The hummingbirds have taken over the backyard to my delight. I saw a hummingbird pee mid-flight and did some google searching and it seems like they need to pee because of their diet while most other birds don’t pee (they go #1 and #2 together).
So, are there other birds that pee or the hummingbirds (I realize there are lots of species of hummingbirds) are unique in this regard ?
To the best of my understanding hummingbird excretory systems are designed essentially the same as any other bird( or the vast majority of birds to give myself some cover 
). It’s just that they have insanely efficient kidneys and are shedding water constantly from their diet so water is pouring out at a much higher rate than solid waste. But that urine and solid waste still comes out the same cloaca.
ETA: Here’s a page on Ruby-throated Hummingbird anatomy with pictures.
My recollection from a long-ago ornithology class is that birds in general have highly concentrated urine. The white stuff that most of us think as bird poop is really pee; little greenish/brownish globs within the white stuff is the actual bird poop. I don’t recall anything about hummers specifically, but it makes sense that since their diet is mostly liquid, that they would produce more dilute urine.
Unlike mammals, which excrete nitrogen as soluble urea, birds excrete uric acid, which is water-insoluble and is excreted as a white paste. If you see a bird dropping, the white stuff is the uric acid, while dark masses represent the feces. There is little water in the droppings of most birds.
Since they have to consume large volumes of nectar in order to get enough sugar, hummingbirds excrete drops of liquid in addition to the white droppings produced by most birds.
I would imagine that other nectar-feeding birds like sunbirds and others must also excrete liquid water, but don’t have specific information on them.
Whether birds “pee” or not depends on how you define pee. A bird’s “pee” is mostly solid with little liquid. A few like hummingbirds excrete liquid water as well, but this doesn’t contain much in the way of nitrogen compounds.
Old saying from my part of the world: “Everything helps, said the wren, as she pissed into the sea”. Those who thought it up, could be reckoned to have been concerned more with figure-of-speech-making, than with biology…
I was awaiting **Colibri’s **response, but can I say, I’m just a little disappointed with the use of the third person here. Back when I was a sapling, we took our usernames seriously, darn it!
As stated above, the white stuff is pee. The black stuff is poo.
Turns out that birds don’t excrete uric acid after all: Bird droppings defy expectations. Apparently the uric acid is converted to other substances by bacteria in the birds’ gut. Well, it’s possible that some birds do excrete uric acid, but not the 6 species these scientists tested.
God bless the scientists who collect & study bird poop, just so we can have better data to argue about.