February 6, 2022: A Bluebird Invasion

Forget Ukraine, the invasion is happening right here!  This week a flock of over 20 bluebirds has stormed into the area, being observed by many people around the lake and it's quite a treat to see them with their bright blue color in winter when most other birds have replaced their summer plumage with more practical, safe, muted plumage.

Eastern Bluebird

This is the first time we've had bluebirds at our feeders though I know others in the area have seen them.  Some range maps (e.g. Cornell) still show their year-round range south of Massachusetts, but we had seen them in southern New Hampshire for years.  Other maps (e.g. Audubon) do show their year-round range extending up to central New Hampshire.  

Eastern Bluebirds feed primarily on insects but in winter their diet consists of fruit and a very diverse set of berries; it seems only in recent decades that they've started to partake in the seeds of birdfeeders.  

Bluebirds aren't picky at the feeder - large or small, seeds are now readily consumed.

It was a cold morning when we first saw them, near zero, and after filling their bellies some of them found a most endearing way to keep warm.

Keeping warm - and keeping watch in all directions.

Bluebirds, like all birds, have no blue pigment in their feathers.  To present their blue color their feathers take advantage of the wave properties of light.  There are tiny air pockets in the cells of the their feathers that have the right dimensions to reflect light such that blue light reflected from each pocket all lines up "in-phase" while other wavelengths are reflected randomly.  Thus the blue wavelengths are reinforced while other colors are diminished, resulting in the bright blue color that our eyes perceive.  [Ref:  Sibley, 2020, What it's like to be a Bird, Knopf, pg. 133]

Blue light is reinforced by a unique feather characteristic.

Blue light is at the short-wavelength end of human's visible spectrum, right up against ultraviolet light, which got me wondering if bluebird feathers might also reflect some UV wavelengths.  Looking into this I found that many birds do see in the ultraviolet spectrum, and in fact use that trait in interesting ways including some that explain avian abilities that had stymied scientists until this was studied.  That's a topic for the future; I have much more I need to learn on that subject, and there was a lot more going on this week to be shared.

We have a spring that flows year round which we let collect in a small pool well protected by hemlock trees and we often see birds and squirrels drinking from it all winter.  But this winter there have been holes in the ice that have opened up - the reason is unknown to me - but they are in fact open all the way through the 14" of ice on Lake Wicwas at this point.  And the bluebirds seemed to prefer this water source, right out in the open.

Three bluebirds take a drink.

That seems like an unnecessary risk considering the known presence of many predators such as bobcats, hawks, and the kestrel we saw a few weeks ago which is especially adept at catching birds.  And there was proof this week of the danger.  On a cross country ski excursion this week I came across a fresh bloody mess beside the trail which had all the indications of gray squirrel meeting its demise at the talons of a raptor.  

Sign of a very recent kill.

Bits of gray fur make me think it was squirrel.

I expected to see more remains of the animal on the ground, but then looking up I saw a big branch hanging right over the spot, a perfect perch for a raptor to feast upon its prey.  Perhaps the rest of the animal was taken off to share with its mate, or maybe I disturbed it and it flew off unnoticed to another dining location.  

Assuming the victim was a squirrel, it's not the last one; the second invasion this week was a ground assault.   The gray squirrels have stormed the yard in force - at one point there were eleven of them out under the feeders even after that one had departed from the land.  

Plenty of squirrels still abound.

And then, another new bird appeared at our feeder during Friday's snow - a pine siskin.

Pine Siskin

This was the third wave of the invasion; I only saw a few but another bird watcher (thanks MT!) reported a huge flock of them at their feeder, so many in fact that they emptied their bird feeder three times in one day.  

If I have seen a pine siskin here before I didn't identify it.  Unlike the easily recognized bluebird, the pine siskin is rather non-descript and I first thought it was a sparrow, but a key identifying feature is the slight yellow band along the edge of its flight feathers and its tail.

You can just make out the yellow bands on the edges of its wings.

The yellow bands are seen in flight but are barely visible when perched.  The pine siskin's beak is also thinner and sharper than a finch's beak.

A sharp, pointy beak.

Also in contrast to the southern-ranged bluebird, the pine siskin is a northern bird, living year-round in Canada and very northern New England, and breeding even farther north from Newfoundland in the east all the way across the continent to Alaska.  According to my new Audubon book (thanks VP!) they move southward when seed crops in the boreal forests are poor.  One of their favorite seeds is that of the hemlock tree so maybe the bumper crop of hemlock cones around the lakes this year will keep them in the area.

Even though I've gone on too long with all the nature sights, I can't let the week go by without a note on the disappointing effect of the weather on the Pond Hockey tournament.  Friday's games were cancelled due to unplayable ice conditions, and then on Saturday the entire tournament was cancelled due to unsafe ice.  According to their report, the weight of pushing the heavy snow from Friday's storm into piles to clear the rinks was so great it was causing the ice to sink and crack and lake water was coming up onto the ice.  They removed all their equipment and gear and had to cancel the entire tournament.  The coming week is forecast to be mild but hopefully it will be cold enough for everything to freeze up for the fishing derby next weekend.  

So on a happier note, I'll close with one more look at those beautiful bluebirds!