Trans.nat.Hist.Soc.Northumbria 64: 111-120 THE PREY OF PEREGRINES FALCO PEREGRINUS AT BREEDING TERRITORIES IN NORTHUMBERLAND A Dixon Pentremelyn, Bwlch, Brecon, Powys LD3 7JJ SUMMARY Analysis of prey remains found at peregrine breeding territories in Northumberland revealed variation in the composition of the diet between summer (April-September) and winter (October-March). Domestic pigeons, mainly in the form of racing pigeons, were the most frequently killed prey species during the summer, coinciding with the pigeon race season from April-September. Domestic pigeons comprised 36% of kills by frequency and 51% by weight during the summer. In the winter, migrant thrushes and wood pigeons were the most frequently killed prey species, accounting for 73% of kills by frequency and 67% by weight. The majority of the racing pigeons killed came from lofts in Scotland and north-east England (69%). Pigeons racing north to lofts in the Scottish Borders, East Lothian, Midlothian, Edinburgh, Falkirk and Fife are predicted to pass through Northumberland and pigeons from these regions made up 25% of all the racing pigeons killed at peregrine territories in this study. Pigeons racing south from Scottish liberation sites to lofts in North Yorkshire and the East Midlands are also predicted to pass through Northumberland and pigeons from these regions comprised 14% of racing pigeons killed. In addition, pigeons from lofts in rural parts of north and west Northumberland made up a further 7% of racing pigeons killed. Many, though not all, of the remaining 54% of racing pigeons were likely to be significantly off-course from their intended flight lines or else were strays already lost to their owners prior to being killed. INTRODUCTION There have been a number of studies investigating the prey of peregrines Falco peregrinus at their breeding territories in Britain, all of which have revealed the wide range of avian prey killed and the predominance of domestic pigeons Columba livia in the diet during the breeding season (Ratcliffe, 1993). In addition, extensive studies conducted in southwest Scotland (Mearns, 1982; 1983) and south Wales (Richards and Shrubb, 1999) have also highlighted the difference in the composition of the diet between the summer and winter hunting periods. Unfortunately, the peregrine s predilection for domestic pigeons has brought the species into conflict with racing pigeon owners in many widespread areas, whilst their depredation of red grouse Lagopus lagopus has meant that they have incurred the wrath of gamekeepers in the uplands of northern Britain. Such conflicts have often resulted in sustained persecution, particularly in districts close to aggregations of pigeon lofts and on managed grouse moors (UK Raptor Working Group, 2000). Whilst the conflict between peregrines and red grouse has been the focus of attention for a number of years the conflict between peregrines and racing pigeons has only recently been the subject of research studies (Shawyer et al., 2000; Dixon, 2002). Furthermore, the detrimental consequences of persecution arising from the peregrine and racing pigeon conflict has tended to overshadow the potential beneficial influence of pigeon racing for peregrine populations. In this study I provide data on the prey species killed by peregrines occupying breeding territories in Northumberland throughout the year and particular attention is paid to the racing pigeon component of the diet. It must be noted that the data in this study are unlike- 111
ly to be representative of the range and composition of prey species in the diet of individual peregrines throughout the year. This is because prey that is killed and eaten away from the breeding territory is not included in the analysis. Peregrines do not confine their hunting and feeding within a restricted area around the nesting site (Enderson and Craig, 1997). This is particularly true outside the breeding season when peregrines can range widely in search of prey and some individuals, of either sex, may leave their nesting areas for extended periods of time outside the breeding season (Ratcliffe, 1993). Thus, prey remains found at breeding sites may reflect the species killed by both sexes or by one sex only at different time periods throughout the year. In particular, this study may underrecord the frequency of red grouse, ducks and coastal waders in the diet of individual birds outside the breeding season. In addition, it must be borne in mind that the diet of non-breeding adults and immature peregrines may differ significantly from that reported at breeding