they’re on the move…

Thousands of birds are flying overhead right now, migrating south from their breeding areas in Canada.  Some might stop over along wooded streams for a few days to replenish their fuel resources, as dozens of small warblers, vireos, and sparrows did last week at our local reservoir.  But an even more impressive migration is taking place along the ridge that runs along the western shore of Lake Superior above the city of Duluth MN.

The forested ridge above the city of Duluth generates rising warm air currents in the fall that migrating raptors (like this Bald Eagle) use to gain the altitude they need to effortlessly soar south for hundreds of miles.

Migrating raptors by the thousands (and some in tens of thousands) are reluctant to cross the expanse of Lake Superior, but they funnel along the ridge line of its western shore, to be counted by volunteer observers of the Hawk Ridge Bird Observatory and photographed by the dozens of bird lovers and photographers who visit daily.

There’s always something to look at when the hawks, falcons, eagles, osprey, etc. are migrating through this area in the fall.

Information about the migration and the peak times of migration of particular raptor species is posted on E. Skyline Drive in northern Duluth, at the crest of the ridge where spectators gather.  Some species like Broad-winged Hawks and Peregrine Falcons have very short migration times, and we happened to be there on a day when 2000+ Broad-winged Hawks flew over.

Overcast skies bring the birds down low, closer to observers, which is ideal for photography, but we happened to be there on a sunny afternoon, and the birds were thousands of feet in the air above us.

Thousands of feet above us, Bald Eagles (large bird center left) circle in the thermals along with dozens of Broad-winged Hawks.  Photo by Debbie Reynolds.

Broad-winged Hawks are smallish, compact raptors common throughout southern Canada and the eastern U.S. during the summer, but they leave North America during a short span of time in September, largely because they are dependent on the thermals generated by warm air currents rising off the land in the fall.  If they wait too long to migrate, warm fall days become unpredictable and so do the thermals they use to gain altitude for migration.

Broad-winged Hawks exhibit unique formations in migration, when they form “kettles” of hundreds of birds circling in the thermals to gain the altitude they need to soar.  The term “kettle” describes the formation of these birds as they “bubble up” from low altitude to higher altitude circling in the thermal, until they reach several thousand feet when they peel away from the kettle to soar downwind toward the next thermal.  Photo from Brandywine Conservancy, Sept 2018.

Soaring, instead of flapping flight, is relatively inexpensive for raptors, and by using the thermals to gain altitude to then soar over long distances to the next thermal, they can travel hundreds of miles before running out of fuel stores.  For Broad-winged Hawks, the journey from southern Canada to northern South America might be 3-4,000 miles and take them about a month.  In optimal conditions, they can travel 300 miles in 6 hours.

Daily count totals were posted at 4:30 at the Hawk Ridge Bird Observatory site. Peak migration times are generally the warmest times of the day, 10 am-2 pm.  According to the chart, the 10-year average count of Broad-winged Hawks at this site is 37,000 birds, but in 2003, observers counted 101,698 in a single day!  That must have been an amazing sight, with birds literally filling the skies.

We weren’t fortunate enough to get close-ups, but we did see a lot of hawks during our short time at Hawk Ridge.

 

Out on a limb

A typical pose for a Merlin, scoping out the landscape below its bare branch for little birdies flying below.

We had a rare opportunity to photograph this little falcon while it scanned for small birds from its perch in a dead tree.  Merlins are known for chasing their prey in rapid flight, so you don’t often get a chance for a decent photo of them.

Those spear-shaped wings and their powerful pectoral muscle are what give this bird the ability to chase and capture small birds. (Photo by Debbie Reynolds)

Smaller than a Peregrine, but as swift and agile, Merlins prey on sparrow-sized birds, small mammals, reptiles, amphibians, and even insects in a variety of habitats from beach shrub-grassy area to coniferous forests throughout the Northern Hemisphere of the Americas, Europe, and Asia.  They are about the same size as the American Kestrel (Sparrow Hawk), but are much stockier, with large pectoral muscles.

Merlins were a preferred falconry bird because of their size and relatively gentle disposition, especially favored by noble ladies in Medieval Europe.  Even today, they are used to hunt small game birds like quail and doves, because of their ability to climb faster than the prey and then dive (stoop) down on them to knock them to the ground.

it’s apple harvest time

The apple trees in the front yard have produced a bumper crop this year, and I decided to do something with them besides making copious quantities of apple butter, applesauce, and dried apples — apple cider!

