Ecological value of different vegetated strip types in providing valuable insect-rich habitats for grey partridge chicks

The intensification and specialisation of agriculture has contributed to farmland wildlife decline, including farmland birds. Grey partridge is a farmland species which has experienced a significant decline across Europe in recent decades. Chick survival rate is a key determinant of grey partridge population change and depends essentially on the availability of insect food. In this study, ground-dwelling and canopy-dwelling insects were collected using pitfall trapping and sweep netting methodologies, respectively, on different strip types in an area established for the conservation of grey partridge. The aim was to further our understanding of the value of different vegetated strip types in providing insect-rich habitats for grey partridge chicks. Overall, wildflower strip (WS) provided the greatest insect abundance. Significantly more ground-dwelling insects were found on WS, natural regeneration (NS) and leguminous strips (LS) than on grass strip (GS). Canopy-dwelling insects were also significantly more abundant on WS compared to all other strip types. This study highlights that WSs may represent important habitats in providing insect-rich food for grey partridge chicks and sowing these strips may therefore play a key role in decreasing chick mortality and supporting grey partridge conservation. It also demonstrates that other different vegetated strip types may still provide strip-specific insect taxa, in addition to other valuable resources. This study recommends a complex mosaic of different strip types to provide key resources for grey partridge, such as insect and plant food, nesting habitats and overwinter cover.

Both landscape heterogeneity and configuration determine Woodlarks (Lullula arborea) breeding territories

Farmland birds have declined in the last decades mostly due to agriculture intensification. The Woodlark Lullula arborea, a farmland species of conservation concern and protected by the European Bird Directive, occurs in a variety of habitats across its geographic range. Although habitat heterogeneity has been recognized as a key feature, the preference or avoidance of particular habitat attributes might differ across its range because different localities may have distinct conditions. Such variation would challenge conservation efforts at the local level. Our aim was to assess habitat associations of Woodlarks and determine whether the habitat attributes identified as important in other locations across its range could be generalised and applied to Austrian populations. In addition, habitat associations can be influenced by land-use change. We examined changes in land use from 2007 to 2016 in 15 municipalities surrounding areas occupied by Woodlarks. We quantified the composition and configuration of the local landscape surrounding 18 singing males’ territories and 16 non-territory sites. We found that the probability of Woodlarks territories increased with landscape heterogeneity between 50% and 70%, increased with dispersed bare soil patches, decreased with overall patch density and were away from dirt roads. Contrary to our expectation, there was no indication of land-use change. In contrast to previous studies, vegetation height, the presence and proximity to woodland were not identified as important habitat characteristics. Thus, some conservation recommendations can be derived from other localities, for example, maintaining or enhancing landscape heterogeneity. However, others should be adapted to local conditions. In Austria, conservation efforts should focus on including dispersed patches of bare soil and limiting the development of dirt roads nearby Woodlark territories, in addition to promoting a heterogeneous landscape.

Metabarcoding insights into the diet and trophic diversity of six declining farmland birds

Knowledge of feeding ecology of declining species, such as farmland birds, is essential to address their conservation requirements, especially when their habitats are suffering important reductions of trophic resources. In this study, we apply a metabarcoding approach to describe the diet composition of six of the most significant farmland birds inhabiting European cereal pseudo-steppes: little bustard, great bustard, pin-tailed sandgrouse, black-bellied sandgrouse, red-legged partridge, and common quail. We further studied seasonal diet variations (autumn to spring) in all species but the common quail, whose diet was studied during spring and summer. We show that study species´ diets mostly consisted of plants, although in the case of little bustard and great bustard arthropods are also highly relevant. Among arthropods, we found high proportions of thrips, arachnids, and springtails, which were previously unreported in their diet, and some taxa that could be used as antiparasitic food. Moreover, we report that little bustard’s diet is the least rich of that of all studied species, and that diet of all these species is less diverse in winter than in autumn and spring. Diet composition of these declining species supports the importance of natural and semi-natural vegetation and landscape mosaics that can provide a wide variety of arthropods, plants, and seeds all year-round.

Losses and gains of fallows drive farmland bird populations over three funding periods of the EU Common Agricultural Policy

Fallow land provides habitat for threatened and declining farmland biodiversity. Policy change under the EU's Common Agricultural Policy (CAP) has been driving the area of fallows over the past decades and influenced trends in farmland biodiversity. We analyzed the impact of changes in fallow area across Germany on species richness and abundance of farmland birds over three CAP funding periods. We examined whether responses to fallow land area were modulated by species habitat preferences and landscape complexity. We combined spatial data on fallow land area from three agricultural censuses in Germany (2007, 2010 and 2016) with country-wide, annual monitoring data on farmland birds. Farmland bird species richness and the abundance of edge- and field-breeders responded positively to increases in fallows. The effect of fallows on bird richness was strongest at intermediate levels of landscape complexity. There was support for an increasing effect strength of fallow land area on field-breeders' abundance with increasing landscape complexity. We conclude that the loss of fallows in the period 2007 to 2016 resulted in strong declines of farmland birds. We predict that a future increase of the proportion of fallow land to 4%, as envisaged in the post-2020 CAP for Germany, will result in an average increase of 7% in farmland bird species richness and of 11% in average farmland bird abundance compared to 2016, but will depend on species-specific habitat preferences. Increasing the proportion of fallow land will be a key lever to stabilize and revert negative farmland bird population trends. An increase of fallow area in all but the least complex landscapes will boost farmland bird richness and abundance of field breeders. Increasing the proportion of fallow land to 4% is projected to, on average, bring farmland bird richness and abundance back to the levels observed in 2007 acknowledging that farmland bird populations were already severely depleted in 2007. A more ambitious expansion of fallow land towards 10%, such as in the context of the EU Biodiversity Strategy for 2030, should be targeted towards areas that experienced the strongest loss of fallows and towards landscapes with intermediate structural complexity.

