birds – Page 3

House Sparrow

About a week ago we had an unusual visitor to our feeders. The visitor himself wasn’t all that unusual, but his presence at our feeders was. It was a House Sparrow, what seemed to be a young male, all by his lonesome.

House Sparrows, like starlings, are among our most well-known and widespread of North American species (somewhat ironic that they’re both introduced), and yet neither occur with much regularity in the rural landscapes where I live or have lived. This is the first House Sparrow I’ve ever had visit one of my feeders (with the exception of the couple of years spent in town, of course). In the country, they’re almost exclusively associated with farms where they pick through spilled grain and the grass seeds from hay.

I love House Sparrows. If I had to draw up a list of my top five favourite species, House Sparrows would be in there somewhere. There’s just something about their ever-cheerful chirps that can warm my heart even on the coldest or wettest days. If I hadn’t had House Sparrows or starlings about during the years that I lived in town I think I would have had a much harder time dealing with living in an urban environment.

And yet, when I saw this guy at our feeder, I had very mixed feelings about it. On the one hand, it was pretty cool to see a new bird for our yard, and one of my favourites, at that. But on the other, I worried for our Tree Swallows and bluebirds.

House Sparrows are notoriously vicious birds, when it comes to disputing property rights. If they want a box, by the phoenix’s last feather, they’re going to have that box. Even if it means murdering the previous tenants. They can not only oust your native residents, they can really damage your local population, because the youngsters from a successfully fledged brood will return to their natal territories and set up shop themselves and before long you’re supporting a small colony of them. Then it becomes a lot of work to try to cull your colony (like Julie Zickefoose was forced to do a few years ago; what happens to the sparrows after they’re caught is up to you, but since they’re non-native and not part of the Migratory Species Act you could choose to keep them as pets instead of euthanizing them) in order to let the native birds come back.

Still, one sparrow does not an infestation make, and I figured we’d just let him be unless I saw him eyeballing any of the boxes, or hanging out with a girlfriend. In fact, he seems to have moved on since then; we haven’t seen him in a few days.

You might be surprised to learn that the House Sparrow is actually declining in Ontario. Between the first Ontario Breeding Bird Atlas and the second (a span of 20 years), the probability of observation* for the species declined by a statistically significant 20%. Most of this decline took place in the Lake Simcoe-Rideau and Southern Shield regions. The border defining the separation between these two adjoining regions is the southern edge of the Canadian Shield, and helps to explain why these are the regions most affected. These areas represent marginal farmland at best, and as agriculture became more industrialized, especially in the prime farming locations in the east and southwest of the province, these low-quality farms were abandoned or allowed to grow in such that they’re no longer suitable for House Sparrows. That said, similar declines have also been noted in Breeding Bird Surveys across Canada as well as in Christmas Bird Count data.

*The probability of observation is one of those annoyingly specific, technically-correct terms that had to be implemented for the atlas to convey what it was the statistics were actually calculating. Because of the way the data was collected, there was no way to compare absolute numbers of the populations of species. Even the absolute number of atlassing squares the species was found in can’t be compared perfectly because of an increase in effort during the second atlas. So what they’re comparing is the probability that the species will be detected in any given square within the first 20 hours of fieldwork.

The black bibs of House Sparrows are a social signal. Many studies have shown that the most dominant males (often, but not always, the oldest) have broad, solid black bibs while young and/or subordinate males have smaller, mottled bibs. (Wikipedia suggests, however, that other studies have not concluded this.) This guy is clearly ranked somewhere at the bottom end of the pecking order. I can only presume that he’s scouting the landscape, looking for a place to set up his own territory. Since House Sparrows are largely sedentary, rarely moving more than a few kilometers/miles, I suspect he came from the sheep farm at the end of the rail trail that I often walk to with the dogs, where I often hear them chirruping. I hope he found a nice place to call home – preferably somewhere away from bluebirds and other native cavity nesters.

Done in by a sapsucker

Sorry to keep you in suspense! Here’s the final photo:

It was a sapsucker after all.

