Double (and triple) exposure

Setting my camera up at the window opposite the bird feeder and shooting at its fastest rate (10 frames per second) allowed me to capture birds in motion flying to and from the feeder.  The House Finches were leisurely about their arrivals and departures, so combining images using SnapSeed photo development software nicely illustrated the flight mechanics involved in a landing in one male House Finch.

Male House Finch landing on a feeder

Same bird, multiple exposures overlain on one image…3 exposures = approx. 0.3 seconds for this particular landing. Note brakes (wings outstretched) applied at the very end of landing.

White-breasted Nuthatches are not only bigger birds (thus taking up more space in my camera’s limited field of view), but came in much faster and departed much more quickly than the finches.

White-breasted Nuthatch landing on a feeder

Not a particularly good landing. It looks like the bird landed a little short of upright, but then they seem to prefer being upside down most of the time anyway. Wings flared much earlier than the finches did to slow their entry speed.

White-breasted Nuthatch leaving a feeder

Got the peanut, and then poof! the Nuthatch is out of the frame in less than 0.2 seconds.

But those little Chickadees are really tough to capture.  They flew in quickly, grabbed a seed or a peanut and departed just as quickly.  I rarely got more than one image of the same bird on approach to the feeder, which meant they were entering the camera’s field of view in less than 0.1 second.

Black-capped Chickadee arriving at a feeder

The Chickadee is using its wings to slow its approach much earlier than the House Finch did, a good indication of the speed with which they move toward the feeder.

Black-capped Chickadee leaving a feeder

And off the Chickadee goes with its treasure…quickly

I guess if you’re little and vulnerable, you need to be quick. And Chickadees definitely are that, quicker than my eye can follow.

Snowy portrait

A great surplus of the fluffy white stuff has been accumulating in the backyard this past week, and there are predictions of more to come.  Squirrels have been busy excavating in the snow looking for fallen seed.  Every now and then, they seem to take a break and just hang out on a branch.

Red squirrel in snowfall

Red squirrels are usually dashing around the backyard, scurrying up branches, hopping from limb to limb. This one stopped for a short rest.

Red squirrel in snowfall

The more typical view of red squirrels, i.e., just before making a mad dash up a branch.

I don’t know what this frantic chasing up and down branches is all about, but I did notice that the red squirrels run toward birds in these same branches that have just come back from the feeder with a seed or a peanut.  Maybe they are hoping the birds will drop whatever they are eating and fly off, leaving the tidbits for the squirrels to find?

How do birds predict the weather?

I’ve noticed that the frenzied feeding activity at bird feeders (see yesterday’s post on “finch feeding frenzy“) usually coincides with a precipitous drop in temperature the next day, but I’ve wondered what enables birds to predict that occurrence.

house finches and goldfinches

Sure enough, the day after I photographed the finch feeding frenzy, the overnight temperature dropped from 20 F above zero to -10 F below. Moderate winds added to the chill making the effective temperature for us humans about -30 F!  No birds visited this feeder the next morning until later in the afternoon when the sun had warmed the air up to just about zero degrees F.

Cardinals, Blue Jays, Nuthatches, Chickadees, Slate-colored Juncos, House Finches, and Goldfinches all made an appearance at the bird feeder during the morning hours the day before the frigid temperature drop.

cardinal and goldfinch-

Mr. Cardinal didn’t stay long — the finch mob must have scared him off.

white-breasted nuthatch-

Nuthatches zoom into the feeder, pick out a peanut treat, and zoom off, while the finches just sit and gobble up sunflower seeds.

But it’s not the temperature drop the birds are predicting, it’s the drop in barometric pressure. Low barometric pressure in one area means there will be air movement from a higher pressure area, and in the winter, that usually means Minnesota will receive a big blast of frigid Canadian air.

And the data bear this out:  barometric pressure reached a low point at noon on the day of frenzied finch feeding and increased almost 30 mm by midnight the next day, bringing with it bright sunny weather but a 30 degree drop in air temperature.

It seems that birds are the only land vertebrates (with a couple of exceptions) that possess a paratympanic (i.e., next to the ear drum in the middle ear) barometric sense organ, and it is derived from the same hair cells in sharks and their relatives that provide those fish with information about their jaw movement relative to the prey they intend to gobble up.

black-capped chickadee-

Chickadees and Nuthatches go for the high energy peanut treats in preparation for a blast of cold weather.

So, is a 30 mm change in barometric pressure (a little over 1 inch) enough to trigger such a feeding response in my backyard finches?  Yes, it is.  Experimental data on White-throated Sparrows showed that they could detect a pressure change of as little as 10 mm:  when barometric pressure was decreased artificially in a chamber holding migratory sparrows, they immediately began feeding when the lights were turned on; when the pressure was higher (and normal), they became active, preening and hopping around in the chamber, but not feeding.

