Veery Lucky

7 07 2007

viewfrompond

Each day I try and take a walk around the Lab of O; in this case, I’m not sightseeing or birding, or even on a trail. I stalk the space within a few meters of the physical building, eyes scanning the ground for a patch of color that stands out from the green or the gravel. Many have spoken of the new Lab as being a beautiful building in a beautiful setting, but upon further reflection, this building’s beauty betrays birds. The energy-efficient, UV filtering windows that offer unimpeded views of Sapsucker Woods pond and the surrounding forest offer birds a lethal reflection of their environment, and from time to time this reflection results in the death of a bird.

A few caveats before I go further: I work for the Lab, and know that everyone working here cares about the issue of windowstrikes. In fact, the oddly proportioned windows in the Observatory of the Visitors’ Center, with their deep mullions and multitude of frame sizes, were originally thought to reduce the likelihood of strikes (and who knows-perhaps they do?). This general pattern was carried out throughout the rest of the building’s exterior, and all of the windows face habitat (except those on the East side of the building). Yet windowstrikes still occur, though my general impression for the past year is that windowstrikes peak during migration periods, with the Fall migration having the highest proportion due to naive juveniles.

thumpveery

The stalking I mention in the first paragraph is a part of my windowstrike monitoring effort here at the Lab. So far this summer, there have been very few reports of birds striking windows (from those Lab staff lucky enough to have a window), and no dead birds have been found beneath the windows. One incident involved the veery pictured above. I received an email from someone on the first floor, north side, that something had struck their window; I didn’t see this email until 15 minutes after it happened, and when I arrived on scene to check on the bird I found a veery sitting calmly underneath the window, breathing regularly but seemingly in a daze. After a few moments in a dark box the bird perked up, and within moments it had flitted off to the low bushes and begun preening (and I breathed a sigh of relief).

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Migration pt 1: Earth-Sun-Moon

13 05 2007

Spring migration is in full swing here in Ithaca, NY.

BAOR in hand

(Guess this eastern beauty…)

Just today while lunching in the yard consuming a pizza made by the Red Baron himself, I was greeted by a number of travelers spending the day consuming the insectivorous vermin so common in the Spring. Baltimore orioles, Tennessee warblers, Canada warblers, black-and-white warblers, American redstart, northern parula, and the (for once!) aptly named yellow-rumped warbler, all graced the leafy bits beginning to grow.

These small puffs of yellow, white, and black (with a little orange thrown in) complement the somber colors of the other migrant yard birds: the mewling gray catbirds skulking in the underbrush, the raspy eastern phoebe investigating the porch roof for nesting, and the plump worm-picking robins that love a recently tilled plot. When added to the titmice, chickadees, and woodpeckers that have persevered through the entire winter, my yard has begun to feel impressively full (I saw 35 species during that lunch!). And each year my wonder returns with these small birds, many of them in the 10-15 gram range, that are able to migrate thousands of miles to return to my backyard. Despite its ubiquity, migration remains a challenge for researchers to study-how can the birds physiologically fly for so long? How do they stay on course? Where do they go?

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Earlybird X-games: pros and cons

16 04 2007

snowy sign

 

Last night a late season nor’easter slammed into Ithaca, dropping 6 inches of wet snow (with another 6+ predicted for today), breaking branches, bringing down powerlines, and creating hazardous travel conditions. In fact, the Lab of Ornithology had to close its doors today and send the masses home because the power went out in Sapsucker Woods, so this little nuthatch is now happily ensconced four feet from a wood stove pumping out heat. To a nuthatch or a chickadee, this storm is little more than a blip in a winter filled with single-digit temperatures, blizzards, and heat-stealing winds. But to the early season migrants this storm represents a real challenge.

 

snowy SOSP

(Song Sparrow catching freshies between wind gusts)

Early spring brings the first waves of migrants to central NY, starting with the partial or nomadic migrants (like American Robins and Eastern Bluebirds), a variety of blackbirds, a smattering of sparrows, and the venerable Eastern Phoebe. And there are three important factors that these early season migrants gamble on to make their migration successful:

  1. Timing
  2. Timing
  3. Timing

snowy AMRO

(Male American Robin facing the wind)

There’s a reason why these first migrants are not small flycatchers or warblers–they have to be resilient in the face of a spate of cold, wintry weather, and able to eke out an existence when the weather turns sour. But let’s not fool ourselves: there’s also a reason why these first birds aren’t winter residents, and an unusually late storm of uncommon strength–or a series of late storms–can result in their demise. A graphic example involving swallows is described over at Monarch’s Nature blog, and we have received several calls at the Lab of O from concerned nestbox owners regarding the plight of early season tree swallows.

