full of air. A goldfinch weighs about half an ounce and the average cardinal about 1.5 ounces. (You can look up the weight of a specific bird at http://www.allaboutbirds.org/)
So when a bird takes on water either by drinking or bathing, instinct tells them to get rid of any useless weight to be a more efficient flyer. As a result, poop happens.
Songbirds can't urinate like mammals because they don't have a bladder. Their kidneys extract nitrogenous wastes from the bloodstream, and instead of excreting it as urea dissolved in urine as we do, they excrete it in the form of uric acid.
Uric acid emerges as a white paste often ejected with the waste from food which is the darker stuff in the center. Both waste products come out together because birds have a single opening called a cloaca, which they use for waste disposal and reproduction.
How do I keep my birdbath clean?
First it is good to change your water frequently and scrub the bath with a good brush. There are also two different products available at Wild Birds Unlimited to help maintain the quality of the water. The first is a liquid you add each time you change the water or there is a tablet you leave in the water for a month.
Birdbath Cleaning Brush This 8" brush is well suited for cleaning birdbaths, as well as for many other household uses. It has stiff, tough polypropylene bristles that will do the job well, and features a comfortable molded poly handle.
Bird Bath Protector is a bio-enzymatic product specially formulated for birdbaths. Prevents organic contaminants from forming including white scale deposits, iron, copper and hard water stains. Uses two unique proprietary technologies; One system helps to prevent the buildup of stains and mineral deposits on the birdbath surfaces, while the second system keeps water clear and free from the organic debris that can make the water cloudy.
Healthy Ponds Birdbath Dispenser treats birdbaths up to 7 gallons. Delivered with two disposable, floating plastic dispensers; each refill is effective for up to 30 days.
Related Article: What Weighs More, Bird's Feathers or Bird's Bones? http://t.co/xRAaxEh