The apple crop on the Honeycrisp tree is looking really good this year.

First step in making cider — pick the tree clean, in this case all of the Sweet Sixteen apples, which were more badly damaged by insects this year than the other trees.

After discarding the “bad apples” the Sweet Sixteen tree yielded about 300 apples.

Then it’s time to cut and chop with my handy food processor, making a finer mash of apple chips for the press.  Processing 60 apples at a time is a lot of work, but yields about 3 quarts of apple juice.

60 apples chopped into mash fills the press to within a couple of inches of the top.  The liquid drains out a spout on the metal tray, but you have to remember to put the pot under the spout before loading the apple mash into the bucket because liquid starts flowing immediately.

Setting up the press entails adding quite a few blocks between the apple mash and the top of the press, so I can really compact the mass.   After pressing the pot will be about 2/3 full of sweet juice.

The end result of the first pressing (in this case just 50 small apples) was 2+ quarts, with the first pressing coming out a dark liquid and the second squeezing (by adding more blocks to the top of the press) a much lighter color.

Pressing apples outside on warm fall days attracts unwanted visitors — some unfriendly Yellow Jackets.  These wasps have been feeding their lavae various insects from the garden all summer, which I appreciate.  But now that job has concluded with the larvae having pupated in the nest, and the wasps need a source of carbohydrate to keep them going — and rotten apples or apple mash are high desirable. It’s best not to reach in and pick apples without carefully noting what else is on them.

You might find Yellow Jackets swarming around rotten apples on the tree or that have fallen to the ground. Photo from https://tackyraccoons.com/tag/yellow-jackets/

But even more annoying is the Yellow Jackets that immediately congregate around an apple press with flowing juice.  It’s amazing how sensitive they are to sugar molecules floating around in the outside air.  I don’t think it took two minutes for them to find the apple press after we started loading the apple mash into it.

As they start drinking the sweet juice, some are swept away by the heavy flow from the press and wind up in my collection pot.  Photo by the Backyard Arthropod Project:  

And so the fall apple harvest proceeds and I’ll be moving on to harvest the crisp eating apples next, and finally the applesauce making apples.  It’s a good thing I only do this once every two years, instead of every year — it’s a lot of work!

Harrier of the marsh

On another trip out to the central Minnesota prairie the other day, we were treated to a fly-by from the bird that used to be called a Marsh Hawk for its habit of hunting vast tracts of wetlands and wet grasslands.  However, because it is closely related genetically to the Harriers of Europe and Asia, it was renamed the Northern Harrier.

A Northern Harrier female in mid-wing flap, flies close to the ground, head facing downward, searching for its next meal.

Harriers are a subfamily of the hawk family (Accipitridae) that includes hawks, eagles, kites, and eurasian vultures, but not ospreys.  As a group they are different from others in the hawk family in being sexually dimorphic (male and female look different), with males distinctively gray and white and females a rich brown and white.

Brown-backed female Northern Harriers are slightly larger (typical of raptors) than the gray and white males.  Both birds exhibit a white rump patch in flight.  Photo by Becky Rosencrans

It’s easy to tell a Northern Harrier from any of the other hawks that hunt in open country by the distinctive white rump patch.

They also differ from their hawk relatives in having distinctive owl-shaped faces, with a specialized disk of feathers on either side of their eyes (like owls) that trap and direct low frequency sounds, like that of a mouse rustling through grass, to their ears.  It is thought that Harriers may use auditory cues to find prey more than visual ones.

A juvenile Northern Harrier photographed by staff at the Missouri Department of Conservation shows the distinctive facial disk of harriers.  Chocolate brown eyes indicate this is a young female, but the color will gradually change to a lemon yellow in the adult.

Because Harriers fly very low over the ground, they are constantly looking down, which is another characteristic that separates them from other hawks that spot their prey from high above the ground and dive down on them.

Typical search posture of a Northern Harrier: wings in a V for efficient gliding and head down picking up sounds or visual sightings of prey.  Photo by Debbie Reynolds.

With its feet extended, this female Northern Harrier may be about to pounce on some unsuspecting rodent moving along in the short grass.  Photo by staff of the Missouri Department of Conservation.

