Playtime in the backyard

Just as the daylight was fading in the backyard, I spied a young fox chasing a very immature, small rabbit around the backyard. This young fox wasn’t interested in eating the rabbit, but certainly seemed to enjoy the chase. All the better to hone its predatory skills. The rabbit did what prey instinctively do when threatened — sat as still as a stone, until the fox turned its head, at which point the rabbit tried to escape. It was quite comical to watch!

Half-grown fox dares the bunny to hop while it is spread-eagled next to it.
Maybe if I poke the bunny…”
“Maybe I’ll just ignore the bunny…”
C’mon, let’s play chase…”

Color me green!

When I went out to pick raspberries this morning, I found something much more delightful than a bunch of mating Japanese beetles (the scourge of the berry patch!) — a couple of 1-inch Gray Treefrogs hiding in plain sight on the green leaves of the raspberries.

From the side, this little one with its dark facial markings and dark lateral stripe was more obvious.

Although this species is named the Gray Treefrog, because they are quite gray with a dark blotchy pattern sometimes, in bright sunlight on a green background, they are well camouflaged as they match their background. In fact, this frog even matches the particular shade of green of the raspberry leaf on which it rests.

I wonder if they eat Japanese beetles? There are plenty of other insects resting on the raspberry leaves for these little guys to dine on. But these frogs are really only active at night, and usually seek shaded vegetation for their daytime rest.
The color matching camouflage is impressive in both the shade (this photo) and the sun (photo above).
How exactly does a gray treefrog become green?
Looking more like the gray treefrog, I photographed this maxi-sized (2.5-inch) adult in the early morning while it was sitting under an evergreen in the leaf litter.

Frog skin contains a stack of color-producing cells called chromatophores, and many frog species like the Gray Treefrog, have 3 sets of them: a deep layer called melanophores that contain a black/brown pigment called melanin, an intermediate layer called iridophores that lack pigment but contain particles that can reflect blue light, and an upper (most superficial) layer called xanthophores that contain yellow pigment.

Now, it should be more obvious how a Gray Treefrog can transform quickly from its gray color that is produced by the dispersion of deep-lying melanin pigment to a bright green color, produced by the interaction of blue-reflected light from the iridophores passing through the yellow pigment of the xanthiphores (i.e., blue plus yellow equals green to our eyes).

The dispersion of pigment in frog skin is controlled by nerves and hormones, which act on the chromatophores to aggregate (condense) or disperse pigment. Physiologically, in a matter of seconds, when melanophores aggregate their pigment to uncover the iridophores and xanthophores disperse their pigment, a gray frog turns green!

Color changes can even happen while frogs are sitting in the dark in my covered water tank. It just depends on their physiological state, the temperature of their environment, and the amount of hormonal or nerve stimulus they are experiencing.

Blooms in the backyard

In the Minnesota backyard, some of the summer blooms are in their full glory, particularly the purple coneflower. Butterflies and bees are drawn to these flowers…

A Great Spangled Fritillary stopped by…
And examined each of the disk flowers in the flower head intensively.
I caught the approach of one of the honeybees buzzing the coneflowers.
And was able to zero in on the bee when it landed.
Even the Goldfinches were checking on the flower heads, I suppose to see if they had made any seed yet. But these flowers have just opened up in the last few days.

Birds that blot out the landscape

We’re on the road again, taking our time traveling west to see how many bird species we can find and photograph along the way. Today as we drove through the farm fields of north-central Iowa’s Lake District, we encountered a large flock of Red-winged Blackbirds doing an imitation of a murmuration of starlings, bunched tightly together as they burst upward from the fields, then turning and spreading apart before they landed again, and repeating the pattern over and over. Their numbers were impressive!

A ball of Blackbirds! (Photo by Debbie Reynolds)
It doesn’t seem like there is even enough room to flap, with neighboring birds flying so close together. It’s when we see densities of blackbirds like this that we appreciate their status as potentially the second most populous bird in North America (after the American Robin).
I didn’t realize until I zoomed in on the previous image that this flock was composed almost entirely of female Red-winged Blackbirds, who migrate north much later than the males do. No red-epauleted shoulders in this bunch.
Meanwhile, hearty male Red-winged Blackbirds, who arrived in cold Minnesota in early March to establish their turf for this next round of “the bachelor” Blackbird, have staked out a spot to attract several of the thousands of females that will soon be arriving at their doorsteps.

Recollection of Easters past

This blog has been cataloging the rebirth of Spring each year since 2012, so I thought it might be fun to look back at what I have posted on Easter each year. Since the dates of Easter vary so widely each year, and because we traveled to distant places some years, the landscapes of Easter scenes from the blog vary markedly.

