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EURO-CES: Constant effort ringing in
Europe
Background
Bird populations are perhaps the most visible, and certainly amongst
the most popular, component of biodiversity in Europe. They also
provide an easily studied indicator of environmental and land-use
change. However, an understanding of why their populations change,
and the environmental reasons underlying such changes requires a
knowledge of the demography of the population, i.e. birth and death
rates, in addition to simple changes in numbers (Baillie 1990).
Ringing, particularly under standard conditions, can provide a useful
estimate of each of these parameters.
With this in mind, a pilot constant effort ringing project was
initiated in Britain in 1981, by a volunteer. In 1986, this became
a nationwide project, the Constant Effort Sites (CES) Scheme run
by the British Trust for Ornithology (Baillie et al. 1986).
Sites participating in the Scheme employ a constant number of nets
in the same locations for a standard number of visits each year.
Using such a protocol, it is possible to monitor, on an annual basis,
changes in:
- adult and juvenile abundance
- productivity (proportion of young birds caught each year)
- adult survival rates (from between-year recaptures).
In Britain, the CES Scheme forms part of an Integrated Population
Monitoring (IPM) Programme, which incorporates the Breeding Bird
Survey, Nest Record Scheme and national Ringing Scheme, which aims
to identify the causes (natural and anthropogenic) of population
changes affecting breeding birds in Britain and Ireland.
Following the development of CES ringing in Britain and Ireland,
other ringing schemes across Europe set up their own constant effort
projects including Finland (commenced in 1987), France (1989), Spain
(SYLVIA, 1991) and The Netherlands (1984).
The MAPS (Monitoring Avian Productivity and Survivorship) program
in North America was set up in 1989 and closely follows the BTO
CES scheme protocols (De Sante et al. 1995, http://www.birdpop.org/nbii/
NBIIHome.asp).
Development of the EURO-CES project
A number of constant effort ringing schemes are now operated across
Europe. At the EURING General Meeting on Helgoland in autumn 1999
there was considerable interest expressed by a number of Ringing
Schemes in trying to standardise, as far as possible, such schemes
across Europe. In addition to allowing schemes to learn from each
other’s experiences, this will lead, ultimately, to the possibility
of comparing trends in population dynamics between countries, and
monitoring populations at a European scale. This is important because
many of the factors that influence bird population dynamics (e.g.
the climate change and the Common Agricultural Policy) operate at
this broad scale.
This project is being led by the British Trust for Ornithology,
in collaboration with the French Centre de Recherches sur la Biologie
des Populations d’Oiseaux. This project has two main aims:
- To assess the current state of CES-type schemes in Europe and
develop agreed protocols for CES fieldwork methodology, data exchange
and analysis.
- To assess the potential for producing combined European trends
/ comparative national trends for a common suite of species.
Guidelines for operating CES in Europe, taking into account its
wide latitudinal range have now been developed and early analyses
have provided encouraging signs that results from schemes in each
country can be combined in a Europe-wide analysis.
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