Crypsis

Recently, I wrote a post about hiding in plain sight, but today I saw a much better example of this type of camouflage when a little Brown Creeper visited the Buckeye tree outside my sun porch window.

The Brown Creeper’s white breast feathers resemble the snow that still clings to some of the branches of the tree, and its mottled back feathers blend in perfectly with the bark.

Only slightly more obvious lower down on the tree, the bird spiraled its way up from the base of the tree, while poking into crevices along the way.  I can’t imagine what it could find on a day like this when the temperature was  -12 F (-24 C)

This tiny little bird weighs only half as much as a Chickadee. It’s hard to imagine how they survive the bitter cold winters of the northern Great Plains.  I assume they do find some little critters in the cracks and crevices of the trees they explore. Eating just one tiny spider will sustain them for another few hours of foraging.

One naturalist wrote about them:  “The Brown Creeper, as he hitches along the bole of a tree, looks like a fragment of detached bark that is defying the law of gravitation by moving upward over the trunk, and as he flies off to another tree he resembles a little dry leaf blown about by the wind.”  Which is exactly what I saw today.

A little creeper

A rarely seen bird (for me) was hunting insects or spiders on a live oak, and I stopped to watch while it foraged.

Brown Creepers (Certhia americana) are cryptically colored small bits of fluff that spiral up and around the trunk ad branches of a tree, continuously moving, in and out of shade and sun, stopping only for a fraction of a second to explore tiny crevices for their hidden prey.

The Cornell Lab of Ornithology website has a great quote that summarizes the peculiarities of this tiny bird wonderfully:

“The Brown Creeper, as he hitches along the bole of a tree, looks like a fragment of detached bark that is defying the law of gravitation by moving upward over the trunk, and as he flies off to another tree he resembles a little dry leaf blown about by the wind.”

Part Woodpecker, part Nuthatch in behavior, they have their own unique style and anatomy.

Their stiff tail feathers prop them up on the tree bark, and their very elongated big toe (hallux) opposes the other three toes to help stabilize them vertically.  The slightly decurved bill is useful for probing into miniscule cracks in the bark of the trees.

Brown Creepers are actually fairly common and year-round residents over much of the U.S. (except the Great Plains) and western Canada, but are rarely seen because they are so cryptic and so quiet.  Spotting what looks like a piece of bark moving in a jerky spurts upward around a tree trunk might lead to sighting one of these cute little brown jobs.

Blending into the bark on which it forages is a good survival strategy.

Note:  I’m back in the deep freeze of Minnesota now, where the temperature was -21 F (-30 C, not counting whatever windchill factor decreased the temperature even more) the night I arrived, an 85 degree difference from the sunny California weather a few hours before.   The Minneapolis paper headline read:  “Brrrrrutal” the next day.

Don’t eat me!

There were a total of 15 Black Swallowtail caterpillars munching on my dill patch this past couple of weeks — not much dill is left.  Now, the mature larvae are about 1 1/2 inches long, and their little round bodies look like the perfect food for the insectivorous birds around here.  But the birds leave them alone.  Why?

Don’t I look tasty?  No, as any bird brain can tell you, yellow and black means “stay back!”

True to that old saying, “you are what you eat”, swallowtail and other caterpillars sequester their host plant’s noxious chemicals in their own bodies, which makes them unpalatable.  (It’s not just the Monarch Butterfly that can do this!)  And they have an added defense just under the skin of the back of their head where two fleshy projections emerge, when the head is touched lightly, to spray bad-tasting terpenes in the face of the would-be predator.   I discovered this interesting feature by accident and managed to photograph the 1 second deployment of the caterpillar’s “horns”.

Bright orange warning flags go up when the head is touched lightly. Unfortunately the display only lasts a couple of seconds.

Unfortunately (for the photographer), the wind was blowing and it was rather cold for caterpillars, so these warning displays were not as active as they might have been.

The first caterpillar got tired of me poking it in the head, so I tried a different individual, who was really too cold to give the flag raising much effort.

The younger larvae of this caterpillar apparently don’t use this chemical defense, and are not as unpalatable because they haven’t eaten enough of the host plant. So they mimic a bird dropping instead, hoping to avoid detection.  In addition, spines projecting from their skin are irritating to tender bird mouths.