territories in this study. METHODS Prey remains and racing pigeon rings were collected from twenty different peregrine breeding territories in Northumberland between July and March from 1998-2002. All the peregrine territories were located in the west and north of the county. Prey remains were collected from eyries and plucking areas in the immediate area of the nesting cliff of each breeding territory. The breeding territories were systematically searched for prey remains and each plucking area was carefully inspected in order to reduce the likelihood of missing the feather remains from small, dull-coloured prey species. In cases where there were the remains of more than one individual of a particular species the minimum number of individuals was recorded. Pigeon rings were located using a metal detector, with particular attention paid to eyries and areas below favoured perches (see Dixon and Lawrence, 2000 for further details). Pigeon rings provide information on the union that issued the ring, the year that the ring was issued and an individual identification number. The main British homing unions issuing racing pigeon rings are the Royal Pigeon Racing Association (ring prefix GB), the Scottish Homing Union (ring prefix SU), the North of England Homing Union (NEHU) and the Welsh Homing Pigeon Union (ring prefix WHU). Using ring registration lists provided by the respective homing unions, it was possible to identify the pigeon club and/or federation to which the ring was issued. This information was used to identify the geographical location of the home loft of each pigeon. The home loft location of racing pigeons that had been transferred between owners in different regions would have been incorrectly identified using this method, however such transfers make up less than 5% of pigeon race flocks (A Dixon, unpublished data). RESULTS Prey species composition In total I collected the remains of 230 different prey items at peregrine breeding territories in Northumberland; 124 from the summer period (April-September) and 106 from the winter period (October-March; see Appendix). There were thirty-four different species represented within this sample and the range of prey was greatest during the summer period; twenty-nine different species found during the summer compared with fifteen 112
during the winter. During the summer domestic pigeons were by far the most important prey species, comprising nearly 36% of prey by frequency and 51% by weight. Other significant prey species during the summer were wood pigeons Columba palumbus (7% by frequency and 11% by weight) and starlings Sterna vulgaris (19% by frequency and 6% by weight). Many of the starlings killed were juveniles, indicating that the roving postbreeding flocks are an important food source from June onwards. During the winter, i.e. outside the pigeon race season, the proportion of domestic pigeons killed dropped dramatically to just 4% by frequency and 10% by weight, indicating that most of the domesic pigeons killed during the summer are racing pigeons as opposed to feral pigeons. Migrant thrushes (fieldfare Turdus pilaris, redwing T. iliacus and blackbird T. merula comprising 65% by frequency and 42% by weight combined) and wood pigeons (8% by frequency and 25% by weight) were the most important prey species killed during the winter. Woodcock Scolopax rusticola also featured significantly in the prey remains (6% by frequency and 13% by weight) during the winter. Unusual prey species found included a whimbrel Numenius phaeopus which was probably killed whilst on spring passage and a yellow budgerigar Melopsittacus undulatus which was found at a territory in the west of the county during the winter. In addition, I recovered three wild bird rings from a starling, a mistle thrush Turdus viscivorus and a song thrush Turdus philomelos. The starling and mistle thrush were recovered within 15 km of their ringing sites in Alnwick and Coquetdale respectively whilst the song thrush was ringed at Gibraltar Point near Skegness in September 1965. As the latter peregrine breeding territory was not reoccupied until the late 1970s at the earliest this song thrush was probably at least twelve years old when killed. Racing pigeons as prey Age profile of racing pigeons killed at peregrine breeding territories Pigeons are raced according to their age with old birds (i.e. pigeons hatched at least one calendar year before they are raced) racing from April to July and young birds (i.e. pigeons hatched the same calendar year as they are raced) racing from July to September. The old bird racing season