Effects of Fire on Birds
Effects of Fire on Birds
from Dan Gleason former Professor of Ornithology at OU and Owner of the WBU in Eugene, OR
The fires currently rampaging across Oregon (and elsewhere) have caused tremendous devastation to thousands of people and forests and destruction of thousands of homes and structures. With such great loss, recovery will be long and arduous. For thousands of people not directly in the path of the flames, the smoke has been difficult to deal with. The air quality in many neighborhoods has been in the hazardous level that can cause respiratory problems. The air quality index readings only go to 300, but the actual readings have been in the 400-500s.
We know that human risk from smoke is great, but how do fire and smoke affect birds? The effects are not as clear cut as we might expect.
Loss of habitat is of concern for many birds. But, most birds are highly mobile and many can escape the flames, especially those that can fly at high altitude, and the nesting season, which makes birds stay in one place, has ended. There is some evidence that low-flying birds may, at times, be overcome by very dense smoke. It’s unclear if such incidents are caused by birds whose health was damaged beyond survivability or if they became disoriented and were unable to escape the smoke and flames.
Habitat loss is real but overall, we might better refer to it as habitat change rather than loss. Very, very intense fire can cause very great destruction, but most fires with a few areas of large destruction have many regions of lesser or minimal damage. Fire can be spotty, leaping over some places, leaving “islands” that may be relatively unscathed or less scarred. These islands, if large enough, may provide some refuge for many species and will help to reseed and regenerate the return of nearby areas. Some fire clears the accumulation of debris and undergrowth. Such conditions may actually be beneficial to the overall health of the forest if one takes a longer view. For instance, some conifers are fire-dependent and need fire to survive as a species. The heat of the fire causes some of the cones to open so that the seeds can be released.
In the case of birds, some species may need to find undamaged habitat to survive. For other species, a fire, once it cools, may provide opportunities that weren’t previously available. Insects will quickly invade fire-damaged areas. Next spring, many of these insects will be numerous and provide a great food resource for birds. Some flycatchers in those areas will have an abundance of food and open areas perfect for them to more easily forage. The trees, or portions of trees damaged by fire will be infested by wood-boring insects who will lay their eggs in the bark or tree wood. The larvae of these insects are attractive to many birds, especially woodpeckers. Black-backed Woodpeckers are attracted to burned areas just for this reason. Western Bluebirds and other birds are also attracted to burns because of the insects that provide a rich source of food. Many cones that have been opened by the heat will still hold many seeds that are now easier for birds to obtain. Birds such as crossbills and White-headed Woodpeckers feed on these seeds in the Ponderosa Pine forests when they are fire-impacted.
Heavy smoke from forest fires contains a large amount of particulate matter that can accumulate in the lungs of humans and other mammals and may cause scarring or inflammation leading to respiratory problems. But it is unclear how much damage is caused to birds by smoke. Obviously, intense, thick smoke near a fire has the potential for harm just as in mammals.
But birds have a very different respiratory system than do mammals. In mammals, the air pathways branch in the lungs into smaller and smaller vessels until eventually becoming very tiny sacs, called alveoli, that are each surrounded by blood capillaries. It is here where oxygen passes from the lungs into the blood and where carbon dioxide leaves the blood, entering the alveoli to be breathed out at the next exhale. Air comes in and exits the mammal's body by the same route. Small particulates in the smoke can become lodged in these alveoli, scarring and damaging these tissues, impairing the ability of the lungs to function well.
Birds do not have this in and out flow and instead have a constant one-way flow of air. Their lungs are small in comparison, and do not expand and contract as do mammalian lungs. Instead, air travels continuously through the lung, not in and out, via tiny vessels lying side by side with blood capillaries. As with the alveoli of mammals, gas exchange occurs here as the walls of these vessels touch. In this continuous flow air system, particulates pass through the lungs with little chance to accumulate and cause damage. The air passageways in birds are connected on either side of the lungs to larger air sacs throughout the body that, along with body wall contractions, help facilitate the flow of air. These air sacs do not provide any of the gas exchange. It is in these air sacs where particulates may settle, but it is unclear what damage this may cause. So, heavy smoke may be disorienting, but it is not well known how much impact directly affects a bird’s health. Studies that show some health impact are studies done on domestic poultry that cannot escape heavy smoke. Studies on wild birds is, for the most part, lacking so we know little about smoke damage to them, unfortunately. (Here's an opportunity for graduate student research, perhaps?)
Some birds such as ducks and grebes may survive fire by remaining on lakes or streams. Some evidence shows harm to some of these birds where they have taken flight and possibly become disoriented and trapped on the ground, unable to reach, or perhaps see the safety offered by the water. (There was a news story on Friday or Saturday about a Blue River Fire official, named Rainbow, that rescued a young grebe on the ground near her fire rig, and she got it back into the river in hopes it will survive.)
Fire will have an immediate impact on many birds but they may not be as harmed as mammals and other animals that cannot flee a large fire. For those of you feeding backyard birds, continue to provide fresh food and fresh water, maintaining the freshness even more than in normal conditions.
Water can be especially important. With heavy smoke, ash can settle out of the air and water sources, such as birdbaths, can quickly accumulate ash. Replace the water frequently to prevent such accumulation. This will help keep the birds from ingesting incidental ash and significant ash deposits may somewhat acidify the water. Seed in your feeders should be fine, just keep a good fresh supply.
At the store we are hearing of greatly increased numbers of birds, and we (Barbara & Dan) are experiencing this personally as well. We have had a large increase in some bird species using our feeders, to the point that Barbara purchased two more long tube feeders to put out. Now all of those perches are attended by goldfinches, mostly, plus the perches of the old feeders, too. There are probably 60 finches using our feeders and birdbath this week!
One other thing I should point out with the heavy smoke. Many of you use the window stickers that we sell at WBU to help prevent birds from flying into your windows. These stickers work because they reflect ultraviolet light which birds see and we don’t. The reflected UV light allows the bird to see “something is there” instead of simply looking at your yard's reflection or at clear glass. With heavy smoke in the air, ultraviolet light is greatly reduced or mostly filtered out. (Notice how yellow the light looks because the blue end of the light spectrum has been filtered out.) With little or no UV light, there is nothing to be reflected by these window stickers and their effectiveness is dramatically reduced or eliminated and thus you may see an increase of window strikes by birds. As the air clears the effectiveness of these stickers will return. We placed a feeder ON the window, which now also makes birds more aware that there is something there…plus the feeder in that location creates wonderful entertainment for our indoor cat!