From Watts Up With That?

Guest Essay by Kip Hansen —  7 February 2023

Hark!  I hear birds singing.   And I hear a study reaching out for attention.

The new study is about stickers that people apply to their windows hoping that they will prevent birds from flying into the window because they think that there is a clear route to some place of safety. 

“A thump on the window, if you’re around to hear it. A dead songbird below. Many people seek to prevent this sorrowful scenario by warning birds away with decals or film applied to windows of homes and office buildings.”   [ source ] 

A 2014 study found: 

“Building collisions, and particularly collisions with windows, are a major anthropogenic threat to birds, with rough estimates of between 100 million and 1 billion birds killed annually in the United States. However, no current U.S. estimates are based on systematic analysis of multiple data sources. We reviewed the published literature and acquired unpublished datasets to systematically quantify bird–building collision mortality and species-specific vulnerability. Based on 23 studies, we estimate that between 365 and 988 million birds (median = 599 million) are killed annually by building collisions in the U.S., with roughly 56% of mortality at low-rises, 44% at residences, and <1% at high-rises.”

National Audubon encourages homeowners to protect birds by applying anti-collision stickers to windows:  “Those homeowners that want birds in their yard are probably killing most of them, unfortunately,” Kummer says. “The more birds that there are in the yard, and the more birds that are closer to a house and windows, the more likely that a collision is going to occur simply by sheer numbers.” “Use a Lot of Decals  — Many forest birds readily dart between branches and leaves, so a single decal will not deter them.”

The New York Times covered the latest study, which only compared two commercial “invisible to the human eye” anti-bird-collision films, it did not study the effect of placing stickers with birds shapes on windows. (the most popular treatment).  There have been other studies of various types that seem to show that stickers can help prevent bird-window collisions – but there are caveats. 

          1) The latest study with window films finds that films on the inside surface of windows are totally worthless – basically, did nothing.  These types of films must be applied on the outside surface of the window.  These films reflect frequencies of light easily seen by birds, but not by humans, all the while remaining fairly transparent. Pretty easy to apply to sliding glass doors leading to decks and patios and other first floor windows.  Not so easy to apply to the windows of office buildings’ upper floors. 

          2)  Other studies (not the new one) have found that adding lots of window stickers to the outside of windows helps prevent collisions.  The most popular seem to be bird-shape stickers.  Dr. John P. Swaddle, lead author of the latest study and author of many similar studies, is quoted saying:  “People who are buying decals and putting them on the windows, they want to do good, they want to do right by the birds.”  but if you are putting the sticker on the inside of the windows “Really all you’re doing is some interior decorating”… “You do have to take the extra step of putting it on the outside of the window.”

Additional recommendations from Cornell’s All About Birds for preventing bird window collisions are (excepted):

Treatments for Existing Windows:

To deter small birds, vertical markings on windows need to be spaced no more than 4 inches apart and horizontal markings no more than 2 inches apart across the entire window.

Tempera paint or soap. Mark the outside of the window with soap or tempera paint, which is inexpensive and long lasting. You can use either a grid pattern no more than 4 inches by 2 inches

Decals. Put decals, stickers, sun catchers, mylar strips, masking tape, or other objects (even sticky notes) on the outside surface of the window.

Dot Patterns and Tape. Long-lasting tape products offer an easier way to apply the correct spacing of dots across your window.

Acopian Bird Savers. Also known as “zen curtains,” these closely spaced ropes hang down over windows.

Screens. Installing mosquito screens over your windows is very effective

Netting. Cover the glass on the outside with netting at least 3 inches from the glass, taut enough to bounce birds off before they hit.

One-way transparent film. Products such as Collidescape permit people on the inside to see out, but makes the window appear opaque on the outside.

Other suggestions are to attach outside bird feeders directly to the windows or to locate bird feeders no more than three feet away from the windows (this is the solution we use at my home, along with exterior window screens on most windows).

