Native Birds At Risk: How Cat Predation Affects Endangered Species
We love our beautiful domestic cats. We adore those fur buddies purring on our lap and feel an immense sadness knowing there is a massive population of intentionally released cats that are free-roaming, and we’re calling them a harmful alien species.
We don’t want to discuss how these sweet creatures are responsible for a 2.4 billion bird mortality rate in the USA annually.
That figure doesn’t include other wild animals and native wildlife that die from predation by domestic cats and the sly feral cat forced to fend for itself.
Cats: major threats to native birds
Animal lovers appreciate the sound of birds chirping in the wild. Many of us erect birdfeeders in our yards to attract bird species because they’re a joy to watch and play a significant role in the environment. But birdfeeders are an open invitation to free-ranging domestic cats, like an ice cream truck rolling up our street.
We also can’t blame the problem on one domestic cat. Cats do what comes naturally: stalk, hunt, and kill. Experts on bird population declines began the debate about the damage free-roaming domestic cats and feral cats had over birds in the early 20th century. Ornithologist Edward Howe Forbush sounded the alarm bell.
Domestic and feral cats live happily in urban, suburban, and rural environments that collide with important habitats within a biodiverse conservation area of species concerned with declining populations.
The problem also isn’t unique to the USA. It’s a global issue affecting the survival of threatened species, from coastal seabirds to nesting birds everywhere. In one wildlife camera study, researchers observed desexed free-roaming cats decimate a tern colony overnight.
Before long, the tern population abandoned their nesting site, and six breeding terns died at the hands of this predatory cat. While six terns might not sound like a big deal, it’s to a species that’s already clinging to the cusp of extinction. It’s a snapshot of a big problem.
Further, many of these cats kill because it’s part of their DNA. They have access to a well-balanced diet at home, unlike their stray cat cousin, that depends on birds and small mammals as their food source.
The study also worked against the trap-neuter-release program, as desexed cats remain proficient killers. What trap and neuter accomplishes is to help reduce cat overpopulation, although that doesn’t save the 2.4 billion birds annually.
Impact of cat predation on wildlife
The University of Wisconsin published a research paper in the 1990s that estimated rural cats killed up to 219 million birds in the state alone. Many debated the estimated figure, but Wisconsin declared a massive hunt on feral cats but later reneged.
Move forward to the 21st century, and one of the most revered institutions in America released a devastating number detailing estimated bird deaths nationwide. Smithsonian and US Fish and Wildlife Service (USFWS) researchers calculated the animals free-roaming cats killed amounted to 1.3-4.0 billion birds and 6.3-22.3 billion mammals annually.
Those numbers raised eyebrows, and of course, people demanded a recount while others got out their proverbial shotguns to kill all free-roaming cats though they used a less offensive term and called for the “removal” of these killer outdoor cats.
And while pet owners might like to shift the blame to feral cat populations, a study from the Netherlands suggests that of an estimated 141 million animals killed, owned cats claim two-thirds.
Cats are opportunistic hunters and an invasive alien species threatening birds. Unchecked cat breeding and their stray cousins have become a global problem, and many countries in the EU, Canada, and the United States are looking for a solution.
Cats are essential companion animals, but they’re also on the list of 100 worst invasive species in the world, which is on us–the human who introduced them to the world and who also failed by allowing them to breed unfettered through neglect and abandonment.
The IUCN, International Union for Conservation of Nature, recorded that free-ranging cats on islands are responsible for animal species extinction rates of 33 modern birds, mammals, and reptiles. That’s 14% in total.
Cats contribute to the decline of mainland bird and mammal populations, and the debate of policies on how to protect both cats and wildlife doesn’t concur.
Trap-neuter programs for free-ranging cats are detrimental to wildlife populations and don’t have the desired or beneficial effect on recovering bird populations. In the US, bird mortality from predation by all cats is in the hundreds of millions, according to a study published by NIH (National Library of Medicine).
All animal lovers empathize with both sides of the dilemma. The question of how many birds do cats kill often raises concerns about human responsibility towards all animals and how to best serve them.
Birds, small mammals, and feral cats deserve our protection. But how do we move forward before it’s too late?
