Early bird catches “worm”

A little Spotted Sandpiper had the entire beach of Vadnais reservoir to itself and moved slowly along the shoreline probing now and then in the mud and under leaves as I stood quietly and watched.

It’s a rather plain looking, medium-sized, chunky-bodied shorebird, missing the spots for which it is named in its winter or juvenile plumage (can’t tell which). But the bird is instantly recognizable as it bobs its tail up and down as it walks, earning it the nickname of “teeter-bob” or “teeter-peep”.
Here and there, the bird probes its bill part way into the mud testing for the presence of buried larvae.
I’m not sure what this behavior is — did the bird hear something, or see something and tilted its head to localize the cue? Spotted Sandpipers hunt primarily by sight, looking for insects or crustaceans in the debris along muddy shores, but they also probe likely looking nooks and crannies where invertebrates may be hiding.
The bird has found something here — it takes a couple of minutes of probing up and down to extract it.
It pulls some yellow and black-striped “worm” from the muddy substrate. The prey might be the larva of a large stone fly or caddisfly.
It looks tantalizing (to a sandpiper) — why not gobble it up?
Nope, have to wash it off — thoroughly! Two or three dunks and swishes should do it.
Now, it’s edible.

Spotted Sandpipers are likely the most widespread breeding sandpiper in North America, nesting from northern most Alaska to the mid-continental U.S. along rivers, lakes, and streams.

And their breeding system is particularly interesting because they exhibit a sex role reversal compared to most other bird species. Instead of the typical female role of incubation and hatchling care, Spotted Sandpiper females “collect” multiple males, laying a clutch of eggs in each male’s nest, which he will then incubate. After they hatch, the male is in charge of protecting and providing food for the chicks, while the female goes off to find another male to mate with.

Female Spotted Sandpipers arrive first on the breeding ground, establish their territory, and then compete with each other for males to mate with. Since females can store sperm from multiple matings for up to a month, the male may be incubating and tending to chicks that are not his offspring! This breeding strategy, called polyandry, is rare among birds but is found in several shorebird species, in Northern Jacanas, occasionally in Acorn Woodpeckers, and in Harris Hawks.

Fishing contest

I watched adult and juvenile Ring-billed Gulls fish for minnows in a shallow area of the Vadnais reservoir the other day. Their acrobatic flights over the water scoping out the potential fish prey was impressive, as was the success rate of their dives. Either the fish were numerous in this area or these gulls are much better dive predators than I appreciated before. During the time I watched them they were successful in grabbing a fish about 50% of the time.

Ring-billed Gulls have surprisingly long wings and are adept at gliding over a patch of water to scope out what might lurk beneath the surface.
Like terns, these gulls will suddenly fold their wings while cruising 50-100 feet over the water, drop quickly to the surface, and enter head first with their beak open to grab an unsuspecting fish. This particular attempt was a failure as the gull came up with nothing.
But this bird was successful, following a full immersion after its dive. The bird took several minutes to position the fish correctly before swallowing, and taking off again.
This youngster grabbed a smaller fish, but immediately flew off with it before swallowing. An adult was fishing nearby, so maybe it flew off to avoid getting robbed by another gull.
Fishing success may have been good here this morning, but the Ring-billed Gull diet usually consists of only about 30% fish, with the remainder made up of crayfish, worms, and a variety of insects from both marshy edges as well as land. Unfortunately, they have become all too used to humans and are frequent scavengers at garbage dumps.
Ring-billed Gulls are one of the most common gulls in the Great Lakes region, breeding in the lower Great Lakes north into mid-latitude Canadian lakes, and then returning to the coastal areas and the southern U.S. and Mexico to overwinter.

the real “snow-birds”

The Fall bird migration is in full swing here in Minnesota, and large numbers of some of the smallest migrants have come and gone already on their long journey from their breeding grounds in Canada and Alaska to their over-wintering areas in Central and South America. These are the species that are obligate insect- or fruit-eaters that simply cannot find enough to eat during the cold winters of northern North America to survive here. So they leave well before the snow flies.