The estimate of ~ 600 million birds being killed by colliding with windows in the United States annually is of course a WAG (wild guess) – but we should accept it as representing some significant number.  If your home has frequent bird-window collisions, you should do something.  I would suggest that frequent means more often than “it happened once”, your call.

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If you find yourself opening the plate glass slider with bird stickers on it to let the cat out – you have missed the real problem.

But we need to compare this to another study – even more shocking:

One of National Audubon’s repeating themes in its fund-raiser emails is to repeat Cornell Lab of Ornithology’s 2019 study’s finding that since 1970, bird populations in the United States have decreased by nearly 3 billion birds. Of course, this is an estimate made up of estimates. But there is probably no doubt that there are fewer birds today than 50 years ago, mostly due to changes in land use: conversion of forests to farms, tall grass prairie to rangeland and corn fields, etc. resulting in altered habitat availability. Some of this (very little) may be marked down to window collisions.

“We estimate that free-ranging domestic cats kill 1.3–4.0 billion birds and 6.3–22.3 billion mammals annually. Un-owned cats, as opposed to owned pets, cause the majority of this mortality. Our findings suggest that free-ranging cats cause substantially greater wildlife mortality than previously thought and are likely the single greatest source of anthropogenic mortality for US birds and mammals.”

Now, let me repeat that “free-ranging domestic cats kill 1.3–4.0 billion birds…annually.” 

Compare that to “since 1970, bird populations have decreased by nearly 3 billion birds” – that’s 50 years.

But for free-ranging cats:   in that same 50 year period — 50 times 2.65 (average of 1.3-4.0) comes to 132.5 billion birds killed by free-ranging domestic cats.

When we say “free-ranging domestic cats” we simply mean pet cats that are allowed outside of a home to roam free, at least part of the day and this obviously includes all feral cats.

Now, our first study today said that “between 100 million and 1 billion birds killed annually” “by building collisions in the U.S”. For building collisions read window collisions – very few birds collide with solid walls.  Now that is a very wide estimate – the higher estimate is ten times the lower estimate. 

But even the very highest estimate  — 1 billion a year — is less than the lowest estimate for the number of birds killed by free-ranging cats: “free-ranging domestic cats kill 1.3–4.0 billion birds…annually.” 

And there is a simple and sensible solution to this problem as well – keep your pet cats indoors and/or confined to your own property. Just like you do with your pet dogs (who will be picked up by Animal Control if they are found running loose). And this would apply to your pet cheeta, your pet tiger, your pet chickens, your pet pot-bellied pig, pet llama – in fact – like you do with all your other pets. 

[ If I’m perfectly honest, there is one pet often intentionally allowed to roam free for a short time each day – pet pigeons.   My father-in-law kept pigeons for years, in a coop that allowed them to fly free (when he raised a hatch) and was equipped with a one-way door for them when they returned, which they always did. ]

If you want to protect birds, keep your cat(s) indoors unless they have an outdoor cat run (such as these).  And encourage your local community to pass local regulations requiring that cats be restricted to their owner’s property.

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Author’s Comment:

I like to write about interesting things – part of the purview of WUWT.

I like birds.  Birds of all kinds.  I like my backyard birds.  I like raptors of all kinds.  I don’t mind when the local raptors take a few of the song birds feeding at my backyard bird feeders.   I even like our chickens – which are rather like little dinosaurs. 

I like cats.  Cats of all kinds.  I like pet cats.  Buy I don’t like free-roaming domestic cats or,  worse, truly feral domestic cats.  They are simply little killing machines – it is their nature and I don’t really hold it against them.

Every time I have mentioned cats as a problem, a battle breaks out in the comments.  There are those who consider cats (and dogs) to be persons and think that they deserve all the rights to which homeless people are entitled.  There are others who feel that truly feral cats should be rounded up and euthanized en masse.    And yet others demand that the Trap Neuter Vaccinate Return (TNVR) approach is the best to deal with the large feral cat population problem. 

Readers may comment on cats if they chose (WUWT has a very liberal commenting policy) but this essay is really about birds – and windows.

Address comments to “Kip” if speaking to me.

Thanks for reading.

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