Population trends of the grey partridge

The grey partridge used to be widespread in agricultural areas throughout Europe however today it is considered a rare bird (Kuijper et al., Reference KUIJPER, OOSTERVELD and WYMENGA2009). Due to the improper and overuse of insecticide preparations, the grey partridge has become almost extinct from Serbian plains, as well as from numerous countries across Europe (Figala et al., Reference FIGALA, PRCHALOVA and TESTER2001; Taylor et al., Reference TAYLOR, MAXWELL and BOIK2006). Small quantities of ingested poisonous substances by insect feeding causes decreased growth and/or weakening to partridges and they therefore become an easy target for predators (Watson et al., Reference WATSON, AEBISCHER, POTTS and EWALD2007; Kapetanov et al., 2012). In winter, rodent baits made of grains coated with zinc phosphide, thalium sulphate or carbonfuranes are used to prevent damage to field crops. Mass intoxications of starved partridges were frequent when such baits were improperly set on the ground (Kapetanov et al., 2012). In long term surveys on partridge populations in Europe, such as in Poland, Great Britain and Hungary (Panek, Reference PANEK2005; Báldi and Faragó, Reference BÁLDI and FARAGÓ2007) a continuous decrease in partridge numbers has been observed. Changes in the landscape and transformation of native land into arable land, the modernisation of agriculture including hard mechanisation and the intensive use of pesticides have all contributed to the rapid decline of partridge populations, to the point of extinction (Šálek et al., Reference ŠÁLEK, MARHOUL, PINTÍŘ, KOPECKÝ and SLABÝ2004; Wubbenhorst and Leuschner, Reference WUBBENHORST and LEUSCHNER2006). The average rate of population decline in the period from 1990 to 2000 was approximately 30% and ranged from 1 to 80% (Birdlife International, 2004). In contrast, in Russia and the Czech Republic, the number of partridges showed an increasing trend (Kuijper et al., Reference KUIJPER, OOSTERVELD and WYMENGA2009).

Pesticide poisoning of grey partridges

The improper setting of baits, in many cases randomly on field surfaces, poses a great threat to game. A lethal outcome five hours after the consumption of only a dozen treated grains has been seen in pheasants (Novotny et al., Reference NOVOTNY, MISIK, KOZLOVA, ONDRACEK, KUCA, VAVRA and RACHAC2011). In the past few decades, cases of both sporadic and mass poisoning of domestic and wild animals have been reported. The use of carbamate pesticides and organochlorine insecticides has predominantly influenced the decrease of partridges (Wobeser et al., Reference WOBESER, BOLLINGER, LEIGHTON, BLAKLEY and MINEAU2004; Novotny et al., Reference NOVOTNY, MISIK, KOZLOVA, ONDRACEK, KUCA, VAVRA and RACHAC2011) and other game fowl (Berny, Reference BERNY2007; Wang et al., Reference WANG, KRUZIK, HELSBERG, HELSBERG and RAUSCH2007; Berny and Gaillet, Reference BERNY and GAILLET2008). In the retrospective study by Novotny et al. (Reference NOVOTNY, MISIK, KOZLOVA, ONDRACEK, KUCA, VAVRA and RACHAC2011), a total of 181 cases of poisoning in wild animals including partridges were analysed. The authors found that the most frequent cause of poisoning was consumption of insects, carcasses or rodent baits, all previously exposed to carbamate pesticides and organochlorine insecticides. It seems such cases represent mostly collateral damage to intensive agriculture (Kapetanov et al., 2012; Mihaljev et al., 2012). Some studies suggest that today partridges are better adjusted to arable fields compared to other game fowl, however they are rarely seen in this habitat. However, Henderson et al. (Reference HENDERSON, RAVENSCROFT, SMITH and HOLLOWAY2009) proposed more selective and a reduced use of pesticides in agriculture as a realistic means to reintroduce partridge into nature. Gabriel et al. (Reference GABRIEL, CARVER, DURHAM, KUNIN, PALMER, SAIT, STAGL and BENTON2009) suggested redirect activities towards organic food production. Kuijper et al. (Reference KUIJPER, OOSTERVELD and WYMENGA2009) stated that the increased pesticide use may have caused direct effects on partridges by poisoning birds, or indirect effects through killing their food. Furthermore, the mentioned authors noted that the reported number of cases that can be attributed to direct effects is relatively small, and indirect effects seem to play a much more important role.

Clinical signs and pathological lesions of pesticide poisoning in grey partridge

Kapetanov et al. (2012) reported that dead partridges were found on fields in close proximity to baits, with prostrated necks, outstretched legs and wide spread wings, indicating poisoning with intra vitam signs of neural excitation (Johnston et al.,1994). The death time was estimated to be less than five hours after bait consumption. Section findings were similar in all 39 carcasses. Due to excitation, mechanical disruption of skeletal muscles was present, particularly on breast muscles. Ingluvial and stomach contents consisted of green masses of alfalfa or wheat, with coloured barley and wheat grains. The colour of grains varied between grey and bright red. Hyperemic capillaries were found on the meninges of the cerebrum and cerebellum.

Qualitative and quantitative analysis of rodent baits (treated seed), the ingluvial and stomach contents of dead birds, for detecting the presence of pesticides is performed by using gas chromatography-mass spectrometry (GC-MS) methods (Poppenga et al., Reference POPPENGA, ZIEGLER, HABECKER, SINGLETARY, WALTER and MILLER2005; Reljić et al., Reference RELJIĆ, SREBOČAN, HUBER, KUSAK, ŠURAN, BRZICA, CUKROV and CRNIĆ2012).

Acknowledgments

This research was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (ТР31084).