So far, the great tit has coped with climate change | Life
Its food supply out of sync, a European bird has escaped population decline – for now
Though climate change has knocked little birds called great tits out of sync with their chicks’ food supply, the birds are maintaining their population numbers, a new study finds. But the way the tits cope may give them only a temporary reprieve.
“It’s buying them time,” says ecologist Tom Reed of the Netherlands Institute of Ecology in Wageningen.
Warmer springs mean that the peak food demands for Parus major chicks come later than the annual burst of local caterpillars. With less food, fewer young survive to leave their nests, Reed reports.
However, the smaller resulting cohort of fledglings faces less competition for winter nuts and other resources. So a greater percentage of the youngsters survive through the winter than previously did, and — so far — this survival uptick has kept the study population from shrinking, Reed and an international team report in the April 26 Science.
These “quite acrobatic little birds” are close relatives of North America’s chickadees, Reed says. Decades ago, researchers set out nest boxes in a Dutch national park, and great tits readily moved in, forming a manageable study population.
Intense monitoring allowed Marcel Visser, also at Wageningen and a coauthor of the study, to realize that the nest timing was going wrong. In 1998, he and a colleague reported that the park’s great tits were one of the first documented examples of birds getting ecologically out of sync with food because of climate change.
Springtime in northern Europe had become unusually warm by the 1980s, and the trend has continued. The birds don’t migrate so they and the insects are exposed to the same weather. But caterpillars are more sensitive to a change in temperature, Reed says. The caterpillars and birds also take their temperature cues at different times in the spring. The differences mean the caterpillars tend to peak a lot earlier. The birds, unfortunately, haven’t kept pace.
With 37 years of data in the new study, researchers also detected that this mismatch is changing evolutionary pressures on the great tits. The breeding pairs that nest a bit earlier now produce more surviving offspring, so the population is getting a little nudge toward the new timing regimen. It remains to be seen whether the climate will change too fast for this slow adaptation to protect the population.
This kind of climate-induced mismatch between animals and their food supply has become a common worry among biologists. Pied flycatchers, small birds that spend winters in Africa, don’t return to Europe soon enough to catch the spring insect bonanza. In West Greenland,, migratory caribou miss the best grazing. And in Norway, puffins are declining as the spring bloom of plankton often misses the main hatching of herring and shrinks the -food supply later needed to feed puffin chicks.
Still unclear is whether any out-of-sync species besides the great tits would get some relief from the benefits of lessened competition among youngsters. “We should be very cautious about suggesting that this is a widespread response to [food-supply] mismatch,” says ecologist Sarah Burthe from the Centre for Ecology and Hydrology in Edinburgh. Many studies, she says, already show that animals raise fewer total offspring in years with significant mismatches.
Abstract of the paper:
By Susan Milius
Science News Web edition: April 25, 2013
DEMANDING DINERS
Lively European birds called great tits haven’t kept up with climate changes that would require earlier nesting. Researchers have uncovered a quirk of population dynamics that’s giving the mistimed population some temporary protection.
Credit: Dreamstime via NIOO-KNAW
Lively European birds called great tits haven’t kept up with climate changes that would require earlier nesting. Researchers have uncovered a quirk of population dynamics that’s giving the mistimed population some temporary protection.
Credit: Dreamstime via NIOO-KNAW
“It’s buying them time,” says ecologist Tom Reed of the Netherlands Institute of Ecology in Wageningen.
Warmer springs mean that the peak food demands for Parus major chicks come later than the annual burst of local caterpillars. With less food, fewer young survive to leave their nests, Reed reports.
However, the smaller resulting cohort of fledglings faces less competition for winter nuts and other resources. So a greater percentage of the youngsters survive through the winter than previously did, and — so far — this survival uptick has kept the study population from shrinking, Reed and an international team report in the April 26 Science.
These “quite acrobatic little birds” are close relatives of North America’s chickadees, Reed says. Decades ago, researchers set out nest boxes in a Dutch national park, and great tits readily moved in, forming a manageable study population.
Intense monitoring allowed Marcel Visser, also at Wageningen and a coauthor of the study, to realize that the nest timing was going wrong. In 1998, he and a colleague reported that the park’s great tits were one of the first documented examples of birds getting ecologically out of sync with food because of climate change.
Springtime in northern Europe had become unusually warm by the 1980s, and the trend has continued. The birds don’t migrate so they and the insects are exposed to the same weather. But caterpillars are more sensitive to a change in temperature, Reed says. The caterpillars and birds also take their temperature cues at different times in the spring. The differences mean the caterpillars tend to peak a lot earlier. The birds, unfortunately, haven’t kept pace.
With 37 years of data in the new study, researchers also detected that this mismatch is changing evolutionary pressures on the great tits. The breeding pairs that nest a bit earlier now produce more surviving offspring, so the population is getting a little nudge toward the new timing regimen. It remains to be seen whether the climate will change too fast for this slow adaptation to protect the population.
This kind of climate-induced mismatch between animals and their food supply has become a common worry among biologists. Pied flycatchers, small birds that spend winters in Africa, don’t return to Europe soon enough to catch the spring insect bonanza. In West Greenland,, migratory caribou miss the best grazing. And in Norway, puffins are declining as the spring bloom of plankton often misses the main hatching of herring and shrinks the -food supply later needed to feed puffin chicks.
Still unclear is whether any out-of-sync species besides the great tits would get some relief from the benefits of lessened competition among youngsters. “We should be very cautious about suggesting that this is a widespread response to [food-supply] mismatch,” says ecologist Sarah Burthe from the Centre for Ecology and Hydrology in Edinburgh. Many studies, she says, already show that animals raise fewer total offspring in years with significant mismatches.
Abstract of the paper:
POPULATION GROWTH IN A WILD BIRD IS BUFFERED AGAINST PHENOLOGICAL MISMATCH
Broad-scale environmental changes are altering patterns of natural selection in the wild, but few empirical studies have quantified the demographic cost of sustained directional selection in response to these changes. We tested whether population growth in a wild bird is negatively affected by climate change–induced phenological mismatch, using almost four decades of individual-level life-history data from a great tit population. In this population, warmer springs have generated a mismatch between the annual breeding time and the seasonal food peak, intensifying directional selection for earlier laying dates. Interannual variation in population mismatch has not, however, affected population growth. We demonstrated a mechanism contributing to this uncoupling, whereby fitness losses associated with mismatch are counteracted by fitness gains due to relaxed competition. These findings imply that natural populations may be able to tolerate considerable maladaptation driven by shifting climatic conditions without undergoing immediate declines.
Those tits are smarter than the greentards. The latter are getting extinct.
ReplyDelete'Great tits ... face less competition for winter nuts and other resources' Duh.
ReplyDelete