A cruise on the Delta

Five rivers feed into the 200,000+ acres of wetlands that make up the second largest river delta system in the U.S. just north of Mobile Bay in southern Alabama. The Mobile-Tensaw delta’s expanse of swamp, bog, natural rice paddies, canals, and rivers makes this area of Alabama a real biodiversity hotspot where you can find more species of fish, turtles, snails, crayfish, and oak trees than anywhere else in North America. Harvard ecologist E.O. Wilson has called it North America’s Amazon, and so it was a real treat to venture out on a small boat to explore some of the smaller waterways of the delta for ourselves.

Wild rice and Phragmites reeds grow along the edges of the river, almost closing off the small waterways in the labyrinth of corridors throughout the delta.
A variety of snails colonize the floating vegetation in the swampy bogs.
Clumps of rice seed fell into the bottom of the boat as we passed through narrow canals. A Yellow Warbler might not be interested in the seed, but there are plenty of insects in this vegetation.
We must look carefully on the river banks before stepping out of the boat — there are plenty of alligators in the delta waters.
Cruising up the Tensaw river we entered a cypress swamp where the trees grow right in the water, completely independent of any land surface.
Cypress forests are a haven for all kinds of birds — small migratory warblers as well as large waders like a Great Blue Heron.
In the Spring, these waterways are lined with brilliant flowers.
Spanish moss hangs from the Cypress’ lower branches, and odd vertical stumps arise from the tree’s roots. Their function is not certain, but they might assist in collecting more sediment to buttress the tree roots in the soft, muddy river bottom.
Honeybee nests can be found where large branches have broken away from the trunk. This is a “honey” tree.
Not only is there great diversity of vertebrate animals in the delta, but there are hundreds of species of insects as well. And some are really big — like the praying mantis..
and this 4-inch lubber grasshopper (which is not fully mature yet).

The southeastern U.S., and the Mobile delta in particular, was a refuge for species driven south during the ice ages of the Pleistocene glaciation. Warm temperatures year-round and plenty of rainfall (averaging 70 inches per year) ensure the most equitable conditions for life to survive, and so it has in this cradle of biodiversity.

Looking back — 2019 in pictures

What a glorious year of travel to such beautiful and interesting places.  I re-worked some of the previously posted and some new images with some new photo editing software (Luminar 4) to accent some of the interesting sites we visited.  I hope you like the results.  Please click on any of the images to see them full screen, and use your back arrow to get back to the blog post.)

From January 2019 posts on crossing the U.S. in winter, this is the central Nevada landscape in winter at sunrise.  Stark and barren of life, but gorgeous in morning light.

Sunset light in the Sonoran desert north of Tucson, in Catalina State Park (January 2019).  Amazing plant diversity here in a warm desert that gets winter rain.

A very lucky coincidence that we stumbled on a huge concentration of Sandhill Cranes and Snow Geese at Bosque del Apache in NM, right at sunset. (January 2019)

We visited the town of Ajijic and Lake Chapala, south of Guadalajara, Mexico, for pickleball camp in March. It’s always nice to escape MN winter weather for a while.

A fun rodeo at Fort Robinson, NE, in July. This was a father-daughter team of calf ropers showing off their skill.

Canyonlands National Park at sunset lights up the colorful mesas and rock formations, July 2019. It’s impossible to take a bad photo here.

Natural Bridges State Park, Santa Cruz CA

Natural Bridges State Park, Santa Cruz, CA with youngest grandchild dancing on the sea cliff. July, 2019.

Such a pastoral scene in Lassen National Park, CA, of the dormant volcano and meadow. August 2019.

Dramatic cliffs overlooking the Crooked River, north of Bend, OR.  With Luminar photo editor, I removed most of the haze from the distance.  August, 2019.

Just as we were ready to head out on a boating adventure on the Rio Claro in the Pantanal of Brazil, the sky lit up at sunrise. Now this is why I love photo editing software like Luminar, because it recovered all the highlights and color that I remembered but were a little too dim to see in my original image. September 2019.

Vast tracts of grassland in the Pantanal region of Brazil are devoted to cattle ranches. Pantaneiro cattle are a special hybrid mix of Portuguese and Zebu (South Asian) cattle bred to survive the heat and aridity here. September, 2019.

Beautiful Cloud Lake in the Porcupine Mts State Park, MI at sunset. There were swans swimming in the lake, but I couldn’t resist adding a few to the sky above (easily done with the double exposure feature in SnapSeed).  So this is a fake — but a pretty one. 🙂  October, 2019.

The Minneapolis skyline at sunset, enhanced using presets in Luminar.  November, 2019.

a remarkable display

There are many amazingly beautiful and colorful birds in the world, but the one with the most remarkable and distinctive display (imho) is the South American Sunbittern. How many birds go from very cryptic to wildly flashy by just spreading their wings?

