Wpływ zmiennych warunków hydrologicznych na liczebność kropiatki Porzana porzana i derkacza Crex crex w dolinie górnego Liwca w roku 2013
Journal Title: KULON - Year 2014, Vol 19, Issue
Abstract
We observed significant changes in the abundance of territorial males of the Spotted Crake Porzana porzana and Corncrake Crex crex on a fragment of the upper Liwiec floodplain (eastern Poland) on an area of ca 6 km2, during 31 May-21 July, 2013. They were caused by a large variation in water level. Numbers of birds varied from 0 to 48 for the Spotted Crake, and from 0 to 43 for the Corncrake (table, figure). The highest density of the Spotted Crake was 8 males/km2, and that of the Corncrake was 7.2 males/km2. The abundance of the Spotted Crake was rather strongly negatively correlated with the level of flood water (Spearman rank correlation: rs = -0.69; p = 0.040), and that of the Corncrake was very strongly negatively correlated with this factor (rs = -0.95; p<0.001). Most Spotted Crakes were recorded at moderately high water level, and most Corncrakes were recorded at the lowest water levels (figure). However, the Spearman rank correlation showed that changes in numbers of these two species were positively correlated (rs = 0.70; p = 0.030). This suggests that some statistics can lead to erroneous conclusions about evaluation of natural events.
Authors and Affiliations
Andrzej Dombrowski, Łukasz Trębicki, Magdalena Sikora
Keywords
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