By Lily Marino
In the bitter cold of northern Finland, bird communities are experiencing a sort of winter-themed crisis that is a microcosm of environmental change. There are two main categories of birds that reside in Finland, nonbreeding (which are referred to as “winter” birds) and breeding birds. During the winter, researchers gathered data from bird species that fit into these two categories. A fascinating new study wanted to pinpoint how winter birds’ adapt to various environmental stimuli.
Community-level studies are used to determine a species’ collective response to a certain stimulus, which in this case is the increase in global temperature per year. A species’ overall awareness and communication of a noticeable change in, say, the length of the winter they experience (which is directly connected to global warming), is called their Community Temperature Index, or CTI. The CTI can be observed by changes in waves of behavior, such as an early migration (for the breeding birds), or a general movement to higher, cooler latitudes (which winter birds may experience). The degree to which a species makes these pattern changes can be compared to the speed at which the global temperature rises, to predict the lasting effects of climate change on the wellbeing of animal species.
The Finland study proved many points over the course of a single winter. First, there was a positive relationship observed between the CTI of winter birds (CTIw) and the latitudes at which those species inhabit. With that data comes a general trend of winter birds moving more north and being replaced in the south by summer-dwelling birds that no longer experience the harsh cold temperatures that have historically been present in the south of Finland. However, the average temperature that those winter birds moved to still are higher than their ideal, optimal winters, indicating that their CTIw is increasing slower than the overall rate of temperature change in the climate.
Additionally, the breeding bird populations have seen days to weeks of shorter periods that they spend in the southern, warmer regions of Finland during the winter. Because the temperature signal for migration north arrives much earlier than it historically did, there has been a gradual increase in CTIb for the breeding birds, leading to unexpected competition for resources with the winter birds. Thankfully, due to an increase in the imports of sunflower seeds (by about four times the original amount) to Finland, birds at the top of their geographical distributions are able to maintain relatively steady populations by utilizing the surplus of food.
It may sound as if these birds are faring just fine using their pure instincts and CTIs to track changes in the climate, but when the research was statistically compared to actual temperature changes measured in the natural Finland environment, the results were alarming. The figure below shows the pace at which birds are adapting to our climate compared to how fast our climate is changing.
Clearly, there is a shocking amount of disparity between the change in temperature and the change in CTI, which can be tough to fix. While this data is focused on a small percentage of all animals that live in the polar hemispheres, it can be generalized to at least all winter and migratory birds in the north. If this pattern were to continue for a number of years, birds would soon be finding themselves in habitats where they either need to adapt to more competition and warmer temperatures, or even become extinct if there is a lack of quick adaptation. At this point, the most any human interference can do is study this information, as we are unable to communicate to these birds when and where they need to go if they want to follow their temperature-driven behaviors. An ecological disaster? Indeed. But as a whole, this is a fascinating phenomenon which can be carefully observed down the road so we are better able to prepare and protect our fellow species from the wraiths of rapid climate change.
Santangeli, A., & Lehikoinen, A. (2017). Are winter and breeding bird communities able to track rapid climate change? Lessons from the high North. Diversity and Distributions, 23(3/4), 308-316. Retrieved from http://www.jstor.org/stable/44214685