Of course, you all knew that, didn’t you? If not by the photos/evidence, then simply by the title of yesterday’s post and which way it was clearly going. But still, I was surprised – and relieved, I have to admit – to discover this, some ways up one of the trees. An answer. Classic (to me) sapsucker sign: stacked, rectangular holes.

But that didn’t explain why five trees were absolutely peppered with little holes, as if someone had come out for shotgun practice there. I’ve seen some worked-over trees, but I’ve never seen sapsucker feeding sign like that. Could these be the favoured trees of a pair that nested in the little swampy bit just a couple dozen meters away? Since sapsuckers don’t winter here, and would be unlikely to remain in one spot long enough during migration to create such a multitude of holes, it would have to have been birds present during the summer months.

To try to find an answer, I pulled out the Birds of North America account for Yellow-bellied Sapsucker and began reading. It makes the note that pairs will usually return to the same breeding site as in previous years, and also indicates that the longevity record for a wild bird (these are usually inferred through the time between two captures of a banded bird, whose age was known when it was first banded) is approaching 7 years. So perhaps if the same pair came back to this site for four or five years, they’d have time enough to riddle a few trees.

Fresh sapsucker wells — Active sapsucker wells. I'd forgotten about these photos, which I took a few years ago, back in Toronto.

Something else I came across, though, which I found interesting, and which may also help to explain what I was seeing here: sapsuckers make two types of wells, one that penetrates to the xylem, and the other to the phloem.

Each ring of a tree ring has both xylem and phloem; the xylem is found closer to the center of the tree, while the phloem is found outward, closer to the bark. The xylem is a network of capillary tubes used primarily for the transport of water, and some nutrients, from the roots of the tree to its leaves. Movement of fluids upwards (against gravity) in this network is passive. Water molecules climb the sides of these tiny tubes through capillary action, drawn upward (usually) by transpiration (the tree “breathing”, losing water through its leaves), or sometimes pushed upward by excess water pressure in the root system.

The phloem, the outer layer, transports sugars and other nutrients throughout the plant, to wherever they need to go. Unlike the xylem, which is actual tubes, the phloem is composed of cells, which pass contents from one to another like a bucket brigade. The phloem is where the sap flows, and where the sugar content is highest. The reason that girdling will kill a tree is that with the phloem destroyed all the way around the trunk, the sugars have no way of making it down to the roots to keep the roots alive.

Consider the two systems as your arteries and veins, with the roots as the heart and the leaves as the lungs. The water starts in the roots (your heart) and is pumped up through the tree’s xylem (your arteries) to the leaves (your lungs). There it picks up sugars (oxygen, in this analogy) which it then carries back through the rest of the tree by the phloem (your veins) before returning to the roots to be cycled through again. Of course, this isn’t a perfect analogy because in our bodies the switchover between arteries and veins isn’t at the lungs as I’ve drawn here but at the tissues where the oxygen is dropped off. But you get the idea. Also, just as there remains a small amount of oxygen in the blood that the veins carry back to the heart and lungs, so too is there a little big of sugar in the water going back up from the roots in the xylem.

Yellow-bellied Sapsucker at well — We actually got to see a sapsucker visiting its wells. The one and only time I've observed this behaviour.

Back to the sapsuckers; the wells that they drill into the xylem are circular, usually in horizontal rows of 3 to 15 holes. Those bored into phloem, however, are typically rectangular and stacked vertically for as much as 20 cm (8 in). What I’m used to thinking of as “sapsucker holes” are their phloem wells.

I’m not entirely clear on why they bore two types, but I would guess it has to do with energetics. Although phloem sap contains >10% sucrose and xylem sap only 2-3% (according to the BNA), xylem sap, by virtue of its density/viscosity and its transport method, flows faster. Although the bird may not need to consume as much phloem sap to obtain the same energy, it would need a lot more wells because of the flow rates. (That said, the BNA indicates that sapsuckers will preferentially choose trees with higher sugar content over trees with lower sugar but higher sap flow. Perhaps in the summer, when they don’t want to be flying all over the territory, they settle for the faster-but-lower-sugar xylem sap flow.)

