s and it has been suggested that the birds relocated to Skomer and Skokholm, although it is not clear how that assumption was made. There were also apparently big colonies on Caldey and Ramsey in historic times, before rats devastated them.

Mathew (1894) made the observation that they were undoubtedly the most common bird in Pembrokeshire with huge colonies on Skomer stating “ there is scarcely a yard of ground free of them” and Lockley et al (1949) thought that around 50,000 pairs were breeding on Skomer and 20,000 on Skokholm. There were clearly many more birds present than there are today. 

The population estimates which have been made since the 1950’s on both Skomer and Skokholm have been consistent in suggesting that around 9,000 to 10,500 pairs may breed there.  Estimates are however subject to substantial inaccuracies because it is not possible to count burrows, as both rabbits and shearwaters breed on both islands in abundance, and estimates have tended to be done by extrapolation of detailed studies in one small part of the islands.

Consequently, in an attempt to provide greater consistency in counting and to provide comparative long term data of population trends, all counts of birds since the 1980’s have concentrated on the maximum attendance by adult birds in the spring. The spring counts in 2003-2007 of around 10,800 individual birds on Skomer and 4,800 on Skokholm  suggests a rather similar breeding population to the 1985-87 Seabird Colony Survey estimate of a total breeding population of  about 10,600 pairs  on the two islands.

Stephen Sutcliffe

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 4

Orange = breeding probable = 2

Yellow = breeding possible = 0

Total tetrads in which registered = 6 (1.2%)

Razorbill - 2003-07

Razorbills nest mostly in loose colonies scattered around broken cliffs in cracks and holes and less commonly on small ledges. In some places just a few birds might breed in suitable sites, so their distribution is slightly wider around the county than the gregarious Guillemot.

 There are many fewer Razorbills than either Guillemots or Puffins but they occupy many more breeding sites around the coastline, especially along the south coast of the county and between Dinas Head and Newport along the north coast.  Their distribution appears to have hardly changed during the last century.

 Razorbills are not easy to count as they nest in scattered, often well concealed, small groups.  In the late 1970s (but for some reason not on Skokholm until the late 1980) the count methodology was changed.  Now all individuals attending the colony (i.e. observed on land), are counted, rather than using the older method of estimating “apparently occupied sites”.   Accordingly population comparisons have since been made using a standard conversion factor of 0.67 across the UK, i.e. for every three birds counted there are two nest sites on average. Even so, because of the problems of seeing birds easily at some sites (where sometimes the birds are very evident and sometimes they hide very effectively, which is possibly weather related), and because of the simple variation in attendance from day to day, the census counts are at best reasonable estimates. 

 Because of these census variables, data needs to be accumulated over a long period of time to assess population changes.  Information for Razorbills at their main breding sites has been collected for more than 40 years. The counts during the Seabird Colony register in 1985 – 1988 found a population of around 6,600 individuals in the county, half of them on Skomer. Seabird 2000 counts between 1998 and 2002 showed a significant increase to c. 9,000 birds during the period 2003–07, with almost 5,000 of them on Skomer.  This is the highest known population level.

Steve Sutcliffe

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 27

Orange = breeding probable = 1

Yellow = possible breeding = not included

Total tetrads in which registered = 28 (5.7%)