Can has Chickadeezburger? How Many Birds Do Cats Kill in Canada?

Far-Side-What-to-Do-cat

In case it slipped under your radar this week, an estimate of the number of birds killed annually by cats in Canada was released, and it is no Far Side cartoon.

In a special issue of Avian Conservation and Ecology (an open-access journal sponsored by the Society of Canadian Ornithologists and Bird Studies Canada), scientists tackled quantifying “Human-related Mortality of Birds in Canada“. When all research teams had weighed in, and all the scientific votes were cast, “death by cat” came in at the top – and we’re talking penthouse vs. lobby here (see Figure 1: “Bird Deaths in Canada”;  presented in a recent Ottawa Citizen article by Tom Spears).

In fact, this graphic is likely quite kind: splitting domestic and feral cats into two categories makes the figure appear as if other sources of human-related mortality are somewhat close in impact to cats, but see Figure 2 below. What the research suggests is that of approximately 268 million birds killed annually via anthropogenic activity, approximately 196 million are killed by either domestic or feral cats - that’s 73%.

Furthermore, estimates of direct mortality by cats do not account for sublethal and indirect effects of cats on bird populations such as reduced parental care and attraction of other nest predators when cats are lurking, and mortality of rodents and other organisms that are prey for some bird species.

A figure like 73% is relatively easy to grasp – nearly 3 out of every 4 birds killed by human-related causes is via cats – but what about 196 million, is that a significant number of birds? How do we place that in context? The author, Peter Blancher, suggests that cats annually kill 2-7% of the roughly 5.2 billion birds breeding in southern Canada (where most Canadians live). Viewed in the light of estimated population sizes of Canadian birds (derived from the Partners in Flight Population Estimates Database), 196 million annual bird mortalities is equivalent to nation-wide populations of:

  • White-throated Sparrows (130 million) + Song Sparrows (60 million), or
  • American Robins (140 million) + Black-capped Chickadees (20 million) + Cedar Waxwings (30 million), or
  • Barn Swallows (5 million) + Chestnut-sided Warblers (13 million) + Gray Catbirds (3.6 million) + MacGillivray’s Warblers (7 million) + Dark-eyed Juncos (130 million) + Northern Cardinals (0.5 million) + …

 

birdDeathsInCanada


Figure 2. Bird Deaths in Canada with Domestic and Feral Cats Combined

 

 

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7 Responses to Can has Chickadeezburger? How Many Birds Do Cats Kill in Canada?

  1. Vicky Smith says:

    Over 10,000 cats and kittens have been TNV*R’d in my area, and continues. As more communities, animal welfare/TNR organizations develop similar programs, the greater headway that will be made. Homes are sought for the cats and kittens suitable for homes, while the remaining outdoor cats are maintained/monitored.

    Efforts continue to educate the public about the need to have their companion animals spayed or neutered, and some areas offer subsidized spay/neuter services. Information is passed on about the benefits of keeping cats indoors and a variety of “catio” designs are shown.

    *vaccinated against some feline viruses and against rabies; also given a topical parasiticide.

  2. James Churchill says:

    Hi Tony,
    Thanks for the comment and for joining the conversation. You have not specifically indicated which of my comments are “quite wrong” and “extremely biased”, but I will respond to the ones you have specifically commented on. If you can be specific about others, then I will respond to those as well.

    1. In your statement you assert that (please correct me if I have misinterpreted) TNR works in the short and long term by, among other ways, allowing for adoption of feral kittens and adults; and sterilizing and vaccinating adults in the population. I believe this is in response to my statement that “…there is very little evidence that [TNR] programs have any sizeable effect on the overall feral cat population, mainly because of numbers – there are simply too many feral cats, actively reproducing, and to achieve any measurable population reduction would involve astronomical costs”.

    In looking at your website (it appears that your organization also recognizes that there is a cat overpopulation problem in your area and that you have been able to “spay/neuter at least 50 cats locally” (is this number up to date?) and help those who cannot afford vet bills to do so. It seems like you would agree with my point that costs for TNR are high and that it has been difficult to achieve a sizeable reduction in the feral cat population relative to the number of feral cats you suggest might be in your entire region (“hundreds of thousands”).

    2. It is not clear whether you were calling me “delusional” or just referring to people in general. To be clear, please re-read my my post and comments to see that I have not advocated killing cats. To date, I have described ways in which the negative effects of owned cats on bird populations could be reduced including keeping them indoors and having them fixed. I see that you describe others on your website.

