Scientific Article for Students

Temperatures on Earth are getting warmer due to climate change. This affects animals in many different ways. Some animals may be able to change their habits and persist in place. Others may need to find new habitats to survive. In mountain habitats, animals have a unique option to escape the heat: climbing higher. The top of a mountain is usually colder than the base. On very tall mountains, you might even find snow during the summertime! So, one way animals could adapt is climbing to higher elevations. Moving uphill may help birds stay cool in the short term. But if you go uphill long enough, you reach the top of the mountain. If a species moves its elevation range upwards, we call this the escalator to extinction. If they remain in their original range but get more common upslope, we call this an upslope lean. How are mountain birds in the Pacific Northwest adapting to climate change? We had three hypotheses to explore (see Figure 1 on p.2). 1. Birds were able to persist in place. 2. Birds became more common at higher elevations, an upslope lean. 3. Birds’ ranges shifted to higher elevations, the escator to extinction. Information about these patterns could help us design more effective conservation strategies in the future. Methods To answer our questions we needed data on the abundance of each bird species over time. Luckily, we found bird surveys from north of Vancouver, British Columbia from the early 1990s. These were in areas of old-growth forest. The site elevations ranged from sea level to almost 1500 m (4900 ft) above sea level. We were able to contact the original team who helped us find their survey sites. We found 112 out of the original 146 sites. But road closures kept us from getting to the other sites. The original team also shared details about their survey methods so we could do the same thing. We spent a month carrying out our own survey. We visited the sites in the early morning, when birds are most active. We kept track of the number of each species we identified and how far away they were from the site. We used this information to make important estimates for each species: their elevation range, their abundance at each elevation, and the optimum elevation, which is the elevation where their abundance is highest. Finally, we used measurements from a nearby weather station to estimate the temperature change since the original study. Results When we grouped all the bird species together, we saw a clear pattern. Most birds had the same elevation ranges as before. But abundance increased at high elevations (Figure 2). We saw a lot of variation among the 22 species we observed. We grouped the changes in bird abundance and range by our three potential patterns. Here’s what we found: Persist in place → 8 species Upslope lean → 6 species Escalator to extinction → 4 species Another 4 species didn’t match any of our hypotheses! We found 2 species became less common everywhere, while 2 species became more common at low elevations. Yearly average temperatures in the study region had risen by 1.0 °C since 1990. Normally, air gets 0.6 °C cooler for every 100 m you climb. To get to the same temperatures as the early 1990s, you’d need to climb up an extra 166 m (545 ft). Discussion We were glad to see that most of the bird species are as abundant now as they were in the 1990s. These birds live in a forest that has not changed very much in the last 30 years. Having a stable habitat has probably helped those bird species avoid the escalator to extinction. Preserving old-growth forests can help a lot! But even in this habitat, we saw big differences between bird species. None of the hypotheses described all bird species, but each described some species. We can’t assume temperature change will affect all birds the same way! One of the species vulnerable to the escalator to extinction is Canada’s national bird, the Canada jay. What makes them vulnerable? Canada jays store food in caches. In the winter, the food in caches freezes, so it doesn’t spoil. With warmer winters, their caches thaw early and spoil, making it hard for them to get enough to eat. That might be why there are fewer Canada jays. We also found that the numbers of Steller’s jays increased. Could Canada jays and Steller’s jays be competing for the same food resources? It will take more research to find out! Conclusion Figuring out how birds and other animals will react to climate change is a big challenge. With a stable, healthy habitat, animals are more likely to survive. We can help by preserving habitats, like the old-growth forests in British Columbia, and helping restore damaged habitats. Observations are really important, too. Keeping track of what birds we see helps us see if an ecosystem is healthy. Can you learn the names of birds that live in your area? Your observations could help future research!