The vivid colors of the eyespots on the wings of the Sunbittern contrast with its otherwise cryptic black and white plumage. (Click on the image to enlarge and appreciate those colors!)

And having such an unusual plumage display isn’t the only thing that is distinctive about this bird.  It is the only member of its family, and its closest relative is the plain gray Kagu that lives in the mountainous regions of New Caledonia (east of Australia in the Pacific Ocean), almost 9000 miles away from Sunbitterns that range from Guatemala to southern Brazil.

How is that possible, you ask?  Because until about 180 million years ago South America was part of a huge southern continent called Gondwanaland that included Africa, Madagascar, India, Antarctica, and Australia, plus many islands in the South Pacific.  Close relatives were isolated from each other when the supercontinent split up into the land masses we recognize today.

In its usual swamp habitat, Sunbitterns consume a wide variety of aquatic prey — insects, dragonfly larvae, water beetles, moths, spider, crabs, shrimp, and earthworms. They may even hunt small fish, eels, and tadpoles.

Sunbittern stalking…using the slow stealthy approach.  But when they want to cover ground quickly, they thrust their head and long neck out, and trot to catch their body up to their head.  It’s a bit comical (see the video link below).

Sunbitterns are one of just 12 species of birds in 5 different families that have been observed to use baits or lures to attract prey.  Typically, birds drop the lure in the water in front of them and then wait to see what swims over to investigate, and then — zap, the prey is gobbled up.

The Sunbittern’s flashy display is meant to startle — which certainly works well on photographers with an itchy finger anxious to follow it in flight.

An award-winning photograph by Debbie Reynolds of a Sunbittern in flight shows off the colorful flight feathers.  (First place in the Birds of South America photo contest by Birds Eye App)

Flashing the eyespots on its wings on landing…photo by Debbie Reynolds.  The pattern almost looks like a Native American design.

But Sunbitterns also perform displays with the wings positioned straight out, or on either side of their head that are meant to attract mates, or as threats to potential competitors.  Check out the video below to see some Sunbittern displays…

Now here’s an amazing (coevolutionary) story…

Yellow-rumped Caciques (members of the blackbird family) enjoy a love-hate relationship with Giant Cowbirds in the Pantanal of southern Brazil.

The players in this story:

Yellow-rumped Cacique

A couple of Yellow-rumped Caciques near their woven nest, in a Cacique apartment house.  Caciques are highly social birds and nest together in high density, each individual female weaving multiple nests (to confuse the predators) in close proximity to her neighbors.  Males help defend the nests from intruders, but they are too busy attracting more females to their apartment house to help with the nest building.

The multiple, hanging, woven nests of the Yellow-rumped Cacique form a huge complex in tall trees in the Pantanal of Brazil.  There may be as many as 200 nest structures in one large “apartment house”.  Note the presence of a wasp nest in the middle of the image — looking like a gray loaf of bread.

Giant Cowbird

Giant Cowbirds, like other cowbirds, are obligate nest parasites, using many other (and smaller) bird species as hosts for their offspring. Female Cowbirds furtively explore potential nests when owners are absent, and then quickly lay an egg and leave. The chick is usually larger than the host chick and grows more quickly, outcompeting the host chick for food delivered by the female.

Well, it’s not exactly love between Caciques and Cowbirds, but the Caciques exhibit a great degree of tolerance for the presence of female Cowbirds who deposit an egg in Cacique nests, forcing the single mothers to raise their {adopted} large, greedy chicks along with their own.  BUT the benefit of this relationship is that the Cowbird chicks have a great fondness for botfly larvae that are ever-present in bird nests, and will pick them off themselves and the Cacique chicks as well, for a little extra nourishment.  In the end, Cacique nests with high degrees of botfly parasitism and Cowbird chicks in the nest actually fledged more offspring.

Yellow-rumped Caciques only lay two eggs in their long, hanging nest, but usually are only able to fledge one chick.  Between botfly parasitism and nest predation by larger birds or monkeys, there is low fledging success in this species in much of its range.

But that’s not the end of the story.  There is another player:  Polistine wasps, medium-sized wasps related to yellow jackets that build a large, papery nest, are aggressive hunters of flying insects, like botflies.

Caciques seek out trees with wasp nests, leaving a respectful distance between their nests and the wasp nest to avoid arousing the insects.  Wasp arousal, however, IS triggered by monkeys and larger-bodied chick predators like Toucans, Caracaras, or Great Black Hawks that move the branches and nests in their search, and most often, the predators are driven away by the wasps.

Yellow-rumped Caciques aren’t always so lax in allowing Giant Cowbird females access to their nest.  In fact, if the nest apartment house is built near a wasp nest, the wasps act like botfly exterminators, and with less risk of botfly larvae debilitating their chicks, the Caciques actively defend their nests against Giant Cowbirds.  The wasps have also been observed to drive away monkeys who try to raid the Cacique nests. So, there is a double benefit of nesting near wasps.