Effect of cat predation on endangered bird species
Many cat owners view their part of the responsibility as a non-starter. For many, predation is something that cats do naturally, and they avoid taking responsibility.
Cat owners even find it adorable when their feline brings them an offering of a dead animal. No one is arguing about a cat’s lethal skill as a predator but not at the cost of urban songbird predation mortality.
However, cats don’t know the difference between a pest animal and an endangered species. Experts studying the magnitude of cat predation on endangered species have gone back to redraw the lines on how they evaluate and calculate the probability distribution of predation rates for birds and mammals. It was no easy task.
Many studies examined the scientific evidence and the problem from every angle of owned and unowned cats, including the following:
- Geographic distribution
- Climate zones globally
- Other unknowns
- Literature-derived US cat population
- House cats vs. stray cats
Using 100 as a calculated lower estimate and giving cats the benefit of the doubt still amounted to 3 to 8 billion mammals killed by unowned cats. These figures support that cats are responsible for the demise of large populations of native and migratory birds.
The project compiled ten studies with 438 specimens and 58 species and found that 33% of birds killed by cats were non-native species. The data for mammals and predation vary significantly by location, and overall for conclusive evidence, further research is essential. Unfortunately, cats don’t keep score, but we know feral cats hunt in their native range.
Complex studies on predation by feral cats suggest that felines are significant contributors to the extinction of approximately 63 bird, mammal, and reptile species and are a threat to 420 species on a global scale. Seabirds are a prime target threatened by cats as these birds don’t have the evolutionary tools to fight off mammal predators.
Native birds which have become endangered due to cats
Birds face an arduous struggle, not just at the paws and claws of cats. Our city skylines, pesticides, traffic corridors, hydro lines, and habitat loss and encroachment don’t leave humans off the list of those responsible for bird population declines.
Cats are to blame (as are humans for introducing and not controlling) for the disappearance of, or threatening the survival of these birds:
- Maui Parrotbill
- Hawaiian Petrel Ua’u
- Palila and Nene
In Europe, the UK, and the USA:
- House sparrows (30% of deaths)
- Eurasian wrens
- Great tits
Australia And New Zealand:
- Fairy terns
- Lyall’s wren
- Paradise parrot
- Kākāpō or owl parrot
- Orange-bellied parrot
Feral cats pose another threat with their feces containing toxoplasmosis, which also affects marine life, like seal monks and other mammals.
Strategies to minimize the impact of cats on native birds
Since domesticated-owned cats are responsible for an estimated two-thirds of animal deaths (Netherland study), the simplest solution is to ask cat owners to restrict their cats from having access to kill native or migratory birds and mammal species.
Simple solutions to prevent cat predation and reduce prey populations:
- A bell on the cat’s collar can significantly reduce predation of birds, and small mammals
- Sonic collars alert prey animals to a cat’s presence
- Cats should have a solid protein diet to help negate their instinct to kill
- Keep your cat indoors an hour before sunset and after sunrise
- Don’t abandon a cat you can no longer care for; make arrangements with a shelter or friend
- Neuter and spay your cats as domestic cats mate with other wild cat species
- Invest in a cat pet tent or enclosure so a house cat can enjoy the outdoors and small birds can visit your garden safely
How can you help protect native birds from cats?
Gardens are vital for healthy bird populations, and urban bird populations rely on humans to supplement their diet. Domestic cats influence wildlife and nature conservation as much as feral cat predation.
If you don’t confine your cat, at least put the bird feeder two meters (six feet or more) away from shrubs or vegetation. Having a free-standing bird feeder helps prevent a cat from ambushing vulnerable birds.
Nesting boxes are a great way to prevent pet cats from attacking baby birds in nests.
Education is one way to remain on the defensive squad in the delicate conversation about the devastating influence of domestic cats on wildlife. But it’s becoming clear that the problem created by humans through ignorance and neglect has come to bite us in the proverbial backside.
It’s time to stop arguing about how domestic cats impact wildlife and make the right decision to protect all species.
It’s not going to be easy. We’ve already debated this issue of feral and pet cats and wild birds for over 100 years. Tick tock, people, tick tock!