Mortality Threats to Birds - Communications Towers

The Problem

Northern Harrier killed on the guy wires of a communications tower. Photo: Hugh Kingery

The U.S. Fish and Wildlife Service estimates that between five and 50 million birds are killed in the U.S. each year after being attracted by the lights on communication towers, and colliding with the tower’s structure or guy wires during night migration. Most incidents happen in poor weather with low cloud during the spring or fall. In at least one instance, several thousand birds were killed at a single tower in one night. At least 231 species have been affected, with neotropical migrants making up a large proportion of all species killed.

Approximately 80,000 communication towers in the U.S. are required by the Federal Communications Commission to be lit, either because they are more than 199 feet tall, are in the immediate vicinity of an airport, or are situated along a major highway. More than 7,000 new towers are being constructed each year to meet the demand for cellular telephone and digital television networks, and this is expected to continue increasing in the foreseeable future.

Despite the level of bird mortality associated with towers, it is likely impossible to prove that these deaths are affecting overall bird populations given the range of other threats operating concurrently. Many of the species affected are abundant and have reproductive ecology designed to cope with high rates of mortality, especially among juvenile birds. However, more than 50 of the species recorded in tower kills are of conservation concern, and any additional mortality must be considered a potentially serious threat to these species. The Tennessee Warbler, a species of significant conservation concern is among the most commonly killed at towers. Despite a concerted campaign by conservation groups to encourage tower construction and communication companies to take the threat to birds seriously, and help fund research on lighting regimes to minimize tower impacts, progress has been slow.

Conservationists have now resorted to legal means to resolve the problem including opposing specific proposed tower construction projects, and requesting a system-wide Environmental Impact Statement on all towers.

The Solution

Towers. Photo: Mike Parr

The U. S. Fish and Wildlife Service (FWS) has issued voluntary guidelines for tower construction aimed at minimizing bird kills. These guidelines include: co-locating new antennae on existing towers; keeping towers below 199 feet; siting towers within existing tower “farms”, and not close to sensitive bird habitat; eliminating guy wires; dismantling inactive towers as soon as possible; using visual markers in areas of raptor and waterfowl movements (both groups are prone to daytime collisions with guy wires); shielding security lighting; and using the minimum number of strobe lights rather than continuous lights on towers that do require lighting. The FWS guidelines indicate that red pulsing or continuous red lights attract birds more readily than white strobe lights. However, no comparison between red and white strobe lights has yet been made, and previous studies have indicated that red lights are less attractive to birds than white. The Federal Aviation Administration announced in February 2004 that it was releasing a guidance memo recommending against continuous or pulsing red lights on towers. The Federal Communication Commission has hired a biologist to coordinate its response to the tower kill issue. Clearly more research is needed to identify lighting colors and patterns that are the least attractive and confusing to birds. These lighting systems should then be fitted to all new towers and retro-fitted to existing towers. Many citizen groups across the country are fighting individual tower construction projects, primarily because towers can be an eye-sore. In some cases, bird conservation considerations have been helpful to these groups. It can be possible to reduce the visibility of a tower, and reduce its potential impact on birds at the same time. Disguising towers in existing buildings, or building them inside forests so that only the antennae extend above the tree tops are two examples.

What You Can Do

Support conservation groups that are working to minimize bird deaths at towers. Write to the Federal Communications Commission to express your concern that they are issuing permits for communication towers that are killing migratory birds. Press for a local zoning ordinance to prevent the construction of towers in your county (see an example of a model tower ordinance in Brevard County, Florida). Contacting a local bird club, state Audubon chapter, and the media may also help build support for your campaign.

Tower Report prepared for ABC, Defenders of Wildlife, Forest Conservation Council, and the Humane Society: "The Scientific Basis to Establish Policy Regulating Communication Towers to Protect Migratory Birds."

ABC's Towerkill Report, "Communication Towers: A Deadly Hazard to Birds".

ABC/Hawk Mountain petition to the FCC to prevent proposed tower construction.

Fish and Wildlife Service Voluntary Guidelines on the siting of towers.

Tower Ordinance for Brevard County, Florida

Towerkill.com Website.

The ABC's of Avoiding Collisions at Communication Towers (USFWS document)

U.S. Fish and Wildlife Division of Habitat and Resource Conservation