On banding birds

Yellow-bellied Sapsucker
Yellow-bellied Sapsucker

Yesterday I started a new job, running the spring migration monitoring program for Innis Point Bird Observatory on the Ottawa River. It’s a short-term contract, running until June (the length of the spring migration, unsurprisingly), but during that period I’ll be out there six days a week. Even after just two days, I’m quickly realizing that my available time is going to be considerably more limited than it was before, and I’m going to have trouble keeping up with everything, at least as I do it now. So, at least for the time being, I’ll be scaling back my blog posts a bit; instead of doing the occasional “Tay Meadows Tidbit”, they’ll all be tidbits, and I’ll do away with the title (which would just get repetitive). Now let’s just hope I can keep my rambly fingers in check!

Common Grackle
Common Grackle

The focus of the migration monitoring program is to monitor birds, of course. It’s a bird banding program, where birds are captured using standardized methodology that allows for comparison of results over many years. Data is collected for each bird caught, including age and sex, weight and fat levels. The former two measurements tell us something about the demographics of the population, which can be useful in detecting and assessing population trends. For instance, if a particular species starts showing a lower-than-normal proportion of young birds in the captured sample, it’s a suggestion that they’re having trouble reproducing successfully, perhaps due to poor breeding seasons because of weather conditions, or because of environmental problems that are causing increased chick mortality. The latter two measurements (weight and fat) are used in assessing the health of the birds arriving at the station. Low weights and fat levels are generally an indication of a bird that’s just arrived from a long flight, but if it doesn’t bulk up quickly in preparation of its next leg (which is detectable through recaptures of the birds again before they leave the site to carry on) then it could be the bird is in poor health, or it’s having trouble finding food. Over and above all that, though, is simply a documentation of the numbers of each species banded. If you start to notice long term trends – for instance, you band fewer of a species now than you did ten years ago – it’s probably cause for concern. The migration monitoring is especially useful for bird species that nest in the boreal, north of what’s sampled by the Breeding Bird Survey, since it’s often the only reliable means of monitoring their populations.

Tree Swallow
Tree Swallow

Of course, each bird also gets fitted with a band that will identify where and when it was banded if it should ever be encountered again. Historically banding was used as a way to track migration routes and patterns, but fewer than one of every 1000 birds banded is ever seen again away from the site where it was banded. That’s pretty slim returns; you have to band a heck of a lot of birds to get even a small sample size. Still, hundreds of banders banding over several decades have built up a pretty good database of re-encounters, and these days we’ve got a decent idea of where birds go. The focus of banding has shifted to population monitoring, as explained above. The bands are still useful for this, though. A substantially higher percentage of birds are recaptured again between their first banding and when they leave the site to finish their migration. By recording their weight and fat levels again next time they’re encountered (for which you need a band in order to be able to identify individuals again) it’s possible to track how the birds are faring and how well the site fulfills its role as a stopover location.

Red-winged Blackbird
Red-winged Blackbird

Advertisements

Easter birds

Red-winged Blackbird

At my parents’ for Easter dinner yesterday, I popped outside for some around-the-house birding while waiting for the turkey to come out of the oven. I decided not to venture further because there’s still quite a bit of snow on the ground, and with the (slightly) warming temperatures it’s quite soft now. Also, the driveway practically requires galoshes to navigate cleanly, and I haven’t unpacked mine from the winter yet.

There was still a fair bit of activity even just around the house, which is where birds congregate due to the presence of the feeders. I had to wait a little while, but I did finally get to see the Red-winged Blackbirds that my mom had reported arrived the other day. They usually come to the seed spread out on the driveway in front of the house, but yesterday they were sticking to the cast-off litter under the feeders in the backyard, possibly because of the seven cars parked in the driveway turnaround surrounding the seed. One also visited the suet a couple of times, which was where I got the best photos of him.

This is just a youngster, a second-year bird, meaning he was hatched last year (as birds’ ages are labeled by calendar year – he won’t truly be a year old till the summer). You can tell because the black feathers on his back and wings are fringed with orangey-brown, a characteristic of young males.

American Goldfinch and Red-winged Blackbird

Behind the blackbird, a couple of American Goldfinches were coming to the nyger feeder. They’ve been mysteriously absent for the last couple of months, only just starting to return recently. I’m not sure where they all went. Normally they spend the winter mobbing the feeders in fairly substantial numbers. The most I’ve seen at a time since mid-winter has been three.