So, if it’s such a craps shoot, why take the chance?

Well, as the saying goes, the early bird gets the worm. The first birds to arrive get first crack at the available habitat, staking their claim and marginalizing the latecomers. The importance of these claims cannot be understated: in many species, females tend to choose the males that have the best territory, and the best territories tend to offer the greatest amount of resources to the adult birds and their rapidly growing fledglings. Since both of these influence a bird’s “fitness” (or how many offspring (i.e. genes) it passes on to the next generation), you would expect there to be strong selection on walking that razor-thin wire between arriving too early (and dying) and arriving too late and having less or no offspring because the prime real estate has been taken. Sort of a “damned-if-you-do, damned-if-you-don’t” situation.

AMRO landscape

(Male American Robin taking shelter from the storm in a black alder thicket)

This evolutionary trend can also interact with migration strategies and changes in resources over time to exploit new habitat. The best example of this is the Blackcap, a European bird that traditionally winters in northern Africa, migrating across or around the Mediterranean. Migratory behavior is inherited, and can show variation such that small percentages of many populations wind up migrating in the “wrong” direction, which is often a dead-end genetically (imagine, for example, the short lifespan of a Red-winged Blackbird that migrated north in the fall!)

In the case of the Blackcap, over the last 50 years there has been a new wintering population that has arisen to the northwest in England, and its continued persistence there is tied to bird feeders (or bird tables, as they’re quaintly referred to there). This migrating population has a shorter, easier migration than the continentally migrating Blackcaps, and as a result these English immigrants arrive on the breeding grounds earlier, in better condition than their North African counterparts, and produce more young (as scientist Stuart Bearhop, of Belfast, describes it: “It’s a bit like getting their towels on the best sun-loungers first.”) Interestingly, these Big Ben Blackcaps appear to prefer punctual Blackcaps from Brittania, and this reproductive isolation has been suggested to be the first step towards the divergence of one species into two.

EAPH awaiting

(Eastern Phoebe basking in the calm before the storm)

In any case, it can be heartwrenching to watch a Phoebe pump his tail as the snow piles up and he patiently waits for something to eat. These early season ambassadors are like extreme sports junkies, living on the edge, and from time to time something more extreme occurs that millions of years of evolution hasn’t quite gotten dialed in. Although I know it happens, it won’t stop me from rooting for them anyway…





Newsworthy nuthatches

20 03 2007

A walk through the woodlands after a fresh snow can bring a needed meditative silence at the end of a busy day. But sometimes silence is short-lived, and if you’ve ever found yourself suddenly surrounded by a flock of scolding chickadees, then you know what I mean! The flipside is that, if you’re ever looking for something interesting in a woodland that seems devoid of birds, listen carefully and you might be rewarded with the buzzy alarm calls used by many of the resident winter birds that live in groups.

BCCH spectrogram

(A spectrogram of the “fee-bee” of a chickadee followed by two buzzy “chick-a-dee” calls, each with 4+ “dee” notes, suggesting a mobbing call)

These alarm calls are like an auditory advertising billboard; with a dominant mid-range frequency, they are repetitive and loud, and it is easy to home in on their source. And often, what you find at that source is something, well, alarming (at least to a chickadee), like a small owl or an accipiter (e.g., the Cooper’s Hawk below).

coopy

It turns out that birders aren’t the only ones using these advertisements to find potential predators. In fact, up to 50 different species have been noted to respond to chickadee alarm calls, and they typically join the group of scolding chickadees in a behavior called “mobbing“. The ultimate function of mobbing is unknown, but past studies have suggested that it may be a social tool to identify predators and/or an advertisement to a predator of the mobbing bird’s knowledge of the predator’s presence. Mobbed predators have been shown to depart more quickly (there’s a neat movie here) than un-mobbed predators, which suggests that resident birds can affect a predator’s foraging habits simply by ruining it’s chances of a surprise attack (and an easy meal). Other animals are known to perform advertisements of their knowledge of a predator’s presence, most notably the “stotting” performances of Thomson’s Gazelles that inform a lurking cheetah that it has been spotted, and a difficult, energy-intensive hunt will result if it proceeds.

