Birds face the challenge of adapting to climate change, but the process of evolution is known to be slow. To gauge the potential impact of climate change on nature, it is crucial to have benchmark species like the great tit that allow us to assess our ability to predict such effects. A team from the Netherlands Institute of Ecology (NIOO-KNAW) has employed innovative methods to catch a glimpse into the future of these birds.
The pressing question is whether species can effectively cope with the impending climate change. The speed at which they can adapt is of utmost importance. Only by comprehending this can we accurately forecast the consequences of climate change on the natural world. “Understanding the pace at which species can keep up with climate change is essential,” emphasizes Marcel Visser, the leader of the research team, “as it is crucial for climate change and evolution to progress at a relatively synchronized rate for species to survive.”
Back to the future
“That is precisely why our research focused on studying future generations of great tits,” explains Visser. “Over the next few decades, natural selection will shape the genetic composition of these birds. To gauge their ability to respond to natural selection, we employed a technique called artificial selection, where we selectively bred birds with early and late laying tendencies in controlled aviaries. We then introduced the offspring of these birds into our long-term population in De Hoge Veluwe national park to observe their performance in comparison to wild great tits.”
“In the forest setting, we observed that the artificially selected birds with early laying tendencies did indeed lay their eggs earlier than the great tits chosen for late laying,” adds researcher Melanie Lindner. “We successfully managed to manipulate their laying behaviors. However, the early laying birds did not exhibit a significantly earlier laying date compared to the wild great tits breeding in the forest. On the other hand, the birds we selected for late laying demonstrated a significantly delayed laying date.”
Ultimately, these early laying birds did not exhibit any greater breeding success than their counterparts in the wild. “Genetic adaptation towards early laying dates, as it turns out, is an exceedingly gradual process.” The findings of this study have been published in the journal Science Advances, with Lindner serving as the lead author.
Ecological relationship problems
Climate change is causing a strain on the ecological relationships of insectivorous songbirds, including the great tit. Their breeding timing no longer aligns with the peak abundance of the insects their offspring rely on, such as caterpillars. This mismatch means that the young great tits miss out on the most nutritious and substantial food source available. While adjusting their breeding timing could potentially mitigate the issue, the extent to which the birds can do so has remained uncertain.
So, what lies ahead for the great tits in the next decade? “Currently, we are observing that climate change is outpacing their ability to adapt,” explains Marcel Visser. “They will struggle to adapt sufficiently, particularly in the most severe climate scenarios, causing the number of fledging great tits to decline steadily.” It is evident that the fast-paced changes brought by climate change will have a detrimental impact on the great tit population.
Camouflage
Despite the ongoing impact of climate change on the great tit, the population numbers have not yet exhibited a significant decline. According to Visser, this can be attributed to density-dependent processes that currently buffer the population effects. The consequences of climate change are currently being “camouflaged” by the natural mortality rate of young great tits. Typically, around eight or nine out of every ten chicks would perish in their first year due to factors such as predation, disease, food scarcity, competition, or chance events. If three of those deaths occur as a result of climate change before the chicks fledge, the survival prospects of the remaining seven will improve. With fewer individuals, there is more food available and reduced competition. However, there is a limit to this buffering effect.
Additionally, the considerable year-to-year variation in weather conditions makes it challenging to precisely measure the impact of climate change on the birds in the field. During the study period, the mismatch between wild great tits and their food source, the caterpillars of the winter moth, happened to be relatively small.
To gain a comprehensive understanding, Visser suggests expanding the research scope to include a broader range of species that collectively form a food network, such as the entire Veluwe natural area.
This objective aligns with the upcoming LTER-LIFE program, set to commence in July. The program aims to develop “digital twins” of ecosystems, facilitating predictions of how global change will affect nature. The Veluwe natural area will serve as the initial case study for this endeavor.
Source: Netherlands Institute of Ecology