Original article Calandra lark habitat selection: Strong fragmentation effects in a grassland specialist Rui Morgado a , Pedro Beja b, d , Luı ´s Reino b, c, * , Luı ´s Gordinho b , Ana Delgado a , Rui Borralho b , Francisco Moreira a a Centro de Ecologia Aplicada ‘‘Prof. Baeta Neves’’, Instituto Superior de Agronomia, Universidade Te ´cnica de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal b ERENA, Ordenamento e Gesta ˜o de Recursos Naturais, Rua Robalo Gouveia, 1-1A, 1900-392 Lisboa, Portugal c Centro de Estudos Florestais, Departamento de Engenharia Florestal, Instituto Superior de Agronomia, Universidade Te ´cnica de Lisboa, Tapada da Ajuda,1349-017 Lisboa, Portugal d CIBIO, Centro de Investigaça ˜o em Biodiversidade e Recursos Gene´ticos Campus Agra ´rio de Vaira ˜o, Universidade do Porto, 4485-661 Vaira ˜o, Portugal article info Article history: Received 5 June 2009 Accepted 2 October 2009 Published online 5 November 2009 Keywords: Agri-environment schemes Conservation Farmland bird Steppe bird Habitat fragmentation Habitat selection Variation partitioning abstract Conserving grassland birds in farmed landscapes requires the maintenance of favourable agricultural land uses over a range of spatial and temporal scales. Here we examined the field and landscape-scale habitat requirements of the calandra lark (Melanocorypha calandra), an obligate grassland bird often associated with open Mediterranean farmland. Breeding and wintering lark densities were assessed in 42 fallow fields in southern Portugal, and related to three sets of variables reflecting field, landscape and neighbourhood effects. Variation partitioning was used to isolate the unique and shared contributions of sets of variables to explained variation in lark distribution and abundance models. At the field scale, the presence of trees and shrubs showed the strongest negative effects on calandra lark. At the landscape scale there were strong positive response of larks to the amount and patch size of open farmland habitats, and negative responses, albeit weaker, to drainage and road densities. Calandra lark distribution and abundance was also positively related to that of conspecifics in surrounding fields, particularly in spring. Results suggest that calandra larks are highly sensitive to habitat fragmentation, requiring fallow fields with no shrubs or trees, embedded in large expanses of open farmland. This supports the view that grassland bird conservation in Mediterranean agricultural landscapes may require a combination of land-use regulations and agri-environment schemes preventing ongoing shrub encroachment and afforestation of marginal farmland. Ó 2009 Elsevier Masson SAS. All rights reserved. 1. Introduction In many regions worldwide, grassland birds have shown pronounced declines due to the conversion of their habitats to agri- culture, forest, and urban land uses (Jones and Bock, 2002; Brennan and Kuvlesky, 2005; Laiolo and Tella, 2006). Despite these pervasive trends, some species have survived within human-dominated land- scapes, mainly occupying habitats resulting from agricultural and pastoral activities such as pastures, fallow land, and even arable or row crops (Best et al., 2001; Delgado and Moreira, 2000; Bata ´ ry et al., 2007). Over the past three decades, however, the progressive inten- sification of agricultural practices has resulted in overall declines of farmland birds, including many grassland species (Barnett et al., 2004; Brotons et al., 2004; Brennan and Kuvlesky, 2005; Donald et al., 2006). At the same time, large-scale rural depopulation and aban- donment of marginal farming land has resulted likewise in the loss of farmland habitats, due to shrub encroachment and afforestation (Preiss et al., 1997; Dia ´z et al., 1998; Santos, 2000; Van Doorn and Baker, 2007; Sirami et al., 2007). As a consequence, much effort has been made to understand the interaction between bird populations and agricultural practices, trying to develop management prescrip- tions that can favour their conservation within farmed landscapes (Kleijn et al., 2006; Barnett et al., 2004; Moreira et al., 2005a; Whittingham et al., 2005; Santos et al., 2006). The conservation of grassland birds in farmed landscapes may be particularly challenging, due to their specialized habitat require- ments over a range of spatial scales (Moreira et al., 2005a; Bata ´ry et al., 2007). On the one hand, these birds may be strongly depen- dent on local field characteristics, such as sward structure and composition (Milsom et al.,1998; Moreira,1999; Barnett et al., 2004), which are largely contingent on the management decisions of individual farmers. On the other hand, grassland birds are affected by the landscape context in which usable fields are located, * Corresponding author at: Centro de Estudos Florestais, Departamento de Engenharia Florestal, Instituto Superior de Agronomia, Universidade Te ´ cnica de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal. E-mail address: luisreino@gmail.com (L. Reino). Contents lists available at ScienceDirect Acta Oecologica journal homepage: www.elsevier.com/locate/actoec 1146-609X/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.actao.2009.10.002 Acta Oecologica 36 (2010) 63–73