Photos by Bob Moul

However, by far the most aggressive defense by caterpillars I have read about is that of Lonomia obliqua, the exceptionally hairy larva of the Giant Silkworm Moth.  if the hairs break off and become embedded in human skin, they cause a chain reaction that basically causes the individual to bleed to death internally.

Caterpillar of the Giant Silkworm moth, Lonomia obliqua. Its hairs contain potent anti-clotting agents.  Stay away from this one!!  Photo by Terra Vermelha.

As more tourists visit the Amazon region where this species lives, there are more reports of envenomation by stepping or brushing against the caterpillar, with subsequent hemorrhagic shock and death just days later.  You can read more about this beast here.

Finch vs Sparrow

I see that my bird classification skills are sadly out of date.  Today I found out that the Indigo Bunting is grouped with the Cardinals, Rose-breasted and Black-headed Grosbeaks, and Flame, Scarlet, and Hepatic Tanagers.  How confusing!  For some reason, I have always lumped little birds with conical (finchy) bills into one group, when in fact, there are definitely two:  finches and sparrows (and then of course, one can further split those two categories into old world (Europe-Asia) and (New World – Americas), but I won’t go there in this post.

So, here’s the low-down on what to call the little finch-like birds in your garden.  (Like all rules, there are, of course,  exceptions to these generalities.)

1) If the male is brightly colored in his summer plumage but the female duller, resembling the winter plumage, the species is likely to be a finch, e.g., Goldfinch, House Finch, etc.

This male hasn’t quite finished decking himself out in yellow and black, but he’s close.

Male House Finches really stand out at this time of year.

Female House Finches have some nice stripes, but lack the brilliant red accent colors of the male.

2)  Sparrows of both sexes sport a mottled brown, black, and white plumage that blends in nicely with their preferred grassy habitat.  Only the juvenile (first year after hatch) birds look different than the adult plumage.

This Swamp Sparrow was singing up a storm, but it was hard to locate him among the dead cattail stems and grasses.

Male and female White-throated Sparrows look identical, but the first year birds have brown head stripes and lack the yellow spot above the eye.

3) Typically, sparrows feed mostly on the ground, scratching under the litter for seeds or insects, while finches are more arboreal, searching for food on the seed heads of perennial grasses, thistles, etc.

Even though there is a feeder full of delicious finch seed right above this bird’s head, it prefers to look in the grass for fallen kernels rather than perch on the feeder.

A photo from last summer illustrates the plumage difference between male and female Goldfinches, as well as their preference for perching on the flower heads to harvest the seed.

4) It may be difficult to see differences in the shape and size of their bills, but finches generally have a stouter, thicker bills for their body size than sparrows.  That rule seems to work if you compare House Finch bills to those of Swamp Sparrows, but it looks like White-throated Sparrows have a pretty thick bill as well.

As I said above, there are exceptions to every rule…but at least I won’t be calling all seed-eating birds sparrows now without thinking about it first.

Sooty Grouse in the backyard

I stepped outside the door to go hiking on the Tahoe Rim Trail near sunset, and ran into a family of Sooty Grouse (hen and four young).  For those who know their birds, these used to be called Blue Grouse, and they do have a small amount of blue showing on their breast feathers.  But overall, this bird does an amazing job of blending into its coniferous forest floor background.

Mother hen led her offspring across the road and up into the forest.

Note how well the young grouse blends into the background.

Sooty Grouse live in montane foothills, near the coniferous border, and range from northern British Columbia along the coast to northern California and all along the Sierra Nevada mountains.  They are permanent residents where they occur, but have the strange habit of actually going to higher altitudes in the winter (contrary to most other species).  They are quite omnivorous in the summer, eating a varied diet of insects, berries, and leaves, but in winter they subsist on a diet of Douglas fir, hemlock, and pine needles.  In order to balance their winter energy budget on such an indigestible diet, their gut elongates and they grow a large fermentation chamber in the part of the gut analagous to our appendix (theirs is called a cecum).

To maintain their cryptic coloration in the winter, their newly molted feathers are a grayish white color, so they blend nicely into the winter snow.

In the spring, the male molts new, bright brown and gray feathers, and develops brightly colored vocal pouches on either side of their neck which they inflate while spreading their tail and parading in front of the female.

photo from Avian Web