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Avian Evacuation

12-13-17 avian evacuation 049A1075

To start with the basics, both the excretory anatomy and the consistency of bird droppings are different from those of most mammals. Birds have one opening, a cloaca, which serves as their intestinal, reproductive and urinary tract. Everything from mating and laying eggs to voiding waste takes place via the cloaca.

Instead of releasing waste as urea dissolved in urine, as we do, birds excrete it in the form of uric acid, which is the white liquid we associate with bird droppings. Why is it white instead of brown? This is due to the biochemical reactions that take place in processing the waste so it can be safely excreted with minimal water loss.

If you look carefully at a bird’s droppings, you’ll usually find a small dark solid blob amongst all the white uric acid. Both acid and solid waste are evacuated from the same opening at the same time. Because they come from two different bodily systems, they don’t have much time to blend.

Most people are not great fans of bird droppings due to the damage (and mess) they can cause. However, some ingenious soul took advantage of this property and concocted a skin exfoliator for sale that consists of nightingale droppings, water and rice bran.

(This post is dedicated to my sister who didn’t quite believe I would actually write a post about this subject much less use this Snowy Owl photograph.)

38 responses

  1. Though some might be offended, I think this is an amazing and fantastic picture. The fact that it was captured, at all is, impressive. (It’s a little like catching your dog or cat yawn.) As they say, “Stuff happens!” Thanks for sharing. (Sorry, sis!)

    December 13, 2017 at 8:03 am

    • Jo

      Yes! My thoughts exactly.

      December 13, 2017 at 5:32 pm

  2. Sue Wetmore

    Well that should tell your sistet never to challenge a naturalist!
    Thanjs fir giving us the poop on this subject.😏

    December 13, 2017 at 8:07 am

  3. Marilyn

    That is something I’d never imagined! The inner workings of this end of birds must be another interesting subject.

    December 13, 2017 at 8:21 am

  4. Kate

    Awesome post!!

    December 13, 2017 at 8:26 am

  5. Patti Steinman

    What a picture!

    December 13, 2017 at 8:39 am

  6. Great post !

    December 13, 2017 at 8:45 am

  7. Kathryn

    Sorry, Mary’s sister! Great 0picture of an odd pose!

    December 13, 2017 at 8:50 am

  8. Peggy Curtis

    Hooray for sisters!

    Sent from my iPad


    December 13, 2017 at 8:53 am

  9. What a capture, Mary – camera ever at the ready! A great Naturally Curious post. 🙂

    December 13, 2017 at 8:53 am

  10. Alice Pratt

    What a dedication to your sister…..and it’s the season to ‘believe’😁 I think it’s a wonderful photo…perfectly timed….’everybody poops and pees’. Besides….we readers are used to seeing photos of various scat, that you jave posted.

    December 13, 2017 at 8:57 am

  11. Wondering

    Another adaptive aspect of uric acid vs urea, is that birds actually concentrate the uric acid into crystals so that a heavy bladder full of mostly water is not necessary. Important stuff if you are trying to reduce weight for flight!

    December 13, 2017 at 8:58 am

    • Yes, Alice. It’s been in almost the exact same location for about three weeks now. How fortunate for us humans!

      December 13, 2017 at 2:43 pm

    • Fascinating! I had no idea about the crystals, but makes a lot of sense! Thanks for writing.

      December 13, 2017 at 2:58 pm

  12. Bern R

    CONGRATULATIONS! After a crazy evening with siblings and feeling a bit beaten up, your lovely photo and words about your sister’s disbelief, just rocked my morning and I am laughing with a whole heart again. You are so awesome! I can’t imagine even trying to get this photo. BRAVA! Mary, you are amazing. Bern


    December 13, 2017 at 9:06 am

  13. Frogcaller


    December 13, 2017 at 9:44 am

  14. bcottam2014

    I had just taken my first bite of breakfast when I spotted this post! A quick adjustment in attitude made it possible to enjoy both… Good work and a great photo! Barry

    December 13, 2017 at 9:47 am

  15. Barry Avery

    I was going to co
    mment that this was related to last night’s election in ‘Bama, but it would have only been appropriate if Moore had won.