Ruby-crowned Kinglets are some of the smallest birds (besides hummingbirds) that pass through this area in the spring and fall. They weigh just half as much as a Chickadee (0.2 ounces or about 6 grams), — tiny bundles of energy that never stop moving for an instant as they continuously search for food.
There are fewer insect blooms in the fall for these birds to fatten up on. Look at the size of the miniscule prey item this bird is after on the underside of the the leaf — it would have to eat hundreds of them to get enough energy to sustain it for one day, let alone try to put on enough fat to provide energy for migration.
Magnolia Warblers, and most other warbler species, are only slightly bigger than the kinglets, weighing about 7-11 grams (0.2-0.4 ounces) depending on whether they have just fattened up to leave an area, or have just arrived desperate to find their next meal.
Eastern Wood-Pewees are tiny little flycatchers (weighing just slightly more than a fat warbler at 0.5 ouces or about 14 grams) that perch on bare branches and fly out to attack insects flying by.
Red-eyed Vireos are about 50% bigger than a Chickadee, weighing in at about 0.6 ounces or 17 grams.

Kinglets, Warblers, Vireos and Flycatchers (like the Eastern Wood-Pewee) eat an insect-rich diet most of the year, but because there are fewer insects around in fall (compared to spring), they often utilize berries, suet, and even seeds as energy sources to store fat for the next leg of their migration. Because insects and fruit are mostly water (70-80%), these tiny birds need to eat about 1.5 times their body weight each day in order to put on just 0.5 grams of fat per day. But that’s not enough to fuel a 500 mile flight to the next stop on migration, so it takes 3-4 days of constant eating and putting on fat to get enough fuel on board.

Philadelphia Vireo with a mouthful of dogwood berry. Fruit-eating birds are really good at separating the nutritious part of the berry from the indigestible parts, and pass the waste through their digestive tract quickly to make room for more berries. (Note: don’t stand under a fruit-eating bird while it’s moving food through its gut!)

Blackpoll Warblers are the kings of metabolic physiology when it comes to putting on fat for long-distance migration. These half-ounce (14 gram) birds double their body weight before flying non-stop for 4-5 days on one leg of their journey across part of North America and the Atlantic Ocean to reach their wintering grounds in the Caribbean Islands and northern South America. That means their little bodies are 50% fat when they take off — literally, butter-balls of bird!

Figure from SciNews, March 2019. A fascinating summary of a study by DeLuca et al. published in the journal Ecology in 2019.
Of course, the bird that defies predictions of how far it can fly on its fat supply is the Ruby-throated Hummingbird — a 3-gram (0.1 ounce) bird that routinely flies 500 miles across the open water of the Gulf of Mexico for 18-22 hours to the coast of South America, rather than follow the longer land route through Central America. Now that’s a physiological marvel!

the chase is on!

We tend to see a lot of songbirds, especially warblers, sparrows, flycatchers, thrushes, vireos, etc., migrating south at this time of year. But September is also prime time to see a lot of raptors as they fly down the ridgeline above Duluth and follow the rivers past the Twin Cities.

Last year at this time we visited Hawk Ridge nature reserve on Skyline Drive west of Duluth. On any given day, tens of thousands of hawks pass over this ridge gaining altitude to soar effortlessly south.

I just happened to be at Sucker Lake in Shoreview one morning when some of the local, or perhaps it was a few of the migrating raptors, tried to cash in on the numbers of jays and robins that had just arrived.

First up was a Merlin (a little falcon smaller than a peregrine but which quite likes to eat small birds). I found him far away in a tree being harassed by Blue Jays. Then he turned on them and tried to catch them, chasing them off their perches. But this excitement was all taking place too far away to get any good photos.

Merlins exhibit the typical falcon profile, but they have dark brown stripes down the breast, and a heavily barred tail.
I’ve highlighted the Merlin as it takes off. It was surrounded by 4 Blue Jays squawking loudly and a Pileated Woodpecker just minding its own business — but all of them are risking an attack by this fast-moving falcon if they get too close.
The Merlin made a dive at one of the Blue Jays and just narrowly missed it as it kind of tumbled down. Merlins are agile and FAST flyers with their swept-back wings and flared tail.

