the nectar thief

Each year, the Ohio Buckeye tree outside my porch window puts out a prodigious number of flower spikes, which reliably attract a few pollinators and one clever nectar thief.

Pollination of these flowers is sufficient for the tree to produce copious quantities of nuts, which are harvested by the squirrels in the fall.

Hummingbirds, bumblebees, and orioles visit the Buckeye tree in the spring, along with a horde of Tennessee warblers.

Tennessee Warblers arrive just as the Buckeye tree is in full flower. How do they manage to time it just right?

Tennessee Warblers really have nothing to do with the state of Tennessee, but do migrate through there, where they were first seen and named way back in 1811.  Like many small insectivores they spend the winter in the tropics, eating insects and nectar, and breed in the Canadian spruce forests where they specialize on spruce budworm and are critical to controlling outbreaks of the moth there.

Though they do visit flowers to consume nectar, they do not perform much of a pollination service for the plants, because they use their sharp beaks to pierce the flower at its base to get at the nectar at the bottom of the flower tube, thus avoiding the pollen on the anthers sticking far out of the flower.

Note where the beak is positioned to the side of the flower at its base. Pollen might inadvertently stick to the bird’s head or breast as it bumps into the anthers, but it might be hit or miss in depositing the pollen on the stigma of another flower.

Their beak is slightly open as if they are biting the flower to open a small hole in its base.

They only visit for a few days each spring, so I guess this must be the peak of their migration through MN this year.  You can see a light dusting of pollen on this bird’s neck and breast.

The sugars in the nectar will be metabolized and stored as fat and should provide these tiny little birds (about 2/3 the size of a chickadee) with the fuel they need to get to the Canadian spruce forest to breed.

(these photos shot with the Sony RX10 iii bridge camera through my porch window — what an amazing little camera!)

A busy day at the rookery

April and May are busy months at Smith Oaks Audubon Sanctuary on High Island, east of Houston.  Great Egrets and a variety of other long-legged waders nest in high density on an island in the middle of a rather large pond.

Some nests are almost within pecking distance of each other. Great Egrets and Roseate Spoonbills are among the earliest nesters here.

The Island is surrounded by water, patrolled by alligators, which keeps potential coyote and raccoon predators from predating the chicks.

Great Egrets are still sporting their breeding plumes, which flair out with the wind,  and are used to attract a mate with an elaborate display.  Unfortunately, thousands of these birds used to be shot each year to collect the decorative plumes to adorn ladies’ hats.

Great Egrets are the symbol of the National Audubon Society, which was initially founded to protect birds from being killed for their feathers.

It looks like this pair are incubating eggs, which have to be turned in the nest every so often to ensure optimal development of the embryos.

The Great Egrets are well into their nesting phase, with some birds standing over their half-grown chicks and others still sitting on eggs.  Males build a large nest platform that may be as much as 3 feet across.  Once he attracts a mate to his nest site, the couple work together to finish the nest, adding a foot-thick layer of sticks to make the nest cup.

There are at least two, very vigorous chicks in this nest, which were beating up in each other until one parent interceded.

These birds typically lay more than 2 eggs, but begin incubating right away. This means the last egg laid in a clutch of 4, for example, hatches four days after the first egg laid, and the youngest chick will be a a great disadvantage in trying to compete with its larger nest mates.  In years when there is plenty of food, it might survive, but its larger siblings might steal its food or pick at it with their sharp beaks, and often this runt doesn’t survive.

Typical sibling rivalry…

Stalking a Kildeer nest

“Would you like to see (and photograph) a Kildeer on its nest?” our fearless leader and master bird photographer, Alan Murphy, said one morning during our photography workshop in Galveston. And thus began the nest stalk and another learning experience about how to approach birds for close-up photography.

One of the Kildeer pair guarding its nest (somewhere in this little path of gravel in a residential lawn), and wary of our approach.

Using our collapsed tripods like a walker and creeping forward on our knees, with faces hidden behind the camera, we slowly narrowed the distance between us and the bird.  And then waited…and waited…until finally the bird relaxed and settled back down on the nest.

The bird approached this spot from one direction, then ran back, then approached from a different direction, and repeated this several times before standing over the nest and gradually hunkering down over it.  But despite our low angle kneeling in the grass, we can’t see the nest, just the bird sitting.

So, we moved ever so slowly, doing the tripod “walker” creep to one side of the nest where there was a clearer view.  That of course flushed the bird off the nest, and we began another waiting period of knee agony.

One of the pair calls to the other to come to the nest, perhaps for defense?

And off they ran, into the lawn, to lead us away from the nest.

But we’re waiting, kneeling behind our tripods and cameras, letting the birds get used to the foreign, hopefully non-threatening, objects near their nest.  And patience pays off, as one of the pair returns to settle on the eggs.

I didn’t see the eggs until the bird actually approached and stood over them. Their camouflage in the gravel is really good.

Slowly fluffing out the breast feathers to surround the eggs and allowing the eggs to come into contact with bare skin, the bird slowly settles over its nest.

And now we leave this pair alone, to continue their parental duties of incubating their developing chicks.

