To review, here's the close-up that showed a Western Meadowlark holding a white squiggly thing with a brown object at one end:
I mentioned that I went out to the same area and dug around just like a meadowlark to try to find the same sort of object. It didn't take very long! I started finding them almost immediately. I kept digging to see if there was more than one option, but this is the only match I found.
I brought it into the lab and took a few photos under the microscope. The first shows the brown object with the white shoot off to the side, and the second is a closer view of a slightly larger brown object:
While digging, I also looked around to see if there was ever anything else at the other end of the shoot, and that was easy enough to find. Below is an example. It was a little too long for a microscope view, so I bent it around so you could see both ends:
And here's one of just the leaves of this plant (different individual), which might help with the identification:
This is Oxalis pes-caprae. It has a variety of common names and is often known as Bermuda Buttercup. But I like the name African Wood-sorrel, as it's originally from South Africa and although it has yellow flowers, it's not a buttercup!
Oxalis pes-caprae is known for having relatively large bulbs (but less than 2.5 cm long) from which underground shoots arise in the fall. In fact, this species is invasive and difficult to eradicate because of the many bulbs that it produces.
I was a little surprised to find out that meadowlarks were eating Oxalis bulbs! But I was also taken aback by the color and texture of the lower surface of the Oxalis leaves!
In the field, many of the leaves were green below, but others were bright pink, as in the image above. I couldn't help taking a closer look under the microscope. I know it's a bit of a tangent, but you have to see this!
Isn't that amazing? I looked at descriptions of Oxalis, and none of them mention this color. Or that the leaves are glandular. [I'm not sure what else this could be (other than glandular), but if you have different ideas, let me know.] CORRIGENDUM 9 November 2013: I've done some additional research, and now believe these are bladder cells. I'll explain a bit more later.
To wrap up, I'll go back to the main topic of this post — the Oxalis bulb being a food source for meadowlarks. Out of curiosity I split open one bulb to see what the meadowlarks were after (see below). When I first started watching the meadowlarks a few days ago, I had no idea it would lead me to the inside of an Oxalis bulb!