Incidentally, in the spring the tree has no leaves yet, and so the sugar movement is all unidirectional – from the storage location in the roots, up through the xylem to the branches so the tree can use it to start making new leaves. Maple syrup is made from xylem sap. As soon as the leaves start to bud out and begin photosynthesizing, and the phloem sap starts flowing, the taste of the collected sap changes (not for the better) and maple syrup season is over. [In the spirit of full disclosure, I deduced this paragraph from everything I’ve just learned about the two types of sap, except for the bit about maple syrup season ending at leaf out because the taste changes, which I already knew.]

What about why sapsuckers arrange the two types of wells differently? This, too, isn’t specifically stated in the BNA account but I have a guess. Because the xylem operates passively, putting a second well above the first does you no good – the sap would leak out at the first well it gets to and the well above wouldn’t function. So they put them side-by-side. They could also do this with the phloem wells, and you do sometimes see multiple stacks of phloem wells side-by-side. But (and here the BNA account does say) sugars tend to back up in the phloem above a wound/well where the transport cells have been damaged (remember, they’re headed down toward the roots, so they accumulate above the well), so when the first well starts to seal up, the sapsuckers drill their second well above it, where the sugars have become concentrated.

I feel I’ve learned a lesson here. (Ironic, because I’m usually pretty careful about double-checking my info, or using language such as “probably”, “might be”, or “I think” if I’m not thoroughly certain.) Hopefully you have, too, and without having had to eat your words! Still, I feel it was a worthwhile lesson, to have learned that cool stuff about sapsucker wells.

Jumping to conclusions

Eastern Hemlock trunks with holes — Part of the grove with the trees in question. The four trunks on the right were peppered with holes, while the two on the left had none.

A little over a year ago, in December of 2009, I was snowshoeing through our woods when I came across a small grove of trees with some peculiar sign on them (sign being the term used for evidence left behind by a living creature, whether vertebrate or invertebrate). Curious, I took several photos and then came home to puzzle it over. Then, feeling I’d reached a conclusion, I posted about it. Last winter I wrote:

My first thought was Yellow-bellied Sapsucker, which drill their sap-producing holes in straight lines. But they weren’t really sapsucker-ish enough. … These were in straight lines alright, but the holes were small, round, and packed together, the lines widely spaced, and man, were there a lot of them. This didn’t look like the work of sapsuckers. I’m fairly sure that these are exit holes of wood-boring beetles, and more specifically, I suspect the Hemlock Borer, Melanophila fulvoguttata. It seems to be a fairly widespread species, never widely abundant but reasonably common. As its name suggests, its primary host is Eastern Hemlock

I finished the post, posted it, and thought little more about it.

Eastern Hemlock trunk with holes (and dog) — A single trunk, showing the extent of the holes. From the thin twiggy branch that comes off the trunk to the left, near the top, all the way down to just above Raven's head... so thick with holes, I don't think there was anywhere where two vertical inches remained hole-free.

Then a couple of weeks ago I got a Flickrmail from someone who’d been trying to find photos of the emergence holes of Hemlock Borers. She wrote to say she kept being directed to my post and Flickr photos, but that she wasn’t entirely sure that I had them ID’d correctly – to her, the straight lines seemed more like the work of sapsuckers. So I went back to my post, had another look, and then wrote her back to politely disagree. I didn’t know what they actually were, perhaps, but I felt confident they weren’t the work of sapsuckers.

I explained my reasoning:

First was simply the tree species in question. I almost exclusively see sapsucker wells on thin-barked species such as birch or aspen. This isn’t to say that other species might not be used, but just that in my experience sapsuckers seem to have a preference for these trees. We have no shortage of either of these, or even of maples or other thin-barked hardwoods, so it seems odd that they would target the hemlocks. (Unless these are very old holes made when the tree was smaller?)

Second was the diameter of the trees. Again, my experience has been that sapsuckers tend to target smaller-diameter trees, usually no more than 6 to 8 inches DBH, though this doesn’t necessarily mean all sapsuckers will do this. But all of the trees showing this sign were at least a foot in diameter.

