Interrogating recent range changes in South African birds: confounding signals from land use and climate change present a challenge for attribution

Abstract

Aim Apparent anthropogenic warming has been underway in South Africa for several decades, a period over which significant range shifts have been observed in some indigenous bird species. We asked whether these range shifts by birds are clearly consistent with either climate change or land use change being the primary driver. Location South Africa. Methods We categorized recent range changes among 408 South African terrestrial bird species and, using generalized linear mixed models, analysed ecological attributes of those species that have and have not changed their ranges. Results Fifty‐six of the 408 taxa studied have undergone significant range shifts. Most extended their ranges towards the south (towards cooler latitudes, consistent with climate‐change drivers) or west (towards drier and warmer habitats, inconsistent with climate drivers but consistent with land use drivers); very few moved east or north. Both southward and westward movers were habitat generalists. Furthermore, southward movers were mobile taxa (migrants and nomads), whereas westward movers were associated with human‐modified elements in the landscape, such as croplands, plantations or buildings. Main conclusions The results suggest that both land use changes and climate change may simultaneously be influencing dynamic range shifts by South African birds, but separating the relative strengths of these two drivers is challenging, not least because both are operating concurrently and may influence some species simultaneously. Those species that respond to land use change by contracting their ranges are likely to be among the species that will be most impacted by climate change if land use practices with negative impacts are occurring in areas anticipated to become climatic refugia for these species. This highlights a pressing need to develop dynamic models of species’ potential range shifts and changing abundances that incorporate population and dispersal processes, as well as ecological processes that influence habitat suitability.

Does timing of breeding matter less where the grass is greener? Seasonal declines in breeding performance differ between regions in an endangered endemic raptor

“…The strong associations between timing of breeding, temperature and rainfall also indicate that climate change may further influence shifts in breeding phenology of southern African birds , Cunningham et al 2013, including raptors (Martin et al 2014), most notably in the southern and western regions where a warming trend has been detected during the past 50 years, and rainfall is predicted to decline (Hockey et al 2011, Cunningham et al 2015. Our results highlight that weather conditions, and most notably rainfall regime, play an important role in determining the timing of breeding of Black Harriers, and likely shapes the regional differences encountered in lay date.…”

“…Recent changes in climate conditions within Africa during the last decades (Hockey et al 2011, Kruger and Sekele 2012, Cunningham et al 2015 may exacerbate the differences among regions and present a challenge for species like the Black Harrier. Indeed, a shift in rainfall and temperature patterns has occurred in South Africa and most notably in the south-west of the country, where most harriers breed: temperatures are getting warmer with less rain falling inland (the same pattern is expected in the western part of the Northern Cape Province, where many "interior-mountain" Black Harrier nests occur), while the opposite trend is expected along the coast (Cunningham et al 2015).…”

Feeling the heat: Australian landbirds and climate change

“…However, the assumption implicit in this approach, namely that climate directly limits survival or reproduction, or both, is questionable. Indeed, observed recent shifts in the ranges of birds have often been inconsistent with the predictions of such models (Okes et al 2008;Hockey and Midgley 2009;Hockey et al 2011). There is growing realisation that the purely patternfocused basis of the climate-envelope modelling approach is inadequate, because it overlooks a multitude of physiological and behavioural processes that mediate links between an organism's fitness and its physical and biological environment (Huntley et al 2010).…”

Movement ecology of five Afrotropical waterfowl species from Malawi, Mali and Nigeria

“…Climate warming could enhance overwinter survival of both short-distance migrants and resident birds in Eurasia, leaving intercontinental migrants, such as Garganey at a competitive disadvantage (Sanderson et al 2006). It may be difficult to distinguish changes caused by climate from those related to land-use changes, because the same species may be most responsive to both effects (Hockey and Midgley 2009;Hockey et al 2011). However, birds that exhibit the greatest flexibility in their movement strategies may be those best able to handle these future global changes.…”

“…The presence of waterbirds at ephemeral wetland sites and movement between them has been shaped by anthropogenic factors (Dodman and Rose 2000;Herrmann et al 2004;Hockey et al 2011) because wetland loss has been exacerbated by degradation through drainage, development, siltation and eutrophication (Petrie 2000). Dam construction has negatively affected the Hadejia-Nguru and the Waza-Logone floodplains (Zwarts et al 2009) and has highlighted the importance of maintaining water availability.…”