A new, cheap method to reduce bird mortality from window collisions

Abstract

Many methods to prevent bird deaths at windows are ineffective, and some useful methods are expensive or displeasing. Here we offer, for free download, an image that ended bird accidents on large windows near a tropical cloud forest area, and propose hypotheses for its experimental evaluation

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UNED Research Journal (ISSN: 1659-441X) Vol. 10(1): 83-84, June, 2018
A new, cheap method to reduce bird mortality from window collisions
Julián Monge-Nájera & Zaidett Barrientos Llosa
Laboratorio de Ecología Urbana, Universidad Estatal a Distancia (UNED), 2050 San José, Costa Rica, julianmonge@gmail.com
ABSTRACT: Many methods to prevent bird deaths at windows are in-
eective, and some useful methods are expensive or displeasing. Here
we oer, for free download, an image that reduced bird accidents on
large windows near a tropical cloud forest area, and propose hypothe-
ses for its experimental evaluation.
Key words: reduction of bird mortality, predator-avoidance behavior,
reaction of birds to cats.
RESUMEN: Un método barato para reducir la mortalidad de aves
por choque con ventanas. Muchos métodos para evitar la muerte
de aves en ventanas son inecientes, y algunos métodos ecaces re-
sultan caros o desagradables. Aquí ofrecemos, para descarga gratui-
ta, una imagen que redujo las muertes de aves en la cercanía de un
bosque tropical nuboso. Además, proponemos hipótesis para su
evaluación experimental.
Palabras clave: reducción de mortalidad, evasión de depredadores,
reacción de aves ante gatos.
Bird injury and death from collisions with win-
dow glass is a signicant problem around the world
(Menacho-Odio, 2015; Hager et al., 2017). Unfortunately,
even though public participation and awareness are
growing (Oviedo & Menacho-Odio, 2015; Kummer, Bayne
& Machtans, 2016), methodological problems limit our
understanding of the problem and its remediation (Loss,
Loss, Will & Marra, 2016).
Some methods to prevent bird deaths at windows
are ineective, and some eective methods are expen-
sive or displeasing (for a methods review, see Cowell,
Dietrich, Sullivan & Messmer, 2017). Here we present
several hypotheses based on observations with a printed
photograph that helped reduce bird mortality on large
windows near a tropical cloud forest area. We include the
photograph (free download)
The building where the test was done is surround-
ed by cattle grassland and is 70 m from tropical ripari-
an cloud forest in Coronado, Costa Rica (10°00’42’’N,
83°57’58’’W). No detailed records were kept because it
was impossible to keep observers in the house all the
time, but our experience is that bird collisions were rare
in the rst ve years. More than half the victims died on
impact, others died after a few minutes, and a few recov-
ered and ew away.
Received 20-X-2017 • Corrected 14-XI-2017 • Accepted 12-XII-2017
After the fth year, secondary vegetation grew closer
to the building and birds started to die every week and
then every day, leading us to look for a solution. After
noticing that no birds hit when our cats were closed to
the windows, we decided to test a photograph of one of
them, a novel idea that to our knowledge has not been
published before.
On May 17th, 2017, we pasted to the base of one win-
dow a 30cm tall color photograph of our cat Negrito (Fig.
1) and no more deaths took place in that window, so on
August 5th, 2017 we added the photograph to the re-
maining seven windows. Since then (almost a year at the
date of this publication) we have only witnessed one bird
death in windows with the cat image (and ve collisions
in which the birds survived).
The idea of using a predator image to save birds is
not new: hawk silhouettes have been used for years, but
they were not successful; basically, only threads, nets or
materials that cover a signicant part of the window had
worked until now (see Klem, 1990, Menacho-Odio, 2018).
We think that previous predator images failed because
they were not realistic enough to scare birds, leaving
only the option of covering much of the glass, which
is often not a desirable practice from the point of view
of the human occupants of buildings, who build large
HYPOTHESIS

84 UNED Research Journal (ISSN: 1659-441X) Vol. 10(1): 83-84, June, 2018
windows to get an unobstructed view of the scenery. In
our experience, this image of a cat, visible from a long
distance thanks to its contrasting colors, shape and size,
prevented further deaths. We hope others will use it and
report on its ecacy, hopefully pasting it in in the out-
side of some windows (to prevent reections) and leav-
ing other windows as experimental controls, to see the
before-and-after dierence in the number of birds dying.
A similar image, but with random areas of black and yel-
low, can be used as part of the control to see if it is real-
ly the cat image that produces the avoidance eect in
birds. If our results are conrmed, tests should be made
to measure the area that each image provides, as well as
the best position of the photograph in the window.
Our hypotheses are that the image of a predator pre-
vents more accidents that the image of an herbivore;
that color images work better than gray images or silhou-
ettes; and that images in which you see the eyes clearly
or show the open mouth of a predator avoid more col-
lisions. Of course, many other hypotheses can be imag-
ined by future researchers.
ACKNOWLEDGMENTS
We thank an anonymous reviewer for suggestions to
improve the manuscript.
REFERENCES
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EDITED BY CAROLINA SEAS
Fig. 1. Cat photograph that prevented deaths from bird colli-
sions when placed on windows near a tropical cloud forest.
See Digital Appendix at: / Ver Apéndice digital en: http://investiga.uned.ac.cr/revistas/index.php/cuadernos