rbnut

Enter the newsworthy nuthatches…

A researcher at the University of Washington recently published a paper detailing the behavior of red-breasted nuthatches exposed to chickadee mobbing calls. Nuthatches are common members of winter flocks of forest birds, and you might expect that they would respond to the alarming calls of chickadees (which they do). The interesting part of the story is that nuthatches respond more strongly to alarm calls made while chickadees are mobbing a pygmy owl (an important predator of small birds in the West) than alarm calls broadcast while chickadees mobbed a great horned owl (a virtual non-predator). The structure of chickadee mobbing calls change with the threat level presented by a predator, with the number of “dees” and the calling rate increasing as the potential threat increases.

So next time you find yourself listening to the eponymous calls of the chickadee, listen carefully like a good nuthatch and you might find that you already know what all the fuss is about: “dee” is for danger!





Feathers + Food = Warmth?

14 02 2007

snowy cardinal

While sitting in my cozy house, furnace on, fleecewear engaged, and a cup of tea at my side, I could see the snow piling up outside the windows and a flash of dark wings every few seconds from near the birdfeeders. Temperatures hovered in the single digits since this morning, with wind chill below zero, and about a foot of snow had accumulated since I fell asleep last night. Those dark wings flashing by tugged at my conscience even upon awakening, motivating me to get out of bed and top off the sunflower and suet feeders that I provide for feathered visitors. And on days like today I am always astounded that there are any birds left alive, especially considering that most species common to central New York woodlands weigh somewhere in the vicinity of 10-25 grams (think of the weight of 2-5 nickels)!

So…When faced with sub-freezing conditions and 20-30 inches of snow, what’s a bird to do?

I would humbly suggest picking up a copy of

The Contemplative Nuthatch’s 5-Step Guide to Surviving the Winter

(illustrated & abridged version)

ATSP pair

1. Get some friends to hang out with, especially if the weather is crummy. Ever notice that nearly all of the birds that hang around in the winter do so in flocks? Having other birds around makes it less likely that something will eat you; more eyes = less chance of a predator sneaking up. Plus, if something does sneak up, you only have to be faster than the guy foraging next to you! Friends are also good at letting you know where the primo food is.

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WBNU at suet

2. Eat. Park yourself in front of a feeder, some seedy plants, or anywhere there is food (preferably the heaviest, fattest foods possible, like black-oil sunflower and suet, yum!) and consume. If anyone gets in your way, pound them and keep eating–unless, of course, they pound you, in which case you should get out of the way. However, don’t eat too much, because it also makes you slower and more likely to get eaten.

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BCCH snow

3. When you can’t eat more, get puffy and rest. Those down feathers are perfect for trapping a warm insulative layer of heat. If you get the chance, tuck a foot or a whole leg up in there. And if you’re a woodpecker–tough luck, because you don’t have any down feathers.

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Downy hiding

4. Stay out of the wind. Here’s an important hint: if the wind is blowing, go to the other side of the tree and avoid it. Seems simple, right? But it works–trust me (or, if you can’t trust a nuthatch, perhaps you’d find solace in Dr. Grubb’s concisely titled 1977 treatise “Weather-dependent foraging behavior of some birds in a deciduous woodland: horizontal adjustmentsin .pdf form) .

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chickerdee

 

the full monty

 

 

5. Roost in a cavity, if at all possible. You’ll never find a warmer spot to sleep than in your own down feathers, nestled in a nook so small that your tail feathers get bent! Old woodpecker cavities, crannies beneath the eaves of houses, even a tunnel in the snow…They’re all warmer than sticking it out in the unforgiving, willies-inducing darkness of night.

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CAWR puff-snow

Finally, whenever possible, combine guidelines 1-4 for the ultimate in energy-saving & crop-filling goodness (steps 2-4 illustrated here by this fully puffed carolina wren, perched comfortably within bill’s reach of a larder full of peanuts and in the lee of the peanut feeder).

PS-To everyone who has inquired about the status of the pair of carolina wrens frequenting my feeders, they have persevered despite winter’s arrival, and appear to be roosting in a large downed tree in my backyard. Keep your fingers crossed…