coincides with the main peregrine breeding period, whilst the young bird racing season coincides with the fledging period prior to dispersal from the breeding territory. I was able to identify thirty-two pigeons killed during the old bird race season at two breeding territories, of which twenty-three were old birds and nine were young birds (Table 1). The old birds were predominantly one or two years old but some were up to five years old. The young birds that were killed during the old bird race season were mainly from lofts in the northeast of England (6/9; 67%), whilst the old birds were mainly from lofts in Scotland (13/23; 57%). Over the entire pigeon race season (April-September), the age profile of the racing pigeons killed at peregrine breeding territories differed significantly in relation to the home origin of the pigeon (Table 2). Significantly more pigeons from lofts in the north-east of England were killed as young birds than from lofts in Scotland and elsewhere (47% cf. 24%; Chi square corr. = 3.763, 1 df, P = 0.05). Home origin of racing pigeons killed at peregrine breeding territories Out of a sample of 1627 racing pigeon rings that were recovered from peregrine breeding territories in Northumberland, 46% were issued by the SHU, 27% by the RPRA, 23% by the NEHU, 3% by the WHU and the remaining 1% by homing pigeon unions from 113
Table 1 Age profile of racing pigeons killed at Peregrine breeding territories during the old bird race season (April-July) Racing Pigeon Age (years old) Age (years) Young Bird 1 2 3 4 5 Number killed 9 10 6 3 3 1 Ireland, France, Belgium and Holland. For the ten-year period from 1991 to 2000 the annual proportion from the four main British Homing Unions fluctuated but none showed any particular trend. Thus, for example, there was no tendency for the proportion of Scottish racing pigeons killed at peregrine breeding territories to either increase or decrease over the ten-year period. I compared the proportion of rings issued to the twenty-one different pigeon racing federations in Scotland with the proportions recovered at peregrine breeding territories in Northumberland (Table 3). Racing pigeons from lofts located in regions around the Firth of Forth, i.e. East Lothian, Midlothian, Edinburgh, Falkirk and Fife, together with those from the Scottish Borders were killed more frequently than would be expected by chance. Pigeons from lofts in these areas made up 54% of all Scottish racing pigeons killed by peregrines in Northumberland; i.e., nearly 25% of all the racing pigeons killed. Conversely, racing pigeons from lofts in western Scotland, i.e. Dumfries & Galloway, Ayrshire and Glasgow, together with those from Aberdeenshire and Moray, were killed less frequently than would be expected by chance. If the relative proportions of the pigeon federations in the sample of rings recovered at breeding territories accurately represent the proportions available as prey, it is tempting to speculate on the race routes of pigeons from the different regions of Scotland. It is possible that pigeons from the Ayrshire, Solway (Dumfries and Galloway) and Glasgow federations pass to the west of Northumberland, probably through Cumbria, whilst those from the Aberdeen and North East (Moray) federations pass to the east, perhaps along the Northumbrian coastline. Conversely, racing pigeons from lofts in the Scottish Borders, Pentland (East Lothian), Midlothian, Central (Edinburgh), North West (Falkirk) and Fife federations are predicted to pass through Northumberland on their normal race routes (Figure 1). Table 2 Age in relation to the home origin of racing pigeons killed at Peregrine breeding territories in Northumberland over the entire race season (April-September). Age of Racing Pigeon when killed (years old) Homing Union Young Bird 1 2 3 4 5 NEHU 16 12 4 1 1 0 SHU 19 23 14 10 4 3 GB 9 12 10 5 5 2 Belgium 1 0 0 1 0 0 Ireland 0 2 0 0 0 0 Holland 0 1 1 0 0 0 114
Figure 1 Representation of the main race routes for Scottish racing pigeons from lofts in the borders, East Lothian, Midlothian, Edinburgh, Falkirk and Fife. For rings issued by the NEHU, 32% were issued to just five of the thirty-seven federations within the union. A greater proportion of the rings recovered at breeding territories came from these five federations than would be expected by chance (Chi square corr. = 292.8, 1 df, P < 0.001). The federations were all based in the more rural parts of Northumberland and were in the same geographical area as the peregrine sites sampled in this study; i.e. the Coquetdale, Northumberland Premier, Border, Tyne & Derwent and Consett federations. Many of the lofts concerned were likely to be within the hunting range of the breeding peregrines and the pigeons were likely to have been killed within a relatively short distance of their home lofts. Racing pigeons from these five federations comprised approximately 7% of all the racing pigeons killed. The remainder of the NEHU rings were mostly issued to federations located to the south of the main sampling area to pigeon clubs in 115