Topsoil Seed Bank as Feeding Ground for Farmland Birds: A Comparative Assessment in Agricultural Habitats

The topsoil seed bank was studied in four types of agricultural bird habitats: fields with cereals, maize, clover and tilled fields of a Mediterranean plain to determine the potentially richest habitat based on food supply for the wintering farmland birds. The diversity and abundance of topsoil seeds differed between seasons but did not differ significantly between habitats. The cereal habitat was the richest in food supply for the overwintering of farmland birds. The topsoil seed bank was dominated by Chenopodium album, Polygonum aviculare and Amaranthus retroflexus. The findings of this study provide insight for low-intensity management of higher-elevation mount agricultural areas of southern Mediterranean by preserving seed-rich habitats for farmland avifauna.

Rural landscape dynamics over time and its consequences for habitat preference patterns of the grey partridge Perdix perdix

Intensification of agricultural practices has drastically shaped farmland landscapes and generally caused a decline in spatial and temporal heterogeneity, thus leading to changes in habitat quality and food resources and a decline for most farmland birds Europe-wide. The relationship between complex landscape changes and habitat preferences of animals still remains poorly understood. Particularly, temporal and spatial changes in diversity may affect not only habitat choice but also population sizes. To answer that question, we have looked into a severely declining typical farmland bird species, the grey partridge Perdix perdix in a diverse farmland landscape near Vienna to investigate the specific habitat preferences in respect to the change of agricultural landscape over two decades and geographic scales. Using a dataset collected over 7.64 km² and between 2001 and 2017 around Vienna, we calculated Chesson’s electivity index to study the partridge’s change of habitat selection over time on two scales and between winter and spring in 2017. Although the farmland landscape underwent an ongoing diversification over the two decades, the grey partridges declined in numbers and shifted habitat use to less diverse habitats. During covey period in winter, partridges preferred also human infrastructure reservoirs such as roads and used more diverse areas with smaller fields than during breeding where they selected harvested fields but surprisingly, avoided hedges, fallow land and greening. Known as best partridge habitats, those structures when inappropriately managed might rather function as predator reservoirs. The avoidance behaviour may further be a consequence of increasing landscape structuring and edge effects by civilisation constructions. Besides, the loss in size and quality of partridge farmland is altered by crop choice and pesticides reducing plant and insect food. With declining breeding pairs, the grey partridge does not seem to adjust to these unsustainable landscape changes and farmland practices.

Long-term dynamics of trematode infections in common birds that use farmlands as their feeding habitats

Background The biodiversity of farmland habitats is witnessing unprecedented change, mostly in declines and simplification of assemblages that were established during centuries of the use of traditional agricultural techniques. In Central Europe, conspicuous changes are evident in populations of common farmland birds, in strong contrast to forest birds in the same region. However, there is a lack of information on longitudinal changes in trematodes that are associated with common farmland birds, despite the fact that diversity of trematodes is directly linked to the preservation of long-established food webs and habitat use adaptations of their hosts. Methods We analyzed the population trends of trematodes for the period 1963–2020 in six bird species that use Central European farmlands as their predominant feeding habitats. Namely, we examined Falco tinnunculus, Vanellus vanellus, winter populations of Buteo buteo, Ciconia ciconia, extravilan population of Pica pica, and Asio otus, all originating from the Czech Republic. Results We observed dramatic population losses of all trematode species in C. ciconia and V. vanellus; the changes were less prominent in the other examined hosts. Importantly, the declines in prevalence and intensity of infection affected all previously dominant species. These included Tylodelphys excavata and Chaunocephalus ferox in C. ciconia, Lyperosomum petiolatum in P. pica, Strigea strigis in A. otus, Neodiplostomum attenuatum and Strigea falconis in B. buteo (χ2 test P < 0.001 each), and Echinoparyphium agnatum and Uvitellina adelpha in V. vanellus (completely absent in 2011–2000). In contrast, the frequency and spectrum of isolated records of trematode species did not change to any large extent except those in V. vanellus. Conclusions The analysis of six unrelated common bird species that use farmlands as their feeding habitats revealed a previously unreported collapse of previously dominant trematode species. The previously dominant trematode species declined in terms of both prevalence and intensity of infection. The causes of the observed declines are unclear; of note is, however, that some of the broadly used agrochemicals, such as azole fungicides, are well known for their antihelminthic activity. Further research is needed to provide direct evidence for effects of field-realistic concentrations of azole fungicides on the survival and fitness of trematodes. Graphical abstract