Using Passive
Integrated Transponders (PIT tags)
to Understand the Peregrine Falcon
Population in Britain
 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. 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
domestic animals (and clients at discos!). 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.
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.
Literature cited
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.
Contact information
mike.mcgrady@natural-research.org
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