Third was the fact that there were SO many holes on each tree, and that every hemlock within this grove had such an excess but none of the surrounding trees showed any signs of damage. I’ve seen worked-over sapsucker trees before, but they typically have a favourite tree or two, not a whole grove of them, and the holes are concentrated in an area of a few or several feet, not as extensive as these were.

Fourth was the arrangement of the holes in the tree. When sapsuckers re-visit trees, they usually drill their new holes clustered near the old ones, like so:

I would consider it unusual for the lines to be so separated from each other.

(Also, sapsuckers typically drill rectangular holes, though I have seen some that are more circular so this isn’t as strong a clue.)

Eastern Hemlock trunk with holes — Many of the holes were in straight rows, like this.

At the end of the post, I’d closed with the comment that I was looking forward to the publication of Tracks & Sign of Insects by Charley Eiseman and Noah Charney. It wasn’t out yet at the time. But now it is, and I have a copy on my shelf! So before I hit send to fire off the email back to her, I thought I’d have a browse through to look for photos of borer holes or other possibilities.

Well, there wasn’t anything in there that looked right. Not giving up, though, I decided I’d go straight to the source, and contact Charley Eiseman himself. He’s helped me out with puzzling identifications in the past, and I thought he might be willing and able to shed some light on this strange sign. I said I’d get back to her once I got a reply from him.

He wrote back, expressing similar thoughts to the woman who’d contacted me initially, though he was very generous in offering some room for doubt at the end:

I don’t have experience with that species, but here are my thoughts: The holes in the third photo are what I think of as classic sapsucker holes. In certain tree species sapsuckers make vertical stacks of rectangular-ish holes, but in most cases (from what I’ve seen in New England–and Mark Elbroch agrees, in his “Bird Tracks & Sign” book, which I used as a model for my own book) they make neat horizontal rows of circular holes, just like that. I’ve watched sapsuckers visit these rows and sip from all the holes in a line, one at a time (in one case taking turns with a hummingbird, which was really neat to see). I also feel comfortable calling the holes in the last photo the work of sapsuckers, albeit slightly sloppier ones. The first photo I’m not sure about, but they seem to be similarly round holes, and the exit holes of a buprestid should be distinctly flattened. It also would be very unusual to see buprestids occurring in that density–I don’t think even an emerald ash borer infestation would look quite like that. I have seen holes like this in hemlocks that seemed to be beetle holes, but I’ve never figured out who makes them, although my first guess would be a scolytine bark beetle of some sort. I’ll let you know if I find anything out about them, and I hope you’ll do the same!

Instead of clarifying the situation, Charley’s comments only served to muddy the water. I knew that they weren’t sapsucker holes, and he didn’t know what they were but didn’t think they were beetle holes, either. So I resolved that, next time I made it back to the woods, I’d return to the grove of trees and have another look.

Which I did, a couple of days ago. I ran off a whole bunch of photos, counted the trunks that had been affected, examined the holes, posed Raven for scale, looked at the trunks from the other side, checked out the neighbouring, unaffected trees, came back and puzzled over them some more.

And then!

And then my camera battery died, just as I went to take the photo of what I noticed that clinched the ID. What spectacular timing, I thought. I stood there and glared at it for a minute or so while I debated whether I should just post the topic with what I had, or defer writing about it until I could come back with a charged camera to get this last photo. Finally, in that hopeful way of someone who doesn’t like the options they’re presented with and wishes the thing would just work, dammit, I flipped the on switch again.

And it turned on!

So I took the photo quick, before it could change its mind. And then I took ten more, of another, unrelated subject, figuring I might as well press my luck since I was out there anyway. And it was still on when I finally turned for home. Not precisely sure what happened with the battery, but maybe it knew I needed a good interlude here to keep you all in suspense.

And you’ll have to stay that way till tomorrow! When I finished up this post it was ridiculously long, over 2600 words, so I thought I’d break it into two parts. (Even this part is still 1400 words!) So check back tomorrow for the answer. But it’s super cool and I promise will be worth it. (At least, I thought so.)