    3. Please provide some support for your statement that “decades of catch and kill methods simply don’t work”. Also, suggesting that catch and kill methods will not work, does not provide any support for your assertion that TNR does work.

    4. That cats are a native species (broadly, a species living within their normal distributional range) in north america is a view that is not shared by any scientist or historian I know. They were introduced into an ecosystem of organsims that had co-evolved for thousands of years when settlers arrived from Europe.

  3. Tony Porcaro says:

    Mr.Churchill is quite wrong on a number of counts in his extremely biased opinions; for one thing TNR does work both in the short and long term in several proven ways such as allowing for the adoption of feral kittens and even adult cats who can be socialized and also adopted as pets; and most importantly any remaining adult cats are sterilized and vaccinated and will no longer produce all those unwanted litters; for those who want to believe that killing can have immediate or even better long term results than TNR they are simply delusional in that even the removal of entire colonies in any given area would result in the remaining or new cats breeding to capacity in their efforts to replace those killed or removed ; furthermore we already know from many decades of failure that “catch and kill” methods simply don’t work; all of this so-called “good evidence” is certainly not corroborated by independent and unbiased statisticians who have examined the very same data; and how do we call the cat species(which we have domesticated) non-native when they have lived alongside humans for over 8000 years, both indoors and outdoors !?

  4. James Churchill says:

    Thanks for the comment, Vicky. This link provides some good ideas for keeping cats away from yard feeders – and a couple that I might try myself this winter! Thanks! Although I think cat proofing is a great way to deter cat predation in the immediate vicinity of the feeders, it unfortunately will only have the effect of shifting the focus of the predation by cats to areas away from feeders and/or towards the birds in neighbouring yards. I would argue that the main concern we should have about the effect of cats on bird populations is not primarily one of reducing the number of predation events we witness in our own backyards (e.g., which will make a bit of a dent and make us feel less like accomplices) but in the ecosystem as a whole. Therefore, I see yard cat proofing as an important activity, but not one that will cause a measurable reduction in birds killed by cats in human-inhabited areas (unless these strategies are adopted by a critical mass of people) and will not reduce predation of birds by cats away from these cat proofed areas that represent a tiny fraction of the Canadian landmass.

  5. Vicky Smith says:

    An internet search will provide you with several humane tips for deterring cats from your bird feeders, gardens and yards. One such example: “Top 10 Ways to Protect Birds from Cats,” from Birding UK and Ireland.

    From a community cats caretaker-guardian and member of a Maritime TNVR organization.

  6. James Churchill says:

    Thanks for the comment, Mary. Research like this is good for defining the extent of the issue and the likely huge impacts to bird populations. We see a few bird kills here are there, but there is good evidence that there are many more that we do not see. An interesting note in the discussion of the paper is that the effect of cats on birds is not limited to breeding grounds – birds are subject to cat predation throughout their migratory journeys and then again on wintering grounds. What can be done and what is being done are interesting questions. The issue is a highly emotional one and often is portrayed as a polarized, standoff between cat lovers and bird lovers. Biologists would say that felis catus is a non-native species that is contributing to the decimation of native bird populations and therefore cat “access” to birds must be reduced. For owned cats this means not letting them outside and having them fixed (so that they are not adding to the growing feral cat population). A lot of organizations have initiated “catus indoorus” campaigns to educate on the benefits (to cats and birds) of keeping cats inside. Handling the issue of feral cats proves trickier. There are huge technical challenges to finding and quantifying feral cats. There has been a rise in TNR programs recently (Trap-Neuter and Release) campaigns for managing feral cat colonies but there is very little evidence that these programs have any sizeable effect on the overall feral cat population, mainly because of numbers – there are simply too many feral cats, actively reproducing, and to achieve any measurable population reduction would involve astronomical costs. We need creative solutions here.

    As you know, in many towns, in the Maritimes at least, there are by-laws prohibiting free-roaming of owned cats…but we can both attest to the fact that that these are either not known or not respected.

    What can we do? Keep tabs on developments around this issue and form opinions on the issue based on sound science when possible instead of anecdotes. Inform others of research like this; some will be offended or skeptical, many will be surprised. Surround your yard by a moat (cats don’t like water do they?). Keep tabs of the number of outdoor or feral cats in your neighbourhood (start up cat surveys? or The Maritimes Breeding Cat Atlas?). I will research some others…

  7. Mary Bent says:

    This article is very eye opening. I am continually chasing cats away from under my feeders. Unfortunately, I have found the odd dead little bird left behind in their wake. It makes me sad, but I can’t sit under the tree with a shotgun. What can we do about it?

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