Avian electrocutions and overhead powerline collisions are a concern affecting raptors worldwide. As electrical distribution networks grow globally, the problems of raptor electrocution are also on the rise. The following are examples of this global concern. In Europe, research has shown that the main cause of death for the large eagles and owls is from electrocution, while in Spain specifically, 48-60% of recorded mortalities of the Spanish Imperial Eagle is a result of electrocutions. Electrocutions have also been a main factor for the decline of the Eurasian Eagle Owl in Italy, Tasmanian Wedge-tailed Eagle in Australia, and the New Zealand Falcon. Also reported is the concern that six of the seven high conservation priority vultures in Africa are negatively impacted by electrocutions. Up to 54% of adult mortality of the globally endangered Saker Falcon is a result of electrocutions. Certainly, in North America, the fate of the Golden Eagle is adversely affected by localized electrocutions.
Properties of Electricity: There are three categories of an electrical system where electrocutions may take place.
Transmission is described as transmitting electricity over long distances. The transmission lines may range from 44 kilovolts (KV) to greater than 500 KV. The greater the KV, the greater the distance of the wires/conductors between each other and the ground. A distribution system receives voltage from the transmission system and reduces the voltage to a usable voltage ranging from 4-21 KV. The distribution lines are smaller than the transmission lines and are the most common lines visible. These are the lines seen along the roadways. The secondary system receives electricity from the distribution system and reduces the KV to a usable household/business voltage ranging from 120-480 volts. The secondary system uses mostly insulated wires.
Powerline collisions cause less mortality than electrocutions. Collisions may be more common in areas where the lines span home ranges, often between nesting and foraging grounds.
How Electrocution Happens:
The three most common forms of electrocution are a result of a flash burn, phase to phase, or phase to ground exposure. A bird on a wire is just that. This bird is energized and is at the same potential as the wire. There is one point of contact on one wire (conductor). This will not result in an electrocution.
A flash burn is the result of an electrical arc causing thermal burns but does not actually enter the body. An electrical arc is a short circuit between two points of contact. There must be a conductive portion (such as wet, dirty feathers). Dry feathers act as an insulator and are less conductive. A flash burn occurs as the electricity moves across the surface of the body and does not penetrate the body. Flash burns may cover large surfaces of the body, and often are only partial thickness. However, third degree burns are possible.
Phase to phase is contact between two wires or conductors. This creates a short circuit at full line potential (wing to wing). This is the most dangerous type of electrocution, often traveling through vital organs, resulting in death.
Phase to ground occurs because electricity is always looking for a path to ground. This occurs when a bird touches a wire and non-insulated pole or pole equipment. This type of electrocution is less severe than phase to phase and can be survivable.
Most electrocutions occur within the distribution system versus the transmission system. With transmission lines, as birds get too close to the lines, they may suffer from an electrical arc vs direct contact. Larger raptors, such as eagles, are disproportionately affected due to their size and wing span to effectively bridge the air gaps around energized conductors. An air gap is the distance through the air between two points of electrical contact. With the accelerated use of pylon pole construction (steel or concrete), these structures often result in path to ground electrocutions.
Important factors affecting electrocution are body size, powerline construction, wet weather and feather condition. Dry feathers provide substantial resistance to electricity disbursement within the distribution system, while wet feathers have 10-15% less resistance. This does not hold true for the high voltage transmission lines.
When a bird is electrocuted, the electrical current will follow the path of least resistance. This results in the nervous and vascular systems being most affected. Depending on the contact points, cardiac or pulmonary arrest may be caused by brainstem damage, paralysis, muscle spasms or direct injury to the heart. At the cellular level, two types of electrothermal damage are noted. Thermal damage is when the electric current generates heat within the tissues. Electroporation is where the electrical pulse creates temporary pores in the cell membranes, thus changing membrane permeability. This is especially true for neurons and myocytes, with often fatal results. This can occur in the absence of thermal injury. With phase to phase, severe internal organ damage can occur causing rupture of viscera, bleeding into the coelomic cavity and around the heart.
Externally, visible signs of electrocution may involve burns to the feathers and skin, edema of the wings and legs, limb fractures secondary to muscular contractions initiated by the current or a fall from the pole, traumatic limb or digit amputations and lacerations at the contact sites.
If a bird survives the electrocution, the damage both externally and internally can be progressive over a two-week period. As tissues die from the thermal burns, rupture of damaged vessels and thrombosis (local coagulation or clotting of the blood) may occur.
are identifying electrocution lesions and documenting any internal damage and broken bones from the electrocution. During this time the veterinarian will be making daily decisions on how to monitor and treat. This may include the following:
♦ supportive care: fluids, pain control, anti-inflammatories, antibiotics
♦ blood thinners to prevent clots from damaged blood vessels and thrombosis
♦ supportive wraps for broken bones
♦ saline wraps with DMSO for edematous extremities
♦ blood chemistries to evaluate internal organ function
♦ full body radiographs to evaluate bones
Progressive concerns center around the fact that slow death of the tissues may occur and it will take one to two weeks to see the full effects of the electrocution.
♦ Evaluate electrocution site daily
♦ Monitor for developing tissue or bone necrosis
♦ Consider surgical debridement of necrotic tissue
♦ May require amputation of digits or extremities
♦ Long term wound care is required
♦ Physical therapy to prevent contracture
♦ Maintaining nutrition
♦ Prevention of secondary bacterial and fungal infections
Recovery from electrocution always carries a guarded prognosis, requiring dedication and time from all involved.