Bird migration involves billions of birds traveling between breeding and non-breeding grounds each year. They spend a significant time migrating and utilize multiple stopover sites to break up long journeys between wintering and breeding grounds. It’s no surprise that when wildfires erupt, birds take flight to avoid the threat.
Birds use a combination of sensory cues, including vision and smell, to navigate their environment. However, the presence of thick smoke caused by wildfires can present challenges for them to find their way. Birds may alter their flight patterns and choose different routes to evade smoke inhalation, resulting in them flying even farther from their usual paths.
Both residents and migratory ones are impacted by fires. When fires are active, the affected areas become inaccessible for birds, compelling them to find alternative locations. This can disrupt their migration patterns, potentially causing exhaustion as they travel longer distances between resting spots.
Birders may have the opportunity to observe uncommon species, but the increased travel can also pose risks to bird survival.
The influence of wildfire smoke on migratory birds extends well beyond the areas where the fires occur. Smoke concentrations at ground level can have effects on bird behavior over an area more than 27 times the size of the burned region. Additionally, smoke can disperse even further in the sky, covering an area up to 44 times larger than the wildfires themselves.
Unlike humans, birds have rigid lungs that don’t expand or contract. Their respiration is supported by air sacs that continually supply fresh air to their lungs. This unique respiratory system allows them to take in more air and oxygen, which is advantageous for sustaining vigorous activities like flight. However, it also makes them more susceptible to toxic gases and fine particulate matter, such as carbon monoxide, dust, and pollution.
Wildfires have a detrimental impact on birds as they have to navigate through thick and toxic air. Even if they manage to flee from the fire itself, the smoke can still affect their health. Smoke can cause damage to lung tissue, making the birds more susceptible to potentially fatal respiratory infections.
Additionally, birds’ migration becomes prolonged and exhausting, which is not an adaptation they are naturally equipped for. This energy deficit can have long-term consequences, potentially affecting their breeding capabilities and overall survival.
Wildfires have a lasting impact on bird populations as they eliminate essential food sources and nesting areas, especially for species that rely on insects, seeds, and plants. The consequences of a large-scale wildfire can cause significant changes in bird population density and diversity, which can have devastating effects on species already experiencing declines due to other habitat and food disruptions.
Nestlings, or baby birds, are more susceptible to heat than adult birds. Due to their small and underdeveloped bodies, nestlings face challenges in regulating their body temperature. Parent birds often sit on their young to provide protection from extreme temperatures. Nestlings have limited mobility and are less efficient at coping with heat stress. Without the shade provided by adult birds, nestlings are exposed to direct sunlight.
The vulnerabilities of baby birds make them particularly vulnerable during a heatwave, especially when they are still in the nest.
In 2020, four Tule geese embarked on their migration from Alaska’s Cook Inlet to California’s Sacramento Valley. However, their journey was disrupted by dense wildfire smoke encountered along the coast. Their behavior deviated from the norm, with one bird returning north and others taking unusual routes. They even landed in unexpected locations, such as the side of Mount Hood.
A study by the U.S. Geological Survey revealed that their migration took twice as long as the previous year, with added mileage to avoid the smoke. This highlights the growing challenges faced by migratory birds due to mega-fires and thick smoke, which often coincide with fall migration. During their journey, numerous fires were active in California, Oregon, and Washington.
Prolonged migrations require more energy and recovery time, potentially impacting the birds’ ability to reproduce and even putting their lives at risk.