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Crop diversity loss as primary cause of grey partridge and common pheasant decline in Lower Saxony, Germany

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ABSTRACT

Background: The grey partridge (Perdix perdix) and the common pheasant (Phasianus colchicus) are galliform birds typical of arable lands in Central Europe and exhibit a partly dramatic negative population trend. In order to understand general habitat preferences we modelled grey partridge and common pheasant densities over the entire range of Lower Saxony. Spatially explicit developments in bird densities were modelled using spatially explicit trends of crop cultivation. Pheasant and grey partridge densities counted annually by over 8000 hunting district holders over 10 years in a range of 3.7 Mio ha constitute a unique dataset (wildlife survey of Lower Saxony). Data on main landscape groups, functional groups of agricultural crops (consisting of 9.5 million fields compiled by the Integrated Administration and Control System) and landscape features were aggregated to 420 municipalities. To model linear 8 or 10 year population trends (for common pheasant and grey partridge respectively) we use rho correlation coefficients of densities, but also rho coefficients of agricultural crops.

Results: All models confirm a dramatic decline in population densities. The habitat model for the grey partridge shows avoidance of municipalities with a high proportion of woodland and water areas, but a preference for areas with a high proportion of winter grains and high crop diversity. The trend model confirms these findings with a linear positive effect of diversity on grey partridge population development. Similarly, the pheasant avoids wooded areas but showed some preference for municipalities with open water. The effect of maize was found to be positive at medium densities, but negative at very high proportions. Winter grains, landscape features and high crop diversity are favorable. The positive effect of winter grains and higher crop diversity is also supported by the trend model.

Conclusions: The results show the strong importance of diverse crop cultivation. Most incentives favor the cultivation of specific crops, which results in large areas of monocultures. The results confirm the importance of sustainable agricultural policies.

Electronic supplementary material: The online version of this article (doi:10.1186/s12898-016-0093-9) contains supplementary material, which is available to authorized users.

No MeSH data available.


a Common pheasant hen density 2007; b common pheasant hen spearman rho correlation coefficients (2007–2014) per municipality in Lower Saxony. Red indicating negative population trends green positive trends. Grey no data (Time span differs to the grey partridge. Pheasants were not recorded in 2005. In 2006 data were sparse and thus also omitted from analyses) (Cartographic base: GeoBasis-DE/BKG 2002, data source: wildlife survey)
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Fig3: a Common pheasant hen density 2007; b common pheasant hen spearman rho correlation coefficients (2007–2014) per municipality in Lower Saxony. Red indicating negative population trends green positive trends. Grey no data (Time span differs to the grey partridge. Pheasants were not recorded in 2005. In 2006 data were sparse and thus also omitted from analyses) (Cartographic base: GeoBasis-DE/BKG 2002, data source: wildlife survey)

Mentions: Between 1991 and 2005 grey partridge density was highest in western and central Lower Saxony (Figs. 1a, 2a). Also, for the shorter study period (2005–2014) that was used for the habitat and trend models, the grey partridge showed a strong negative trend over the entire study area (median: rho = −0.79, 1st and 3rd quantiles: rho = −0.94 and −0.47), with the severest decline in western Lower Saxony (Fig. 2b). Since the start of data collection in 1991 the common pheasant had its highest population densities within the westernmost parts of Lower Saxony (Figs. 1, 3a), it also showed a negative trend between 2007 and 2014; however, it was somewhat less severe (median: rho = −0.60, 1st and 3rd quantiles: rho = −0.81 and −0.17). The pheasant also declined most severely in the westernmost areas of Lower Saxony (Fig. 3b).Fig. 2


Crop diversity loss as primary cause of grey partridge and common pheasant decline in Lower Saxony, Germany
a Common pheasant hen density 2007; b common pheasant hen spearman rho correlation coefficients (2007–2014) per municipality in Lower Saxony. Red indicating negative population trends green positive trends. Grey no data (Time span differs to the grey partridge. Pheasants were not recorded in 2005. In 2006 data were sparse and thus also omitted from analyses) (Cartographic base: GeoBasis-DE/BKG 2002, data source: wildlife survey)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5016946&req=5

Fig3: a Common pheasant hen density 2007; b common pheasant hen spearman rho correlation coefficients (2007–2014) per municipality in Lower Saxony. Red indicating negative population trends green positive trends. Grey no data (Time span differs to the grey partridge. Pheasants were not recorded in 2005. In 2006 data were sparse and thus also omitted from analyses) (Cartographic base: GeoBasis-DE/BKG 2002, data source: wildlife survey)
Mentions: Between 1991 and 2005 grey partridge density was highest in western and central Lower Saxony (Figs. 1a, 2a). Also, for the shorter study period (2005–2014) that was used for the habitat and trend models, the grey partridge showed a strong negative trend over the entire study area (median: rho = −0.79, 1st and 3rd quantiles: rho = −0.94 and −0.47), with the severest decline in western Lower Saxony (Fig. 2b). Since the start of data collection in 1991 the common pheasant had its highest population densities within the westernmost parts of Lower Saxony (Figs. 1, 3a), it also showed a negative trend between 2007 and 2014; however, it was somewhat less severe (median: rho = −0.60, 1st and 3rd quantiles: rho = −0.81 and −0.17). The pheasant also declined most severely in the westernmost areas of Lower Saxony (Fig. 3b).Fig. 2

View Article: PubMed Central - PubMed

ABSTRACT

Background: The grey partridge (Perdix perdix) and the common pheasant (Phasianus colchicus) are galliform birds typical of arable lands in Central Europe and exhibit a partly dramatic negative population trend. In order to understand general habitat preferences we modelled grey partridge and common pheasant densities over the entire range of Lower Saxony. Spatially explicit developments in bird densities were modelled using spatially explicit trends of crop cultivation. Pheasant and grey partridge densities counted annually by over 8000 hunting district holders over 10 years in a range of 3.7 Mio ha constitute a unique dataset (wildlife survey of Lower Saxony). Data on main landscape groups, functional groups of agricultural crops (consisting of 9.5 million fields compiled by the Integrated Administration and Control System) and landscape features were aggregated to 420 municipalities. To model linear 8 or 10 year population trends (for common pheasant and grey partridge respectively) we use rho correlation coefficients of densities, but also rho coefficients of agricultural crops.

Results: All models confirm a dramatic decline in population densities. The habitat model for the grey partridge shows avoidance of municipalities with a high proportion of woodland and water areas, but a preference for areas with a high proportion of winter grains and high crop diversity. The trend model confirms these findings with a linear positive effect of diversity on grey partridge population development. Similarly, the pheasant avoids wooded areas but showed some preference for municipalities with open water. The effect of maize was found to be positive at medium densities, but negative at very high proportions. Winter grains, landscape features and high crop diversity are favorable. The positive effect of winter grains and higher crop diversity is also supported by the trend model.

Conclusions: The results show the strong importance of diverse crop cultivation. Most incentives favor the cultivation of specific crops, which results in large areas of monocultures. The results confirm the importance of sustainable agricultural policies.

Electronic supplementary material: The online version of this article (doi:10.1186/s12898-016-0093-9) contains supplementary material, which is available to authorized users.

No MeSH data available.