Nestbox tidy-up

Last week we had a string of really warm days. I took advantage of one of these gorgeous, sunny afternoons to take the power drill and the puppy and walk back through our fields to clean out the nestboxes of last year’s nests. (Raven came along too, but declined to help.) I’d done the same thing last year, at nearly exactly the same date. It really does take the nice spring weather to motivate me to go out and take care of the task, even though there isn’t really any reason I couldn’t do it earlier in the winter, or even in the fall.

I visited nine nestboxes, though we have twelve officially on our 30 acres: one of them I just plain forgot about, but the other two are in serious need of repair (or better yet, replacement) and I declared them out of commission for this season. The boxes are all, with the exception of two, ones that were already here when we moved in. In fact, they look like they’ve been here for many years already, weathered and covered in lichen as most of them are. It doesn’t seem to put the birds off, though, and until such time as I can get my spare cash and spare time to coincide, we’ll probably just make do with these.

The first one I opened is the above. It’s one that Dan put up for me halfway through the summer on a stake at the corner of my veggie garden. Being in a (relatively) high-traffic area, plus absent at the start of the season, it came as little surprise that the box’s inaugural residents were House Wrens. I love these little brown birds, so full of spunk and cheer. Growing up we never had them around our house. It wasn’t till I was in university and won a nestbox somewhere, and gave it to my parents to erect near their house, that we had our first wren move in. I don’t think they’ve been without one in their garden since, and the only year that I missed having one was the spring we were at the lake house. (We probably could have got one there, too, but simply didn’t have any boxes up.)

Box number three: another wren. (I’m going to take these out of order, because it tells a better narrative.) Wrens build very distinctive nests. They like for their cup to be at or just below the level of the entrance hole, so in deep boxes this means filling the box up with something. Their material of choice is coarse twigs. And they stuff the box with them. Sometimes they’re so tightly wedged in that you have to wrestle with it to get it out again, and when the material does come out, it almost invariably retains its cube shape. (The odd one falls apart. Must be a young bird: still learning.) Only at the very top, and usually tucked against the back wall, is there anything other than twigs: their small concave nest is woven with fine grasses.

Box number eight: a third wren. Surprisingly, there were only three wren-rented boxes among the group. I seem to have neglected to include the tally in last year’s post, but I think there were five, and our available rental accommodations didn’t include the veggie garden box at the time which, if not included in this year’s tally, leaves only two. There were definitely more, anyway. Possibly a couple of those from last year were re-nestings, second broods from later in the year, and so there really were the same number of wren pairs this year as last. Also, at least one wren moved up to by the house, where there weren’t any boxes last year. I find it interesting how the resident of a box isn’t necessarily the same from one year to the next.

Box number seven. This is a good example of that. Last year when I cleaned out this box the previous summer’s resident had been a chickadee. I was really hoping that the chickadees would reuse it this year, since I had heard a male persistently hanging around that area and singing. If they tried, though, then they were evicted before they could get building. Last summer’s tenants were Tree Swallows. They build shallow nests of thin dried grass, and almost invariably include one or more white or mostly-white feathers. The white feathers here are a giveaway, though I also remember there being nearly-fledged young in this box when Dan and I checked it late last summer.

Box number five: this one also fledged Tree Swallows last summer. But they were some messy swallows. In the previous nest, the nest structure, including the fluffy feathers, is still mostly preserved. In this one, there’s so much packed poop that the stop was just a solid crusty layer. Eeew. I’ve seen this in the occasional swallow box, and I’m not sure why some get like this and some don’t. Perhaps in boxes like this, the nestlings reach fledging age (which also happens to be the age when the parents stop removing the fecal sacs) just as the weather turns cold and rainy for a stretch, so they spend a few days stuck in the box before leaving?

Box number four belonged to one of our Eastern Bluebird pairs. This one also raised a full brood of chicks to fledging, which we got to see when we checked the boxes last summer. I sometimes have trouble telling the bluebird nests apart from the tree swallows, but the bluebirds are generally frugal with their feather use in comparison, and often make deeper nests – two or three inches of grass instead of just one or so.