Tyne & Wear, Durham and Cleveland. For rings issued by the RPRA, 32% were issued to pigeon clubs in north-east England (mainly North Yorkshire) and 19% were issued to pigeon clubs the East Midlands region. Many of these clubs regularly fly on the north road and race their pigeons from liberation points north of the lofts, including sites in Northumberland and Scotland. The remainder of the RPRA rings were issued to clubs in north-west England and North Wales (11%), Cumbria (9%), Derbyshire and South Yorkshire (8%), West Midlands (8%), London (8%), south-west England (4%) and Ireland (1%). Pigeons racing home to lofts in North Yorkshire and the East Midlands from Scottish liberation points are predicted to pass through peregrine breeding territories in Northumberland during racing and pigeons from these areas comprised nearly 14% of all the racing pigeons killed. DISCUSSION Prey species composition The method of collecting prey remains is likely to be biased towards larger prey species such as domestic pigeons as the feathers can be detected more easily and remain on site for longer. Non-avian prey is also likely to be under recorded and the remains of rabbits Oryctolagus cuniculus were found at breeding sites but it was not certain that these were the result of peregrine kills. At one site quarrymen reported seeing peregrines passing rabbits to juveniles in flight (per. R Jewitt). Elytra from small beetles were also found in many pellets but it was possible that these came from the guts of starlings that were eaten. Shotgun pellets were found within a matrix of pigeon feather pulp in one pellet hinting at the possibility of some carrion feeding or else the capture of a live pigeon with shotgun injuries. In a study conducted between 1975-80 in south Scotland, Mearns (1983) found that between March-July domestic pigeons made up 49% of kills.within this total there was variation among breeding habitats with the percentage of domestic pigeons killed ranging from 39% in mixed inland habitats to 50% on sheepwalks. Redpath and Thirgood (1997) reported that domestic pigeons comprised 55% of kills on grouse moors in south-west Scotland and 46% in northern England during the summer (June to September), whilst Ratcliffe (1993) presented data for the period 1945-77 indicating that domestic pigeons comprised 53% of peregrine kills in Lakeland. My estimate of 36% domestic pigeons in the prey of Northumberland peregrines compares most favourably with that of Mearns (1983) who reported a figure of 39% by frequency in mixed habitats. However, the data from other studies are not directly comparable because of differences in the times of year used and the types of breeding habitats under study. The peregrine territories sampled in this study were in forestry, sheepwalk and mixed inland habitats. None was on managed grouse moors. The breeding density and or breeding success of peregrines is likely to be influenced by food supply and in particular, the availability of racing pigeons (Dixon et al., Submitted A). A reduction in the supply of racing pigeons could have a serious impact on breeding peregrines in Northumberland. Whether this would be reflected in a reduction in breeding numbers or breeding success is unclear and any effect would be influenced by their ability to switch to alternative prey species. Few wild bird species are as profitable as racing pigeons in terms of their ease of capture and weight, and thus a switch to alternative prey is likely to increase energy demands on breeding peregrines through more time spent hunt- 116