And why is it just the birds that have evolved this magnificently sensitive sensor?  In addition to predicting weather fronts, the barometric sensor is most useful for maintaining level flight at a particular altitude during migration.

What about mammals, especially humans?  Can we detect changes in barometric pressure?

gray squirrel foraging in a snow bank

Gray Squirrels were out in numbers looking for seed scattered in the snow by the finch mob.  Did they know what was coming the next day?

Only one species of bat possesses a physical sense organ that detects barometric pressure, but mammals, including humans, can sense changes in pressure in their ears, sinuses, sometimes joints, but there is no specific receptor for the sensation.  Rather it is changes in pressure within a confined cavity that elicits the sensation, and not in everyone.

Finch feeding frenzy

The behavior of my backyard birds is often just as telling as the latest weather report.  Judging from the frenzy of activity going on at the bird feeders today, the thermometer must be headed for negative numbers again.

house finches and goldfinches-

There must have been 2 or 3 dozen House Finches and Goldfinches mobbing this feeder in waves.

house finches and goldfinches-

A few waited their turn in the bushes opposite the feeder…

house finches and goldfinches-

Most of the time the birds took turns amicably.

house finches and goldfinches-

But there’s always a bully in the bunch. The red-headed male House Finch at top right tried moving a female House Finch off her perch.  But she beaked him once or twice and he moved away.

house finches and goldfinches-

Moments later, he was over on the left side of the feeder trying to move a male House Finch away from his perch. But he lost that battle, too, and flew away.

house finches and goldfinches-

I never realized how pretty Goldfinches are in flight with their striking black and gold wings.

The finches monopolized the feeder continuously for 10-15 minutes and then disappeared for an hour or two.  Then the frenzy started up once more, but again dissipated.  It must take quite a while to move all that bird seed from their crop and stomach into the lower part of the intestine for digestion.

When it’s too cold to grab a peanut

The porch thermometer read -10 F (-23 C) and there was bright sun in the backyard, but there were no birds and no squirrels present at or under the feeders.  Finally about 10 a.m., the first foragers appeared.  The thermometer had worked its way up to just under 0 degrees F (-18 C), but the wind was blowing, so windchill temps would be well below 0 F.

male northern cardinal-winter plumage

Mr. Cardinal monitored the surroundings while Mrs. Cardinal foraged at the bird feeder.

female northern cardinal

She is finding the discarded sunflower seeds left by the chickadees and nuthatches who pitch them out of the feeder in search of peanuts instead.  The wind is fluffing out her feathers, but also carrying away her body heat.

White-breasted Nuthatch stashing a peanut

This White-breasted Nuthatch is stashing a peanut in a bark crevice, where it will hammer at it until it breaks off pieces it can eat.  I wonder if the crevices are more apparent when they are upside down, or it’s easier to break them up when they come at it upside down????

White-breasted Nuthatch stashing a peanut

After much hammering away, the Nuthatch has reduced the peanut (directly under its beak) to just a small chunk.

White-breasted Nuthatch basking on a cold morning

You know it’s cold when you see a Nuthatch pause for several minutes in its foraging efforts to bask in the sunlight. The bird’s back was directly facing the morning sun.

Black-capped Chickadee

Peanuts are the preferred high-energy foods on subzero days.

Black-capped Chickadee drilling a peanut

The Chickadee’s method of eating the peanut is much different — grasping the nut with its foot, the bird drilled into it to break off small chunks.  But peanuts at -10F must be brick hard, because this bird drilled it over and over and was only able to break off small bits.  After much effort it finally flew off with the nut, perhaps to its roost hole.

American Goldfinch and Black-capped Chickadee

The Goldfinch watched the Chickadee eating a peanut but made no attempt to go find some food for itself at the feeder.

Two birds exhibiting contrasting strategies for surviving harsh winters in the northern temperate climates:  Goldfinches turn up their metabolic furnace to keep their body temperatures stable on extremely cold winter nights; they do this by harvesting fat-rich seeds (like sunflower seeds) and keeping their fat reserves high.  Chickadees are primarily insectivores that do eat seeds in the winter, but typically conserve their internal fuel resources by lowering their body temperatures at night — just in case they need it to find food the next day.

Black-capped Chickadee

The heartiest of little winter birds…Chickadees are survivors!

By noon, the wind had picked up, and the temperature had dropped again, on its way down to an overnight low of -27 F (-32 C), and I didn’t see birds at the feeder for the rest of the afternoon.  I hope they survived overnight!