Next up was a smaller raptor, a Kestrel (sparrow hawk), which would have preferred to dine on smaller prey like goldfinches or small sparrows, rather than the Blue Jays that were dive-bombing it. All I got was a look through my binoculars before the Kestrel flew off and took refuge in the pines to hide from the jays.

And then a large Cooper’s Hawk flew onto a low perch and took a look at the jays but ignored their squawks, focusing on something much bigger — the Pileated Woodpecker, still minding its own business.

This is a juvenile (hatched this summer) Cooper’s Hawk, and it’s hungry! I watched the bird make half a dozen attempts to catch something as it flew back and forth from tree to tree.
A female or juvenile Pileated Woodpecker, very far away, but completely oblivious to the Cooper’s Hawk eyeing it from about 100 yards away.

The Cooper’s Hawk made no attempts to nab the Blue Jays encircling it wherever it perched, and instead made several dives at the woodpecker, trying to pluck it right off the trunk of the tree. The action looked something like this:

A quick take-off…
Followed by a few wing flaps, as the Cooper’s Hawk quickly makes its way from one set of trees to another.
The hawk returns and is now flying directly at the tree where the woodpecker is working.
You might think the Woodpecker would try to fly away at this point — but perhaps he is actually more vulnerable flying. Woodpeckers aren’t the fastest flyers as they flap, flap, glide over the landscape.
This is looking a little more dangerous for the woodpecker! Hawk in full attack mode.
The hawk puts on the brakes, flaring its tail and dropping its wings to slow down. It might have tried to knock the woodpecker off its perch, but the woodpecker seems to have turned to face its attacker. And Pileated Woodpeckers do have a pretty fearsome weapon to defend themselves from this kind of frontal assault — a very large and sharply pointed bill.

I think the woodpecker won this confrontation, and eventually the Cooper’s Hawk flew off to pick on some, other less formidable prey.

Mrs. Pileated, foraging on the tree right outside my porch windows, showing off her sturdy beak that can pound holes in hardwood trees with ease.

the “good morning” hummingbird

What could be more pleasant than to sit outside on a coolish, bright sunny morning with a cup of coffee and a camera watching Ruby-throated Hummingbirds forage on Salvia flowers? The light was harsh and full of high contrast until the birds visited just the right flowers…

Salvia flowers are the right color, the right depth for the hummingbird’s bill and tongue, and the right fit for its head to pick up pollen from the flower’s protruding anthers.
Peek-a-boo, it looks like the hummer is keeping an eye on me while I’m keeping an eye on it.
I never get tired of watching their acrobatic flights between flowers as they probe each one for the tiny bit of nectar at the bottom of each floral tube.

Soon these tiny bundles of energy will undertake a giant-sized migration south to the Gulf coast. There they will again stock up on sugar-rich nectar to convert to fat stores that supply the energy for them to cross the Gulf of Mexico (the smallest birds to do so), without stopping, to get to their overwintering sites in Central America.

Because of their high requirement for sugar during their migration, they become frequent visitors to backyard nectar feeders at this time of year. To keep these little dynamos healthy on migration, remember to change the sugar solution in your feeders every 3-4 days, so it doesn’t grow mold or bacteria.

it’s feeling fallish

We spent a beautiful morning walking along the St. Croix river at Afton State Park recently, and I noticed that it seems more like fall weather now, and a lot less like summer. What a difference a couple of weeks makes in the climate here.

