fledgling

I have collected a great backlog of photos over the last couple of weeks. I’ve been taking photos with my usual regularity, but posting less often as the spring bird season wears on and I grow more and more tired from the three-A.M. wake-ups and gradual accumulation of sleep deprivation. The last day of banding is Monday, after which I should (following a few days’ recovery period to catch up on rest) be back to a more usual posting schedule.

These photos were taken a week ago, May 26. Back in mid-April a pair of Eastern Phoebes started showing interest in the old phoebe nest sitting on top of the bat box that hangs high under the roof overhanging the front door. Phoebes will re-use old nests from previous years, something that not too many birds do, generally because for most species last year’s nest usually disintegrates in the winter weather. Phoebe nests are built on ledges under overhangs and are normally fairly protected from the elements, allowing them to endure for many years. The adults will return to sites from which they successfully fledged young the previous year, and will refurbish the old nest with some new moss and fine-grass for lining. When we moved in last summer there was a brood of young phoebes just about ready to leave the nest, and it’s likely that the pair that arrived to use the nest this spring were the parents of last summer’s nestlings, as well.

Two weeks of incubation and the eggs hatched, and then two weeks of catching bugs from the garden and stuffing them into hungry maws and the young birds fledged. During the whole process the phoebes were pretty tolerant of our comings and goings, and especially of Raven, who would lie in the shade on the porch for long stretches. Phoebes, robins, Tree Swallows… all pretty easy-going birds, when it comes to human activity. Once the chicks hatched the adult would often be seen perched in the maple tree a short distance away, cheeping at us with his “I’m not crazy that you’re there but I’ll just wait here as long as you don’t do anything drastic” call note. Dan set up the plastic lawn chairs under the maple, and could sit there in the shade in the afternoons and watch the hard-working adult flycatching in the garden, probably averaging a bug every minute or two.

When the youngsters fledged, all five of them, they hung about the yard for a few days. In particular they seemed to favour one of the pines at one corner, and could often be spotted low in the branches. One afternoon Dan called me outside, saying the five fledglings were all perched together in some open branches of the tree. Fledglings will usually allow you to approach fairly closely (the younger they are, the closer you can get before they flush) and I eased up to within about ten feet of them, carrying my long lens to try to get a few photos. At that young age they’ve still got their fleshy yellow gapes (the bright yellow both acts as a guide for the parents to know where to stuff the food in the lower light of the nest site, and also as a visual stimulus that triggers an instinctual need to feed it within the adult bird – cowbirds use this instinct to their benefit when parasitizing nests, as they’ve got the biggest, brightest, flashiest gapes of all the nestlings) and their short tails, but the gapes will disappear in a few weeks, and the feathers will be full grown in next to no time.

The adult perched on the old, weathered well handpump, chirping his displeasure at my presence so close to his young. I took my photos quickly, and then headed back inside to let them get back to the important business of eating and growing.

This afternoon as I passed him on the porch, Dan pointed up to the old phoebe nest. The female is already settled in, incubating her second brood of the summer. In birds that will nest a second time the female often leaves the male before the first chicks are weaned to finish raising them to independence while she goes back to the nest, spruces it up, and starts laying her second clutch. By overlapping even just this little bit they get an extra few days or a week of the summer in which to raise their young. This might be her final brood of the season, as they’ll be due to fledge at the start of July, but if they were so inclined (and some birds are, though phoebes usually only raise one or two broods a year) their early-spring start means there’d probably be time enough to raise a third brood which would fledge mid-August. On the other hand… if I were the phoebe, by July I’d be looking forward to taking a break before having to head south again.

Dan has an ongoing series called the Nest Files on the Frontenac Birds blog, and he profiled the Eastern Phoebe last year. You can pop over there to read more about their nesting habits, and to see some photos of the nest and eggs.

We were back to Maplewood Bog today for MAPS visit #3. We’d got 20-25 captures on each of our first two visits, and were expecting something similar today, perhaps a handful more as some young start to fledge and move around. Imagine our surprise, then, when our day-end total finished up at 45 captures, more than double what we’d had the previous visit!

