604 Flexibility in phenology and habitat use act as buffers to long-term population declines in UK passerines L. Salido, B. V. Purse, R. Marrs, D. E. Chamberlain and S. Shultz L. Salido (larlad@ceh.ac.uk) and B. V. Purse, Centre for Ecology and Hydrology, Bush Estate, Penicuik, Midlothian, EH26 0QB, UK. LS also at: Univ. of Liverpool, Environmental Science, Liverpool, L69 3 BX, UK. – R. Marrs, Univ. of Liverpool, Environmental Science, Liverpool, L69 3BX, UK. – D. E. Chamberlain and S. Shultz, British Trust for Ornithology, he Nunnery, hetford, Norfolk, IP24 2PU, UK. SS also at: Inst. of Cognitive and Evolutionary Anthropology, 64 Banbury Road, Oxford, OX2 6PN, UK. Ecological responses to environmental change are wide-ranging, from alterations in the timing of life-history events to range and population changes. Explaining the variation across species in these responses is essential for identifying vul- nerable species and for developing adequate conservation or mitigation strategies. Using population trend data from the UK Breeding Bird Survey, this study examined the association between long-term population trends (1994–2007) and phenological, life-history and resource-use traits of UK passerine species. Phenology, as well as productivity and resource use were signiicantly associated with long-term population trends. Average laying date and irst clutch laying period were key predictors, with higher population growth rates associated with earlier laying dates and longer laying periods. his suggests that lexibility in the duration of reproductive periods bufers species against environmental changes. Average laying period was particularly important for migrant species. Flexibility in laying dates for these species is constrained by their arrival dates; mean change in arrival date over a twenty-ive year period strongly predicted population trends amongst migrant species. Besides the key role phenological lexibility plays in bufering population declines, we also showed that more productive, generalist species were less likely to have declining populations than species with specialized habitat requirements, particularly those associated with farmland and urban areas and those reliant on highly seasonal food items (i.e. invertebrate eaters). hese results underscore the need for a multi-faceted approach to understanding the mechanisms governing population trends. Additionally, species’ sensitivity to environmental change is likely to depend on interactions between species-speciic phenology, habitat and resource-use traits. here is compelling evidence that human activities are leading to climate change, resulting in increasing pressure on terrestrial biodiversity (Jetz et al. 2007, Rosenzweig et al. 2007). Ecological responses to recent climate change are wide-ranging, including alterations in the timing of life- history events (arrival of migrants, appearance of butterlies and lowering, Both and Visser 2001, Crick 2004, Parmesan 2006), range changes (Parmesan et al. 1999, homas and Lennon 1999, Parmesan 2007) biodiversity loss (Lemoine and Böhning-Gaese 2003) and population dynamics (Julliard et al. 2004, Both et al. 2006). Climate change, however, is not the only environmental change afecting bio- diversity. Habitat loss and modiication are also known to be key drivers of population change. For example, the wide- spread population declines and range contractions in farm- land birds in the UK in the last 50 yr have been linked to agricultural intensiication (Chamberlain et al. 2000, Vickery et al. 2001, Benton et al. 2002, Newton 2004, Atkinson et al. 2005). Various other studies in Europe have reported signii- cant declines in populations of both woodland and farmland specialist birds which could be partly attributed to increasing intensive management practices of both forests and farmland (Julliard et al. 2003, Gregory et al. 2007). As there is substantial inter-speciic variation observed in the magnitude and direction of responses to environmen- tal change, identifying the mechanisms underlying species’ responses is essential for developing adequate conservation strategies for the most vulnerable species (Jiguet et al. 2009, Végvári et al. 2009). Across Europe, threats to wild birds and to other elements of biodiversity are currently moni- tored using population changes in indicator species from diferent breeding habitats (Gregory et al. 2005, Newson et al. 2006). Woodland and farmland breeders are thought to be at greatest risk from habitat fragmentation (Chamberlain et al. 2000, Atkinson et al. 2005, Amar et al. 2006, Hewson and Noble 2009) and the latter are targeted in the UK by management options such as use of wild bird seed mixture and skylark plots under environmental stewardship schemes (Vickery et al. 2004). A greater understanding of the mecha- nisms underpinning species ’ diferential responses to envi- ronmental change may be obtained by relating responses to biological traits. For instance, life-history and resource use traits have been associated with avian population trends. Productivity and brood number have been found to have positive efects on population trends (Végvári et al. 2009) whereas larger body sizes and longer development periods Ecography 35: 604–613, 2012 doi: 10.1111/j.1600-0587.2011.06797.x © 2011 he Authors. Ecography © 2011 Nordic Society Oikos Subject Editor: Erik Matthysen. Accepted 19 August 2011