Glass windows have existed since as long ago as 290 CE, if only in a limited supply of small sheets. It seems fair to say that window glass has enriched human aesthetic, cultural, physiological, and psychological well-being for at least 16 centuries. Even one small pane is enough to admit a bit of the sun’s light and warmth into an enclosed space. The tendency of builders—and the willingness of their clients—to use this product in large quantities apparently resulted from the need of human society to seek safety within the solid walls of dwellings away from the reach of marauders. Sheet glass permitted viewing the out-of-doors from the comfort and protection of indoors.
In the Middle Ages, ecclesiastical interests led to the lavish use
of both tinted and clear panes. These windows were used in the cathedrals of
Europe and then in the domestic dwellings of the rich, especially in Tudor
England. The technical ability to manufacture large sheets of glass was
developed at the turn of the 20th century. With the building boom that
followed World War II, 1945 to the present, flat glass has become a
prominent, even dominating, construction material used in the majority of
human dwellings and other structures. In 2009, 6.6 billion square miles (17
billion square kilometers) ) of flat glass was manufactured worldwide, which
is about the area of the U.S. state of Delaware, at a value of $23.54
billion. The amount of glass used in construction has continued to increase
annually.
The history of window glass as a source of bird fatalities is similarly
ancient and progressive. The confirming obituaries, however, do not begin to
appear in the literature until well after 1800, with the development of
modern ornithology in Europe and North America. Thomas Nuttall published the
first scientifically documented window fatality in his 1832 “A Manual of the
Ornithology of the United States and of Canada.” He described how a hawk in
pursuit of prey flew through two panes of greenhouse glass only to be
stopped by a third. The next account was by Spencer F. Baird and his
colleagues Thomas M. Brewer and Robert Ridgway in Volume 1 of their 1874
three-volume work “A History of North American Birds.” They described how a
shrike struck the outside of a clear pane while attempting to reach a caged
canary.
To put the scale of losses by various human-related bird killers in perspective, my speaking and writing, starting in the late 1980s, included “sound bite” tactics. The purpose was to capture the attention of anyone who might be moved to listen and take action. One such tactic involves comparing bird losses at windows to those from higher-visibility oil spills. Prominent oil spills that have captured international attention as environmental disasters include the Exxon Valdez disaster and the more recent Deepwater Horizon fire and spill in the Gulf of Mexico. By any assessment, the Exxon Valdez oil spill was a horrific environmental disaster. The oil tanker Exxon Valdez released 260,000 barrels of crude oil into Alaska’s Prince William Sound on March 24, 1989. The spill was estimated to have killed 100,000 to 300,000 marine birds. The 2010 Deepwater Horizon spill is estimated to have caused as many as 2 million bird deaths. By contrast, in the 1970s my original and lowest estimate of losses from window collisions in the U.S. alone was 100 million bird kills a year. This minimum window-kill number equals the toll from 333 annual Exxon Valdez disasters and 100 Deepwater Horizon oil spills every year. Yet those writing in the media about assaults on the Earth’s environment are either unaware, unconvinced, or willing to overlook the horrific loss of bird life occurring at windows.
In 2013, expressing concern and emphasizing the interconnectedness of
life, Travis Longcore and P.A. Smith, writing in the journal "Avian
Conservation and Ecology," warned that avian deaths from windows and other
human-associated mortality factors pose a growing deleterious effect on the
world’s ecosystems and the goods and services birds provide them.
In a money-centered world, those goods and services are getting increased
attention, especially considering what it might cost to have humans try to
do the same work. Pest control is one service birds provide that contributes
to productive yields of valuable crops such as coffee and grapes. They also
provide public health benefits such as consuming insect disease vectors and
scavenging the dead. They play a role in pollination and seed dispersal and
provide high-quality fertilizer from seabird guano. Birds also serve as
ultra-sensitive indicators of environmental health on the local, regional,
and global levels. The “web of life” that Alexander von Humboldt described
as essential to the health and very existence of humankind is as relevant
today as it was when he wrote about it two centuries ago. Like every other
living being, birds are an essential part of that complex, interacting
super-organism that encompasses all life.
One of the most dramatic pest control events occurred in 1848, in what is
now the city of Great Salt Lake, Utah. To many, the event was a true
miracle. California gulls (Larus californicus) descended on the so-called
“Mormon crickets” (Anabrus simplex), an insect that is not actually a
cricket but a katydid that grows to 8 centimeters (3 inches) and voraciously
consumes vegetation. Crops and even their own are on the menu during their
swarming phase that can see them move across 2 kilometers (1.2 miles) of
agricultural fields in a day. These gulls were credited with saving about
4,000 Mormon pioneers by eating the katydids and preventing them from
consuming their second harvest. As a grateful tribute, a monument to the
California gull today stands prominently in Salt Lake City, commemorating
the life-saving service of this bird to people.
The services of mosquito-eating birds contribute to limiting the spread and
prevention of malaria, yellow fever, and other diseases. This is a
particularly important aid in tropical climates, where several species, but
especially martins and swallows, have protected Indigenous people from the
earliest times until now. Vultures the world over are specifically adapted
to removing the dead and with them the accompanying organisms that spread
diseases among humans and other animals. At the turn of the 21st century,
the dramatic disappearance of vultures in India virtually eliminated the
service they provided in scavenging livestock carcasses. The consequence of
this loss was an estimated 48,000 human deaths between 1992 to 2006 from
rabies and a cost of $34 billion to the national economy. Other
vulture-connected health-related costs of $24 billion were linked to the
increase in scavenging feral dogs and rats that carry rabies and bubonic
plague, respectively, in addition to other human-susceptible diseases.
Hummingbirds offer pollinating services for commercial flowering plants
and many human foods. The dispersal of seeds by fruit-eating birds ensures
reforestation and with it ecological succession that consists of a chain of
changes in habitat that provides homes to variously adapted life—including
diverse bird species and the food and shelter they require to survive and
sustain healthy populations.
One practical service birds provide is preying on insects across the boreal
and temperate forests of North America. Given the number of species preying
on insects, collectively the presence of birds can have meaningful
consequences for the health of the trees in these forests. Martin Nyffeler
and his colleagues, writing in the journal the Science of Nature in 2018,
estimated that the world’s insectivorous birds annually consume 400 to 500
million metric tons of insects per year. Forest birds account for 70 percent
of this amount, or greater than 300 million tons a year. Especially for
forests, the ecological and economic importance of birds eating harmful
insect pests has tangible worldwide value.
Daniel Klem Jr. is the Sarkis Acopian Professor of Ornithology and Conservation Biology at Muhlenberg College, Allentown, PA
Return to Book Recommendations