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The Bird Perch Equation

Want to find out the best bird perch size for your pet bird? Break out the rulers and calculators — there's a math equation for it.

Anastasia Thrift
Posted: September 29, 2006, 5:00 p.m. PST

Woman with kitten
Green-cheeked conure by Gina Cioli/BowTie Studio/Courtesy Catherine M. Cross
There is not a one-size-fits-all pet bird perch.

The first place to start when choosing perches is your own pet bird. Your bird's feet will be a different size from any other bird’s — even within the same parrot species. We all have unique feet; they’re not automatically the same size as our family member’s or neighbor’s. For birds, the same follows — one size does not fit all.
Larry Nemetz, DVM, an avian-only vet in Southern California, once assumed that all birds within the same species would naturally have the same-sized feet — until he noticed another pattern emerging. “I started seeing a lot of soreness and arthritis in my patients, and wondered what was going on.”

Two months of data collection later, he compared results on a spreadsheet and saw the truth — every patient he saw, even ones of the same bird species, had different-sized feet. That meant they all had specific perching needs. Were they on the wrong-sized perch? 
That got him thinking further. “How could we come up with a guideline for perch sizes if species alone couldn’t tell us anything?” Nemetz, it turns out, was in agreement with other avian experts: A bird’s foot should wrap 75 percent around a perch for optimal comfort.

“We’re looking for the best, long-term perching figure for pet birds. This may differ from how wild parrots roost, but for our purposes a 65- to 75-percent wraparound figure is ideal.” This factors in elements such as secure gripping and foot stress.

Add It Up — The Perch Equation
To arrive at this 75 percent, or three-quarter, wraparound figure, use the following formula: FL (foot length) = 75% x p d (perch circumference measurement; “d” equals diameter).

So, if a cockatiel foot is 38 millimeters long, then a perch diameter should be roughly 16 millimeters to allow for a three-quarter wraparound (37.68 = 75% x 3.14 x 16).

Nemetz said that small birds may be difficult to measure, so an eyeball estimate of what 75- to 65-percent around looks like would work, “if you don’t want to go into the math.”

Greg Rich, DVM, an avian vet in Louisiana, said the 75-percent wraparound is a good rule of thumb. “Sizing perches by [species] size only makes it difficult to categorize the 100 or so more common pet bird species.” The goal in specific sizing is to reduce the strain on the proximal tarsometatarsus, the bones (a series of joints, like a finger) that are most utilized in perching birds. The proximal tarsometatarsus should not be sitting flat on a perch all the time.

Dr. Rich broke it down: “If the perch is too big, there is potential for pressure sores at the junction of the first inside toe (digit #1) and the first forward toe (digit #2) and for the birds to fall off their perch while sleeping because the toes are not grasping properly.”

Different Perch Diameters For Different Perch Uses
Use the 75-percent formula to determine what size perch would be best for your bird. Place this perch in the highest spot in the cage, where your bird will sleep. This high spot is where birds — which are on their feet at all time — will stay solidly in one place for the longest period of the day.

“We recommend a perfect fit perch for roosting,” said Kathleen Grey of Parrotdise Perch manufacturing in Alberta, Canada, who relies on the 75-percent number to correctly size a perch as well.

For grooming perches, select one with a slightly larger diameter than the sleeping perch. Stepping up and down on this larger surface will incorporate the nails and file them. “Diameter should be slightly larger so the foot reaches halfway around,” said Colorado avian vet Dr. Lisa Paul. “The climbing and moving action is what will manicure the foot.”

“My birds like to hang upside down, so the diameter has to be on the small side,” said Dianalee Deter, owner of Good Feather bird store in Colorado. She encourages this form of exercise and makes sure there is at least one smaller-sized perch in her macaws’ cages.

 Straight wooden and plastic dowels cannot be the only option in a cage; movement to and from various-sized perches is necessary for birds to exercise and build callouses. A multi-sized perch of varying diameters is one excellent choice for promoting foot exercise. The change in shape will encourage active use of different muscles.

“If a sore grows slowly, it will turn into a callous,” said Nemetz. “For a bird that is constantly on the wrong-size perch, the sore will grow quickly and lead to bleeding and more damage.”

Three Perch Rule
The magic number, when it comes to perches, is three: one sleeping perch, perfectly fitted for maximum comfort; and two others of varying material and size. A cage with three perches has ample variety, without getting crowded.

Place the three perches in different areas and heights within the cage. Climbing from perch to perch increases exercise and gets those bird feet moving. Perch variety helps alleviate boredom and can emulate a bird’s natural environment.

Be aware of perch placement in relation to food and water dishes. Do not put perches directly above the eating area. Fecal droppings and debris on the bird’s tail will contaminate food and water. Also watch for birds that perch on dishes. They may need a more comfortable alternative nearby, to relieve any discomfort from sitting too long on thin dish edges.

Measurement Conversion
If you don't have a junior high textbook handy, here's how to convert millimeters (those increments small enough to measure budgie feet) into inches. Take the cockatiel example of a 38-millimeter-long foot. First, turn millimeters into centimeters by multiplying them by 0.1:
38 mm x 0.1 = 3.8 cm
Then, divide that by 2.54 to get inches:
3.8 cm ÷ 2.45 = 1.496 in
Now, use the 1.496 in measurement to determine the diameter in inches of a perch appropriate to this cockatiel. Perch diameter is represented by “d”: 
1.496 = 75% (p  d)
1.496 = 0.75 x 3.14 x d
1.496 = 2.355d
1.496 ÷ 2.355 = 0.63
d = 0.63 in

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The Bird Perch Equation

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Reader Comments
Great discussion. But, what isn't clear is whether you include the toe nail when evaluating the length of foot wraparound around the perch. That is very significant.
Rob, Maumee, OH
Posted: 5/14/2014 1:10:46 PM
Very interesting. I always make sure we have a variety of perches. It makes me uncomfortable to look at if there aren't enough perches, or they are all the same
Qing, Rochester, NY
Posted: 2/3/2013 12:45:54 PM
Excellent article
valerie, glen oaks, NY
Posted: 2/1/2013 9:20:44 PM
great article
joan, franklin square, NY
Posted: 2/1/2013 9:16:22 PM
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