It’s been a very long time since the last Theropod Thursday post, and I promise to increase the posting ratio a bit in the near future. Theropods are cool – after all, they are the sister group to the really cool dinosaurs, the Sauropoda that include my beloved Plateosaurus! But they are also extra cool because we can study things on them we simply can’t study on any other dinosaur group. That’s because theropods are the sole branch of the dinosaur tree that is still around. People call them birds, because the necessity to give a name to these feathery flying animals is older than the realization that they are just a part of the great overall dinosaurs, but at the core of even the most stupid chicken or tiny songbird there is a vicious predator hidden away that’s just waiting for someone to beat up!
Also, many birds are surprisingly smart – think corvids, the crows, magpies and ravens clan! But even much more mundane birds have some neat tricks up their feathery sleeves. Here’s one bird that does something cool that I have known about forever, that I have seen traces of, and that I have actually watched being done – but never so far been able to get good photos of.
Great Spotted Woodpecker (Dendrocopos major). They are quite common in Germany, and there are always several around our house. The first three years after we moved here to Berlin there was a breeding pair nesting very close by; I found young barely able to fly in our garden. Now there is a breeding pair close by, maybe in one of the trees at the edge of the forest 50 yards away. The bird in the picture, however, lives in Stuttgart, where I happened to get the rare chance to take photos down into a tree from a window at my parent’s flat. That’s nice for several reasons, one being that for once I was not pointing my camera at a bright background, which made balancing the exposure easier than a typical against-the-sky shot would have been. Another reason is this:
The bird was busy hacking away at something on the branch, and not with the typical staccato beating that’s related to communication or wood&bark removal (to get at food living in and under the bark or in rotting wood). It also wasn’t the powerful rapid-fire hacking that’s used to dig cavities for nesting. Rather, what I saw was a series of deliberate individual picks, the sound of which (a bit like single shots of a nail gun two yards away) was what had drawn me to the open window in the first place. In between the pecks the bird looked at the object it was hacking at, and twice picked it up and put it back down:
A walnut! A tiny one, as the tree was not properly grafted and thus grows only tiny nuts. Still, the ratio of dead nuts from this tree is low, and there’s lots of nuts, so it offers a reliable source of food in late summer for all those capable of opening the nuts.
What I was seeing in action here was the use of a Spechtschmiede, literally a woodpecker smithy or anvil. There seems not to be a special English term for this – we Germans have a penchant for creating those combined nouns for technical terms. Interestingly, there’s not only no special term for this, but also no mention of the associated behaviour in the English wikipedia or anywhere else. Basically, a Spechtschmiede is a place where woodpeckers (and others) are able to lodge an object tightly so that they can peck it open. Woodpeckers use them for generations and carry items to them for quite large distances. In this case the bird was lucky, as the source tree of the nut itself happened to offer a good anvil, too. That’s not unusual for walnut trees, which have a very smooth bark on young branches, but a very rough and grooved one on older branches, and which when planted near buildings require regular generous trimming. Where you cut off a branch there is a high chance that over the years an area with ample broken bark is created at the base of the new shoots branching out. Also, such young shoots tend to be weak, bend down over time and rip open on the top side. In general, dead trees, breaks in the bark of living trees, but also has-been-dead-trees-turned-fence-posts are favourites for Spechtschmieden. Here’s what the place looked like after the bird had flown off.
A typical case for a walnut tree: bottom left you can see where a bigger branch had been cut, and the young shoot was long and thin and directed into the crown (thus received little light – don’t be cheated by the sunlight in the pic; the inside of a densely grown walnut crown is quite dark!), and bent under the weight of its leaves. A tiny tear in the bark on top developed over the course of a few years into quite a large welt, which now can receive one of the small nuts and hold it fixed. It is also entirely possible that the woodpecker improved the quality of the Schmiede by removing some wood and bark to make it larger.
I’ll end this with a more typical perspective of a woodpecker: up into a tree with the
bird theropod sitting on the stem. This one I took right in our front yard, where the artificially increased elevation of the yard versus the tree’s base plus the fact that statistically, there’s practically never anyone moving in our yard meant that the bird let me get very close. The situational awareness of many birds is quite astounding; they have a pretty good feel for what’s normal and what’s not normal and might mean a predator sneaking up on them! For example, the birds in our hedgerow will completely ignore us, grandma, our neighbours and our neighbours’ dog, but fly off immediately when a rare visitor like my parents come into the yard. This woodpecker quite clearly considered me and my approach route as mostly harmless, whereas a women coming down the sidewalk got it to fly off when she was still three time as far away as I was.