Some kinds of birds are doing better in our changing climate, and others are declining. These changes are happening in similar ways in both the U.S. and Europe.
Those are the findings of a new study in the journal Science.
Phil Stephens is a senior lecturer in ecology at Durham University in the UK, and he’s a lead author of the study.
Stephens and an international team of researchers studied data on more than 500 common species of birds over a 30 year period (1980-2010) in both Europe and the U.S.
“We used those data to make an index of the extent to which the climate has been impacting the common birds," Stephens said. "So that indicator allows us to detect whether climate change has been playing a role in the abundance of those birds, and if so, to what extent,” he says. “And our major finding was that it has been playing a detectable but strong role, and that the extent of the effects on the two continents appears to be very similar.”
A snapshot from the study:
US species that are increasing (but with decreases in some southern states) – potentially as a result of changing climates: Darter (Anhinga) – currently restricted to the southeast but declining in Florida (where climate suitability is declining) and increasing further north. Cassin's kingbird – found throughout the southwest and into the Rockies, declining in Arizona (where climate suitability has declined) but increasing in the north of its range (where climate suitability is increasing). Orchard oriole – widespread from the Rockies to the east coast is declining in the south (where climate suitability is declining) and increasing in the north (where climate suitability is increasing). US species that are declining – potentially as a result of changing climates: Canada warbler – is declining throughout its range in northeast US, where climate suitability has been declining over recent decades. White-throated sparrow – again, has declining populations and declining climate suitability throughout its breeding range in the northeast US. Common grackle – widespread from the Rockies to the east coast is declining in most of its range, concomitant with declining climate suitability.
Stephens says some species are doing poorly in the southern end of their range, but they're doing better at the northern edge.
He said warbler numbers in the northeastern U.S. are changing.
“So things you might expect to see in Michigan, are tending to decline there," he said. "Whereas they might be increasing farther north in Canada.”
He says birds that rely on specific food sources or narrow preferences for habitats (such as wetlands) are more susceptible to changes in climate.
Breaking links between species
Stephens says as some bird populations shift north, links between predator and prey could break up.
“Communities typically have a long history of co-existence between species," said Stephens. "Let’s say for example, the prey they eat, the caterpillars and so on, and also birds and plants. So there will be a lot of tight linkages between these pairs of species, and what we’re seeing here is a suggestion that climate has already led to major upheavals in the composition of communities."
He says it'll take time for new linkages to form.
Stephens says one of the most important implications of this study is that it illustrates that we can already see the consequences of climate change.
"We anticipate that climate change will become more pronounced over coming decades and increased in its speed," he says. "I think it reminds us that policymakers, many of who signed up to important commitments to limit emissions at last year’s Paris Climate Conference, really need to be held to account over that and maybe even become more ambitious in what they’re aiming to do.”
