Northward expansion of a desert bird: effects of climate change?

Geographical expansion of species is a common process. Environmental changes over long timescales have produced new conditions that have allowed some species, including both plants and animals, to increase their range of distribution following such changes (Blondel & Mourer-Chauviré 1998, Svenning & Skov 2004). But such modifications can also come about on shorter timescales, mainly due to the effects of human activity (Johnson 1994, Sanchez-Lafuente et al. 2001, Wehtje 2003). More recent changes in distribution range seem to be related to current climate change (e.g. Valiela & Bowen 2003) and some predictions for the future have been made (Peterson et al. 2002). Available climate data for the past century indicate an increase in mean global temperature (IPCC 2001). Such temperature increases affect living species in different ways, including physiological adaptations (Clarke 2003), changes in phenological patterns (Walkowszky 1998) and/or changes in their distribution. Studies of such effects in southern latitudes of the Northern Hemisphere are scarce (but see Peñuelas et al. 2002, Sanz 2002) despite the rapid alteration of Mediterranean biodiversity owing to the combination of both climate change and human pressure (Santos & Telleria 1995, Sanz 2002, Opdam & Wascher 2004). Sanz (2002) pointed out the particular interest in studying how Mediterranean species respond to climate change in order to predict likely responses to future changes in the Mediterranean region.Peer reviewe