Yesterday I had the opportunity to spend the morning at the TTPBRS research station. It was a lovely day, and as I’d spent the weekend indoors tackling other (interesting, but not outdoor) projects on my computer, it was nice to get outside for a while. It was a busier morning than I gather they’d had over the weekend, and the final tally of birds banded was a little over 50. The species included many Song Sparrows (while I was in the bander’s seat, anyway, it seemed like every other bird I banded was a Song Sparrow), juncos, and Golden-crowned Kinglets, with a few other odds and ends such as Eastern Phoebe, Ruby-crowned Kinglet, and American Tree Sparrow thrown in for variety.
Also among them were two Yellow-bellied Sapsuckers, including the striking male pictured above (in sapsuckers, males have a red throat, while in females it’s white). It is possible to age most birds based on a number of criteria in their wing and tail feathers, but for most songbird species you can only really determine whether during the previous breeding season (so, last summer) they were an adult or a young bird. Woodpeckers are an exception to that, you can usually determine back one year further. In the case of the above male, he was an after-third-year – meaning that 2008 is at least his fourth (“after-third”) calendar year, if not more (birds are generally aged according to calendar year to make it easier to keep track of). You can’t determine his age with more precision than that, but it still means we know he was hatched either in or prior to 2005. So he’s a good old boy.
Later in the morning I spotted another bright male who flew across my path and perched on the trunk of a birch tree. I couldn’t see his legs, so I don’t know if it was the same one as we’d banded earlier. As I watched him, he systematically checked out a set of sap wells that presumably he had drilled earlier. Although I couldn’t see it from my distance, I presume he lapped up what sap had oozed from the holes since last time he visited. He was only there less than a minute, but he checked out all four holes.
Look at him stretch that neck to reach the last one without moving!
Once he left, I went up and checked out the tree he’d been at.
He’d drilled five holes, which were all running slightly, although the sap trails on the bark weren’t substantial. I’m not sure why sapsuckers drill their holes in such a neat line like that, but I would assume that it has something to do with ease of checking them (like in the above photos; he didn’t have to move to reach them all). Probably the sapsuckers won’t tell us if we ask them, so we’re left to make our best guess.
He landed on another tree not much further from the first which, when I went to check it, had a single hole drilled into the trunk. Right next to it, however, was one that was half-started. What I find particularly interesting is how a woodpecker is very methodical in its drilling – it’s not like driving a nail where you keep pounding the same spot. Instead, and as you can see here, they actually chisel out a section of the bark which they can then chip off, exposing the softer wood underneath (which is easier to hammer through). I guess after he’d done one on this tree he was either disturbed, or decided that the sap from this one tasted funny.
Underneath the fresh work you can see a couple of old, scarred-over wells from years past.
Here’s another tree that was visited in years past. There’s probably a number of different years represented there, judging by the relative scarring of some holes to others. Sapsucker holes are often square or rectangular, rather than round, which you can see well on this tree. Nearly all of the trees with sapsucker wells (old and new) down there are birch. The trees around the station are probably 90% birch and cottonwood, but the cottonwood doesn’t seem to appeal to them at all. My guess would be that there’s enough of a difference in the thickness of the bark between birch and cottonwood, and there’s enough birch in the area, that they can afford to be picky about the trees they choose.
An old section of sapsucker wells, now so scarred over it’s forming a cracked swelling in the trunk. The wells don’t do serious damage to the tree, aside from this sort of thing. It’s not all that different from tapping maple trees for their syrup. The main concern would probably be the potential for the tree to be infected by a fungus through the open wound, and even that is rare.
Aside from the obvious benefit to the sapsucker, the sap wells are often visited by other creatures as well, including many nectar-feeding insects and hummingbirds. For these guys the sap provides a sugar-rich source of food in the early spring, before many flowers have started blooming, and can often be invaluable for their survival through that period. I have yet to see a hummingbird visiting a sap well in the spring – by the time they reach us here, in early May, there’s already a fair bit blooming.