Subject: Lighting the Bridges
Date: Nov 19 22:21:44 1998
From: Nancy Creighton - NCreighton at email.msn.com
Martin Muller shared this post with Tweeters last May. An excellent source
for additional information is the web site for FLAP, the Fatal Light
Awareness Program: http://www.flap.org/
Martin wrote:
While discussing Seattle "illustrious" mayor's less-than-bright plans to
light up Seattle's skyline in celebration of the coming millennium, someone
asked about bird mortality and lighted structures; the apparent
contradiction that something lit-up for visibility would cause birds to fly
into it.
While researching all aspects of Pied-billed Grebe biology I came across
papers on long term studies at a TV tower on Tall Timber Research Station,
Leon Co., Florida. The following is based on two articles by Robert L.
Crawford published in the Bulletin of the Tall Timber Research Station No.
18 (Nov. 1974) & 22 (July 1981).
For 25 years, from October 1958 to September 1980, daily searches of the
ground/buildings around this (now 308m/1,010 ft) tower resulted in the
collection of 42,384 dead birds, representing 190 species.
Most species killed at the tower were nocturnal migrants. Most significant
factors that cause these fatal collisions (aside from the obvious reason
that the structure was placed there, MM) appear inclement weather and
attraction to lights.
Apparently the birds take off under clear conditions and run into a frontal
or storm system. Rather than landing in the dark the birds continue flying,
at low elevation, running the risk of colliding with tall structures.
Artificial lighting is the second factor significantly correlated with
fatal
collisions. The combination of bad weather and lights apparently produces a
disorienting
effect on birds. This has been noted at lighthouses, street lights,
buildings, television towers, bridges, boats, automobiles and ski lifts. In
addition to collision with the lighted structures themselves, birds also
collide with unlighted structures or the ground around lighted structures,
especially near extreme bright lights. Disoriented birds flutter around the
lights, apparently looking for a horizon with which to orient themselves,
finding that every new course taken is wrong (based on other senses than
visual). The birds may continue to fly around the structure until they
collide with the structure, other birds, or the ground; many reach the
ground dazed ("tame") but alive.
Collisions also occur under conditions of good weather with good
visibility,
and sometimes no collisions occur during bad weather. Our understanding of
the phenomena is incomplete, but bad weather and lights definitely do cause
bird mortality around tall structures.
Back in 1981 well over 1000 papers had been written about this subject, so
this summary does not do all views/opinions on the subject justice. But I
hope it provides a quick answer, and for more serious students a starting
point.
Let's present a forceful and informed contingent at the meeting Nov. 23rd.
Janet Keen
West Seattle