Choosing a totally repeated or partially-repeated sampling strategy to assess both population changes and distribution: the case of Italian breeding birds

Tellini Florenzano G., Fornasari L., De Carli E., La Gioia G.

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Abstract:

We tested how well different point-count sampling strategies can be used both as measures of species’ population indices and as a source of distribution information. Four sampling strategies were compared using Italian monitoring data (MITO2000). The strategies differed in terms of the number of random and repeated point-counts. To test the effciency of each strategy as a population index, the population indices per grid-unit were compared between-years (2000 vs 2001) with Spearman correlation and Syrjala test; to assess data usefulness for chorological purposes, the no. of species signifcantly detected was assessed for each strategy. Strategies involving both repeated and non repeated counts seem to give a useful compromise to gather both population and distributional data, though it would be better, at least in terms of cost, to plan different programmes for these two important attributes of the avifauna.