where do birds poop from

Occasionally I rerun a favorite older post. This one was originally published in May of 2015. For this version I’ve edited the text, changed the title slightly, tweaked the formatting and added a photo.

For reasons that will become obvious, this post brings back strong memories of my teaching days and the many opportunities this particular subject gave me to use a sophomoric sense of humor with my high school students as a teaching tool. With this presentation I’ll resist most of those opportunities but knowing me, I’ll probably slip one in.

Since you’re reading this you’re probably a birder, bird photographer or nature lover so you’ve seen your share of pooping birds. But bird poop isn’t really “poop” in the traditional sense – its composition is quite different from mammal poop, including that of humans, and that incredibly fortunate adaptation originated with the shelled egg.

Most mammals excrete their toxic nitrogenous wastes in the form of urea but birds and reptiles produce uric acid instead. There’s good reason for that. Urea is soluble in water and in mammals is excreted in dissolved form in their familiar urine, which is mostly water. But birds as developing embryos must survive their time in the egg with their toxic wastes also enclosed within the shell which is a problem not faced by live-bearing mammals. If birds produced water-soluble urea, the urea would quickly build to toxic levels throughout the egg and kill the embryo. So birds produce uric acid instead. Uric acid is insoluble in water and crystallizes out of solution and is stored harmlessly within the egg, and separately from the embryo, until hatching.

After hatching, birds concentrate and store uric acid within the cloaca before it is voided. Birds can excrete 1 gram of undissolved uric acid in less than 3 ml of water but mammals require up to 60 ml of water to excrete the same amount of urea so this is also a weight-saving device for flight. Water (urine) is heavy. Imagine birds trying to take off or maneuver in flight with their “tank” (urinary bladder, a structure lacking in birds) full of heavy, sloshing urine…

In birds, sexual products (sperm and eggs), metabolic wastes (uric acid) and digestive wastes (feces) must all pass through the cloaca (which literally means “common sewer”). The cloaca is a storage chamber opening to the outside at the vent. So birds have only one opening to the outside for elimination of these products, while mammals typically have two.

Sorry for all the heavy reading but this explains some things we’ve all seen in the field. Birds excrete uric acid in the form of a relatively thick white paste (darker digestive wastes that haven’t been eliminated through the mouth as pellets may also be included) instead of water- based urine, as in mammals.

That paste collects on habitual perches and many of us call it “whitewash”. It can be aggravating to photographers because some see it as unsightly in their photos. It’s more than aggravating to car owners. Because of its insolubility in water, whitewash is incredibly persistent. I don’t think Noah’s floods would wash it away.

This rocky perch, part of a huge boulder on the slopes of Antelope Island’s Frary Peak, is a favorite perch for birds like Red-tailed Hawks, Chukars, Western Meadowlarks, Rock Wrens, Sage Thrashers and Lark Sparrows but I seldom use any photos of birds using this perch because the rock is so heavily stained with incredibly bright and persistent whitewash. Several years ago I noticed that even after a huge rainstorm the whitewash had been unaffected so using some bottled water I attempted to scrub away a tiny portion of the whitewash as a test. It simply would not come off.

Water is often referred to as the “universal solvent” but obviously even water has its limits.

Several of the following s are soft but I think they’re sharp enough to make my points.

Some birds take in so much water in their diet that excess amounts of it must also be voided – many hummingbirds are a case in point. Flower nectar is mostly water so hummers have to ingest a lot of water to meet their nutritional requirements.

I photographed this one as it was feeding on Rocky Mountain Bee Plant on Antelope Island and just happened to push the shutter button as it voided some of that excess water. The water also contained some white uric acid (out of solution of course) but as you can see it’s mostly water.

Prior to nesting season the diet of Williamson’s Sapsuckers is made up almost entirely of tree sap harvested at sap wells like you see here.

Here you can see the male of the mated pair taking a sap break in-between bouts of defending (or attempting to establish) his nesting territory from the likes of Northern Flickers, Mountain Bluebirds and Red-breasted Nuthatches.

