Search

Capsule: Overall numbers of Peregrines are higher than previously recorded, due primarily to the growth of lowland populations, despite declines in many upland areas.Aims: To estimate the breeding population of Peregrines, and changes in this population over time, as well as to relate variation in trends and observed breeding success to variation in region, breeding site type and other ecological influences.Methods: Two types of survey methods were used. Site-based visits focussed on locations where Peregrines were known to have bred previously, while area-based searches aimed to find all Peregrines breeding in randomly chosen 5 km × 5 km squares. Findings from each method were used to estimate population size in different parts of the survey area. Breeding outcome and site type were assessed for most of the pairs found during either survey.Results: In 2014, the breeding population of Peregrines in the UK, Isle of Man and Channel Islands was estimated at 1769 pairs. This is 22% larger than the pop...

Capsule Numbers of breeding Peregrines are now higher than ever recorded and the recovery of the species within the UK has continued since 1991. Aims To estimate the current Peregrine breeding population and its changes over time by recording breeding evidence and nesting range occupancy at known and potential Peregrine eyries. Methods Attempts were made to check all potentially suitable Peregrine nesting locations for signs of Peregrine occupation. Causes of nest failure were documented where possible. Estimates of occupancy of nesting ranges that could not be visited were based on the proportion of ranges occupied from visited nesting ranges in the same region. Results In 2002, 1530 Peregrine nesting ranges were estimated to be occupied, comprising 1456 pairs or single birds confirmed as in occupation, and 74 estimated extras (5% of total occupied nesting ranges) that were not visited. Including non‐breeding singletons holding nesting ranges, the UK and Isle of Man figure of ‘Ratcliffe pairs’ was 1437. ...

Capsule Daily food intake gave the best indication, with 7–23% of the pigeon population estimated to have been taken. Aims To assess the numbers of Scottish racing pigeons taken by Peregrines, based on the recovery of racing pigeon rings from Peregrine eyries and on the daily food intake (DFI) of Peregrines. Methods The estimate based on ring recoveries was derived from examination of the flight histories of birds whose rings had been recovered during searches at Peregrine eyries. The DFI-based approach involved deriving estimates of the biomass and number of Scottish racing pigeons taken based on the Peregrines' mean daily food requirements, and involved a comprehensive synthesis of available Peregrine dietary data. Results Estimates of the number of Scottish racing pigeons killed by Peregrines, during the 2002 racing season, were a minimum of 3083 from ring recoveries and between 25 283 and 78 385 based on DFI. This represented 1% and 7–23% of the estimated total Scottish loft population respectively. T...

Capsule The population of Peregrine Falcon in the central-eastern Italian Alps is much larger than previously thought. Aims To assess the status of the species in the Alps and re-estimate the overall Italian population size. Methods We monitored a Peregrine Falcon population of 45 territorial pairs between 1998 and 2003 in a 3570 km2 study area located in the central-eastern Italian Alps. Results All nests were on large cliffs at a mean elevation of 830 m (range = 250–1950 m). The population trend was stable at a mean density of 1.16 pairs/100 km2. Mean nearest-neighbour distance between territorial pairs was 5.1 km. The percentage of pairs consisting of an adult male and an immature female was low (1.3% of 225 breeding attempts). Mean laying date was 11 March, the percentage of successful pairs was 46%, and the mean number of fledged young was 1.10 per territorial pair and 2.40 per successful pair. Diet was dominated by Turdidae, Columbidae and Corvidae. Density, diet and breeding performance were compar...

Capsule Since pesticide controls, it has expanded from a pre-pesticide baseline of 41 pairs to over 100 pairs. Aims To describe the population's pattern of recovery and identify constraints on its annual productivity. Methods Occupancy and productivity data were collected from all known and new ranges in Cumbria, UK. Statistical methods were employed to describe temporal and spatial patterns. Possible effects of weather were investigated using meteorological data. Results The population recovered from eight pairs, with birds preferentially recolonizing 41 traditional ranges. The highest occupancy levels were 100 ranges in 1997 and 1998. Many new ranges were in peripheral and atypical locations, although some resulted from the splitting of traditional ones. The central core now has the highest recorded density (> 9 pairs per 100 km2). As occupied ranges increased, the mean nearest neighbour distance declined to an asymptote (approximately 3.5 km). Simultaneously, maximum values were observed for the percen...

A survey of quarry-nesting Peregrines conducted in the Republic of Ireland between 1991 and 1993 estimated that 65 quarries were occupied by Peregrines. There was a marked east/west gradient in occupancy with most occupied quarries in the east. Occupation of quarries by Peregrines is primarily influenced by cliff height.

A survey of Peregrines in the breeding season of 1991 gave an estimated total of 1283 pairs occupying known nesting territories in Britain and Northern Ireland. 1214 territories were found occupied, 53 by apparently single birds, and 141 known territories (9%) were not visited. Overall territory occupancy was 83%. The figure of 1283 pairs represents 147% of the overall population level believed to exist in 1930–¸39, and 167% of that counted during the previous national survey, in 1981. The net increase was geographically uneven, being greatest in a broad zone from the eastern Grampians to South Wales, whereas numbers were still well below pre-war level in coastal south-east England. In coastal and western inland areas of the northern Highlands, numbers have declined since 1981. Throughout the UK, many coastal populations have substantial proportions of territories occupied by nonbreeding birds. Population growth has involved both an increase in breeding density and expansion of breeding distribution, the ...

A second partial survey of breeding Peregrines in the Republic of Ireland was undertaken in 1991, duplicating the methodology and areas covered 10 years previously. The survey located 123 occupied territories; when corrected for incomplete coverage a total of 141 was estimated, an increase of at least 23–26% since 1981. Birds have also recently spread onto quarries, mainly outside survey areas; these have been surveyed independently. Overall, there were an estimated 350–355 occupied territories in the Republic, 17–18% of which were in quarries. Breeding range is shown to be limited by weather, operating through the interaction of spring rainfall levels, cliff size and cliff orientation. On cliffs >¸36 m high untenanted territories are only found in high-rainfall areas and oriented NW to NE. With decreasing cliff size, the vacancies affect a broader spectrum of cliff orientations, and at lower rainfall levels. Most currently unoccupied natural cliff sites appear to be vacant because of weather limitations,...

The results of sample surveys, representing the major ecological divisions, indicate that Ireland holds more Peregrines than estimated previously. The species is recovering well from the earlier effects of pesticides.

(1962). Chlorinated hydrocarbon residues in the egg of a Peregrine Falcon (Falco peregrinus) from Perthshire. Bird Study: Vol. 9, No. 4, pp. 242-244.