Free-roaming cats are the single largest human-caused source of bird mortality in the U.S., ahead of window strikes, vehicles, and every other human-caused factor combined. That's not a knock on cats, it's just what happens when a skilled natural predator has unrestricted outdoor access to a landscape full of nesting birds.

It's not one-sided, though. The outdoors is dangerous for cats too. Indoor cats live an average of 10 to 15 years, according to research out of UC Davis, while free-roaming cats average only 2 to 5. Vehicles are the leading cause of death for outdoor cats, and here in the Conejo Valley, resident coyote and bobcat populations, along with great horned owls and red-tailed hawks, all pose a real risk to a cat left outside unsupervised. 

A catio gives your cat the enrichment of the outdoors while removing nearly all of that risk in both directions: birds are safe from the cat, and the cat is safe from cars, predators, and disease exposure from other animals.

Catios scale from small and simple to elaborate, and there's a workable option for almost any home:

• Window box catios are the smallest and most affordable option. They mount directly to an existing window using support braces, giving a cat a screened-in perch to watch the yard without taking up any floor space. This is the easiest starting point for renters, apartments, or anyone testing the idea for the first time.
• Cat tunnels are narrow, elevated, screened runs, often used to connect a window or cat door to a larger enclosure elsewhere in the yard. They're a good way to route a cat safely across a patio or along a fence line.
• Freestanding catios (3-sided, attached to the house, or 4-sided and fully standalone) offer the most room to roam, climb, and lounge, and larger designs often include space for a human to sit inside with the cat. These typically connect to the house through a cat door in a wall, window, or door.

You don't need to be a professional carpenter to build a catio, though all three routes below are legitimate depending on your budget and time:

• DIY from a plan set: downloadable plans typically run $40 to $70, with materials from a standard lumber or home improvement store adding roughly a few hundred to $1,500 depending on size. This is the most budget-friendly route if you're comfortable with basic tools.
• Kits: pre-cut, pre-measured panels that ship to your door and assemble in a day. More expensive than a plan set but faster and more forgiving for a first build.
• Custom-built: a hired designer or contractor builds to your yard and vision. Costs vary widely, from roughly $2,500 for a simple window catio up to $30,000+ for elaborate multi-structure setups with connecting tunnels.

A few design details worth getting right:

• Use small-gauge, escape-proof wire mesh (roughly 1"x1" or smaller) rather than standard chicken wire, which a determined cat or a raccoon can bend or tear.
• Include a secure latch, and consider a double-door "airlock" entry if the catio opens directly to the outdoors, so a cat can't dart out when you go in to clean or refill water.
• Balance sun and shade. A polycarbonate roof panel over part of the space provides weather protection; leaving another section open mesh keeps airflow good in our summer heat.
• Add vertical space. Shelves and perches let a cat climb and survey its territory, which is most of the enrichment value of the space.
• Keep any plants inside the catio non-toxic to cats, and skip a permanent litter box inside as a full replacement for an indoor box, a small attached litter box for convenience is fine, but cats should still have indoor litter access.

• Los Angeles Catio Tour
• Keep Cats Safe and Save Birds’ Lives (Audubon Society of Omaha)
• Video: Pet cats kill 10x more than natural predators!
• Video: Trap, Neuter, and Release: Bad for Cats, Disaster for Birds (HD)
• Frequently Asked Questions