Although several historical records of breeding at sea level exist, the ring ouzel seldom nests below 300 m. Steep-sided valleys and ravines are favoured habitats with most nests placed on rock outcrops or ledges. Abandoned buildings and walls will sometimes be used, as well as dense bracken or heather. Little is known about the ecology of the ring ouzel in Ireland. Some basic studies would be most valuable.
Eight other birds could be said to be characteristic but not dependent upon mountain and upland areas. These are, in descending order from the summit: peregrine falcon, raven, hooded crow, hen harrier, meadow pipit, merlin, red grouse and the golden plover. Both the red grouse and golden plover also occur on lowland blanket bogs and they are discussed in Chapter 4.
The peregrine and raven inhabit all the major inland and coastal mountain systems where there are suitable cliffs for nesting. They are equally at home in coastal cliff habitats. Both are widespread throughout the country. The numbers of breeding peregrines in the Republic prior to 1950 was estimated rather uncertainly at some 180–200 pairs. A dramatic population decline, similar to that experienced in Britain, followed during the 1950s and 1960s. Possibly as few as 14 pairs were thought to have been successfully breeding in Ireland by 1970.50 This was due to the presence in the countryside of seeds dressed with organochlorine chemicals to prevent insect attack on crops. These were eaten by the woodpigeon, stock dove and rock dove which in turn were preyed on by peregrines which accumulated in their bodies an ever increasing load of the persistent chemicals. If not directly killed by the poison, sub-lethal levels interfered with the metabolism of calcium, affecting its deposition in egg shells. The resultant thin shells led to a high incidence of egg breakages, and elevated residue levels in the embryos brought about a decline in breeding success. Without enough young birds recruited, the population went into serious decline. It was only when the chemicals were withdrawn that the population began to recover. In 1981 all Northern Ireland and approximately 50% by area of the known breeding range in the Republic were surveyed and at least 278 breeding pairs noted.51 Today there are probably over 500 breeding pairs throughout the whole island. Numbers are still increasing with most of the old traditional breeding sites once again occupied while new sites are being established. Quarry-nesting peregrines, first noted in the late 1970s, are on the increase. A survey of 48 quarries, active and disused, in nine counties of eastern Ireland in 1991 and 1992 revealed 21 breeding pairs. If this occupancy rate was extended to all the 300 quarries in the Republic then there may be up to approximately 130 breeding pairs of peregrines in this somewhat unusual habitat.52 In 1977 some 35 pairs bred in Northern Ireland quarries.
Comeragh Mountains, Co. Waterford, where ring ouzels breed.
In 1986 Noonan carried out a study of peregrines breeding in 2,025 km2 of Co. Wicklow and found 34 territories, or one pair per 60 km2.53 The 12 successful eyries produced 2.4 fledged chicks per nest. This figure compared with 2.17 fledged chicks from a longer-term study in five southeastern counties in Ireland over the period from 1981–6. However, when these results were expressed as the mean number of chicks fledged per pair of peregrine holding a territory the figure was only 0.91 chicks. It was also found that breeding performance at coastal, compared with inland, sites was higher with 0.95 and 0.78 chicks respectively produced per pair of peregrines holding territory.54
Ravens are more numerous than peregrines in Ireland with an estimated population of 3,500 breeding pairs in 1988–91.55 However, this would appear to have been a gross over-estimate, and the true breeding population is more likely to be in the order of 1,000 pairs, divided between mountain, upland and coastal habitats.56 Their shared interests in sometimes similar habitats with peregrines can lead to spectacular aerial encounters. But how do two large and extremely agile birds get along together when they require similar breeding sites? The mechanism for apportioning out available cliffs is not clear but may well be based on precedent of who got there first. If either occupant moved off, for whatever reason, or died, the site would be up for grabs. Their mutual respect for each other has been witnessed and filmed by the author in aerial encounters during which a peregrine will playfully stoop on a raven that will suddenly flip over on its back and point its massive claws upwards, without actually grappling with the peregrine.
Historically ravens were relentlessly persecuted by man because they were perceived as predators of young lambs and sickly sheep, and by 1900 only a few pairs survived in a small number of remote coastal areas. With the relaxation of this murdering grip at the beginning of this century, a remarkable population increase commenced which has led to the species unfurling into virtually all the hills and mountain areas of the country. In a study of ravens in Co. Wicklow during 1968–72 a population density of one breeding pair per 25.3 km2 was found, close to the one pair per 23.9 km2 recorded in north Wales moorland for enclosed sheep farms. In both Wicklow and Wales the raven occupied generally similar habitats.53 Highest densities are in the western uplands where the greater sheep numbers provide the attendant supplies of carrion – the amounts of which were indicated by a study on the blanket peatlands around Glenamoy, in west Mayo, during the early 1970s. The stocking levels on these bogs at that time was roughly one ewe per ha, and losses between October and April were estimated at about 7–10% of total numbers. On average about 1.0–1.4 carcasses per km2 per month became available to the predators. It was also found that carcasses weighing 30–35 kg disappeared in less than two weeks, indicating the intensity of scavenging by ravens, hooded crows and foxes.57
The hooded crow is more a bird of the uplands but, like the peregrine and raven, it has an interest in other habitats, as evidenced by the large population in Ireland, estimated at about 290,000 pairs. The success of the species is a reflection of their ability to adapt to all available food sources. A constant feature of the mountains and uplands, hooded crows move around singly or in pairs, always on the scrounge for sheep carrion or nests of other breeding birds that are quickly plundered. In the mountains and uplands they generally build their nests in low, often isolated trees but will also resort to cliffs and low bushes. Essentially carrion feeders, they have done well in recent years, seldom short of a dead lamb or ewe whose carcasses have increased proportionately with higher stocking densities. During the winter hooded crows often come together in large roosts: close to 170 individuals were counted in one flock at Youghal, Co. Cork on St Patrick’s Day in 1978. As a subspecies of the all black crow, hooded crows will interbreed with the black carrion crow and produce fertile offspring. However, the opportunity for matrimony is not great in Ireland as the carrion crow is scarce, and found principally in the northeast of Ireland – although it has been creeping down southwards towards Dublin in recent years.
The hen harrier is most likely to be seen quartering moorland below 500 m, especially in areas covered by young forestry plantations which, in their early stages of development, offer excellent breeding habitat for the species. A dense growth of tall vegetation such as heather is also suitable nesting habitat. Formerly widespread throughout Ireland, these docile-looking birds were persecuted by gamekeepers to the point of extermination in the second half of the nineteenth century and were thought to have become extinct in 1954. Fortunately a few pairs were lurking in the Slieve Bloom Mountains, Co. Laois, and on the Waterford/Tipperary border. Numbers picked up dramatically as large areas of amenable breeding habitat became available to the species through a reinvigorated State afforestation programme. By 1973–5 there were 250–300 breeding pairs on the Irish uplands.58 Since then, however, they have declined again, dropping to probably fewer than 100 pairs. Reasons advanced for this reversal relate to maturing forestry plantations together with the clearance and reclamation of marginal uplands, representing a loss of breeding and hunting habitat for the species.59 However, this explanation is not entirely satisfactory as afforestation is not a thing of the past and new plantations, providing renewed attractive habitat, are still being created all around the country. Today most of the estimated 60–80 pairs are located in the uplands of Kerry, Limerick, Cork, Clare, Tipperary and Laois.60