Climate change is a crisis that has affected every corner of the world. Increasing temperatures, air pollution, and extreme weather are just a few of many changes happening to our environment this second. As a result, animals have had to make adjustments to their behaviors to adapt to the changing climate. Some environmental challenges have been so great that animals have had to do more than just change their individual behavior; they’ve had to evolve. Evolving, also called evolution, is the process of animals becoming more suited to their environment through generations. A single animal cannot evolve; instead it happens across a species as their DNA, a microscopic internal code that programs reactions in all living things so they function and grow, changes over time. Babies will have a combination of their parents’ DNA, and if their parents’ DNA is suited to the changing environment, the babies will likely grow up with the same beneficial characteristics. Evolution happens because some animals are more survivable, or have traits better suited for their environment, and therefore will have more opportunities to have offspring, passing on their DNA. When a whole species DNA changes to be more suitable for the environment it is said to have evolved. Concerns that climate change is changing our environment so rapidly that animal livelihood is in danger have triggered many studies on animal climate responses. One such study recently found evidence that the pied flycatchers, a migratory species of bird, could be one of the many animals that has evolved as a result of climate change. 


Migratory birds have an internal circannual clock in their brain that is responsible for triggering the birds’ migration in the spring and fall. Both molting and reproduction timing are associated with migration, and controlled by the circannual clock. The scientists hypothesized that rising temperatures from climate change would result in the birds adjusting their internal clock, changing the average timing of their migration behaviors. Because this is a behavior that would happen over generations, the researchers examined data collected from 1981 and 2002, giving the birds 21 years to themselves to adjust to climate change. The researchers acknowledged that the time gap theoretically could cause experimental errors, but they assured that considerable care was taken when finding results, especially in finding data through the same experiment design. 


Cross comparing the data from the two years, the researchers found overwhelming support for their hypothesis that the pied flycatchers circannual clock has evolved. In the replicated fall, the birds showed a 10 day delay in observational migration behavior in 2002 compared to 1981. Male birds, who develop faster than females, also showed a delay in the end of their first molt. The opposite was seen in the winter and spring as the birds prepared for their next migration. This time winter molts began around 8 days earlier in 2002, and ended 14 days earlier. The spring timing index also advanced on the calendar happening a little over 9 days earlier. To make sure that the data they found was mirrored in the wild the researchers analyzed data from a continuous 46 year field study on the pied flycatcher. They found that over the 21 year period between the 1981 and 2002 study, wild pied flycatchers now lay their eggs 11 days earlier in the spring. Because the changes in the pied flychatcher’s behavior were changed in both directions, instead of one large timeline shift, the researchers have even support for their hypothesis that the pied flycathcer’s circannual clock has gone under evolutionary change, rather than just a behavior change. 


Right now it is unclear if animals will be able to quickly evolve in response to climate change. Because of this research we now have evidence that migratory birds, an animal largely affected by climate change due to its circannual clock and multiple homes, may be able to adapt. Future research may investigate specifically why these behavior changes took place, and if these changes will be enough for the pied flycatcher. Though no matter this specific reason, this research, and countless other scientific research, shows the extreme effect climate change is having on the environment, and the animals that occupy it. It is therefore our responsibility to reduce our impact on the environment immediately. 



Helm B, M. Van Doren B, Hoffmann D, Hoffmann U. 2019 Oct 24. Evolutionary Response to Climate Change in Migratory Pied Flycatchers. Current Biology. 2023; 1-18.