The peregrine falcon (Falco peregrinus) population in Britain (currently +/-1500 occupied ranges) has largely recovered from declines caused by organochlorine pollutants. Despite this, in some areas the population is declining. Persecution and perhaps contamination are seen as the main threats, but their relative importance in different parts of the country is not known. Changes in prey abundance and distribution has also probably affected peregrines. Since the 1970’s a relatively large proportion of peregrines in the UK have been ringed as nestlings. However, there have been relatively few recoveries (33) of breeders from ~6000 ringed as pulli (J. Clarke pers. comm.), so little information on dispersal and recruitment has come from the ringing effort. Recently, the proportion of peregrine nestlings that are ringed has declined, perhaps due to waning interest by ringers grown tired of low ring recovery rates.
Information on peregrine demography and recruitment are generally lacking and are two of the main gaps in understanding this species in Britain. Monitoring turnover is especially important in relatively long-lived species like the peregrine where adult and sub-adult survival has a greater potential impact on overall numbers than does reproduction (Wootton & Bell 1992). Despite the large (voluntary) effort to monitor peregrines and ring their nestlings, data on turnover and recruitment generally are not collected because few individual breeding peregrines can be identified. What information is available is from a period when the population was known to be recovering from the effects of organochlorine pollutants (Mearns and Newton 1984), is limited in geographic scope (Horne and Fielding 2002) or is being collected in a relatively small, ongoing effort (McGrady 2003).
Since 2002 Natural Research has been collecting data on peregrine demography and recruitment. Working in cooperation with members of Scottish Raptor Study Groups we caught breeding peregrine falcons in southern Scotland and northern England, and fitted these and peregrine nestlings with BTO rings and PIT tag rings. PIT (Passive Integrated Transponder) tag rings are metal rings that contain a uniquely identifiable ‘microchip’ like those used to identify pets and livestock. A reader is used to identify and store tag ID data. This system has been used successfully to examine recruitment, site fidelity and dispersal in merlin in the UK (Wright 2003).
Since 2003, 407 PIT tags have been fitted, and Natural Research has provided local Scottish Raptor Study Groups with tag readers. We have captured 61 adults, encountered 30 adults in more than one year, and read 17 BTO ringed birds from outside our study. In 2006 we fitted 164 tags to peregrines and identified 13 breeders by their PIT rings alone.
Despite our success in capturing breeders and ringing peregrines of all ages, we are interested in expanding the effort by encouraging and supporting collaboration with ringers. In order to support more work on individually marking peregrine falcons, Natural Research is offering, to authorized ringers, supplies of PIT tag rings for use on peregrines. These rings are size G and are fitted in much the same way as a normal BTO ring. As time passes and centres of effort are identified, Natural Research will make available to the local collaborator(s) a reader, which when set in the nest can identify the falcon when it visits the scrape. Even if one does not care to collaborate on the PIT tagging scheme, we would like more peregrine nestlings to be ringed using BTO rings.
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Acknowledgements: SNH and EN provided licenses, BTO provided ringing permits and many ringers and raptor workers have helped both directly and indirectly with this study.
Horne G., Fielding A.H. 2002. Recovery of the Peregrine in Falcon Falco peregrinus in Cumbria, UK, 1966-99. Bird Study 49: 229-236.
McGrady, M. J. 2003. Confidential report to the British Trust for Ornithology, English Nature, and Scottish Natural Heritage on efforts to trap breeding peregrine falcons in UK in 2002. Unpublished.
Mearns, R. and Newton, I. 1984. Turnover and dispersal in a peregrine Falco peregrinus population. Ibis 126: 347-355.
Wright, P. A. 2003. Recruitment, site fidelity, and dispersal of merlins Falco columbarius from the southeast Yorkshire Dales, England. Ringing and Migration 21: 227-233.
Wootton, J. T., and Bell, D.A., 1992. A metapopulation model of the Peregrine Falcon in California: viability and management strategies. Ecological Applications 2:307-321.
Photo: M. McGrady