Wednesday, August 14, 2013

Down to the Bones

Four days have passed since I found the dead song sparrow fledgling in our backyard. In that short time, the body has been reduced to a sticky pile of bones and feathers — not by beetles or flies, but by slugs and, primarily, ants.

Yesterday, I was able to get a pretty good view of the puncture through the top of the bird's skull. Whether it was by beak or canine, the predator had little trouble piercing the fledgling's thin, delicate bone.

Today, the ants were still numerous, and busied themselves with picking away at every bit of food possible. One of the sparrow's legs had been separated from the rest of its body, and one ant in particular was making quite the show of gnawing away at it:

It was really quite fascinating to watch this individual working away at the leg. All but one of the toes had already been removed.

 

Also interesting to see was the interaction and communication between various ants.

I don't know an awful lot about ant hierarchy, but it was pretty obvious which ones were dominant. Physical communication comprised of jaw- and antennae-touching, pushing, and chasing. I was lucky to get a few of these confrontations on video:

 


I made one other unexpected observation this afternoon: while taking another look at what remained of the sparrow, I saw the soil beneath it suddenly start to heave. This could only mean one thing: burying beetles! I looked beneath the carcass, and sure enough, there was a lone burying beetle (crawling with mites, of course) — likely Nicrophorus tomentosus, as its thorax was covered in yellow hair. This was a different burying beetle species for our yard, as previously I've only seen Nicrophorus orbicollis.

Monday, August 12, 2013

Teamwork!

Here's a quick update on the status of the song sparrow fledgling I wrote about yesterday! I took a look at the bird this evening — it was covered in ants and several large slugs, and the body was reduced to little more than a pile of feathers and bones:

Closer inspection of the skull revealed a puncture in the top of the cranium — perhaps from a canine tooth, or maybe from a sharp beak! We'll never know for sure.

This was an interesting process to witness, and it was certainly much different than the burying beetles' disposal of the robin. It was a surprise to see the ants and slugs working side-by-side, and as far as I could tell, they seemed to tolerate one another's presence.

Sunday, August 11, 2013

Fledgling Food

Yesterday, while doing some garden-tending the backyard, I found a dead sparrow fledgling at the base of a pine tree. A few ants and a fly had arrived, but other than that, there wasn't yet much of an insect presence.

I was immediately struck by how small the tail was compared to the rest of the body. At the same time, its legs and feet were disproportionately large —a tell-tale sign of a young bird. There was a bit of a gape remaining at the corners of its beak and its feathers were mismatched, as they'd still been growing in at the time of the bird's death. The down was very soft, almost fur-like.

Fledgling II

One wing was missing, as was most of the inside of the bird. I'm unsure of what killed this sparrow; it's easy to blame the cats that wander our street and backyard, as they've brought down birds on our property before, but I have a hunch it wasn't a cat that did this. The raccoons and foxes have been quite active in our area as of late, and one of them could very well have been the culprit, too.


I'm not quite certain what species of sparrow this was. With fledglings, it can be especially difficult to tell sparrows apart, but I'm leaning toward song sparrow (Melospiza melodia).

After I finished photographing it, I left the body near where the robin was entombed by burying beetles last month. This evening, I paid a visit, only to find that an entirely different insect was busy attending to the corpse:

Ants! Several dozen large ants were chewing away at the sparrow, carrying away bits of flesh. The head of the bird was nearly reduced to just the skull; no fly eggs were to be seen. In this case, the body belonged to the ants — not the beetles, nor the flies.

 

 

Sociable