ing and the need to make a greater number of kills. The number of pigeon fanciers in Britain is currently declining at a rate of around 5% per annum, a situation which does not bode well for the future of the internationally significant peregrine population in the UK. There are many reasons for the decline in the sport but increased losses due to raptor predation is often cited as a major cause, particularly in Scotland (Scottish Homing Union, 1998). During the winter, the reduced availability of domestic pigeons is compensated to some extent by the arrival of winter migrants. Redwings, fieldfares and blackbirds are frequently killed at breeding territories in the winter, together with wood pigeons. The latter can be found in large flocks throughout Northumberland in the winter and it seems that peregrines have a propensity to hunt flock-forming species at all times of the year. The high frequency of wintering woodcock in the diet is likely to reflect the suitability of conifer plantations in the uplands of Northumberland for this species but their frequency in the prey remains is also likely to be biased. Plucked woodcock feathers are highly visible and the head or bill is frequently left uneaten; furthermore they are most active at dusk and dawn when peregrines are most likely to be near the breeding site before and after roosting during winter. Racing pigeons as prey For the period April-September, the majority of the domestic pigeons killed at breeding territories are racing pigeons as opposed to free-living feral pigeons (Dixon and Richards, 2003). As there were few lofts and little arable land in close proximity to the peregrine sites investigated in this study it is reasonable to assume that most of these birds were caught as they passed through the breeding territories. Some of these pigeons would have been killed as they returned to their home lofts on race or training flights, some may have been young birds ranging during exercise and others would have been killed as they passed through the breeding territory after they had already become lost i.e. strays. In Northumberland, racing pigeons registered with the SU and the NEHU were killed most frequently, comprising 69% of all racing pigeon kills. A further 14% were from lofts in north-east England (mainly North Yorkshire) and the East Midlands, many of which race on north road routes. Only 17% of racing pigeons killed by peregrines in Northumberland originated from lofts outside these areas. These pigeons came from lofts elsewhere in England (13%), Wales (3%), Ireland and continental Europe (1%). Pigeons originating from lofts in Wales, Ireland and continental Europe represent a relatively insignificant proportion of all the racing pigeons killed by peregrines in Northumberland. In addition, racing pigeons from Ireland and continental Europe are likely to have already been lost to their owners prior to being killed by peregrines as no race or training routes to these destinations pass through Northumberland. Most lofts within the WHU now fly from the south-east, many having switched from north road racing during the mid to late 1990s (Dixon, 2002). Most lofts within the NEHU are located south and east of the peregrine territories sampled in this study, mainly in the conurbations of Tyne & Wear, Durham and Cleveland. Pigeons in this area are mainly trained and raced from liberation points to the south of their home lofts, so few would be expected to pass through the peregrine breeding territories during a direct homing flight or during normal exercise around the loft. Consequently, most of the pigeons with NEHU rings would have either overshot their lofts during homing flights or strayed from their home loft prior to being killed. However, 32% 117
of the NEHU pigeons were from federations in rural parts of Northumberland that coincided with the peregrine territories sampled in this study. Many of these pigeons were likely to have been killed in relatively close proximity to their home lofts either during racing, training or exercising. During normal exercise from the loft young birds range widely when developing their homing skills (normally during May and June), thus young birds from lofts in rural Northumberland are particularly susceptible to attack by local peregrines. This is a possible explanation for the finding that more young birds from the NEHU were killed than from other unions and that most of the young birds killed during the old bird race season were from the NEHU. The potential impact of peregrine predation on Scottish racing pigeons is currently the subject of a research study being conducted by the Central Science Laboratory on behalf of Scottish Natural Heritage and the Scottish Homing Union. It is outside the scope of this study to try and quantify the detrimental impact of predation on racing pigeons by peregrines in Northumberland. However, the data indicate that most of the direct losses are borne by fanciers with lofts in the same geographical area as the peregrine territories, i.e. regions around the Firth of Forth and Scottish Borders, together with those in north-east England and