27 June 2008

A birdbath mystery

About a week ago I started seeing small seeds, resembling cherry pits, on the bottom of the birdbath in the backyard. I empty out the birdbath and fill it with fresh water almost daily and the next day the the pits, usually about 3 or 4 of them, appear in the bath.


The birdbath is under a plum tree. So, first, I thought those were plum pits, but a comparison test proved otherwise.

On the left is a plum pit, on the right a pit from the birdbath.

This test also made me realize that these pits couldn't be left behind by an animal picking at a cherry while sitting at the edge of the birdbath. Look how much stuff is still left on the pit of the plum that I ate and how clean the other pit is in comparison. Aha! So, the birdbath pits are either defecated or regurgitated after having been thoroughly cleaned by the eater's gastrointestinal tract. But fecal matter is usually not associated with these pits. Therefore, I am assuming they are regurgitated. But, by whom?

This morning I filled the birdbath at 9:55, went inside, came back out again at 10:10 to startle an American robin (Turdus migratorius) in the birdbath, which flew away. And there was one of those pits in the birdbath. Now I am suspecting that the robins are using the birdbath as their vomit receptacles.

According to this article:
[Adult American robins] were observed feeding on domestic cherries, and some were known to carry cherries as far as one-half mile to their nestlings. The ground beneath such nests was often littered with cherry pits.
I still need to see or photograph one robin in the act to prove that it's them who are leaving their pits in the birdbath.

I also don't know where the closest cherry tree is. My immediate neighbors don't have one.


John said...

Could it be defecated and the fecal matter dissolved in the water?

xoggoth said...

That is odd.

I have a cherry tree outside my office window and it is being completely stripped by birds, in order of criminality:

a) Blackbirds
b) Hooded crows
c) Starlings
d) Other thrushes

I have not seen any swallow the fruit, although I suppose the crows could manage it, and they do carry whole fruit away. What they mostly do is eat much of the flesh and drop the rest.

I have also noticed some very messy beaks completely clean a few minutes later (probably the same bird as blackbirds are aggressively territorial) so your birdbath may be a convenient beak cleaning place.

Does not explain very clean pits though, they would have been dropped already.

xoggoth said...

An American Robin is a Turdus? Thought that was normally the thrush family.

Anonymous said...

All of (American robin, European blackbird and European robin) are in the thrush family.

Cherry pits come out pretty cleanly from the cherries (no strings, like your plum pit), so it could be vomiting of excreting. I would guess that carrying around extra seeds (while they made their way through the digestive tract) would be inefficient, and regurgitating them would lighten the load.

Thanks for sharing the story! Lisa

Anonymous said...

Actually the small European Robin Erithacus rubecula is no longer classified in the family Turdidae (thrushes and chats). According to at least some experts, the European Robin is now in the family Muscicapidae, an old world flycatcher.

Turdus thrushes are much larger, and usually have spotted breasts. You can see this in the juvenile of the American Robin Turdus migratorius.

The American Robin and the European Robin are not very similar in appearance at all. The American Robin was given the name "Robin" by European settlers only because it has a red breast. The European Robin is much smaller and more delicate with a red face and bib.

European robins are small, solitary, very territorial, and do not migrate. Their song is an extended, very attractive warbling sound.

Susan H.

Anonymous said...

blackbirds regurgitate very clean cherry stones. I feed blackbirds all the time and they do it all the time and I dont feed cherries.