The first Easter photo on the blog (April 8, 2012) was of eldest grandson holding a garter snake. A warm spring with the snow gone, the grasses greening up, and lots of animals emerging from “winter sleep”.
In 2013, Easter fell on the last day of March, and Minnesota still had a lot of snow and cold weather. That didn’t stop real Minnesotans from getting out to celebrate the holiday with a walk on a frozen lake.
In 2014, we were in northern California on Easter in late April (20) when I found a baby Scrub Jay poking its head out of nest. New life in the Springtime!
My Easter hike on April 15, 2015 at Grass Lake was rewarded with images of Ospreys mating, as the pair returned to rebuild the previous year’s stick nest on their 70 foot platform.
An early Easter on March 17, 2016 didn’t give us much to cheer about with winter conditions in MN, but I found some moss that was sprouting its spore capsules on a warm log in the forest at the Old Cedar Ave. bridge. The photo was taken with the magnifier app on my cell phone!
In 2017, we had traveled to Cave Creek ranch in southeastern Arizona where we found a Great Horned Owl roosting in a large tree in the parking lot of the local restaurant where we ate on Easter Sunday, April 16. I don’t know if this tree cavity had been its nest that year but it was quite a deep crevice in a huge tree trunk.
On Easter Sunday April 1, 2018, I posted my favorite landscapes of Peru where we had traveled during the previous month. This shot was taken on a 14,500 foot pass in the Andes on our way to Puna, Peru.
Easter Sunday April 21, 2019 found us traveling through the Wichita Mts. in Oklahoma on our way south to Texas for a bird photography workshop in Galveston. This mama Prairie Dog must have been feeding a lot of youngsters at this time in the spring season of rebirth.
Last year in 2020, we were at the beginning stages of a frightening year of death, and my Easter portrait of a Kildeer nest filled with fake Easter eggs was my attempt to bring a little smile to my readers.

A year later, the corona virus is still with us, but we look forward to Spring and the seasons beyond with more hopefulness and expectations than this time last year. I hope you feel the same, dear Reader.

nest competition

We made an unusual sighting today — a pair of Canada Geese defending their chosen nest site high in a canopy tree from passing Bald Eagles! What makes it unusual is that the geese had staked out a former eagle nest as their own, and were prepared to fight for it with a couple of immature and one adult Bald Eagle that flew by (the latter carrying a stick to add to its nest).

No amount of the Eagle’s threat from flying over or landing above these pugnacious geese could move them from their perch. Judging from the size of the nest, it could have been the place where the juvenile eagle flying above them was reared last year.

Fellow photographer Debbie was shocked that Canada Geese would nest anywhere but a raised hummock in or near a lake, and what were they doing so high up in this tree?

A more typical Canada Goose nesting site on a tiny island in a pond, safe from the marauding dogs, foxes, coyotes, raccoon, as well as Great Blue Herons.

But I had seen this behavior from the geese before:

One year, this nest platform belonged to the local Osprey pair, who added hundreds of large and small branches to complete the nest on a 60 foot tall platform.
The next year, a Canada Goose female claimed the Osprey nest platform before the Ospreys returned in the spring, and she successfully reared a half dozen chicks here. The ospreys have not used this platform since — perhaps because the geese beat them to it, and they defend it successfully.

So what is up with these geese nesting in what we think of as un-goose-like nest sites?

Going back a couple of centuries, during the late 1800s and into Depression Era 1900s, the “giant” race of Canada Geese (the big ones we mostly see today) were almost completely extirpated from North America by unregulated hunting, egg collecting, and habitat destruction. They might have disappeared altogether if it weren’t for a tiny population discovered in Rochester, Minnesota, in the 1950s and some captive birds being bred in Boone County, Missouri. Some of these geese were used in a captive breeding program in the 1960s, and by 1981, 6,000 geese were released to the wild at 63 sites to repopulate the “giant” race of Canada Geese throughout North America. It’s hard to believe today with the huge numbers of these geese that roam fields, parks, and wetlands that the species was almost an ornithological footnote.

The belligerent, aggressive behavior of territorial Canada Geese makes them anything but a footnote in ornithological history.

