The population of a widely dispersed bird species is relatively unaffected by warmer springs, indicating that some species may be adapting to shifts caused by climate change, reports a study published in the journal Science.
The research assessed the impact of earlier springs on a well-studied population of great tits, a bird that ranges across Europe, the Middle East, Central and Northern Asia, and North Africa. The study found that while the availability of the main food source for great tit chicks — caterpillars — has shifted faster than the birds’ hatching time, the adverse impacts have been counterbalanced by increased juvenile survival rates and immigration, maintaining the population.
A statement from the Norwegian University of Science and Technology explains:
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“Earlier springs have caused caterpillars to hatch and grow earlier than they used to. But great tits, which catch caterpillars to feed their young, have not been able to advance their timing of egg-laying to keep pace with the caterpillars. This has caused an increasing mismatch between the peak availability of caterpillars and the hatching of baby great tits, which has caused early offspring survival in great tits to decline.
“That might make you think that great tit populations would also go into decline, but nearly four decades of data on great tit populations shows that this loss of great tit young in the spring has been offset by increased juvenile survival as well as increased immigration during winter. Thus, the mismatch in timing has not caused a decline in pre-breeding population size.”
Overall, a 3.7°Celsius increase in late spring temperatures during the four-decade study period has not affected great tit population growth.
Young great tits in nest. Image courtesy of Netherlands Institute of Ecology (NIOO-KNAW)
The researchers conclude “these findings imply that natural populations may be able to tolerate considerable maladaptation driven by shifting climatic conditions without undergoing immediate declines.”
While the results bode well for the great tit, a generalist that has thrived despite widespread conversion of wildlands across its range, other species face a more uncertain future. A large body of research suggests that many other species, from polar bears to pikas and koalas to leatherback sea turtles, are gravely imperiled by shifts wrought by climate change. Loss of habitat will make it more difficult for some species to migrate in response to changes in temperature, precipitation, sea level, or food availability.
Great Tit (Parus major). Luc Viatour / Lucnix.be
CITATION: Thomas E. Reed, Vidar Grøtan, Stephanie Jenouvrier, Bernt-Erik Sæther, and Marcel E. Visser. Population Growth in a Wild Bird Is Buffered Against Phenological Mismatch Science 26 April 2013: 488-491. DOI:10.1126/science.1232870