Woodpeckers as Indicators of Forest Bird Diversity

Abstract

Abstract: We analyzed the usefulness of woodpecker species ( family Picidae) in predicting the diversity of other forest bird species using the Polish Ornithological Atlas data on species distribution in Poland. We used the database (n = 2317) to examine the patterns of woodpecker occurrence in atlas plots and to test how well the occurrence of woodpecker species is related to the occurrence of other forest birds. The occupancy of atlas plots by particular species varied from 98.5% in the Great Spotted Woodpecker ( Dendrocopos major) to only 2.4% in the Three‐toed Woodpecker ( Picoides tridactylus). Woodpecker species richness in plots varied between 0 and 10 species, with a mean value of 4.3 species per plot. The occurrence of particular woodpecker species in plots with different woodpecker species richness was associated with the degree of specialization in particular species. Examining the entire data set, we found a positive relationship between woodpecker species richness and the number of species of other forest birds. These relationships were confirmed in three smaller regional data subsets with at least eight woodpecker species present (northeast Poland, r 2 = 0.78, p = 0.0001; east Poland, r 2 = 0.53, p = 0.0001; Carpathians, r 2 = 0.53, p = 0.0001). The mean number of forest specialists increased from 6 to over 30 species in plots with 0 and 9 woodpecker species, respectively. Also, the mean number of woodland generalists increased steadily with woodpecker species richness. Our results confirm the suitability of the woodpecker group as part of an indicator system for assessing avian diversity at the landscape scale. We suggest that in countries or regions in Europe where data on bird diversity are not readily available, woodpecker surveys could serve as a good tool for assessing the diversity of forest birds at the landscape scale.