Factors affecting Common Quail’s Coturnix coturnix occurrence in farmland of Poland: is agriculture intensity important?

0 P. Chylarecki Museum and Institute of Zoology, Polish Academy of Science , Wilcza 64, 00-679 Warsaw, Poland Over the last four decades, the majority of European farmland birds have shown marked population declines attributed to the intensification of agriculture. The Common Quail is a widespread farmland breeder across most of Europe. Its populations have shown marked decline, particularly pronounced at the end of the previous century. Ongoing agriculture intensification may be the factor responsible for the observed declines; however, links between species occurrence and farming intensification have not been addressed so far. We analyzed factors affecting the occurrence of the Quail in Poland using data from 722 1 1-km study plots and a set of 22 environmental variables, including proxies for agriculture intensification. Predictors were aggregated using PCAs and related to species presence/ absence data using GAMs. The best-supported model of the species' occurrence included eight variables and was clearly better (AIC weight = 0.54) than other models. Quails preferred open fields, showing high photosynthetic activity in March or June, with rather low precipitation and often at relatively high altitudes (up to 900 m a.s.l.). Importantly, quails were more frequent on plots located in regions with rather high inorganic fertilizer input, and showed no avoidance of areas with a high level of agriculture mechanization. We postulate that singing male quails are attracted to areas with medium or high intensity of agriculture but it may represent a maladaptive habitat choice enhanced by changing agriculture practices and peculiarities of the quail's breeding strategy. Given the results, the quail cannot be classified as a good indicator of extensive traditional agriculture. - The decline of farmland birds observed over the past four decades across Europe is probably one of the most widely documented and publicized patterns of concerted population changes in conservation biology (Krebs et al. 1999; Donald et al. 2001; Benton 2007). Linked with intensification of agricultural practices, it spawned a large body of research on possible drivers of the observed changes (Chamberlain and Fuller 2000; Donald et al. 2001; Benton et al. 2002; Gregory et al. 2004; Newton 2004; Donald et al. 2006; Wretenberg et al. 2007; Butler et al. 2010). As a side issue, it also promoted further research on indices used to quantify and aggregate information on changes in abundance of multiple species (Gregory et al. 2005; van Strien et al. 2012). However, not all farmland bird species are equally vulnerable to changing farming practices and the observed patterns of population changes do differ between countries, hampering our understanding of the exact mechanisms driving the observed changes (Fox 2005; Wretenberg et al. 2006; Reif et al. 2008; Tryjanowski et al. 2011). The Common Quail Coturnix coturnix is a widespread breeder across most of European farmland, but it is also one of the most enigmatic species of this habitat. It is the only species of Phasianidae that undertakes long-distance migrations, spending the winter in the Sahel zone. Migratory habits and Sahel wintering grounds are factors making the species more vulnerable than others to population declines (Sanderson et al. 2009). A large decline of the European Quails population was observed in 19701990, followed by a shallow decline hence after, coupled with some increase noted in northern parts of its range (BirdLife International 2004; Sanderson et al. 2009). Consequently, the continental population is classified as depleted and the quail is categorized among species with unfavorable conservation status in Europe (Species of European Conservation Concern, SPECs) in category 3 (BirdLife International 2004). The quail is known to be excessively harvested (mostly hunted) during autumn migration, particularly in the Mediterranean basin (Gallego et al. 1997; Puigcerver et al. 1998; Sarda` -Palomera et al. 2012), which is a cause of concern, addressed recently by the EU management plan (EC 2009). The Quail is highly mobile within a single breeding season, with individual birds dispersing between distant breeding sites. Probably, most European breeders first reproduce in northern Africa and the Mediterranean basin (south of 40 N) in MarchApril, and only then migrate to central and northern Europe to breed there for the second time in late MayJuly (Guyomarch et al. 1998; EC 2009). Quails arriving to central and northern Europe in late spring also include reproductively active birds hatched from first broods a couple of weeks earlier (Guyomarch et al. 1998; EC 2009). No doubt, male quails found on central European breeding grounds are highly nomadic, with a majority of radio-tracked birds staying no longer than 2 weeks in a single place (Herrmann and Dassow 2006). Habitat preferences of the quail are rather poorly identified. A wide variety of crops are reported as preferred by the species (George 1996; Guyomarch et al. 1998; EC 2009; Sard a`-Palomera et al. 2012), with no clear pattern emerging and inconsistent results regarding different countries and spring vs. autumn-sown crops. Probably, certain features of the sward structure (height, density of stems) may be more important than plant species or their variety. A radio-tracking study conducted in the farmland of East Germany was probably the most revealing one, showing that the quail preferred areas covered with dense to rather sparse, mediumheight vegetation on sandy soils, with many weeds, often set-asides and spring-sown cereals, legumes, flax, and lupin (Herrmann and Dassow 2006). The reported preferences for fallow land as breeding sites and for spring-sown cereals as singing places (Herrmann and Dassow 2006) do imply, however, that agricultural intensification is a possible threat, as the share of fallows and spring-sown cereals decreases with the increasing industrialization of farming practices in temperate Europe (Chamberlain and Fuller 2000; Wilson et al. 2009). Widespread use of pesticides in modern agriculture decreases the species preferred food supply during the breeding season, lending further support to the idea that modern farming is rather incompatible with habitat requirements of the quail (EC 2009). Agriculture intensification and associated habitat loss were identified as being of main importance for the species fortunes in the EU (EC 2009). Recent papers describing the habitat preferences of quails (Sarda` -Palomera and Vieites 2011; Sarda` -Palomera et al. 2012) did not address the issue, as they did not examine variables related directly to the intensity of agriculture among all other predictors. We decided to extend the approach and analyze factors shaping the quails occurrence, using not only climatic variables but also an extensive set of covariates describing land use and indices of agricultural intensification. In this way, we wished to examine more (...truncated)