Box number six: our other bluebird box. I was surprised and delighted to discover we had two bluebird nests on the property, since the previous year we’d just seemed to have the one. We found this one later in the season with eggs, which led me to believe it might be a second nesting. As with the previous nest, this one has a couple of inches of dry grass forming the base.

But the clincher was the blue-green eggs; as a member of the thrush family (same as robins), their eggs are robin-egg blue. It was by these that we knew for sure who was using the box last summer. Unfortunately, the eggs never hatched. Being a later nesting, with eggs at mid-June, I wonder if it simply got too hot for them and they died. There were four when we checked last year, but only three when I opened the box up last week. At some point, one of the eggs had been broken open; by whom, I don’t know. It would be difficult for any land vertebrate to get up to the box because the post has a wide baffle on it, and there aren’t any trees or shrubs nearby. We don’t have cowbirds or House Sparrows in the area that I might consider as possible culprits, either. Also, the other three remain intact. It’s a mystery.

Box number two had two residents last year. The top material is pretty obviously the work of a wren, while the bottom stuff looks to be from a bluebird. Bluebirds seem to be fairly non-confrontational tenants and don’t put up much of a fight when someone with a sharp tongue and quick beak (like wrens or House Sparrows) decide they want the space for themselves. This seems to have been what happened last year. When we opened this box up last June, the wrens had already moved in and had half-grown babies.

And box number nine seemed to be the same. The poor bluebirds seemed to have gotten shunted around a bit before they were able to settle into one at last. I don’t know if there’s anything you can do to keep wrens from ousting the bluebirds once the bluebirds have picked a box. Perhaps all you can really do is put up more boxes, so there are more options for everyone.

Last stop, headed north

It’s been a good winter for northern birds, between the Bohemian Waxwings that have stopped to visit, and the Evening Grosbeaks that came by a few times early in the season. We didn’t see the grosbeaks again after those first visits, but the waxwings were semi-regular visitors over the winter. They move around an area, spending time first here, then there, so we’d see them daily for a few days or up to a week, and then they’d disappear for a few weeks, foraging in other spots.

Earlier this week, we had a couple of days, back-to-back, where the waxwings stopped by again. On previous visits it had always been overcast, and the birds backlit against the cloudy sky. Hardly ideal photography conditions. This week, though, they paused in the big maples in our front yard, late in the afternoon with the sun slanting in at an angle that lit them up against a clear blue sky. They were pretty high, so it still wasn’t ideal, but it was considerably better than previous encounters I’ve had with them here.

I used the super-zoom on Dan’s camera to get a few photos of these beauties while they were here, because how many more chances will I get this winter? Odds are, this is probably the last time we’ll see them until next winter. Soon they’ll start making their way north, following the advancing spring, till they reach their breeding territories up along Hudson Bay and points east and west.

Bohemians have the distinctive habit of perching in flocks at the tip-tops of tall trees and just sitting there for minutes at a stretch, sometimes as long as ten or fifteen. They churr to each other, and preen, and doze, and hop about between branches, maybe move to the next tree for a bit. And then at some mysterious signal, they all decide they’re sufficiently rested to move on and they take off all at once. Even silent and backlit, this behaviour is enough for me to know what I’m looking at when I spot a flock of them.

The first day they dropped by our front yard, the mysterious signal seemed to be linked to the fetching of my camera, but on the second afternoon they stayed for a little while. There were a couple dozen of them, but the only one that wasn’t tucked away behind some branches (at least from where I was standing in the house) was this individual. I can’t say I’m an expert on Bohemian Waxwings, but I believe this one is a female: the “bander’s bible”, an amazing tome filled with the sum of everything we know about bird moult and plumage, indicates that in female Bohemians the black chin gradually fades into the gray breast, while in males the black chin ends in a sharp line (like this photo, I guess?).

It was nice of them to stop in one last time before they head north. I hope we see them again next winter!