Faculty of Biology, University of Latvia
EEB
Hard copy: ISSN 1691–8088
On-line: ISSN 2255–9582
Acta Univ Latv (2005) 691: 93–109
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Environmental and
Experimental
Biology

Acta Univ Latv (2005) 691: 93–109

Orginal Article

Impact of changes in agricultural land use on the Corncrake Crex crex population in Latvia

Oskars Keišs1,2*
1Department of Zoology and Animal Ecology, University of Latvia, Kronvalda Bulv. 4, Rīga LV-1586, Latvia
2Laboratory of Ornithology, Institute of Biology, University of Latvia, Miera 3, Salaspils LV-2169, Latvia
*Corresponding author, E-mail: grieze@lanet.lv

Abstract

Data on Corncrake numbers and agricultural land use were collected in 68 freely chosen sample plots (0.67 - 44.38 km2; mean = 8.42; SD = 7.458) in Latvia 1984 - 2004. The annual TRIM index of Corncrake numbers in Latvia increased significantly during the study period (p < 0.003). The total area of all abandoned agricultural lands have increased significantly (p < 0.0006) at the expense of cultivated pastures (p < 0.015) in the survey plots. The area of intertilled crops also decreased (p < 0.07). The area of both cultivated and uncultivated meadows increased significantly during the period of 1989 - 1998 (p < 0.005), and decreased in 1999 - 2004 (p < 0.025). The habitat-specific annual TRIM index of Corncrake numbers was positively correlated with the TRIM index of area of uncultivated meadows (p < 0.001), all meadows combined (p < 0.001), uncultivated pastures (p < 0.05) and abandoned agricultural lands (p < 0.0025), but negatively with the TRIM index of area of intertilled crops (p < 0.05). The total Corncrake TRIM index was positively correlated (p < 0.002) with the total amount of precipitation during the Corncrake breeding season (May - July). The highest breeding density (on average – 3.05 males km2) was observed in abandoned grasslands, followed by uncultivated meadows > abandoned arable lands > cultivated meadows > other (miscellaneous) habitats > uncultivated pastures > shrubland > winter crops > cultivated pastures > spring crops > intertilled crops. More Corncrakes than expected were observed in abandoned grasslands, uncultivated meadows and abandoned arable lands (p < 0.001), but Corncrake numbers were smaller in winter crops, cultivated pastures, spring crops and intertilled crops (p < 0.001). Despite the recent increase of the Corncrake numbers in Latvia, the projected long-term dynamics since 1940 show a significant decrease in numbers (p < 0.0001) due to decrease of area of suitable habitats (e.g. meadows) in Latvia.

Key words: agricultural land use, Corncrake, Crex crex, habitat preference, population trends.

 
Acta Univ Latv (2005) 691: 93–109
 DOI: http://doi.org/10.22364/eeb
EEB

Editor-in-Chief
Prof. Gederts Ievinsh



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