Fwd: window/building design criteria to prevent bird strikes

Subject: Fwd: window/building design criteria to prevent bird strikes
From: Hugo Phillipps <>
Date: Fri, 28 Jun 2002 09:49:51 +1000
Hi everybody -

Below is a message sent by Paul Nealen of the University of Pennsylvania to
the Ornith-L list.  It may be of interest, especially to architects,
builders and property managers - and to those who live or work in buildings
with bird-strike problems.


I've collected below a summary of responses I received to my original
query regarding design criteria for reducing bird window strikes.  Bird
window strikes have been of relatively little concern in the building
trades, but are of great concern in ornithological and environmental
circles. There have been a number of scientific studies of
strike-reducing means (most by Daniel Klem of Muhlenberg College).

Birds hit windows for 3 reasons: 1) they either don't see them, and
attempt to fly through them, 2) they see habitat reflected in them and
attempt to navigate to some point in the reflection, or 3) they are
attracted to lights on buildings at night, and fly near to them. There
are a variety of means, of varying efficacy, to reduce bird strikes from
these causes.

1) Prevention of direct sight paths through the building seems to be one
critical area, and one that may be easy to avoid in any sizable

2) Wise placement of feeders and exterior plantings: if they are very
close to the building (< 3 m), strikes due to fly-through are reduced
(as detection of exterior glass panes is improved by proximity), and
mortality due to strikes is reduced because the short flight path
prevent the bird from achieving full velocity/momentum. One idea on
large urban buildings is the placement of rails and ledges along a
building, which induce some close visits by resident birds.
Alternatively, plantings > 12 m way tend to reflect less in exterior
glass, although this effect is reduced by both building and planting

3) Exterior nets or screens over windows are perhaps the best option,
but one that impacts user view from both inside and out. They also
require maintenance.

4) Window angle may be a critical feature. Tilting exterior windows
(even just a few degrees downward) may reduce bird strikes, without
requiring extra maintenance or a reduction in visibility. I'm awaiting
more details from an Indiana environmental center which has used this
technique, and claims it to be very effective.  [Has anyone more
information on this criterion???]

5) Marking patterns on exterior glass are also useful. Klem's studies
are of just this; a variety of striping patterns have been tested and
shown to reduce strikes. More importantly, we have local and leading
examples: Swarthmore College has committed to the use of fritted glass
on a portion of the exterior of its new science building. This is glass
to which has been applied either small particles of glass (which are
then melted onto the surface) or a painted-on appliqué of glass
particles, resulting in a slightly frosted appearance. The good news is
that the cost is relatively minimal, if designed into the window
construction. Likewise, Babson College (Massachusetts) has used such
glass in its new construction. At both colleges, tests are underway (and
more planned) to determine the efficacy of this treatment. The treatment
can applied with varying coverage and degree of shading, so virtually
any design could be accommodated. It's also effective in reducing
greenhouse effects and heat retention.

Check out the Swarthmore Science Center Web site
( and the "Green Team"
contributions to the project
(  This is an
impressive group, and, as far as I have seen, they are at the forefront
of environmentally-responsible design.

My thanks to all who responded to my queries (especially Dan Klem and
Carr Everbach) - please forgive me if I have misinterpreted any of your
responses.  To others concerned about this issue, please post any
new/different information!  I've passed all of this information to the
planning committee for our new Biology building here at U Penn, and am
awaiting to see what use of it they make...

Cheers, and thanks to all,


Paul M. Nealen, Ph.D.                   tel: 215-573-2653
Biology Department                      fax: 215-898-8780
University of Pennsylvania
Philadelphia, PA 19104-6018             

Hugo Phillipps
Communications Coordinator
Birds Australia
415 Riversdale Road
HAWTHORN EAST 3123, Australia
Tel: (03) 9882 2622, fax: (03) 9882 2677
Email: <>
Website: <>

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