And there is still more to the story.

Yellow-rumped Caciques also seek out big trees on islands in their riparian habitat to build their apartment houses, because Caimans or Giant Otters in the rivers will attack and eat anything that tries to cross the river onto the island, such as snakes that are adept at climbing trees with an appetite for chicks.  In these situations, Caciques will also be intolerant of Giant Cowbirds presence.  Female Caciques stay close to their apartment house, foraging individually rather than in a group, so that there are always large numbers of them present to mob predators and Cowbirds and drive them off.

Adolescent Yellow-rumped Cacique females may not breed until they are three years of age, but stand guard at the nest apartment house ready to drive away predators and Cowbirds.

An adaptable breeding strategy, coupled with their high degree of sociality for nest defense, helps the Yellow-rumped Cacique survive in a world full of predators and parasites.

the love life of the Greater Rhea

At least one species of large flightless (ratite) bird inhabits each of the major southern continents: the ostrich in Africa, the emu in Australia, and the Rhea in South America.  All probably followed a parallel evolutionary path of flightlessness and gigantism from their flighted ancestors, once their continents had broken away from the southern supercontinent of Gondwanaland during the Cretaceous period.

Evolution of flightless (ratite) birds, from MappingIgnorance.org

While traveling through the Cerrado of Brazil, we spotted Rheas many times, as they foraged in agricultural fields and grassy, open areas of the Cerrado.

Question: How do flightless birds get over a fence?

Answer: they go under it!

Rheas stand over 5 feet tall, supporting their elongated neck and football-shaped body on long legs.  They are not particularly attractive, with their loosely feathered plumage that usually looks disarrayed and scraggly.

Three large, wide-spaced toes and long, sturdy legs support this 80 pound, giant omnivorous bird.

They do have pretty brown eyes, though.

Rheas spend a lot of their time, head down, walking slowly through open grassland or crop fields hunting for tidbits of grain, grass, insects, perhaps small nestling birds, or anything else edible to pick up and toss back into their gullet.

During the non-breeding season, they may be shy, and run from perceived threats. This bird is moving at a fast trot, but Rheas can run almost 40 mph, using their outstretched wings as rudders to steer right and left.

Other than being large and flightless, Rheas seem mostly unremarkable.  But not when it comes to their love life.

Males engage in chest-bumping and neck thrashing to establish their nesting territory.

Two male Rheas are duking it out, pushing against each other breast to breast while beaking each other.

Once they have established who is top dog in a particular area, a male actively courts and copulates with a number of females.  Then he builds a nest by trampling and scraping out a grassy disk, pushing dirt away from the center until he has built up a mound three feet across and 30 inches deep and invites his courted harem of females to lay their eggs within.  Before he begins incubating his clutch of eggs, there may be somewhere between a dozen to 50 eggs in his nest mound.  Incubation takes about a month, and the eggs hatch within hours of each other.  The chicks are protected by the male for up to six months.  So each male is making about a 7 month investment in his offspring.

Male Rhea and chicks (photo from https://www.animal.photos/bird4/rhea-gtr.htm)

Meanwhile, in a complete reversal of the usual female role in nurturing their offspring, the females have wandered off, looking for other, likely males with whom to mate, and deposit more of their eggs in another nest, leaving that male to incubate and rear their chicks.  They will have nothing further to do with the rearing of their chicks.

This complicated “romantic” breeding strategy has the fancy name polygynandric, which simply means males breed with more than one female (like Red-winged Blackbirds) and females breed with more than one male (like many shorebird species).

Footlose, and fancy free, a female Rhea, can just lay her eggs, and then walk off.

So, does this peculiar breeding strategy work?  As you might imagine, incubating such a large number of eggs might be disadvantageous, and in fact, only about 3/4 of such large clutches actually hatch.  Worse yet, territorial males sometimes give up incubating duties to another male so that they can go collect another harem at another nest site.  And 65% of the males were found to desert their nests in the middle of incubation, either because of disturbance from predators, livestock, or humans, or for no apparent reason.  In one study of 34 Rhea nests, only 20% hatched any chicks at all.

With this low reproductive success, Rheas in South America are a near-threatened species, especially with more of their Cerrado habitat being converted to agriculture.

Scenes from the Cerrado – plants and their pollinators

Although we visited the Cerrado in the dry season, there were many shrubs and trees putting out new leaves and flowers, even in the absence of any trace of rainfall for the past 6 months.  Extensive underground aquifers that fill during the rainy season are tapped by deep roots of most of these plants, ensuring that they can flower and produce seeds when their pollinators and seed dispersers are present.

