Raven - 1949 status

Corvus corax corax

Numerous and increasing resident.  Probably not less than eighty pairs breeding, of which about sixty pairs nest on the coastal and island cliffs, the rest inland, sometimes on trees.  Bertram Lloyd records a pair nesting in a fir tree near Angle as long ago as 1931.  Breeding at Treffgarne Rocks (mentioned by Mathew, who though there were about twenty nests in the county, include "a nest or two in . . Ramsey and Skomer").  Four pairs Skomer 1946.  One pair breeds regularly Grassholm.  Clutches of six eeggs are common and one of seven has been recorded (Major W.M.Congreve).  Flocks of up to fifty seen together July-October, notably on West coast.

R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society

Raven - 2003-07

Although Ravens are found mainly on the coast of Pembrokeshire, breeding on sea cliffs on the mainland and on the offshore islands, they occur quite widely in the open hilly areas and also across lowland farmland where there are suitable natural outcrops, quarries or wooded areas with mature trees for nest sites.

Raven nests are quite large bulky structures and most are usually not too difficult to locate. Within a territory they may utilise one of several alternative nest sites in a particular year. In some years old, unused nests can be taken over by other species such as Peregrines.

Using only confirmed and probable breeding categories, because of the likelihood of wandering non-breeding or foraging adult birds being included in the possible breeding category, Ravens were found in 133 tetrads during the 1984-88 atlas period. During the 2003-07 atlas survey, they were found in 144 tetrads, based on the same breeding categories, a small and probably insignificant increase of 8%. However, the proportion found at inland tetrads was higher, approximately 70 tetrads during 2003-07, compared with 57 tetrads in 1984-88, an increase of about 23%.

Donovan and Rees (1994) estimated that during the period 1984-88, the total breeding population was about 140 pairs. Of these 12 pairs were reported on the offshore islands, at least 65 pairs were breeding around the outer coast and the inland population was estimated to be about 60 pairs.

The locations of Raven nest-sites along the south Pembrokeshire coast were recorded during the most recent tetrad-based breeding survey (2003-07). This was done to help inform an assessment of the mainland coastal Raven breeding population during the latter atlas period. Occupied Raven nest sites were plotted on a map between Angle (Sheep Island) and Penally, a sample distance of a distance of about 42 km. (Haycock, unpublished data).

The average breeding population in this region in most years of the survey period was 12 pairs (about one pair every 3.5 km). The total length of coastline checked also included unsuitable habitat such as sandy bays/beaches etc, so the density is closer to one pair every 3 km if only suitable coastal nesting habitat is included.

If this linear density is representative of the whole of the Pembrokeshire coastline (estimated to be about 246 km long, based on the length of the National Trail on the open coast and the outer mainly cliff-sections of Milford Haven, as far up the waterway as Milford Haven and Pembroke Dock) then the mainland coastal breeding population could be as high as approximately 70 pairs. Numbers of pairs reported breeding on the offshore islands in 2003-07 were generally similar to those reported during the earlier atlas period.

Assessing the breeding density of the inland population is more difficult as, being quite widely dispersed, they are not so easy to census.  Most of the mature woodland and forestry blocks in the county are probably occupied by at least one pair.  As the number of inland tetrads with confirmed or probable breeding records appears to have increased over the last 20 years, assuming the original population estimate to be reasonable, then it is unlikely that the inland population is less than 60 pairs.

When combined with the coastal and island breeding pairs, a total population of not less than 140 pairs, and possibly up to 150 pairs seems quite a reasonable estimate.

Bob Haycock.

 

Fieldwork 2003-07 (based on 490 tetrads) 

Red = breeding confirmed = 108

Orange = breeding probable = 36

Yellow = birds reported but with no signs of breeding

Total tetrads in which registered = 144 (29.4%)

Inland breeding tetrads= 70 (48.6% of breeding tetrads)

Raven - 1994

Breeding resident

Ravens have increased in Pembrokeshire since the time of Mathew (1894), who thought that 20 pairs nested. By 1949, Lockley et al. were able to note that the population had grown to not less than 80 pairs, 60 of them on the coast and islands.

A reasonably accurate assessment of the present population can be made following the fieldwork of the Breeding Birds Survey of 1984-1988. Ravens were found breeding on the offshore islands and the mainland cliffs and on crags and in trees in most areas inland. On the islands, 12 pairs were reported breeding, with 65 pairs around the outer coast. The inland population has been estimated by omitting the 'present' category from the map, as such records could represent wandering non- breeders or foraging adults from nests in adjoining tetrads. The resultant map plot suggests that about 60 pairs breed inland, making a total county population of about 140 pairs.

They have a tendency to flock after the breeding season, although many individuals seem not to become involved and some breeding territories remain occupied throughout the year. Flocks of up to 80 have been noted on Skomer in September (when fledgling Manx Shearwaters are probably the attraction) and of up to 250 at Dudwell from August (attracted by discarded offal from the slaughterhouse). The Skomer flock generally disperses in October but the Dudwell gathering persists longer and up to 170 have been recorded there into April ( these are presumably non‑breeding birds). Ravens also form communal roosts during the winter, the sites being subject to periodic change. Up to 150 were noted roosting at Walwyn's Castle in 1954 and up to 263 at Roch in 1964, but most roosts feature 30-50 birds.

They are highly mobile birds and are seen passing over all parts of the county. Some may be wanderers from outside Pembrokeshire, for there is evidence to confirm this: nestlings ringed at Skokholm have twice been recovered in north Wales, which suggests some degree of interchange.

Young birds from the quarry at Goodwick Moor used to be exported to replenish the population at the Tower of London.

            

Fieldwork 1984-88 (based on 478 tetrads) 

Red = breeding confirmed = 91

Orange = breeding probable = 42

Total tetrads in which registered = 133 (27.8%)

Inland breeding tetrads= 57 (42.9% of breedng tetrads)

Donovan J.W. & Rees G.H (1994), Birds of Pembrokeshire

Raven - 1970s breeding

 

Red = breeding confirmed

Orange = breeding probable

Yellow = breeding possible

Raven - 1980s winter atlas

The BTO winter atlas showed that Ravens were present in most 10km squares during the winters of 1981-82, 1982-82 and 1983-84.

The darker the colour, the higher the relative total count for each 10km square.  The darkest blue represents over 74 birds seen in a day.

The largest roost recorded during this period contained 160 birds.

Graham Rees

Raven - 1894

Species account from M Mathew, 1894, "The Birds of Pembrokeshire and its islands"

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