A thorough literature review covering 570 bird species from across the globe has found that climate-driven changes—in distribution, phenology and abundance—have already had negative impacts for 24% of bird species (Pacifici et al. in review). Given the paucity of data available for South America, Africa and Asia, this figure is likely to be a considerable underestimation. Of the species studied in detail, only 13% have had a positive effect from climate change, whilst the effects remain uncertain for nearly half of all species studied.

Of those species negatively impacted, declines in abundance and range size are the most common impacts, with reduced survival rate, breeding success and recruitment being less frequently cited as causes of these effects (Pacifici et al. in review).

Climate is a critical factor in determining species’ geographical ranges (Pearson and Dawson 2003). Although it is difficult to causally link an observed shift in a single species’ range to changes in climate, the consistent patterns documented for avifauna around the world are compelling. As global temperatures have risen, species’ ranges have moved poleward in latitude and upwards in elevation, though there is variation in these responses (Auer and King 2014, Environmental Protection Agency 2014 ,Virkkala and Lehikoinen 2014, Gillings et al. 2015, Zuckerberg et al. 2009, Archaux 2004, Peh 2007, Popy et al. 2010, Maggini et al. 2011, Forero-Medina et al. 2011, Reif and Flousek 2012,Harris et al. 2012, Tingley et al. 2012, Freeman and Freeman 2014). Taken collectively, these observations provide convincing evidence that climate change is already impacting the distribution of avian communities. 

In North America, over 200 bird species have experienced northward range shifts consistent with climate change (e.g. La Sorte and Thompson 2007, Hitch and Leberg 2007, Zuckerberg et al. 2009). Similar findings have been reported in Europe (Gillings et al. 2015, Thomas and Lennon 1999, Brommer 2004), where the largest climate change induced range shifts have been recorded (Maclean et al. 2008). However, despite this, the magnitude of these responses may still be insufficient to keep pace with climate change. In France, for example, the temperature increase since 1989 is equivalent to a northward shift of 273 km; however, over the same period there has only been a 91 km northward shift in bird community composition (Devictor et al. 2008). Effectively, birds are lagging behind climate warming, and the long-term implications of this discrepancy could be profound.

Climate warming has had a notable effect on the temperate seasons—with markedly earlier springs and a delayed onset of autumn (Menzel et al. 2006, Schwartz et al. 2006). In general, there has been a trend towards earlier spring arrival of migratory species (Butler 2003, Gordo and Sanz 2006, Jonzén et al. 2006, Tøttrup et al. 2006, Beaumont et al. 2006) and earlier breeding (Forchhammer et al. 1998, Crick and Sparks 1999). However, these phenological responses have not been consistent across taxa. Many bird species—having evolved to synchronise the timing of their annual routines (e.g. migration and breeding) with the life cycles of other species (e.g. predators and prey)—are becoming increasingly ecologically mismatched (Visser et al. 1998, Both and Visser 2001). For example, whilst the brood-parasitic Common Cuckoo Cuculus canorus has advanced its migration only modestly, many of its host species are now arriving at the breeding grounds considerably earlier (Saino et al. 2009). Those species unable to adequately respond to climate change may find themselves at a considerable disadvantage (Ahola et al. 2007, Møller et al. 2008).

Given that the rise in global average temperature has been relatively modest to date, the number of documented impacts on the world’s avifauna is sobering. It suggests that the impact of future climate warming on biological communities, and consequently ecosystem integrity, could be severe.

This case study is taken from ‘The Messengers: What birds tell us about threats from climate change and solutions for nature and people’. To download the report in full click here.