The State of Europe's Common Birds 2008 - European Bird Census ...

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The State of Europe’s Common Birds 2008Photo by D. Jirovský (wildbirdphoto.eu)Both papers represented a milestonein reference to PECBMS, mostly asa source of information about themethods used to calculate speciesindices and indicators.Another paper, published quiterecently (Gregory et al. 2008), usesexamples from the UK and Europe toillustrate the state of play regardingthe use of birds as indicators. The UKexperience provides an excellentexample of turning scientific data intopolicy measures in natureconservation, which has subsequentlybeen followed by other countries. Alsoat European level, the common birdindicators proved to be successful interms of use in policy and in fact theyrepresent one of very few fullyoperational biodiversity indicators inEurope.The Great Reed-warbler Acrocephalusarundinaceus is expected to benefit from climatechange (Gregory et al. 2009). In Poland, it hasalready been shown to be adapting well by shiftingits laying dates, probably to optimise foodresources (Dyrcz and Halupka 2009).from national or regional breeding birdmonitoring schemes can be analysed,supranational species indices can be generatedand multi-species indicators can be calculated byaveraging the resulting indices. The paper showedhow data collated by skilled volunteers and bymethods and survey designs that differ slightlybetween countries can be combined to producerelevant multi-national results. It also describedhow and why national species indices need to beweighted by population size in order to producerelevant supra-national figures. The paper alsoshowed that common farmland birds in Europehave declined steeply since 1980, and thatevidence elsewhere shows that the main driver offarmland bird declines is agriculturalintensification.The PECBMS European data werealso used for explorative analysis ofspecies trends, particularly of forestspecies (Gregory et al. 2007). This showed thatsince 1980, forest specialists have declinedmore than forest generalists, but trendsdiffered regionally, and interestingly forestspecies in Central and Eastern Europe haveshown stability or even increased. Anindependent study demonstrated that forestspecialists have increased in the CzechRepublic, most likely as a result of increasingforest coverage and age (Reif et al. 2007). AtEuropean level, among common forest birds,long-distance migrants and residents onaverage declined most strongly, whereas shortdistancemigrants were largely stable, or evenincreased. There was some evidence to suggestthat ground- or low-nesting species declinedmore strongly on average, as did forest birdswith invertebrate diets. It also appeared thatin a small number of species, year-to-yearvariation in abundance can be influenced bycold winters. However, much more researchneeds to be done to understand trends offorest bird species and their driving forces.22
The State of Europe’s Common Birds 2008Another topic of PECBMS research is rapidclimatic change, which poses a threat to globalbiodiversity. Evidence is accumulating thatclimatic change in recent decades has alteredmany biological phenomena across the globe,including the geographical ranges andabundance of plants and animals, and thethe second step was to construct a climaticimpact indicator based upon the divergence inpopulation trends between species expected tobe positively and negatively affected by climaticchange. This work detected a significantpositive relationship between interspecificvariation in population trend and the change inFigure 13 | Weighted population trend of speciespredicted to gain range in response to climatic change(30 species).Figure 14 | Weighted population trend of speciespredicted to lose range in response to climatic change(92 species).timing of events in their lives such as growth,reproduction and migration. Scientists andpolicy makers are calling for the developmentof indicators of the impacts of climatic changeon biodiversity based upon these phenomenathat summarise impacts over many species andlarge areas. The purpose of such indicators is tosummarise sets of related impacts, to describehow they are changing in an accessible way, toraise awareness of the biological consequencesof climatic warming, and to assist both insetting targets for the reduction of impacts andin guiding the implementation of mitigationand adaptation measures. PECBMS has madepractical progress by working with academicsand other experts to develop a biologicalindicator of climatic change impacts in twosteps. The first step was testing the performanceof projections of change in the extent of species’geographical range (based upon climaticenvelope models) as predictors of observedinterspecific variation in long-term change inpopulation size of land bird species over a largepart of Europe derived from the PECBMS.Having found a robust relationship of this kind,potential range extent between the late 20thand late 21st centuries, as forecast by climaticenvelope models. The derived indicatormeasures divergence in population trendbetween bird species predicted by climaticenvelope models to be favourably affected byclimatic change and those adversely affected.The ‘Climatic Impact Indicator’ has increasedstrongly in the past twenty years, coincidingwith a period of rapid climatic warming inEurope. The key messages to emerge from thestudy are that climate change is having adetectable effect on bird populations at aEuropean scale, including evidence of negativeas well as positive effects on their populations.The number of bird species whose populationsare observed to be negatively impacted byclimatic change is three times larger than thoseobserved to be positively affected by climatewarming in this set of European land birds (seeFigures 13 and 14). The potential links betweenchanges in bird populations and ecosystemfunctioning are not well understood. It issuggested that increasing climatic effects mightalter ecosystem functioning and resilience.23
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