So, you guessed it, the sapsucker soon voided a big batch of excess water. After the eggs are laid these birds begin to consume lots of ants and at that point their wastes would also include darker indigestible chitin from their exoskeletons.

There’s another consequence of birds having a cloaca and eliminating sexual products, sperm and eggs, through the cloacal opening.

Since most birds lack a penis (ducks, geese, swans and large ratites are exceptions), sperm must be passed from male to female through the awkward process of pressing their cloacal openings together. Some folks call this act the “cloacal kiss”.

OK, I’ve babbled on for too long. I hope you’ll forgive, or at least tolerate, the bio-geekiness of this post. It may not be for everyone but this stuff fascinates me so…

You guessed it: the sapsucker quickly voided a sizable amount of extra water. Following the laying of their eggs, these birds start eating a lot of ants, which causes their waste to contain darker, indigestible chitin from their exoskeletons.

Another effect of birds having cloacas is that they can expel sperm and eggs through the cloacal aperture.

Some birds, like many hummingbirds, require excess water to be eliminated from their diet because they consume so much of it. Hummers need to drink a lot of water to meet their nutritional needs because the majority of flower nectar is water.

Since most birds lack a penis (ducks, geese, swans and large ratites are exceptions), sperm must be passed from male to female through the awkward process of pressing their cloacal openings together. Some folks call this act the “cloacal kiss”.

Birds like Red-tailed Hawks, Chukars, Western Meadowlarks, Rock Wrens, Sage Thrashers, and Lark Sparrows love to perch on this rocky boulder, which is part of a huge boulder on Antelope Island’s Frary Peak. However, the rock is so heavily stained with incredibly bright and persistent whitewash that I rarely use any photos of birds using this perch. A few years ago, I noticed that the whitewash remained unaffected even after a significant downpour. As a test, I tried cleaning a small section of the whitewash with bottled water. It simply would not come off.

Mammals and birds create nitrogenous waste products that the body needs to eliminate. A byproduct of this waste in both, is ammonia. Ammonia is converted by mammals, including humans, into urea, which is expelled in urine. Ammonia is converted by birds into uric acid, which manifests as the thick, white paste that we usually refer to as bird poop.

This is how birds avoid flying while carrying a full bladder. But the real bird poop is often brown in the center of that white paste. Birds’ cloaca, the single exit for their reproductive, digestive, and urinary tracts, allows their feces and urine to exit at the same time. Therefore, the brown or green trace that is frequently observed in the white uric acid paste is actually our excrement.

According to Brendan Boyd, a PhD candidate in the biology department at York University in Toronto, the white material found in bird poop is actually their equivalent of human urine.

I recently purchased a new white car, which is fantastic because it hides the bird droppings when parked in front of the trees. Why do birds have white poop when the vast majority of creatures have brown poop?


Where do birds poop and pee?

Birds have one hole to get rid of waste, called a cloaca. The cloaca is the multitool of a bird’s anatomy: It leads to the urinary, digestive and reproductive tracts. It’s through this hole that birds simultaneously pee and poop onto cars and unsuspecting humans.

Do birds poop where they lay eggs?

Birds pass eggs out of their cloacas to the outside of their bodies through the vent opening. This is the same place stool and urine (both the clear liquid urine and the white, solid, chalky uric acid part), exit. To pass out normally, without getting stuck, the pointy end of the egg must face the vent.

Do birds poop where you feed them?

“And backyard bird feeding has always been the most common and widespread practice of feeding wildlife.” In situations where birdseed is spread out with easy access, like on a platform feeder, birds may poop right into the feed. If another bird eats the contaminated seeds, it can spread salmonella.

Do birds have one or two holes?

Do birds actually have only one hole to pee and defecate? Yes. It’s called a cloaca – defecation, urination, and reproduction all use the same opening. All vertebrates other than mammals have a cloaca, and so do monotreme mammals and marsupial moles.