Pesticides and Birds

Gail Langellotto / CC BY-NC-ND 2.0

Set aside the pesticides.

Most of us are familiar with the impacts of DDT and its subsequent ban from use. Still, a wide variety of pesticides used today are dangerous or toxic to birds. The cost in bird and other wildlife losses due to pesticide use in the United States is approximately 2.2 billion dollars annually. Herbicides, insecticides, and anticoagulant rodenticides (ARs) are a serious concern in urban areas, as they impact the food and habitats that birds depend on.

We acknowledge that there are serious risks associated with leaving some pests uncontrolled. Pesticides are important tools for controlling some dangerous pests. But in many cases we can reduce pesticide use and reduce risks to wildlife through changes in behavior or changes of mind. Read on to learn about some specific categories of pesticides and some less- or nontoxic alternatives.

Second-generation Anticoagulant Rodenticides

Second-generation anticoagulant rodenticides (SGARs) are commonly used type of rat poison. SGARs work by preventing blood from clotting which causes a poisoned animal to bleed to death internally. While a single dose is usually enough to kill a rat, SGARs work slowly, allowing a rat to feed at a bait station more than once, increasing the concentration of poison in its body. It can take several days for a poisoned rodent to die, during which it will continue to live, travel, and feed.

This is where birds, as well as other wildlife and pets enter the picture. Pesticides meant to control rodents enter the food chain. Urban raptors like Cooper’s Hawks and Barred Owls, which play an important role in urban rodent control and thrive in cities, are non-target species affected by SGARs. “Non-target species,” or animals impacted by rodenticides not intended for them, may feed on a poisoned rat. SGARs can accumulate within the tissues of animals eating poisoned rodents, which can increase to lethal levels. This is called secondary poisoning. According to the Urban Raptor Conservancy, “Worldwide, all studies that have tested dead animals for exposure to anticoagulant rodenticides in liver tissue show strong evidence of poisoning in birds and mammals (Quarles 2011).”

Throughout the Seattle area, bait boxes containing SGARs can be found along city streets, in yards, parks, and on school properties. Before any building can be demolished within Seattle City limits, the property owner must first complete a rat abatement certification process, where bait boxes are placed around the property for a minimum of 15 days. SGARs are everywhere.

Rat poisons do not treat root causes of rodent infestations. Their mechanisms of action can lead to painful deaths for rodents and the animals that eat them. 

Short-eared Owl/Susan Ward/Audubon Photography Awards

Rodenticide-free solutions

  • Remove potential food sources: keep pet food indoors and ensure trash can and yard waste/compost bins have tightly fitting lids.
  • Eliminate rat nesting spots: remove places that rats may hide such as stacks of cardboard, wood, or other human-made debris piles on your property. Ensure there are no entry points for rats in your home.
  • Mind your vegetation: rats also nest in ivy and blackberry thickets. Remove these invasive species and plant native vegetation that will attract a variety of wildlife and be less appealing to rats.
  • Use alternative lethal control methods: Though these traps require dealing with dead rats up close, they are more humane and likely preferable to a poisoned rat dying in your home or killing birds via secondary poisoning. Snap-traps and CO2 powered traps are used without toxic chemicals.
Applied Herbicides

Herbicides, often used near roots or sprayed directly onto plants to remove invasive species or weeds, can harm birds by reducing food resources and contaminating habitat. Bird species that rely on berries and seeds like the Cedar Waxwing are at risk for herbicide consumption. Unlike humans, birds cannot read signs warning of herbicide application and may ingest food from a recently sprayed plant.

Additionally, herbicides pollute bodies of water such as lakes and streams. Most commonly, they enter surface water in runoff or leachate. The runoff from herbicides degrades the surrounding vegetation that provides habitat and food for many bird species. The US EPA has stated that “herbicides may contribute to other stressors (e.g., instream habitat alteration via riparian devegetation),” listing further impacts on ecosystems birds rely on. Though acute toxicity to animals is likely only when they are applied in sufficient quanities, several types of herbicides bioaccumulated in fish populations, which are then eaten by  birds like gulls, osprey, and terns.

Osprey/Jim Verhagen/Audubon Photography Awards

Herbicide-free solutions

  • Do some research on “weeds” you find: they may not be weeds at all. Resist the initial urge to apply herbicides. Rather, attempt to pull, replant, or manually discard unwanted plants. The Washington State Noxious Weed Control Board has an easy to use tool to help identify weeds.
  • Manually remove and prevent unwanted plants: while removing some plants is tricky, there are several strategies that may be used independently or in combination to combat weeds or invasives. After removing unwanted vegetation, plant native species in their place to help prevent regrowth.
  • Use a natural “herbicide”: alternative options exist. Corn gluten, boiling water, or diluted rbbing alcohol are effective weed killers for use in yards and other green spaces.
Insecticides

Though insecticides are predominately used in the agricultural industry, the effects also impact urban environments. With numerous farmland bird populations declining, the concern with the overuse of insecticides applies to a wide range of native bird species.

Neonicotinoids, or neonics for short, are a category of insecticide that have been found to directly impact bird species. For migrating birds, opportunities to feed are crucial during their stop-overs. When a bird consumes fruit or seed from an area treated with neonics, the bird may experience adverse effects such as weight loss, which can weaken the bird and delay the rate at which they migrate, especially in songbirds.

When insecticides are used on a residential scale, such as on the exterior of a home, dead insects may litter the area near the application site. Birds that find insects dead from insecticides such as wasp spray, ingest them without knowing the toxicity of the chemicals responsible for the insect’s death. Additionally, spraying insecticide and ridding a yard of insect species including bees and other pollinators removes the foundation of food webs for birds and wildlife.

 

Insecticide-free solutions

  • Try a natural insect repellant: using soap spray or diatomaceous earth for the exterior of homes, and neem oil for gardens and yards can provide safer alternatives to chemical-based insecticides.
  • Reconsider your relationship with bugs: remember how important bees and other pollinators are to food webs. 96% of terrestrial birds feed insects to their young. Spraying for bugs in a yard can wipe out food resources for feathered friends. No bugs means no baby birds.
  • Be mindful of how your food is grown: if you are able to select your own food to purchase, consider buying certified organic produce, which is required to be grown on land free from insecticides for at least three years. For tips on growing your own food, visit Seattle Audubon’s page Habitat at Home.