Now what does this history have to do with geese nesting in eagle nests and on osprey platforms? Observations of Canada Geese nesting high on bluffs above the Missouri River were recorded as early as the Lewis and Clark expedition of the river. But I think natural selection, especially the selection that resulted in culling their numbers almost to the point of extinction, could have played a part in explaining the flexibility of Canada Goose nesting behavior. The geese that survived the pogrom of overhunting were probably the ones that sought out remote places that were hard for hunters to get to, like cliff faces or raptor nests in tall trees. Survivors were probably the birds that used unpredictable and untraditional nesting places, not only to avoid being found, but because their traditional nesting sites had disappeared with human activity there. Today, Canada Geese nest in a variety of habitats, usually in wide open spaces with open fields of view: islands in rivers, the tops of beaver lodges and muskrat house, cliff faces, high nest platforms, and yes, raptor nests — even those of Eagles!

the tiny garden

A taste of spring hit the backyard as temperatures soared into the 60s the other day, and major amounts of snow melted. When I walked into the wetland beyond the backyard I was greeted with signs of life awakening after the long winter — like this tiny garden on a rotting log.

A tiny one-inch across mushroom nestled in among several different species of moss. Spore capsules of moss tower above the green vegetation — the better to spread their tiny spores to a new site on the log.
A second, even tinier mushroom is growing beside the bigger one. If I knew something about moss, I could tell you how many different species there are here in this 4 square inches of log.
A veritable forest of mossy leaves support the towering trunks of the sporophyte part of the plant with its knobby capsules waving in the breeze.
Meanwhile, a pair of Mallard ducks, keeping a close eye on me as I walk by, is taking advantage of early snow melt to rest in a shallow pond.

Synchrony

One of the fascinating things about bird migration is the patterns in which the birds fly and maneuver in a group as they move along. We are all familiar with the classic V-formation of bird flight, which we have been told is the most aerodynamic way for large groups of birds to fly together. But how exactly does the V-shape work, and how are the birds using it?

I happened to be sorting through a bunch of images of large birds flying in groups together and noticed that there didn’t seem to be a consistent pattern in their wing movements from bird to bird. In fact, it looked disorganized rather than the synchrony I had expected.

A flock of Canada Geese flew toward me in a quasi-V-formation in August, 2020. Young birds often “train” with their parents before actual migration begins, both to get their flight muscles in shape, and to learn how to fly efficiently in V-formation.
A different flock of Geese looked a little better organized in their V, but the wing flaps of individual birds didn’t match up.

In a unique study of imprinted young Bald Ibis that were being trained to fly from their breeding area in Austria to a wintering area in Italy, transmitters were fitted on the birds to provide data on their flight mechanics during V-formation flying.*

Bald Ibis chicks were imprinted on humans and trained to fly behind an ultra-light aircraft. Data from GPS transmitters attached to the backs of the birds was used to assess whether birds truly were making use of the V-formation for aerodynamic reasons. Photo from study by Portugal et al. 2014 in Nature.

Bottom line: what matters is how close and where (left, right, or center) a bird is relative to the bird in front of it. As the lead bird flaps down, it pushes that air up and over its wingtips; the bird behind can take advantage of that updraft (as lift) if it positions itself a certain distance behind and just to the right or left of the lead bird. Therefore, it doesn’t need to flap downward as hard in order to stay aloft. And that is the energetic savings of following rather than leading. How simple! But proximity behind the lead bird is critical, because the updraft from the wing tips is spatially limited.

Perfect wing synchrony in these Trumpeter Swans as they fly in a tight formation.

If you think of the pressure wave of the downward wing flap of the lead bird as a sine curve, the best lift is achieved if the following bird stays in the same place as the lead bird on that curve. It’s similar to the “push” you get by drafting at an angle off a bicyclist just ahead of you. Since the lead bird is continually flapping, the following bird must continue to flap in exactly the same phase in order to get the benefit.

Wing beats of lead and following birds are synchronous (in the same phase) when the following bird catches the “upwash” of air from the lead bird’s wing flap.

However, if following birds are too close or too far from the lead bird or directly behind the lead bird, synchrony is actually less efficient because instead of catching the upwash air, it might be catching the downwash instead — which would necessitate flapping harder and expending more energy.

Wingbeats are asynchronous and opposite (out of phase) when following birds are too close to the lead bird or flying directly behind them. In this case, the following bird positions itself to stay out of the downwash of the lead bird.
Flying close together makes more sense, as long as it’s not too close!

A fascinating summary of this unique study on the Bald Ibis appeared in Nature News, with a video that more clearly explains what I have tried to describe above.

*S. J. Portugal, et al. Upwash exploitation and downwash avoidance by flap phasing in ibis formation flight. Nature, 16 Jan 2014.

the prolific and versatile American Robin

American Robins rank third in numbers behind Red-winged Blackbirds and introduced Starlings as the most common bird in North America. To what do they owe their great success, compared to Cardinal and Bluejays, for example?