We had a good number of chickadees caught, including part of one family that I’d noted had been foraging in the trees near the net. On my way to check said net, I’d paused to photograph the adult birds and their youngsters in the tree canopy. Not the best angle, looking up at their bellies, but good enough for the blog. I ran off a couple dozen photos and then moved on to the net, where I found a couple of the fledglings waiting for me. They were returned to the site once they were banded, to be reunited with their family.

One of the things that drew my attention to the family group was the constant chirring of the young birds. The fledglings will slightly spread and flutter their wings, and chirr at the parents to encourage them to feed them. The noisiest ones are the ones to get fed first, so natural selection has driven them to become quite noisy. I could hear them from 50 meters/yards away, begging at their parents. Since chickadees aren’t very secretive, as birds go, it didn’t take me long to find them.

I watched for a bit as the parents foraged through the branches, catching food, preparing it for the young (for instance, pulling a caterpillar out of a cocoon, which is what I think the adult was doing here), and then stuffing it in their maw. Unfortunately, I didn’t think to get a photo of either of the youngsters while I was banding them, which is too bad, they’re irresistibly fluffy little birdlets, with thick yellow “lips” at the corners of their beaks (these turn into a bright yellow mouth, when the bird opens its mouth to beg – another evolutionary tactic to stimulate parents to feed them).

It was interesting to discover that our banding captures weren’t heavily biased toward young birds, as is often the case when numbers spike like that. Two-thirds of the birds we caught were adults, and while some were likely breeders that were nesting in the area, probably about half of those were likely either early or failed breeders, birds who’d already raised a brood to completion, or whose nests were predated, or who never managed to attract a mate, that were dispersing from their territories to wander around and forage while they moulted. This was one such chickadee, looking scruffy as can be with half of its feathers regrowing in.

It was a female, which I could tell by parting the feathers on her breast (done with a carefully aimed stream of air that makes the left and right feather tracts separate like the parting of the Red Sea). Females of most songbirds and some other species will lose the feathers on their bellies (either by naturally moulting them, or by plucking them) during the summer breeding season. This exposes a large patch of skin, which then becomes vascularized and cushioned with a thick pad of fluid. They use this to incubate the eggs, as having the eggs up against the skin is much more effective than trying to incubate through feathers. Once the breeding season is done they need to regrow those belly feathers, which is what you can see here.

It’s interesting to note the colours of the feathers. Although a chickadee’s belly is white, when you see it perched on a branch, only the outer half of the feather is actually white. The inner half is dark, and this is actually true of many birds. Darker feathers are structurally more dense because of the pigments contained in the barbs (just like how brunettes usually have thicker hair than blondes), so this offers the bird better insulation close to the body without sacrificing the visible plumage colouration.

This last photo is of the same bird’s leg. You can see she’s now banded – a little circlet of aluminum that sits about her ankle like a bracelet, and slides or turns as she moves her leg. But what I was really taking a photo of was her thigh. She’s dropped all of the feathers from this thigh, exposing the skin. This is really illuminating in terms of seeing how a bird’s leg works. In our own limbs, our muscles run most of the length of our bones. A short piece of tendon joins the muscle to the bone, close to whichever bone is being moved. Your biceps, for instance, runs most of the length of your upper arm, with just short pieces of tendon near your elbow and shoulder.

A bird’s leg is different. The only muscles that are used for controlling the entire leg and all of the toes are contained up near the body, in the thigh. From there, long, narrow tendons run down the entire length of the bird’s leg to connect to the particular joint they need to move. This is how birds can have such tiny, thin legs, which don’t freeze in the winter. Muscles produce a lot of heat, and if you can minimize how much muscle is contained in limbs away from the body, you can minimize your heat loss. Even better, if you can do away with muscle mass away from the body, there’s virtually no heat to be lost. A minimal amount of blood travels to the legs and feet, cooled through countercurrent circulation (arteries are lined up side-by-side with veins, so that blood that’s going down to the foot transfers its heat to the blood that’s coming back up to the body, leaving little heat still in the blood to be lost to the air when it reaches the foot). Muscle is also weighty, and birds are designed to minimize the amount of weight they carry on their body (for instance, having evolved hollow bones), so by reducing the amount of muscle necessary to operate the foot they can reduce their body weight.

Tag: fledgling

Baby phoebes

Chickadee chicks and moulting mom