    December 13, 2017 at 9:58 am

  16. bunny

    taking coffee black and no cereal with milk this morning. let’s hear it for siblings. by the title i expected some mass migration and had to seriously adjust my vision when the foto came up….great shot.

    December 13, 2017 at 10:03 am

  17. Kathie Fiveash

    It is interesting that birds with such a big pouf of soft feathers below the cloaca eject their waste with such force. I’ve noticed their vent feathers with poop. That happens often to my hens, and the result is yucky to say the least – and I’m sure hinders the ability of the feathers to keep them warm and dry. And in the case of a bird that flies, it would also add weight. Great photo, Mary!

    December 13, 2017 at 10:09 am

    • Kathie Fiveash

      This should have said that I have noticed hawks, eagles, herons and others eject their poop forcibly, preventing contamination of their vent feathers – which my hens sometimes do not do successfully.

      December 14, 2017 at 9:24 am

  18. Amazing capture! And a topic most are Naturally Curious about but probably afraid to ask.

    December 13, 2017 at 10:39 am

  19. Haha. Love it!!

    December 13, 2017 at 11:09 am

  20. Susan Fraser

    But of course you would post this and we would appreciate it. We are, after all, curious naturalists. You share the greatest photos of nature that many of us have not had the opportunity to see, let alone photograph. I always enjoy/appreciate these and your informative write-ups and the comments of your readers. Thank you for it all.
    [I’ll bet your sister appreciates your talent, as well.]

    December 13, 2017 at 11:12 am

  21. Dianne Rochford


    Tell your sister that we love whatever you post!!!!!!

    What do you think about my Christmas tree that will not drink??????

    :-), Dianne >

    December 13, 2017 at 11:43 am

  22. Susan Holland

    Of course I knew you would post it! How could you not? … I like to think I just challenged you to be sure that you would.
    As the aforementioned somewhat more squeamish “little” sister, I am always proud, excited and educated by Mary’s posts! I have been amazed my whole life by the passion she has for nature and her ability to encourage the rest of us to feel that same wonder she does. And I learn something new from her almost every day!
    Keep posting, Mary….and I have learned my lesson about daring you to post something. Actually….I think I should have learned my lesson about daring you to do things many, many years ago!

    December 13, 2017 at 12:19 pm

  23. Peter Denis

    I can’t believe it! One that missed my windshield!

    December 13, 2017 at 12:44 pm

  24. Viola

    ah-ha! I salute Mary Holland for telling it as it is. How else would the rest of us learn?! Nature is not always pretty but she is real. Keep up this good work, Mary. I never miss one of your entries.

    December 13, 2017 at 1:26 pm

  25. Alice Pratt

    Is this the same owl that ate a vole…that you posted about last Wednesday?

    December 13, 2017 at 1:55 pm

  26. Alice Pratt

    Snowy must enyoy it’s ‘winter vacation home!” Several years ago, biking on the road along Duxbury beach, MA, we were so fortunate to see a Snowy….from a distance…but it was so fun! Their yellow eyes are amazing.

    December 13, 2017 at 3:31 pm

  27. Stephanie Olmsted

    Your sister obviously doesn’t know us very well!

    December 13, 2017 at 4:58 pm

  28. Cordelia Merritt

    Hi Mary – this is priceless! I’ve forwarded it to my offspring since they all have at least one of your books. – and since they have sisters. Happy holidays and much love to you and Sadie and Otis. Cordie >

    December 13, 2017 at 5:59 pm

  29. Sue S

    What an incredible photo…talk about timing!!! Very informative blurb too catching me by surprise that I didn’t know I would be so interested in bird poop. Not sure the exfoliate you mentioned will be added to my skin care products.

    December 14, 2017 at 5:42 am

  30. Lin Peyton

    Mary, I hope your sister has printed and framed this post!!!!

    December 14, 2017 at 11:06 am

  31. Karen P Maxon

    You are just awesome.

    December 14, 2017 at 2:37 pm

  32. Bill On The Hill...

    Absolutely Stunning Mary! Judging by all the generated comments, a most impressive shot… Take a look in your e-mail Mary, I left you a surprise attachment on a Great Cormorant shot in the Bretton Woods region in the White Mountains back in 2012…

    Bill Farr… :>)

    December 15, 2017 at 2:18 pm

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