Lastly, Northern Harriers differ from many of their hawk relatives in their reproductive biology.  Where most hawk, eagle kite, vulture, etc. species form a strong male-female pair bond that may last several years, Northern Harrier males will try to court, attract, and feed multiple females on their territories (polygyny).  This behavior maximizes the number of offspring a particular male produces, especially if he maintains a territory rich in available prey (small mammals, birds, amphibians, snakes, even insects), but it also promotes better protection of chicks in vulnerable ground nests because there are multiple individuals present in an area to drive away aerial predators like owls and eagles, as well as fox, coyote, mink, racoon, etc.

Predation pressure is probably the reason that Harriers often roost together on the ground, sometimes even teaming up with their competitors, the Short-eared Owls that also inhabit the same wide-open prairies.  Lots of eyes to watch their backs…

another little bird at the slough

I went back to the same place in the Grass Lake slough where I found the Solitary Sandpiper the other day, and found a juvenile Green Heron fishing for its lunch in the duck weed scum.

A bumper crop of Green Herons were produced in the backwaters of the Grass Lake slough this year. This is one of 8 individuals I saw on this particular day (all in different places in the slough, so no repeats).

After a few minutes of watching the heron change locations, look around, and waiting for it to catch something…

Out of the corner of my eye, a little brown and white bird trotted out in front of the heron, and proceeded to walk toward me, quite unafraid.

Killdeer are distinctive brown and white birds with a broad black neck band and red lining around the eye. But even more distinctive is the trilled “kill-deer” made over and over as a warning or an announcement of their presence that you frequently hear on gravel paths or large expanses of short grass where they forage.

But eventually the bird walked too close to me and realized I wasn’t an inanimate object.

Too close for comfort, and then the inevitable, quick take-off…

Faster than you could move the camera, the bird was out of the frame and off to better foraging spots, calling “kill-deer” over and over as it flew.

what are you eating, little bird?

While I was photographing the beautiful wildflowers, bees, and butterflies at the Grass Lake slough last week, a Solitary Sandpiper (a type of shorebird) almost walked across my toes as it pecked in the sludge at the edge of the slough.

Solitary Sandpipers are, in fact, solitary, rarely seen in the company of other shorebirds. They forage along the shore of fresh water sources throughout most of northern North America (Canada and Alaska in the breeding season), and despite having a long bill that could probe deeply into the mud, they forage on the surface of the water for bugs, worms, crustaceans, spiders, tadpoles, etc.

The bird picked up what looked like juicy prey items, dropped them, picked them up again, squeezed it a little with the tip of its bill, dropped it again, picked it up again, threw it off to one side, went and found it and picked it up again, etc. In all of the hundreds of photos I took of the bird catching prey, I never saw it actually ingest anything.

But I was curious what potentially edible items the bird was finding in the muck, so I sent some photos off to my aquatic biology (and pickleball) friend to help me identify the victims of this bird’s torture.

This worm-like prey item being squished between the bird’s mandibles is possibly the larva of a Crane Fly. The bird squished this one several times until it became a flattened ribbon.

Plucking this item from the same vicinity as the last one, the bird threw what might be a Crane Fly pupa around into the muck and then plucked out again. It didn’t wiggle like the larva did, so maybe the bird thought it was a stick.

The bird picked this giant water bug up a few times, always by the front end. These bugs have a strong proboscis with which they can inflict a painful pinch. Thus, their common name — toe biters.  In Asia, people are fond of eating the 4-inch variety of this critter.

It took the bird just a few seconds to find a new prey item, which it deftly sorted from algae and other vegetation.  What sharp eyes this little bird has.  Given a pair of tweezers, I doubt a human could pick out these invertebrates from the algal muck — I certainly couldn’t.

Hovering specialists in the backyard

A wide variety of animals can fly (more than just birds, butterflies, bees, or bats), and among those flyers, a select few can perform aerial acrobatics, like hovering — suspended in space, defying gravity in the process.

A few of those hovering specialists passed through the backyard this summer, and I attempted to capture their effort one wingbeat at a time.  And this is by no means easy when the subject a) darts from one hovering location to another in a millisecond (the hummingbird and the dragonfly) and b) is so small it’s difficult to focus on it (the dragonfly and the hoverfly).  The video clips below illustrate the difficulty.

A Ruby-throated Hummingbird in a sea of red Cardinal flower, delicately moving from blossom to blossom while beating its wings 80 times a sec.  I could stop the wing motion of this bird with the camera shutter speed at 1/2000 of a second.