The beach along the Minnesota side of the St. Croix river is deserted…just the way I like it. There are a few warblers around, geese are flocking up in preparation for migration, and the last of the summer wildflowers are holding onto their blooms, just a little longer.
A somewhat bedraggled Great Spangled Fritillary was foraging on the Sneezeweed flowers — just about the only wildflowers left along this shoreline of the river. This is one of the largest, and longest lived butterflies here in MN. It mates in June but doesn’t lay eggs until August and September, somewhere near a patch of violets, on which its larvae will feed in the spring.
Cedar Waxwings were acting like flycatchers as they perched and then sallied out to catch whatever insects were flying by their perch.
And the ever-present and numerous Canada Geese are now gathering in large flocks to prepare for migration. Here they come downriver right at us…
They fly so closely together you would think their wings would get in the way of each other. In fact, so close that two birds on the right side of the photo look like one bird with four wings!
Nothing symbolizes fall in Minnesota like these flights of Canada Geese.
Fall may be my favorite season, even though it leads into my most dreaded season of bitter winter. But I love the fall weather and color as the landscape begins to glow.

the warbler that acts like a nuthatch

Black and white Warblers are bark specialists, moving up and down or around the trunks and major branches of trees as they look for spiders, insect larvae and bark-inhabiting insects of all kinds. In their search, they often resemble Nuthatches that may travel upside down along tree trunks and branches.

A female (or juvenile) B&W Warbler checks the topside of the branch before searching the underside.
What else might be hiding underneath?
Special long toes on this warbler’s feet help them cling to a branch upside down.
As they work down a tree trunk, their posture looks just like a Nuthatch, with whom they might compete for bark-loving prey. But this style of foraging is unique for a warbler.

Social distance

We humans have learned a lesson in observing increased personal space during the Covid pandemic — a lesson birds observe on a regular basis, not from anxiety about spreading disease, but more in response to their size, their level of thermal comfort, or their need for protection.

Big-bodied Wood Ducks sit relatively close together during the period when they are molting annually into their new suit of feathers.

These male Wood Ducks are good-looking even in their “eclipse”, or alternate, non-breeding plumage, as they rest in the shade around the edge of the pond. This temporary look gives them some camouflage protection while they are molting a fresh set of flight feathers. Later they will undergo another, partial molt to renew their bright, breeding coloration. At this time, Wood Ducks are fairly tolerant of each other’s presence, and sit quietly like bumps on a log (literally!) hoping not to be noticed by predators.
kind of like standing in line at the supermarket…6 feet of distance, please!
Pigeons perch closer together than the ducks on a warm day, obviously not from a need to stay warm, but to avoid getting picked off by a passing raptor by presenting a larger target and more confusion about where to strike. Social birds are social for good reasons!

However, social distance between birds depends greatly on their size and the ambient temperature in some species, increasing when it’s warm and decreasing when it’s very cool.

When the temperature drops, social distance collapses, and birds pile together to conserve body heat, like the Eastern Bluebirds did at a local park last winter during our week of -20F weather. (Photo by Scott Mohn, in a blog post on Feb. 7, 2021).

Scott Mohn found just such a collection of male Eastern Bluebirds huddling together on a tree limb at Como Park golf course on this cold morning and graciously allowed me to use his image. (Click on the image to see it full screen). Notice these are all male bluebirds, which would not tolerate each other’s presence during the breeding season. But for the purpose of winter survival, they are bosom buddies.

There are lots of examples of this huddling behavior in small and large birds during adverse weather conditions, where social distance and personal space becomes far less important than survival!

Check out the collection of images of birds huddling for warmth at this website for Bored Panda.

Statues

Patience is the goal for hunters like herons and egrets as they stalk their prey. Thus, most of the time we see them, they look like bird statues. Patience is essential to their success as predators, as their prey get used to the presence of stick legs and begin swimming close enough to be quickly grabbed from above. And the strategy works: on average, herons and egrets have about 70% success with each strike they make at a prey item. I’m not sure human fishermen could claim that high value.

Here are a few views of these birds at their best remaining inert.

Two Great Egrets exhibiting nice symmetry as they look in opposite directions for little fish moving beneath them.
A Great Blue Heron gets really low in the water to follow the fish creating little ripples in front of it.
This juvenile Green Heron sat very still for several minutes, and finally began getting into attack mode as it spied some little fish below.
Not even another egret flying in distracts the other two from their search.
Down at the other end of the slough is a group of fledgling swallows waiting to be fed. I waited 15 minutes for a parent to come back and feed them, and they sat completely still the entire time.
Very cute, they were! I wonder what they would have done if a Cooper’s Hawk flew over…