All bird-watchers in Carmarthenshire will be familiar with the Raven. The largest member of the crow family, it can be found throughout the county in a wide variety of habitats and landscapes. Often, attention is first drawn to the presence of Ravens by their far carrying and evocative cronking call, uttered intermittently as they pass high overhead. For some bird-watchers the species holds a fascination that is difficult to explain to others who essentially see them as ‘just big crows’. Nevertheless, few would disagree that there is something magical about the sight of a pair Ravens rolling and calling in the sky above the barren hills of central Wales or the ease with which they cut through the wind as they career along the coastal cliffs. In this short article I shall give some information on the biology of the species and its current status in Carmarthenshire, which will hopefully be of interest to Raven enthusiasts and non-converts alike.
During the breeding season, Ravens are territorial and defend their immediate nesting area from others of their kind as well as from Carrion Crows and birds of prey. Outside the breeding season this territorial aggression is not so pronounced and some adult territory owners may temporarily leave their nesting ranges to join feeding flocks, though most appear to remain within their home range. In fact large flocks of Ravens tend to comprise mainly non-breeding birds, mostly sub-adults that have yet to establish breeding territories. These large flocks are more commonly seen during the winter at which time the birds also gather at communal roost sites. It is thought that these roosts act as ‘information exchanges’ where Ravens can learn the location of food sources to the mutual benefit of one another. Large numbers can gather at rich feeding areas such as rubbish tips, Kite feeding stations and at livestock carcasses. Interestingly, many birds within flocks seem to associate in pairs but it is not known if these bonds persist through to breeding.
Key to the Raven’s success is its catholic diet, ranging from grass seeds and tree buds through insects and small vertebrates to the carcasses of large mammals. The composition of the diet varies seasonally but in Carmarthenshire sheep carcasses are an important food source, especially on open common land. In spring, the placenta left in the fields when lambing takes place out of doors is also a particular favourite. Stilt-born and dead lambs are soon found, whilst sickly and moribund lambs are no doubt vulnerable to attack especially if no alternative carcasses are available, I have never actually seen a Raven attack a living Iamb hut have no reason to doubt those who claim to have witnessed such an event. The Raven’s beak is a powerful tool capable of tearing open the skin of dead lambs but the wool and tough skin of bigger sheep presents a formidable harrier, so feeding birds concentrate first on the bodily apertures (eyes, mouth and backside). When groups are watched feeding at a large carcass they can be seen to jostle for position to gain access to the softer flesh, whilst others stand on the sidelines waiting for an opportunity to feed: a scene reminiscent of vultures in some wildlife documentary.
The Raven’s ability to exploit a wide range of food sources means that they can occupy many different habitats and they can be found breeding along the coast, in urban areas, in lowland farmland, in woodland and forestry as ‘cell as in the uplands, Once a breeding range has been adopted the resident birds will normally return annually and use one or, more usually, several nest sites within the range. Subsequently, new birds may occupy the range when one or both of the occupants die and so a tradition of nesting in that area is established, The locations of many of these traditional ranges remain remarkably fixed over decades or e~ en centuries with generations of Ravens breeding at the same site. Nests can grow to an immense size as additional material is added to the structure over the years: a nest used annually in a cleft of one Carmarthenshire beech tree is over 2 m high, the base of which has decayed to soil over the years.
Ravens are early breeders and nest building often begins in February with pairs in lower-lying areas beginning incubation before the end of the month, though many of those nesting in the uplands do not complete their clutches until the first-half of March. Raven clutches range from three to seven eggs, with five or six being the usual compliment. Incubation begins before the clutch is complete, sometimes starting with the first egg aid, so hatching ends lobe asynchronous. Newly hatched broods frequently exhibit a gradation in size from the first to last hatched chicks and commonly the smallest chicks succumb within the first week after hatching. This form of brood reduction is the norm and doesn’t appear to be obvious related to food supply at the time of hatching as it commonly occurs at nesting ranges where food, in the form of sheep carcasses, is plentiful. It’s possible that factors which determine the onset of incubation during the laying period have a significant influence on the degree of brood reduction hut the reasons as to why it occurs remain unknown. The phenomenon of brood reduction at Raven nests means that fledged brood sizes are often much smaller than clutch sizes and most pairs fledge between one to four chicks, with larger broods being infrequent.