the east Midlands who fly the north road route. The race routes to these locations pass directly through Northumberland. Pigeons originating from lofts in these regions comprise 46% of all the racing pigeons killed by peregrines in Northumberland. Many, but not all, of the racing pigeons originating from lofts in other areas are likely to be stray birds already lost to their owners or which have deviated significantly from a direct homeward flight route. It is impossible to determine the proportion of racing pigeons that would have homed successfully if they had not been killed by peregrines. However, it is likely that the pigeons that were killed whilst far away from their home loft and intended flight route would have been less likely to return home than their counterparts that were closer to home or their intended flight route. REFERENCES DIXON A (2002). Attacks by Birds of Prey on Racing Pigeons. Report to the Confederation of Long Distance Racing Pigeon Unions of Great Britain and Northern Ireland, University of Lancaster. DIXON A and LAWRENCE A M (2000). The past and present status of the Peregrine Falco peregrinus in Breconshire (vc 42). Welsh Birds 2: 280-291. DIXON A and RICHARDS C (2003). Estimating the number of racing pigeons killed at Peregrine territories in South Wales. Welsh Birds 3: 344-353. DIXON A, RICHARDS C, LAWRENCE A and THOMAS, M (2003). Peregrine (Falco peregrinus) predation on racing pigeons (Columba livia) in Wales. pp. 255-261. In: Birds of Prey in a Changing Environment. (Ed. Thompson D B A, Redpath S M, Fielding A H, Marquiss M and Galbraith C A). TSO, Edinburgh. ENDERSON J H and CRAIG G R (1997). Wide ranging by nesting Peregrine Falcons (Falco peregrinus) determined by radiotelemetry. Journal of Raptor Research 31: 333-338. MEARNS R (1982). Winter occupation of breeding territories and winter diet of Peregrines in south Scotland. Ornis Scandinavica 13: 79-83. MEARNS R (1983). The diet of the Peregrine Falco peregrinus in south Scotland during the breeding season. Bird Study 30: 81-90. 118
RATCLIFFE D A (1993). The Peregrine Falcon. Second edition. T & AD Poyser, London. REDPATH S M and THIRGOOD S J (1997). Birds of Prey and Red Grouse. Stationery Office, London. RICHARDS C and SHRUBB M (1999). The prey of Peregrines Falco peregrinus in South Wales. Welsh Birds 2: 131-136. SCOTTISH HOMING UNION (1998). Attacks by Peregrines and Sparrowhawks on Racing Pigeons in Scotland. SHU, Hamilton. SHAWYER C, CLARKE R and DIXON N (2001). A study into the raptor predation of Domestic Pigeons. DETR, London. UK RAPTOR WORKING GROUP (2000). Report of the UK Raptor Working Group. HMSO, London. 119
Appendix Avian prey remains identified at Peregrine breeding territories in Northumberland. Summer (April-September) Winter (October-March) Prey Species Wt. Frequency % Frequency % (g) (%) Weight (%) Weight Mallard Anas platyrhynchos 1063.1 (0.8) 3.3 0 0 Red grouse Lagopus lagopus 637.2 (1.6) 3.9 0 0 Coot Fulica atra 800.1 (0.8) 2.5 0 0 Lapwing Vanellus vanellus 230.3 (2.4) 2.1 1 (0.9) 1.6 Golden plover Pluvialis apricaria 220.1 (0.8) 0.7 1 (0.9) 1.5 Common snipe Gallinago gallinago 110.4 (3.2) 1.3 0 0 Woodcock Scolopax rusticola 300.1 (0.8) 0.9 6 (5.7) 12.5 Curlew Numenius arquata 885.1 (0.8) 2.7 0 0 Whimbrel Numenius phaeopus 480.1 (0.8) 1.5 0 0 Redshank Tringa totanus 175.1 (0.8) 0.5 0 0 Black-headed gull Larus ridibundus 288.1 (0.8) 0.9 0 0 Domestic pigeon Columba livia 375.4 (35.5) 50.6 4 (3.8) 10.4 Wood pigeon Columba palumbus 453.8 (6.5) 11.1 8 (7.5) 25.2 Budgerigar Melopsittacus undulatus 65 0 0 1 (0.9) 0.5 Swift Apus apus 44.1 (0.8) 0.1 0 0 Skylark Alauda arvensis 38.2 (1.6) 0.2 0 0 House martin Delichon urbica 18.1 (0.8) 0.1 0 0 Meadow pipit Anthus pratensis 20.4 (3.2) 0.2 0 0 Robin Erithacus rubecula 17.1 (0.8) 0.1 0 0 Blackbird Turdus merula 103.5 (4.0) 1.6 17 (16.0) 12.2 Fieldfare Turdus pilaris 100.1 (0.8) 0.3 24 (22.6) 16.7 Song thrush Turdus philomelos 65.1 (0.8) 0.2 2 (1.9) 0.9 Redwing Turdus liliacus 63 0 0 29 (27.4) 12.7 Mistle thrush Turdus viscivorus 125 3 (2.4) 1 1 0 0 Willow warbler Phylloscopus trochilus 11.1 (0.8) 0 0 0 Goldcrest Regulus regulus 6 0 0 2 (1.9) 0.1 Long-tailed tit Aegithalos caudatus 9 0 0 1 (0.9) 0.1 Blue tit Parus caeruleus 10 0 0 2 (1.9) 0.1 Jackdaw Corvus monedula 223 4 (3.2) 2.7 1 (0.9) 1.6 Carrion crow Corvus corone 505 3 (2.4) 4.6 0 0 Rook Corvus frugilegus 310 1 (0.8) 0.9 0 0 Starling Sturnus vulgaris 78 23 (18.5) 5.5 7 (6.6) 3.8 Chaffinch Fringilla coelebs 24.1 (0.8) 0.1 0 0 Goldfinch Carduelis carduelis 17.1 (0.8) 0.1 0 0 Unidentified small passerine 20.2 (1.6) 0.1 0 0 120