From a U.S. Geological Survey news release based on the research article cited below:
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Tule white-fronted geese take off from Summer Lake Wildlife
Area USGS image |
Since 2018, researchers from the USGS Western Ecological Research Center have been tracking the migratory pattern of tule geese. To do this they “marked” with GPS trackers few individual tule geese that breed in Alaska and northern Canada and winter in Washington, Oregon and California as well as Texas, Mexico and Central America with GPS-tracking devices.
The USGS was tracking the tule geese because the tule goose is a “Species of Special Concern” in California with a population estimated at fewer than 10,000 birds. The tule geese are especially susceptible to disruption to its migration. Tule geese exhibit strong site fidelity, the tendency to use the same migration paths and return to the same stopover locations year after year, and they fly in formation which conserves their energy by reducing wind resistance and allows for tracking by tagging only a few individual geese.
Formation migration along to the same stopover points normally make migration more efficient and help maintain social cohesion for many migratory birds. However, these strategies can also make it more difficult survive unexpected obstacles like wildfire smoke. Tule geese are at additional risk because of their small population size.
Although the 2020 fire season was the most extreme on record, it exemplified patterns of increased wildfire size, number, timing, return frequency, and extent which are linked to climate-driven changes in precipitation and temperature affecting fire ignition and severity. (Overton et al. 2021, Goss et al. 2020, Weber and Yadav 2020).
The 2020 wildfire season affecting the western United States reached unprecedented levels in September with 116 fires that consumed 20,822 square kilometers. (Overton et al 2021) It reflected a pattern of increased wildfire size, number, frequency and extent which are linked to climate change and are expected to grow worse in the future.
“Everything coincided such that we could watch this unfold in almost real time,” said Cory Overton, a USGS wildlife biologist and lead author on the study. “It’s virtually impossible to see this type of event without preparedness and good fortune … It’s pretty incredible.”
During the migration the geese encountered dense smoke. The geese responded to thesmoke by pausing their migrations, altering the direction or altitude of flight, or both. Some geese stopped their flight for two to three days until the smoke cleared. Geese that flew through smoke or directly over fires had disorganized flight paths, sharp increases in altitude to fly over the smoke plume, and stopovers in non-traditional habitats far from traditional migratory pathways. All of the marked geese eventually arrived at their destination of Summer Lake, Oregon, but the average migration in 2020 took more than twice as long as in 2019 (nine days versus four days) and covered an additional 470 miles (757 km).
These longer and farther flights resulted in much higher energy expenditure than a typical migration. The scientists estimated that the geese would need several extra days to recover from the resulting caloric deficits. These energy deficits could lead to increased mortality or lower reproductive rates, suggesting that smoke disruptions could ultimately put vulnerable migratory bird populations at greater risk to some of the changes associated with climate change. Plans to reduce carbon dioxide emissions under the Paris accord or reduce methane emissions under the Global Methane Pledge will not have a large enough impact save this bird population. We need another plan to preserve the tule geese.
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