Hummers move their wings in a figure-eight pattern, rather like the sculling motion of the hands of water ballet performers make to keep them static in a column of water. Forward and backward movement of the wings cancel horizontal movement, and the lift provided by the figure-eight motion keeps them suspended vertically.

A stocky bee mimic, the drone fly (Eristalis tenax) took up territorial residence outside my backdoor, hovering near the peonies in May.  One of the most widely distributed species in the world, drone flies maintain small territories near flower beds to attract females, occasionally darting out to chase off intruders.

Freezing the drone fly wing beat in time required the fastest shutter speed on my camera dial (1/8000 of a sec).  Two tiny wings propel the fly forward, backward, or keep it motionless in space, moving faster than the eye can see them — sort of like a helicopter rotor.

Dragonflies hover with two sets of wings, i.e., four moving blades swooping independently through the air.  Normally, dragonflies dart along the shores of ponds and streams, moving quickly from spot to spot, but occasionally they pause in their patrol efforts to hover over particular spots they are defending or to advertise their presence to females.

The 4-spotted Skimmer hovered almost motionless in space in front of me as I tried to focus on its abdomen.  Although the wings look synchronized in this view, front and back pairs move independently, as illustrated in the video below.  The wingbeats flutter in a blur to the human eye, but they beat at a much slower rate than those of hummingbirds or drone flies, and I was able to capture static shots at 1/1000 of a second.

It’s a most impressive feat of flying that is demonstrated by these animals, and one that has been copied by human engineers seeking to copy vertical take-offs and hovering efficiency in aircraft.

look-alikes (and not)

The Grass Lake slough at Snail Lake regional park is teeming with butterflies, especially Monarchs, which may be congregating here for their southward migration.  The Monarchs especially seem to like the meadow blazing star and don’t even mind sharing it with a lot of other butterflies, bees, etc.

The number of flowers present on meadow blazing star is one reason that butterflies congregate on it. The fact that it provides a lot of nectar at a time (late August) when butterflies are migrating is another.

Plenty of nectar to go around for Painted Ladies (also migrating by the thousands in late summer), Monarchs, bumblebees, honeybees, and a few stray beetles.  The orange, black, and white pattern of the Painted Lady is similar to that of Monarchs, but they are not mimics and the two are easily distinguished from one another.

But one of the many Monarch butterflies I photographed wasn’t a Monarch, but a Monarch mimic, the Viceroy, and these two unrelated species ARE difficult to tell apart.  Can you spot the difference(s)?

Both species exhibit the bold orange and black pattern on the wings as well as the pattern of white dots on the black head and thorax of the insect. 

The biggest difference in coloration of the two species is the bold black horizontal (sort of) stripe on the hind wing of the Viceroy, seen from above or below.  The thick black lines on the hind wing of the Viceroy are similar to those of a female Monarch but are much bolder than the male Monarch’s, which also has a distinctive dot on each hind wing.  In addition, Viceroy butterflies are smaller in size, only about 2/3 the size of a Monarch.

But where Monarch caterpillars grow up eating milkweeds containing poisonous cardiac glycosides which they sequester in their bodies (and wings), Viceroy caterpillars eat willow, poplar, and cottonwoods — not at all poisonous. Bird predators find Monarch butterflies extremely distasteful and will regurgitate or spit them out. Viceroy butterflies that most closely resemble their poisonous cousins in coloration are better protected from predation, and thus, the mimics survive to reproduce.

And then there are these two, apparently dissimilar butterflies, flitting around the same plants, often displacing each other from the same flowers.

The Eastern Tiger Swallowtail comes in two colors: yellow and black, and black.

Not at all look-alikes, in fact, color-wise, they couldn’t look more different, except for the pattern of white dots around the margin of the wings and the distinctive iridescent blue splashes of color on the back end of the hind wings.  So, what’s going on here?

Male Eastern Tiger Swallowtail butterflies are almost always yellow with black stripes.  Females on the other hand vary between yellow morphs and black morphs.  And, the black morph is more commonly found in the southeastern U.S. where a similar-colored, poisonous and unpalatable Pipevine Swallowtail butterfly occurs.  These are the “look-alike” models for the Tiger Swallowtail (and other Swallowtail butterfly species) to copy.  Interestingly, the proportion of female black morphs of the Tiger Swallowtail is higher in southern populations because of genetic (sex-linked) process that makes black morph females produce mostly black morph females, and yellow females produce mostly yellow females!