At hatching the chicks are pink and naked, save for a few wisps of down, and are very susceptible to chilling, especially in the wet, cold spring climate of Carmarthenshire. Once hatched the female broods the chicks attentively until they are about ten days old after which time she starts to leave the nest more regularly to help her mate find food for the young. By this time, the skin has darkened and the backs of the chicks have grown a fine, dark brown down giving them some ability to maintain body heat. The wing feathers start to sprout from their sheaths in the second week after hatching and by three weeks old they are well-feathered and require little brooding. They are fed on food regurgitated by the adults throughout the time they are in the nest and for a while after they fledge. They remain in the nest for around seven weeks and before they eventually leave they tentatively explore the branches or ledges surrounding their nest, sometimes roosting outside the nest. Most broods in Carmarthenshire leave the nest in late May and during the summer month’s family parties are often seen exploring the countryside within the breeding range, the adults distinguishable by their moulting wings. By early autumn these family parties break up, with the adults remaining on their breeding range and the youngsters joining the non-breeding flocks. Ravens do not breed until they are at least two years old and for many the onset of breeding does not start until they are even older. Ringing and marking studies suggest that the chances of a fledgling surviving to breed are very low but conversely it is thought that the survival rate of established breeding adults is high.
Ravens are probably now more abundant in Carmarthenshire that at any time in the last 200 years. During the 19th Century and the early decades of the 20th Century Ravens were heavily persecuted in the name of game preservation, while shepherds striving to eke out a living in the hills killed others. For many years the breeding population was confined mainly to the remote uplands where they bred on rock faces in the hills of the Towy catchment and Mynydd Du. In addition, the first half of the 20 Century saw the arrival of traveling collectors to ‘Wild Wales’ who plundered many of the nests in the Carmarthenshire uplands. For the egg collectors, the nesting season was traditionally opened with a foray into Wales to take Raven eggs and certain well-known localities were robbed virtually every year. Some to managed to rear broods from replacements clutches but often these were taken too when the collectors made their second tour of the district in pursuit of Peregrines. Nevertheless, the remnant population persisted and the demise of the large game-shooting estates after the First World War brought some respite and numbers began to increase. By the middle of the century Ingram and Morrey-Salmon reported in their county avifauna of 1954 that the Carmarthenshire population had increased considerably. The concomitant expansion from the uplands into lower-lying habitats saw the adoption of trees as nesting sites and the colonisation of areas without crags.. In the south of the county, new nesting crags were created with the abandonment or enlargement of many limestone quarries stretching from Mynydd Du to Kidwelly, but still the majority of Ravens in Carmarthenshire nest in trees.
The breeding population of Carmarthenshire in the early 1990’s was put at around 100 pairs in ‘Birds in Wales’ but this is likely to have been a rather conservative estimate. Whatever the true situation at that time, it is clear that over the last decade or so the population has increased still further and I estimate that it now stands somewhere between 200-250 pairs. Breeding density has increased, particularly in lowland areas where much of the population increase has occurred, such that nests are fairly regularly spaced at an average of about two kilometres or so across the county. The non-breeding population has increased too, perhaps to a greater extent than the breeding population and flocks of 60+ birds have been recorded in the county in recent years. This increase in both the breeding and non-breeding population suggests that survival rates have improved in the last decade, perhaps through greater food availability or a reduction in the illegal use of poison baits.
The future of the Raven in Carmarthenshire is closely tied to the fortunes of agriculture, particularly the way which livestock farming is carried out. The survival of many smallholder farms is uncertain and sheep stocking densities are linked to the system of EU subsidy payments. A greater emphasis on agri-environment funding in the future is likely to lead to a reduction of sheep stocking densities particularly in the uplands and this in turn could result in a reduction in carrion available for foraging Ravens, Improved husbandry on lowland farms, together with new regulations relating to the disposal of carcasses may also reduce the availability of carrion and/or placental remains on the lower, enclosed ground away from the open common lands of the hills. However, over the years the Raven has proved to be a very hardy and adaptable species and it seems likely that the call of the Raven will continue to be a characteristic feature in the Carmarthenshire landscape for a long time to come.