Acta Univ Latv (2005) 691: 93–109

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

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.