Swallow birds are often welcomed for insect control, but their distinctive mud nests on homes and structures can become a nuisance. Species like Barn and Cliff Swallows build these nests, resulting in droppings, mess, and potential damage to exterior finishes. Finding a remedy requires methods that are effective in deterring the birds while remaining compliant with federal wildlife protection laws. This guide outlines safe, proven, and lawful strategies for managing swallow activity through exclusion and deterrence.
Understanding the Legal Constraints on Removal
Any action taken to remove swallow nests must first consider the legal protections afforded to these birds. Most swallow species are protected under the Migratory Bird Treaty Act (MBTA), a federal law that prohibits the taking, possession, or destruction of migratory birds, their eggs, and their nests without a permit. Violating this act can result in significant penalties.
The legality of nest removal centers on the definition of an active versus an inactive nest. An active nest contains eggs or young birds, and it is illegal to disturb or destroy such a nest without explicit authorization from the U.S. Fish and Wildlife Service. Permits for active nest removal are issued only in extreme circumstances, such as a documented health or safety risk.
An inactive nest, which is empty, or a nest under construction without eggs or young, may be legally removed. Property owners can remove old nests during the non-breeding season, typically between September and February, after the swallows have migrated south. Partially built mud nests can also be removed repeatedly during early construction, provided no adult bird, eggs, or young are present.
Physical Exclusion: Blocking Access to Nesting Sites
Physical exclusion is the most permanent and effective method for preventing swallow nesting activity. This approach involves installing barriers that physically deny birds access to the specific surfaces they need to build their mud structures. Exclusion measures must be implemented before the nesting season or immediately following the legal removal of an inactive nest.
One reliable exclusion method is specialized bird netting used to block access to eaves, overhangs, and recessed areas. The netting creates a physical barrier, preventing swallows from reaching the 90-degree corner where the nest is anchored. A mesh size of 3/4 inch (1.9 cm) to 1 inch (2.5 cm) is adequate to prevent entry.
The netting should be installed tautly at an angle, extending from the outer edge of the eave down to the side of the building. This angle, typically around 45 degrees, eliminates the sheltered corner swallows seek for nest stability. Loose netting should be avoided, as it can look unsightly and potentially pose an entanglement risk to birds.
Alternatively, property owners can install angled barriers or slick surfaces to eliminate the required nesting ledge. Commercial products, often made of smooth PVC or metal, can be mounted under eaves and ledges. This creates a steep, slippery slope that prevents the adhesion of mud pellets. Since the birds cannot gain a foothold, they cannot create the foundational shelf needed for their nest.
Another option involves stringing monofilament line, such as fishing line, in a parallel or zigzag pattern beneath the eaves. The lines should be spaced about 12 inches (30 cm) apart. This creates an unstable and confusing environment that dissuades the swallows from attempting to attach their nests, and the method is often less visually noticeable than netting.
Sensory and Visual Deterrence Techniques
When physical exclusion is impractical, property owners can employ sensory and visual deterrents to make the area undesirable for nesting. These methods aim to confuse or startle the birds, though their effectiveness is temporary, as swallows quickly become accustomed to static objects. Deterrence is most successful when combined with other methods or when devices are moved frequently.
Visual deterrents work by mimicking a predator or creating unsettling movement and reflections. Reflective materials, such as Mylar tape, holographic strips, or reflective eye diverters, can be hung near the nesting sites. The flash of light and movement caused by the wind makes the area seem unsafe or unstable to the birds.
Another visual strategy involves using predator decoys, such as plastic owls or inflatable balloons marked with large eyes. These decoys exploit the swallows’ natural fear response, but they must be repositioned every few days. If a decoy remains in the same spot for an extended period, the swallows will learn it poses no genuine threat and will resume nesting nearby.
Auditory deterrents, including devices that broadcast distress calls or predator sounds specific to swallows, can be employed. These sounds play on the birds’ instinct to avoid perceived danger or occupied territory. Ultrasonic devices, which emit high-frequency sound waves inaudible to humans, are available, but their effectiveness is variable and often limited in open outdoor environments.