Decline in shorebirds linked to climate change, experts warn
Eurek Alert
Climate change could be responsible for a substantial decline in populations of shorebirds, say researchers from the Milner Centre for Evolution at the University of Bath, following a study published in Science analysing population data over a period of 70 years.
Historically, the rates of nest predation – eggs being stolen from nests by predators – are higher in the tropics, presumably due to higher variability of potential predators.
To counter this, shorebirds such as plovers and sandpipers migrate to the Arctic to lay their eggs as a safe place in which to build their nests and raise their young. Tropical birds, on the other hand, tend to have longer lifespans and longer periods of seasonal reproduction so their populations can generally withstand higher nest predation.
However an international team of researchers, including researchers from the Universities of Bath and Sheffield, have found that rates of daily nest predation in the Arctic have increased threefold in the last 70 years.
Rates of daily nest predation in the North Temperate Zone, which includes Europe, most of Asia and North America, have doubled.
Other studies have shown that over the same period, the survival of adult shorebirds has decreased due to habitat deterioration or hunting.
This “double whammy” of fewer babies hatching and decline in the survival of adults has had a devastating effect on population numbers, with species such as the Spoonbill Sandpiper (Calidris pygmea) becoming critically endangered.
The authors of the study in Science analysed data from 38,191 nests of 111 species in 149 locations across all continents.
The data suggest that the marked increase in nest predation in the Arctic and North Temperate Zone, in contrast to a smaller change in the tropics and Southern hemisphere, is linked to climate change.
The reasons for the increase in nest predation however are still unclear. The authors suggest it could be due to shift in the diet of predators towards eating more eggs instead of other food sources or perhaps change in predator species composition.
For example, lemmings, a key part of the Arctic food web have experienced a crash in numbers due to altered snow cover as a result of increased ambient temperature instability over several decades. With a lack of lemmings at many Arctic locations, predators may be searching for alternative prey in bird nests.
The authors also suggest that changes in vegetation or changes in behaviour or distribution of nest predators such as foxes may also be a factor contributing to the increased predation of shorebird nests.
Professor Tamás Székely, Royal Society Wolfson Research Merit Award holder from the Milner Centre for Evolution at the University of Bath, said: “These findings are alarming.