The Kildeer nest is simply a scrape in the gravel, where the eggs lie with pointed ends toward the center (usually). Their irregular shape ensures that they will roll in a circle near the nest, not away from it. And the splotchy pattern on the shell blends in nicely with the dirt and gravel. (Photo by Debbie Reynolds)

i would never have thought we could approach a nesting bird like this and get this close.  But patience, and some knowledge of what a particular bird will tolerate pays off in the end.  A good learning experience.

Bathing beauties

Flying nonstop for almost a day across the salt water of the Gulf of Mexico makes migratory birds thirsty and ready for a cleansing bath before preparing for the next leg of their journey.  The fresh water drip and bathing pool setup at our Alan Murphy photography workshop on Galveston Island was the perfect lure for some of the beauties that stopped by.

Bird bath set up for photography by Alan Murphy.  Orioles waiting to bathe on the branch above the bird bath.

Photogenic perches  are suspended from tripods next to the bird bath, and a wooden replica of a summer tanager, which can be animated to swish water, entices would-be bathers from the lower right corner of the pool.

For example, this is the kind of shot you might get focusing on a bird that landed on the branch that leads down to the upper left corner of the bath.

Using 600 mm of telephoto at this relatively close distance allows this handsome male Orchard Oriole to fill most of the frame, and the trees and grass in the background to be mostly blurred.

Sitting is a camouflaged blind about 25 feet away, all the photographers (like me in the far corner) have to do is sit and wait for the birds to stop by.

some of the action we saw…

Painted Bunting waiting a turn in the pool.

Painted Bunting bathing vigorously, getting all the dirt of migration out of its feathers.

Orchard Orioles seem to like bathing together, for safety in numbers, I guess.

Male Indigo Buntings who will be so fiercely aggressive to one another once they land on their breeding territories, nevertheless band together to forage and bathe at this stopover on their migration route.

Mockingbird getting really wet…

The first step in getting feathers dried off and in shape for flying is a really good shake. Note all the flying dander coming off this bird.

You would think that if feathers can get this wet and disarranged by bathing, birds would be vulnerable to rain storms, and flight would be compromised.  But this doesn’t usually happen, because when birds preen their feathers to reshape them after they bathe, they apply a waxy coating obtained from the preen gland at the base of their tail.  So when a resident Great-tailed Grackle gets in the bird bath, water beads off the surface of its feathers.

This grackle was much too big to fit in the frame at 600 mm!

Orioles in action

Baltimore and Orchard Orioles were probably the most common birds we saw and photographed during our week in Galveston at the Alan Murphy photography workshop.

The males are quite easy to tell apart: the slightly larger Baltimore Oriole is on the left, Orchard Oriole is on the right in the photo below.

These two males don’t normally sit this closely together without displaying some aggression toward one another.

Orioles love oranges, and there was some aggressive competition for access to the one or two half oranges placed near the water drip and bird bathing pool outside our photo blind.  Watching their interactions, it was easy to determine the pecking order among males and females of both Oriole species.

An immature male Orchard Oriole might try to displace an adult…

But they usually did not succeed.

Larger-bodied and more aggressive Baltimore Orioles always excluded Orchard Orioles from getting near the orange.

Male Baltimore Orioles were very aggressive toward one another, often grabbing each others beaks.  Perhaps the more orange the bird is, the more dominant it is.

There were lots of aggressive interactions between immature males, even in the absence of an orange.

Females were usually not attacked or threatened, unless they tried to feed on the oranges.

Oriole interactions were interesting to watch, and no birds lost feathers or blood in their scuffles.

Obese superathletes!

When have you ever seen the words obese and superathletes linked?  However, this is an apt characterization of the small migratory birds that undertake 12 to 20 hour flights across the open water of the Gulf of Mexico on their northward spring migration.

Female Black and White Warbler, normally weighs about 10.2 grams, but may bulk up to 15 grams with fat reserves to fuel a trans-Gulf migration.

Trans-Gulf migrants take off from staging areas in the Yucatan peninsula in early evening, fly all night at about 5000 feet using celestial cues for direction, and land on the southern U.S. gulf shores sometime the next afternoon — a flight marathon.

This male Indigo Bunting must have been so busy metabolically turning food into fat stores that he didn’t complete his feather molt before leaving on his northward migration.

At an average flight speed of about 30 mph, birds could travel the 600 miles across the Gulf in about 20 hours; with a tailwind, they might average as much as 45 mph and get there sooner.  But they usually don’t stop on the coast, and instead fly inland to the cover of trees and shrubs where they might find the insect, or seed, or fruit resources they need to fatten up for the next leg.  Bad weather and southerly head winds that prolong the flight time leave birds exhausted of fuel so that they literally “fall out” of the sky onto oil rig platforms or land on the barrier islands.

Orioles love oranges and grape jelly, but this female Baltimore Oriole apparently craves protein during her migratory stopover.  She tore off the butterfly’s wings before consuming its body.

How do birds fuel this flight Marathon?