Note added after posting: Valerie Cunningham who writes a bird column for the Minneapolis Star Tribune uses a more reliable source for estimates of bird populations in the U.S. and Canada. According to the Partners in Flight Database, the American Robin is THE most numerous bird in North America, at an estimated 370,000,000 birds, far outpacing the Red-winged Blackbirds (160,000,000) and Starlings (86,000,000). So that makes what I have said below even more impressive!

An American Robin eyeing the few remaining fruits available at this late date during the winter.

One strategy for being prolific: breeding early and often — producing as many as three clutches of chicks during a breeding season lasting from April to July. Robins are one of the earliest to nest, and continue to raise broods until the flush of insects has diminished in late summer.

Robins consume a lot of invertebrate prey during the spring and summer. Earthworms are a favorite on the menu for their chicks, but they also hunt aquatic invertebrates by the pond’s edge as well as insects hopping through the grass.

Another strategy for being versatile is their flexibility in changing diets as the seasons progress. We think of Robins as being primarily fruit eaters, and they do consume a lot of fruit in fall and winter — indeed, as much as 60% of their diet over the course of a year may be fruit.

Fall is the time to pig out on crabapples.
The fall crop of juniper berries feeds a variety of fruit-loving birds: cedar waxwings, warblers, mockingbirds, robins, even cardinals dine on these nutritious little morsels.
Later in the winter, with most of the chokecherries, hawthorn, dogwood, crabapple, even sumac crops depleted, Robins resort to consuming less palatable buckthorn berries, many of which have dropped off the trees by then.

This dietary switch from eating mostly animal prey to consuming mostly fruit is not trivial. There are major changes in gut anatomy, changes in types of enzymes synthesized for digestion, and amount of food to be consumed and the rate it is moved along the digestive tract daily that must take place during a short transition time of about two weeks. Ask any vegetarian what happens when they try to eat meat and you get a sense of what Robins must deal with twice a year as they switch food sources. So, we must credit their dietary versatility for their ability to survive and become one of the most common birds in North America.

But here’s a new wrinkle in the Robin’s key to success in surviving the food desert of the late winter landscape in northern latitudes — fishing! Recently someone posted photos (on Facebook’s Minnesota Birding site) of Robins fishing for minnows near the edge of a pond free of snow. One or more Robins poked a hole in thin ice, big enough for minnows to find as a place to gulp some oxygen in their severely anoxic swampy pond, and the patient Robin simply pulled them up for a meal.

Now that’s a clever bird! And its success does not go unnoticed. (Photo by Laura Segala.)
Moments later, a bunch of Robins want to try fishing at the hole. (Photo by Laura Segala)

This is not one isolated instance of American Robins eating fish. There are reports in the scientific literature as early as 1954 of Robins feeding on dead shiners, as well as newspaper articles documenting Robins hanging around bait shops for the dead minnows being thrown out.

American Robins are truly versatile and adaptable — and as a result are very successful in populating North America.

Mornings along the creek

Today is two months after the winter solstice (Dec 21), and we now have two more hours of daylight each day (almost 11 hours). More importantly, the sun rises each day 13 degrees higher than it did on the winter solstice (35 vs 22 degrees above the horizon), and it is now more than half way to its maximum altitude in our summer sky on June 21 (68 degrees).

What does this mean for us winter-weary Minnesotans — spring is ever near! Cardinals and Chickadees are singing up a storm on sunny mornings when the radiant heat of the sun can actually be felt through the chilly (20 F) air. The polar vortex is history, and it’s time to get out and enjoy the end of winter, — like taking a morning walk along the Sucker Lake creek.

This creek connection between Vadnais and Sucker lakes is a popular spot for mallards and Trumpeter Swans because the water is open and flowing all year. Unfortunately, there is nothing at all for the waterfowl to eat here because it has been picked clean over the previous months.
A Trumpeter Swan swimming through the ice chandeliers on the creek…
A pair of mallards takes off right in front of me.
At the north end of Sucker Lake, over 100 Trumpeter Swans swim in a small pool of open water near the inlet.
A mixture of adults and juveniles (brown heads) have been congregating here throughout the winter, spending nights and mornings on the water before flying off to forage in agricultural fields. Toward the end of the winter, swans and other wildlife (e.g., deer) spend more time resting and less time actively foraging, since there is very little left to feed on and whatever is there is probably well-covered by snow. By resting more, they expend less energy and conserve their energy reserves.
Morning nap time…
Last year’s offspring (swans with gray-brown heads and necks) remain with their parents through the winter, and perhaps pick up a few good tips on where to find food during this period.
Mom or Dad Swan tried a new place to look for submergent vegetation, and the youngster follows.
Long necks are definitely good for reaching into tight spaces, and this adult must have been finding something because it kept at it for several minutes.
Taking a break from all the morning’s activities…