The males, like this guy, are starting to get their brilliant summer yellow plumage. You can see it all beginning to come in around his face. In the middle of winter you can still tell the males from the females despite their relatively drab plumage because some males will retain slightly brighter yellow faces. Also, their wings and tails are a sharp, crisp black, rather than the duller brownish-black that females sport.

European Starling

The starlings have settled in. There’s at least a couple of pairs present now, with the two males often counter-singing to each other from their respective territorial perches. This particular male seems to have chosen the north peak of the house as his nest site of choice. Here he pauses in his singing to check out the activity (me) below. Two starlings, a Blue Jay and a White-breasted Nuthatch are the birds to have discovered the suet dough, so far. The nuthatch takes respectable small pieces, but the other two species really toss it back when they visit the feeder.

Red-shouldered Hawk

While standing out there watching the feeder birds, I glanced up at a crow crossing the the sky, and happened to spot, up high behind it, this Red-shouldered Hawk moving with purpose to the north. It was right at the reach of my (relatively) short 300mm lens, this is a close crop on the original image. There are a pair of Red-shoulders that live in the neighbourhood every year. I’m not sure where they nest, other than that it’s somewhere to the west of my parents’ place. I regularly hear them calling from that direction in the summer.

I recall some years ago there being some concern over decreasing populations in the province, but I think these declines are more limited to the southwestern portion, west and southwest of Toronto. That said, the recent Ontario Breeding Bird Atlas recorded them in quite a number of areas where they hadn’t been 20 years ago. There is some likelihood that this is due in part to new surveys that were implemented for the species by Bird Studies Canada in 1991, contributing a lot more targeted effort than took place in the first atlas. Still, even taking this into consideration, the results of the atlas are encouraging, and probably suggest increasing forest cover in the south of the province as abandoned fields regenerate. They remain an uncommon species in most of my “home range”, and I’m always pleased to see one.

Also on the raptor front, although I wasn’t able to get a photo, I spotted a Turkey Vulture circling over the escarpment, the first of the season. They migrate south for the winter, so are always a welcome sight in the spring. Come summer you can usually see at least one or two over the escarpment where the topography of the cliffs creates great thermals for soaring. During the peak of migration you can have up to a couple dozen.

Common Redpoll

This Common Redpoll has been hanging around the feeders for a little while, she was there earlier in the week as well. She doesn’t seem to be doing too well, although I’m not sure what she might be ill with. She was feeding periodically, and moving around on the ground, but at other times would just sit on the feeder perch or at the top of the birdhouse in the centre of the garden, looking around but otherwise not doing much.

She’s identifiable primarily because she’s always fluffed up into a near-spherical shape. Fluffing like that is a bird’s way of putting on extra layers – when we would go grab an extra sweater, the birds will fluff up their feathers. The amount of fluffing is similar to the number of layers of clothing, as the air pocket trapped under the feathers, which traps warm air close to the body, will increase as the feathers are further raised. None of the other birds were fluffed this much, it wasn’t that cold out. Birds that are sick will usually fluff their feathers as well, I suspect in a similar reaction to our burying under the covers when we have a fever and are suffering chills.

She was too active for me to consider trying to catch her, and she is continuing to eat, so that’s in her favour. However, she was still sitting at the feeder at dusk, one lone redpoll. I hope she gets well.

Common Redpoll

Cotton candy for blackbirds

Edit: This post was recently included in the 182nd edition of the Friday Ark, a blog carnival focusing on animals of all sorts.

Cattail head

I’m sure we’ve all seen these in our local wetlands, cattail heads that have become all poofed out as winter progresses, like so much cotton-candy on sticks. I’d never given it much thought before, and if I had I suppose I’ve just assumed that the fluff has something to do with the cattail releasing its seeds to the wind, much like milkweed does.

A few weeks ago, my mom bought the book Insects: Their Natural History and Diversity (with a photographic guide to insects of eastern North America) by Stephen A. Marshall. Steve Marshall is a prof at the University of Guelph, where I did my undergrad, and was one of the instructors leading the Ecuador field course that I took. I didn’t spend much time with him (I knew the other prof better), but he was a really nice guy. So I thought it was cool that Mom had got this book, and I sat down to leaf through it. I was primarily interested in the 40-someodd pages of moth plates, and while flipping through those I spotted an image of fluffy cattail heads. Intrigued, I read the plate caption associated with the figure.