We know that a 30 gram bird like the Baltimore Oriole flying at 30 mph expends about 4-5 kcal (= 4-5 Cal) of energy per hour of flight, or about 10 times their basal level of metabolism.  In flying the 20 hours to cover the 600 mile distance, Orioles would then expend about 80-100 Cal (equivalent to a cup of blueberries or a small piece of raisin bread).  Each gram of fat metabolized liberates 9 Cal, so this flight marathon would cost about 9-11 grams of fat.  For a 30 gram Oriole, this amounts to 30-36% of their body mass lost over the course of a day, and which must be replenished before the next leg of migration.  No wonder they feed so voraciously at their migratory stop-overs.

But small birds like this male Magnolia Warbler typically put on fat equivalent to 50-70% of their non-migratory body mass!  The extra fuel reserve takes them farther inland, or may make a difference in sustaining flight against strong headwinds.

Migratory birds are indeed obese superathletes — storing, metabolizing, and turning over 50-100% of their body weight on a daily basis as they undertake their long distance migration.

and how about this metabolic marvel…

Female Ruby-throated Hummingbird feeding on milkweed nectar.

Tiny 3 gram (one-third the weight of a Warbler!) Ruby-throated Hummingbirds annually make the trans-Gulf migration by doubling their body weight, loaded with 3 grams of fat.  We know they cross the gulf rather than go around it because they have been found on the Mississippi coastal barrier islands, and occasionally fall out in bad weather on the oil rig platforms.

The great migration

After an intensive week of up-close and personal photography of spring bird migrants on their way north (while attending Alan Murphy’s bird photography workshop in Galveston Island, Texas), I have new-found admiration for their journey, as well as thousands of photos to scan, edit, and do something with.

Yellow Warbler male, weighing about 10 grams, less than a packet of ketchup.

Some readers may think “the great migration” refers to the mammal migration through the Serengeti, which is indeed impressive. But equally astounding is the 600 mile (1000 kilometer) leap of faith that small birds, some weighing less than a half teaspoon of sugar, make by flying directly across the Gulf of Mexico from the Yucatan peninsula to the gulf shores of the southern U.S. (Texas to Florida).

Gray Catbird

In fact, the choice is made for them to fly directly across the Gulf, because to go around the Gulf by land is three times the distance (about 1800 miles), with no guarantee of food to replenish fuel stores, more predators to avoid, and a much longer transit time (days instead of hours) before they reach the U.S.

Route of trans-Gulf bird spring migrants

More than 1/2 Billion birds fly over the Gulf during spring migration, including the Warblers, Tanagers, Orioles, Buntings, Grosbeaks, Cuckoos, and Flycatchers we eventually see during summer breeding season in the northern and eastern U.S. and Canada.

Baltimore Oriole male

Eastern Wood-Pewee

Yellow-billed Cuckoo

How do they manage this feat? That will be the subject of the next post — please visit the blog again tomorrow.

the Flint Hills

Explorer Zebulon Pike coined the term “flint hills” for the rocky, flinty limestone-rich tall grass prairie that runs north to south down the eastern 1/3 of Kansas into Oklahoma.

Rolling prairie as far as the eye can see, dotted with cattle.

Early settlers found the ground much too rocky to farm, but it made good cattle pasture. Today, the prairie is managed by regular burning, which returns the previous year’s nutrients to the soil, and creates a lush green carpet.

The contrast of green, previously burned and yellow-brown, unburned prairie is obvious on opposite sides of the highway.  We just barely outran the thunderstorm that was moving east as we drove south.

The Flint Hills are the most dense coverage of tall grass prairie in all of North America. Imagine what this must have looked like in the early 1800s when huge herds of buffalo roamed the prairie.

Why is this extensive formation here, you might wonder?  Because 250 million years ago, this area and much of the Midwest was covered by a shallow sea, where silt and sand, as well as the carbonates from the rich invertebrate fauna in the sea, were deposited in layers.  Erosion of softer materials over time left the rocky, flint-

Buried treasure

April blizzards create new challenges for wildlife, already limited by the diminished resources available.  Can squirrels really remember where they hid some buried treasure last fall?  Apparently so.

After the blizzard, gray squirrels ventured out in the deep snow, digging holes down to the dirt surface in search of their buried treasures.
This shot begs for a clever caption. Got any ideas?

It looks like the squirrel found what it was searching for — a dried up walnut.

I wonder if they can smell nuts under snow cover?

April blizzard

After a week of warmth in California weather, we returned to a Minnesota “spring” blizzard, complete with wet snow, fierce winds, icy rain, and frigid temperatures.  Pity the poor migratory birds that came here to replenish their energy before continuing north.

Fox Sparrow looking forlorn about all the snow covering the vegetation.

The icy crust was too hard for them to scratch below in search of fallen seeds from the feeders.

Slate-colored Juncos were everywhere scavenging fallen seed.

This House Finch was eating the snow!

Male Northern Cardinal standing tall, trying to look in the feeder to find seed.

Female Northern Cardinal, not finding much to eat with the snow covering all the feeder holes.

American Goldfinch males have turned their bright yellow spring breeding colors. But it doesn’t seem like spring weather now.

Hopefully this is the last of the white stuff we will see this spring.