Frosty pane

It’s -21F (-29C) and the temperature is still dropping. My kitchen window is completely covered with “fern feathers”.  The ice crystals have grown from single stalks to full fledged sheets of ice as the temperature outside the window drops.

frosty pane

Initial formation of crystals enlarges quickly in the intense cold.

frosty pane

The ice crystals sort of resemble palm fronds that have fallen to the ground.

frosty pane

More Cranes at Sunset

Looking over the photos from our recent trip to the west coast, I remembered I had shot some video clips of the Sandhill Cranes arriving at their overnight roost on the Rio Grande floodplain at Bosque del Apache, New Mexico.

It was an all-too-brief encounter, but the video will give you an idea of what it was like…

They have an impressive wingspread when you see them up-close.

Sandhill Cranes, Bosque del Apache, NM

Should have stayed in Arizona!

Minnesota’s weather for the coming week is why I should have stayed in Arizona.

Weather forecast

I could be looking at this landscape.

Catalina State Park, Tucson

Catalina State Park, Tucson

Catalina State Park, Tucson

And enjoying some different sorts of birds like this…

Female Ladder-backed Woodpecker

Female Ladder-backed Woodpecker on mesquite.  This is a smallish woodpecker that hunts insects on cactus and low shrubs as well as in pinyon pine and juniper at higher elevation.  It pays to be a little smaller and more agile in the desert where the bird has to navigate various cactus spines and bush thorns in its search for prey.

Black-throated Sparrow

Black-throated Sparrow, aptly named, but often referred to as the desert sparrow,  because it is the typical sparrow seen in the most arid of desert scrubland where it finds enough seeds and insects to sustain itself.

Vermillion Flycatcher

Male Vermillion Flycatcher, a diminuitive flash of color in arid desert greenery.  They can be found in riparian areas in the southwestern U.S., and southward through Mexico, often sitting on a favorite flycatching perch waiting for a juicy bug to fly by. 

Minnesotans love to joke about their weather.  A friend posted this on Facebook the other day…

Minnesota weather in “minnesotan”

Minnesota weather in “minnesotan”

Mammals in the living desert

Although it is far easier to find birds in the southwestern deserts, more than 100 mammal species live there too, a few in some of the harshest and most challenging environments.  Most are usually active only at night or in the twilight that precedes sunrise or follows sunset.  Why?  Because daytime temperatures can be very hot, water is limited so keeping cool by evaporation is dangerous, and there aren’t very many places to retreat to cool shade.

Sonoran desert at Palm Desert, CA

No place to hide from the heat in this leafless, spiny forest of cactus, unless you’re a small, burrowing rodent.

Mammals cope with the heat by avoiding it, storing it, unloading it, or offsetting it by consuming the water-filled bodies of their prey.  Here are a few examples of these strategies in mammals of the Living Desert Zoo in Palm Desert, CA.

Avoiding the heat: bats, rodents, kit fox, coyote, mountain lion, bobcat

Big carnivores need to retreat to sheltered crevices or caves during the hot daytime hours, while mice can keep cool in underground burrows.  Their dense fur is an adaptation to keep them warm on clear, cold desert nights, and in the winter.  In addition, water lost by panting to keep cool can be replaced by the body water in their prey.  Their home range might even include a water source like a spring or pool.

Mountain Lion, Living Desert Zoo, Palm Desert, CA

Bobcat, Living Desert Zoo, Palm Desert, CA

Coyote, Living Desert Zoo, Palm Desert, CA

Storing the heat: pronghorn antelope, bighorn sheep

Large-bodied herbivores can’t escape the heat, so they tolerate it by storing it in their large body mass, and allowing their body temperatures to fluctuate several degrees over the course of the day.  Heat gained during the daytime can be unloaded by radiation or convective cooling at night.  Bighorn sheep can withstand dehydration for several days (to a level that would kill a human) and can replenish all of their body water immediately upon drinking.

Pronghorn Antelope, Living Desert Zoo, Palm Desert, CA Bighorn Sheep, Living Desert Zoo, Palm Desert, CA

Unloading the heat:  jackrabbits, mule deer

Both deer and rabbits seek shade during the day, but use their very large and well vascularized ears to radiate heat away from their body.

Mule deer, Living Desert Zoo, Palm Desert, CA Jackrabbit, Living Desert Zoo, Palm Desert, CA

Fennec foxes from Saharan and Arabian deserts use a similar strategy to unload heat from highly vascularized, over-sized ears. Apparently the large surface area of their ears also helps them hear prey moving around under ground.  It’s interesting to see such convergence of strategies in unrelated animals from different continents.

Fennec, Fox, Living Desert Zoo, Palm Desert, CA

And what about the unlovely Javelina?

Javelina, Living Desert Zoo, Palm Desert, CA

They look ill-suited to be desert dwellers with their short extremities, stocky bodies, and bristly hair.

Their solution to the challenges of desert life?  Live near the water and stay in the shade, for example, under a trailer!