DOI: 10.5061/dryad.sn02v6x40
title: The potential of fallow management to promote steppe bird conservation within the next EU Common Agricultural Policy reform: Distance sampling dataset on farmland bird community

description: Agricultural intensification promoted by the European Common Agricultural
 Policy (CAP) has driven the decline of farmland and steppe bird
 populations. Policy tools to improve the environmental performance of the
 CAP – including Agri-Environmental Schemes (AES) and Greening – have often
 failed, and the new EU agricultural reform (CAP post-2020) offers a new
 opportunity to integrate effective measures addressing farmland bird
 declines. Fallow land and its management have proven beneficial for
 endangered steppe bird species by providing good quality habitat, and
 therefore has potential to become an effective conservation measure. We
 used a Hierarchical Distance Sampling community model to evaluate the
 ability of different conservation regimes to increase the abundance of 37
 bird species including endangered steppe birds and other farmland birds in
 13,309 ha of fallow land in north-eastern Spain. The conservation regimes
 were based on different management prescriptions associated with AES,
 Greening and a local conservation measure promoting extensive fallow
 management targeting seven steppe bird species (Targeted Fallow
 Management, TFM). The positive effect of conservation measures increased
 as their design was more targeted to specific species. TFM increased the
 abundance of target and other farmland species, while AES and Greening had
 either no effect or negative effects on bird abundance, respectively.
 Effects of other Greening conservation measures related to landscape
 heterogeneity such as crop richness and field size were variable across
 the community. Policy implications: The success of Targeted Fallow
 Management as a conservation tool highlights the value of applying 1-2
 agricultural practices just before the breeding season in fallows located
 in optimal places for target species, to enhance the abundance of target
 steppe birds and other farmland bird species. We translate our findings
 into specific guidelines that we recommend including within the new
 eco-schemes and AES present in the CAP post-2020.
description: Bird surveys were performed by 7 professional observers between 6
 and 10 a.m. in good weather conditions (i.e., no rain, wind speed &lt;
 20km/h, and temperature between 15ºC and 30ºC). Each survey was conducted
 by a single observer, who walked along the transect and collected data
 following a distance sampling protocol (Buckland et al. 2001). Birds were
 recorded on both sides of the transect when first observed either visually
 or aurally, and observations were assigned to five distance categories
 (0–25 m; 25–50 m; 50–100 m; 100–200 m; 200–500 m). Data was analyzed by
 using a multi-year hierarchical distance sampling community
 model.
description: The bird data has a distance sampling format (one row per
 observation) and the ReadMe file contained in the excel describes the
 co-variates for the observation model. The co-variates for the abundance
 model (conservation measure surfaces) are provided on a separate
 file.