Climate change is affecting the lives of many organisms on Earth, but how does it impact the reproductive output of birds?
A new study published in the Proceedings of the National Academy of Sciences examined changes in the reproductive output of 104 bird species worldwide from 1970 to 2019.
The study found that larger birds and migratory birds are more vulnerable to climate change than smaller, sedentary species.
How climate change affects bird reproduction
LUDOVIC MARIN/AFP via Getty Images
The study investigated the potential effects of global climate change, specifically warming, on offspring production for over 100 species from over 200 bird populations across all continents, as per Phys.org.
The researchers examined data for each of these bird populations over 15 to 49 breeding seasons to see if changes in local temperatures and precipitation were related to changes in the average number of offspring produced per female per year.
The researchers also considered whether climate change may affect offspring production by interacting with other attributes of the birds, such as body mass, migration status, habitat needs, human impacts on local landscapes, the protection/conservation status of sites, and whether the birds can produce two broods in a single breeding season.
The study found that across the 201 populations of wild birds, offspring production generally declined in recent decades.
There was, however, a great deal of variation among populations and species.
Increasing local temperatures during the chick-rearing period of the breeding season reduced offspring production in most migratory birds but increased in many small birds and sedentary birds that do not migrate.
Warming temperatures were also linked to lower offspring production in large birds.
The researchers hypothesized that these changes were caused by the effects of climate change on species' life histories and ecological traits, which influence clutch size and rates of nesting failure over time.
The study highlighted some examples of how different bird species responded to climate change in different ways, as per Eurekalert.
For instance, a population of prothonotary warblers in southern Illinois increased its reproductive output by 40% over five decades as global and local temperatures rose.
The researchers attributed this to the fact that these warblers are small-bodied, sedentary, and can produce two broods per year.
They also nest in natural cavities that may buffer them from temperature extremes.
On the other hand, a population of common eiders in Greenland decreased its reproductive output by 50% over four decades as local temperatures increased.
The researchers suggested that this was because these eiders are large-bodied, migratory, and produce only one brood per year.
They also nest on open tundra that may expose them to more predators and parasites as snow cover declines.
The study also noted that some bird populations may be able to adapt to climate change by adjusting their timing of breeding or their choice of nesting sites.
For example, a population of great tits in England advanced its breeding date by 11 days over five decades as spring temperatures increased.
This allowed them to match their peak food demand with the peak availability of caterpillars.
The study concluded that understanding how climate change affects bird reproduction is important for conservation and management efforts.
The researchers suggested that more long-term studies are needed to monitor changes in bird populations and their responses to climate change.
They also recommended that conservation actions should consider the specific traits and needs of different bird species and populations.