Bottom line:  you have to look closely when identifying a butterfly, because it might be a mimic!

Comparison of three common swallowtail butterfly mimics and their model, the Pipevine Swallowtail. From butterfliesathome.com

return of the big, scary black wasp

I haven’t seen the Great Black Wasp (Sphex pennsylvanicus), a type of digger wasp, for eight years, when I first found this fearsome looking insect in my backyard feasting on the nectar of swamp milkweed.  But this week I found several of them pollinating the flowers of a wildflower I have never seen before — Spotted Bee Balm.

A 1.5-inch long, fearsome-looking all black wasp with long legs and blue-black wings.  

The wasp inserted its head all the way into the flower and came out again with a nice dusting of pollen to take to the next flower.

The Great Black Wasp is also known as the Cicada Killer, for its habit of stinging and paralyzing orthopteran insects (grasshoppers, cicadas, etc.) to provide food for their offspring.  The prey are paralyzed after being stung in the head and abdomen and are then deposited in an underground nest. A single egg is laid on the underside of just one of the two to six prey items placed in each nest chamber as the larva’s food source during its development.

spotted bee balm

Spotted Bee Balm is a relative of the more common pink or red Bee Balm.  Flowers are arranged in whorls along the stem of the plant.  Multiple stems bearing flowers present a rich source of nectar and pollen for pollinators, but the stems die back in the winter, and the plants regrow from the roots only 1-2 years before dying out.

White bracts separate clumps of flowers on the stem and the flowers seem to open sequentially rather than all at once, so pollinators would be encouraged to revisit particular stems and whorls of flowers.   

This fragrant flowering plant, found mostly in the eastern half of the U.S.,  is especially attractive to large-bodied bumblebees, carpenter bees, and digger bees, as well as a variety of other nectar- or pollen-feeding insects.  It flourishes in dry, sandy areas, disturbed areas along roadsides and railroads, old fields, and prairies.  I don’t know why I have never seen it before this, but I would certainly like to add it to my prairie garden.

Wildflowers at the Grass Lake slough include a wide variety of perennials like Spotted Bee Balm.

a most particular flower

Walking around Tamarack Nature Center in White Bear Lake, MN the other day, I saw some unusual plants in wetter patches of the prairie.

white bottle gentian

This is the white form of Bottle Gentian – the more typical flower color is lilac to deep purple color.

Although the flowers look like buds that aren’t yet open, this is the typical mature flower presentation with its petals closed up tight.

The petals are tightly closed at their tips.

You have to wonder how or whether such a flower can get pollinated.  But it turns out that this plant is very particular about which pollinators it allows to perform the pollination service.  In this case, it requires large-bodied bumblebees that are strong enough to separate the tips of the petals so they can crawl into the flower to pick up the pollen and nectar within.

The bumblebee is about as big as the flower, and uses its front legs to separate the flower tips and push its head into the flower, with the body following.  Photos from naturallycuriouswithmaryholland.wordpress.com .

As the bumblebee enters the flower, it pushes its thorax against the flower’s reproductive parts, rubbing pollen onto the exposed stigma, pollinating it.  By vibrating its wings and body inside the flower, the bee causes that flower’s anthers to release pollen onto the surface of the bee, which it combs off into pollen sacs later.  The nectar is located at the base of the flower, so again, it requires a large bee with a long tongue to reach the nectar source.

In the video below, you can see how hard the bee works to get into the flower and hear the buzzing while the bee is completely encased by the flower. (Video by NaturalistDave Nature Video)

Typically, the bumblebee will visit just one flower of the group at the tip of the plant, moving to the next plant after exiting a particular flower. This ensures the cross-pollination which is required for seed set. When pollinators are excluded from these flowers, only 4% of the flowers were able to produce seed, but when pollinators were allowed, 96% of the flowers produced seed.

Why would bumblebees go to all this work to get into such a tightly closed flower, when there are so many other flowers with nectar and pollen to harvest in the prairie?  Or are there?

Bottle Gentian times its flowering for periods when there are fewer bumblebee pollinated flowers available.  Bee Balm (center) has finished flowering on this prairie and goldenrod has not yet bloomed, so the rich nectar and pollen resources in Bottle Gentian represent a good alternative.