Peregrine Falcons and Bridges
Symbiosis is defined as an interaction between two different organisms living in close physical association, typically to the advantage of both. Although bridges are not alive, they do have a lifespan, and in Massachusetts both Peregrine Falcons (Falco peregrinus) and bridges are benefiting through the presence of each other. The Peregrine Falcon is a majestic bird of prey and known as the fastest animal on the planet. In level flight it can fly about 60 mph, but in a dive or stoop, one bird was clocked at 242 mph! These speedy falcons hunt pigeons, ducks, and other birds in flight, and are listed under the Massachusetts Endangered Species Act (MESA).
Historically, peregrines in Massachusetts nested on narrow ledges on cliffs. Although bridges are not natural cliff habitat, they provide ample perching opportunities for sight hunting and nesting, and some breeding peregrines have taken up residence on these structures.
Peregrines don’t build nests, but lay their eggs on accumulated debris on exposed ledges. This leaves eggs and chicks vulnerable to the elements. To boost nesting success, MassDOT and MassWildlife installed seven nest boxes on bridges across the state where breeding falcon pairs have been documented. Over time, MassWildlife biologists have observed increased numbers of falcon chicks produced by peregrines using the boxes.
So how do bridges benefit from falcons? It is all too well known by engineers (and birders) that bridges are a favorite roosting habitat for pigeons, birds whose guano can pile up on bridge surfaces. Pigeon guano traps moisture and speeds up the oxidation of structural steel, creating rust. Rusting structures increase maintenance requirements and can reduce a bridge’s lifespan. Fortunately for the bridges, peregrine falcons excel at hunting pigeons, and state biologists and engineers have seen a reduction in pigeon populations at bridges with nesting falcons.
Symbiosis is defined as an interaction between two different organisms living in close physical association, typically to the advantage of both. Although bridges are not alive, they do have a lifespan, and in Massachusetts both Peregrine Falcons (Falco peregrinus) and bridges are benefiting through the presence of each other. The Peregrine Falcon is a majestic bird of prey and known as the fastest animal on the planet. In level flight it can fly about 60 mph, but in a dive or stoop, one bird was clocked at 242 mph! These speedy falcons hunt pigeons, ducks, and other birds in flight, and are listed under the Massachusetts Endangered Species Act (MESA).
Historically, peregrines in Massachusetts nested on narrow ledges on cliffs. Although bridges are not natural cliff habitat, they provide ample perching opportunities for sight hunting and nesting, and some breeding peregrines have taken up residence on these structures.
Peregrines don’t build nests, but lay their eggs on accumulated debris on exposed ledges. This leaves eggs and chicks vulnerable to the elements. To boost nesting success, MassDOT and MassWildlife installed seven nest boxes on bridges across the state where breeding falcon pairs have been documented. Over time, MassWildlife biologists have observed increased numbers of falcon chicks produced by peregrines using the boxes.
So how do bridges benefit from falcons? It is all too well known by engineers (and birders) that bridges are a favorite roosting habitat for pigeons, birds whose guano can pile up on bridge surfaces. Pigeon guano traps moisture and speeds up the oxidation of structural steel, creating rust. Rusting structures increase maintenance requirements and can reduce a bridge’s lifespan. Fortunately for the bridges, peregrine falcons excel at hunting pigeons, and state biologists and engineers have seen a reduction in pigeon populations at bridges with nesting falcons.