Which method is most suitable for censusingbreeding populations of red-backed (Laniuscollurio) and great grey (L. excubitor) shrikes?

Northern Shrike (Lanius excubitor) Science Article 7


Up to now, studies have shown that it is very difficult to estimate accurate numbers of shrike(Lanius spp) breeding pairs. During our shrike biology research in Western Poland this problemwas evident. Actual breeding pair numbers were derived from a combination of specialcounts in the pre-breeding period, intensive nest searches and colour ringing. Empirical testshave shown point counts and line transect methods, with regard to Red-backed (Lanius collurio)and Great Grey (L. excubitor) Shrike population size estimates, to underestimate numbersseverely. Furthermore, we have found that the ‘improved mapping technique’ underestimatesthe actual numbers of Red-Backed Shrike breeding territories by as much as 45-80%. It underestimatesthe actual numbers for the Great Grey Shrike by just under 40%. In the case of theRed-Backed Shrike, the accuracy of results from the ‘improved mapping technique’ was negativelycorrelated with the population density. However, we did manage to achieve accuratenumbers of shrike breeding pairs, but only by using specific methods. For the Great GreyShrike, counts during pair formation period yielded the most precise results and for the RedbackedShrike, intensive nest searches proved to be the most effective method.

P. Tryjanowski, M. Hromada, M. Antczak, J. Grzybek,S. Kuzniak and G. Lorek, Ornis Hungarica 12-13: 223-228. 2003

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