Turns out, those fluffy cattail heads you see in the middle of winter aren’t just the cattail doing its thing. Sure, it will naturally begin to loosen the fluff and lose some to the wind. But the cotton-candy formations? They’re the work of a tiny, drab little moth called the Shy Cosmet (Limnaecia phragmitella). Its caterpillars are appropriately known as Cattail Caterpillars. They feed on the seeds of the cattail in the fall and spring, overwintering inside the head as a larva. In late spring they pupate and emerge as an adult moth in early summer.

Cattail head

In order to ensure that they have a secure home for the entire duration of their stay, they spin tiny silken threads that act as a web holding all the fluff inside. The cattail will still loosen its seeds from the stalk to try to spread them on the wind, but the caterpillar’s netting holds them in place. The result is a rather lumpy cotton-candy appearance.

I thought this was all pretty cool, so I did a bit of searching on the web and discovered a post about the Shy Cosmet, made recently, by Gerry Wykes at Naturespeak (he calls Detroit home, so is within my rather broad neck of the woods). In it he brought in a cattail head and gently dissected it to expose the caterpillars hiding within. Now, I suppose I could have just taken him at his word, but I really wanted to go out and have a look for myself. Insatiable curiosity. In the name of science, of course. I brought in two heads for good measure, and opened them up in a tub to contain any wandering worms.

Cattail fluff

Gerry indicated that it would take a moment or two for the caterpillars to poke their heads out of the fluff, that they wouldn’t be immediately visible. So I sat there and patiently waited. And waited. Nothing happened. No heads, no tails even, not a hint of movement. I’ll admit that they should all be dormant at this time of year, but since he’d had such luck with his coming out as soon as they were warm, I was beginning to wonder if I’d picked a dud cattail head, one that really was simply just loosening up its fluff.

Cattail seeds with caterpillar frass

So I started gently teasing apart the clumps. I found lots of what looked to be frass in with all the seed heads. The seeds are tiny, flat and boxy at the end, and brownish in colour. The frass, on the other hand, was gray and round, spherical. There was lots of it, but no caterpillars associated with any of it.

Finally, after standing with my head bent over this dish for many minutes, I discovered one. Only one, just a single, lone, under-developed caterpillar. Perhaps the cattail head had already been picked over by foraging birds and this was the only guy to have survived. Perhaps there never were many to begin with, maybe I missed one or two. But I went through the entire two cattail heads and only found one. By the time I was done, they looked like this:

Cattail fluff

Cattail Caterpillar

Here’s the caterpillar. I found him tucked in a clump of relatively undisturbed fluff, nearly comatose. He wiggled a bit when I first picked him out, but didn’t go anywhere. Gerry was describing his caterpillars crawling all over the place, making getting a good photo difficult. Mine was very photogenic.

Cattail Caterpillar

This is the caterpillar posed with my mom’s finger for scale. He was tiny. Tiny tiny. This is why I wouldn’t be surprised if I missed a couple others, although I was paying close attention. Below is the caterpillar beside a measuring tape. You’re looking at the inches side of the tape. Each one of those black dashes is 1/16″. See? Tiny tiny, it’s not that my mom has big fingers…

Cattail Caterpillar

Cattail Caterpillar

I actually found the dried husk of an older caterpillar in the fluff as I was starting to clean up. This gives you an idea of what it should grow to before pupating. He’s got a ways to go.

These little caterpillars form one of the primary food sources for Red-winged Blackbirds upon their arrival here in the spring. It seems like they’d need to eat a lot of them to get much nutrition, but evidently it works for them. A couple springs ago I got a photo of a female Red-wing poking at cattail heads. I thought at the time she was looking for nesting material, but having learned this, it seems apparent that she was actually searching for caterpillars. Who knew? Cotton candy indeed.

As for the book, I highly recommend it. It’s got great photos for an identification reference, and excellent information to complement them. The notable entomologist E.O. Wilson is quoted on the cover: “I wish I’d had Stephen Marshall’s book when I started out in entomology. Its countless photographs and notes bring alive the vast diversity of the insect world.” That’s like Roger Tory Peterson endorsing a bird reference book. There’s so much cool stuff in the book, lots to look at. The only downside: it weighs a tonne. Probably almost literally. At 730 pages and nearly two inches thick, a field guide it’s not. Still, it has the best collection of printed moth photos I’ve seen, plus so much other stuff, I ended up getting a copy myself (should be in the mail). It retails in store for $95, though generally cheaper online, but I found a copy on eBay for $33 plus shipping, so if you look around you should be able to get a good deal on it. Amazon has it on sale for $60. It’s also got a couple images of inside the book so you can take a peek before you buy.