A simple fence across an open field may seem innocuous, but it can actually be dangerous, even fatal, to birds. But how can you determine if a fence is a threat, and how can you make it safer for wild birds?

Types of Problem Fences

Not all fences are problematic for birds, but light, hard-to-see fences that stretch across open fields can be a serious threat. The most threatening fences are those that birds have difficulty seeing, such as straight wire or barbed wire fences.

Electrified fences are an additional concern, particularly for large birds that have a greater risk of electrocution. More rustic designs, however, such as split rail or wooden fences, are much more visible and are far less threatening to birds.

Birds Hurt by Fences

All birds are at some risk when they come into contact with fences, especially if those fences are not designed in safe, bird-friendly ways. Electrical fences, in particular, can harm birds of all sizes if they are not properly grounded. In general, however, larger birds face greater threats near fences, and species that are especially at risk include:

• Raptors: Birds of prey such as harriers and owls with wide wingspans that fly low over fields may not see a fence until it is too late to avoid a collision.
• Game Birds: Grouse, quail and pheasants that stay on the ground and stay low in flight are more likely to encounter problem fences.
• Large Wading Birds: Herons, egrets and cranes with large wingspans are at risk near fences if they are flying low in the vicinity of the structure.

How Fences Hurt Birds

Fences can be dangerous to birds in several ways, such as…

• Collisions: Even a simple collision with a sturdy fence can be deadly by causing broken bones, internal hemorrhaging and other injuries. While most birds are able to avoid collisions with larger fences, collisions can occur at night or in poor visibility conditions, or birds may collide with a fence when they are startled into flight and are unable to evade the obstacle.
• Electrocution: An ungrounded fence is a serious danger to birds, but most electric fences have safety features to ensure they stay grounded even if damaged. If a bird has a large wingspan, however, and their wings touch different wires of different voltages, the bird can be violently electrocuted. If death is not immediate, the resulting injuries can impair the bird’s ability to fly, forage or evade predators.
• Tangling: Getting tangled in a fence is the biggest risk birds face. Barbs on a wire fence can snag in a bird’s plumage, and as the bird struggles it can damage its feathers or create flesh wounds. If the bird is unable to free itself, it may face starvation, hypothermia, infections and could be hunted by predators interested in easy prey.
• Wildfires: Electric fences that are not properly maintained may inadvertently spark wildfires, and fires can also be sparked after a bird has collided with an electric fence. Those fires can rapidly consume large tracts of vital habitat, destroying food sources, nests and leks, forcing birds to move into less suitable habitat.
• Inhibiting Migration: Large fences topped with bold lights at night can disrupt bird migration. Birds migrate using the moon and stars to help plot their path, and an unnatural light source on a fence can be disorienting, causing birds to lose their way, in addition to the other hazards that large fence may pose.

The Border Fence

The proposed border fence between Mexico and the southwestern United States presents its own difficulties for birds. The proposed fence is larger and more extensive than any fence crossing individual fields, and if completed, this single fence can have a dramatic impact on migrating birds, particularly for species that already have limited ranges and will be less likely to find safe ways around the fence to their northern breeding grounds.

How You Can Help

It is impractical to remove all fences just for the sake of wildlife, and similarly, it would be impractical to ban materials such as barbed wire that are the most efficient and cost effective fencing material available for large field fences. Care can be taken, however, to make all fences more bird-friendly.

• Keep fences well maintained without loose sections or other hazards, and check electric fences periodically to ensure they are operating properly.
• Remove unnecessary fencing sections necessary and design fences to be the minimum necessary height for their intended purpose.
• Add ribbons, colored balls or other objects to fences to increase their visibility, especially along large sections in open fields away from buildings or other structures.
• If possible, choose materials other than barbed wire for fences.
• Plant brush or shrubs along a fence to help make it more visible. This will also provide a small section of sheltered habitat to benefit birds.
• Turn off lights along a fence during peak migration periods in spring and fall.
• Know how to contact bird rescue organizations in case you find injured or tangled birds.

Fences can be an unintended threat to birds, but if care is taken when designing and using fences, that threat can be minimized and birds do not have to suffer the unintended consequences of colliding with, tangling in or being electrocuted by fences.

Photo – Great Horned Owl Tangled in Barbed Wire © Ken Lockwood / Eagle Valley Raptor Center