The common raven (Corvus corax) is a highly intelligent bird species increasingly found in human-populated areas, drawn by opportunities for food and nesting. Their presence near homes and agricultural sites can lead to conflicts, including nuisance noise, property damage, and the destruction of crops or young livestock. Successfully managing these conflicts requires non-lethal methods because the common raven is protected under the Migratory Bird Treaty Act (MBTA). Lethal removal, including trapping or shooting, is generally prohibited without specific federal and state permits, which are only issued after non-lethal methods have been attempted and proven ineffective.
Eliminating Attractants
Deterring ravens begins with removing attractants, primarily food and water sources. Ravens are opportunistic omnivores and scavengers, with a diet including insects, small mammals, eggs, and human garbage. Any accessible food source acts as an open invitation, encouraging the birds to establish themselves nearby.
Securing residential waste is foundational; trash cans should have locking lids or be fastened with bungee cords to prevent them from being opened or tipped over. Since ravens can rip into plastic bags, all garbage must be fully contained within a secure receptacle. Managing pet food is equally important, requiring feeding pets indoors or immediately cleaning up any uneaten food left outside.
Compost piles and gardens also need attention, as ravens will forage through exposed kitchen scraps and garden waste. Covering compost heaps completely or using fully enclosed compost bins helps eliminate this easy food source. Minimizing standing water, such as addressing leaky outdoor faucets or removing unused bird baths, can also make an area less appealing, especially during dry seasons. These steps reduce the incentive for ravens to congregate, making other deterrence methods more successful.
Physical Exclusion Methods
Physical exclusion methods are the most reliable solution because they completely block access to a targeted area. Bird netting is highly effective for protecting high-value resources like fruit trees or small garden plots, creating an impenetrable barrier. For ravens, a two-inch mesh size is recommended; this size excludes the large birds while allowing light and air to pass. Netting must be installed tautly and securely to prevent the birds from finding or creating gaps to crawl through.
For structural areas like building ledges, eaves, or antennas where ravens attempt to roost, specialized deterrents are necessary. Bird spikes, which are blunt-tipped wires or plastic prongs, prevent the birds from landing on narrow surfaces without causing them harm. Similarly, bird wire or specialized electrical track systems can be installed along perching sites to make the surface unstable or mildly shocking, discouraging the birds from landing.
Preventing nesting inside structures is achieved by installing chimney caps and vent screens. Ravens build large stick nests in sheltered areas, and screening off access points prevents them from using vents or flues as safe nesting sites. While exclusion devices on structures can be challenging due to the large surface area, these barriers are the most permanent way to achieve exclusion of ravens from specific spots.
Sensory and Auditory Deterrents
Sensory and auditory deterrents create an environment ravens perceive as dangerous or uncomfortable, encouraging them to leave. Visual deterrents like reflective tape (often Mylar) or shiny objects can be hung in trees or near vulnerable areas. The flashing light and movement produced by the reflection is meant to startle and confuse the birds.
Another visual technique involves using effigies like scarecrows or predator decoys. However, ravens are highly perceptive and quickly realize that stationary effigies pose no real threat, leading to habituation. To maintain effectiveness, these visual deterrents must be moved frequently or supplemented with other methods to prevent the ravens from adapting to their presence.
Auditory deterrents, known as bioacoustics, use recordings of distress calls or the cries of natural predators. These sounds trigger an instinctive escape response, making the area seem unsafe. To remain effective, the sounds must be played sporadically and at random intervals to prevent the birds from learning the pattern and ignoring the warning. Combining these sensory tools, such as using distress calls alongside motion-activated sprinklers, creates a multi-sensory approach that maximizes the impact and prevents the ravens from becoming accustomed to a single tactic.