One of these small shrub/trees was quite common, and was particularly noticeable because of its huge displays of large, white flowers.

This is the Pequi tree, (Caryocar brasiliense), whose large white flowers produce copious nectar and pollen.  It blooms only during the dry season — July to September.

The leaves of Pequi trees are leathery, an adaptation to living in an arid environment. The flowers are rather large (bee in the top flower provides size comparison) and white with lots of yellow stamens.  They produce copious nectar throughout the night, which is higher in sugar concentration in the morning than the evening.

Artistic view of the Pequi flowerhead

If there were a single plant species whose absence would markedly affect insect, bird, mammal, even human populations in the Cerrado, the Pequi would be it.

Pollination is done mainly by bats at night, but the plant is also visited by nocturnal moths, wasps, and ants, all feeding on the nectar produced by the flowers.  In the daytime, no nectar is produced, but bees and wasps visit the flowers to feed on pollen.

Hummingbirds may be found on the flowers at dusk and in early morning, cashing in on that last sweetened formula of nectar the flowers put out.  Guira, White-lined, Palm, and Siaca Tanagers along with Curl-crested Jays also frequent the flowers at dusk as well:

Colorful Guira Tanagers sip the nectar, eat the flowers, and munch on the seeds of the Pequi.  Photo by Dario Sanches.

Curl-crested Jays hang around the Pequi trees in the very early morning hours, perhaps to feast on the insects that are attracted to the flowers. (Photo by Debbie Reynolds)

Glittering bellied Emerald hummingbirds are one of many hummingbird species that depend heavily on the nectar provided by flowering trees.

But that’s not the only role that Pequi plays in the Cerrado.  Well-pollinated flowers produce a bounty of nuts, eaten by animals and especially favored by indigenous people of the Cerrado.

Pequi seeds in Cuiaba, Brazil market (Photo by Mateus Hidalgo).

The pulp surrounding the seeds has been described as aromatic, fruity, and cheesy, and can be eaten raw or used to flavor other dishes.  The seeds (with spines removed) are roasted and eaten like peanuts, or crushed to extract their oil, so the whole fruit has great commercial value.  Pequi trees are typically planted around villages for residents to harvest the tree’s bounty.

Why do some birds have such long tails?

Aerodynamically speaking, tails are a drag for a bird that needs to gain lift to remain airborne, so tails should be short and flexible to act as rudders in flight.  Yet some birds (especially males) sport elongated, ornate, feathery ornaments at the ends of their bodies intended to attract the opposite sex.  These long tails are indeed an impediment to flight, but the birds’ ability to fly with such a handicap is a signal to the female of the male’s fitness as a mate.

In other species, both sexes have a forked tail with elongated outer tail feathers and shorter inner tail feathers —the most well known example being the Barn Swallow, a bird famous for its rapid changes of direction in flight as it pursues insects.  A number of other bird species exhibit similar tail structures, but you have to wonder how this sort of a tail helps aerial insect foragers?

Swallow-tailed Kites, named not only for their tail similarity to Barn Swallows, but also for their darting flight patterns as they pursue insects, can rapidly change direction, fly upside down or even backwards moving only the outer tail feathers as they glide on extended wings through the air.

While on hikes in the Pantanal in Brazil, we had an opportunity to watch Fork-tailed Flycatchers foraging from a favorite perch, as they sallied out and back in tight circles.

Fork-tailed Flycatcher sitting with its elongated tail streamers fluttering in the breeze.  These birds are commonly found foraging in open fields and riparian pastures, from Mexico to Argentina, and rarely wander up the east coast of the U.S. in migration.

Some rapid-fire photos of their predation attempts might help illustrate how elongate outer tail feathers are used to produce the quick direction changes in these aerial foragers. (Successive images of the bird’s flight have been super-imposed on the original image of the bird perching.)

From its perch, a Fork-tailed Flycatcher soars upward on a foraging attempt.

Is that curl in one outer tail feather purposeful or just a result of wind?

Super-imposed images of the Fork-tailed Flycatcher as it descends back to its perch.  The change in the flexion of the upper outer tail feather looks more purposeful.

So, how do these elongate outer tail feather assist in rapid direction changes in these birds?

In a study of the aerodynamics of flight in Barn Swallows, Åke Norberg noted that the outer tail feathers are drooped below the rest of the tail surface to increase lift and reduce drag in the tail. (This mechanical advantage is similar to the way flaps on the wing of fixed aircraft function to achieve lift.)  Norberg further demonstrated that the arc of the central shaft of the outer tail feather and its elongated streamer are adjusted continuously as the bird turns in tight circles, ascends, or descends. Alternate lift/drag differences on the two sides of the tail enable rapid changes in direction.  Thus, the longer the tail, the more efficient the flight in complex aerial patterns.

Presumably, the same advantages of tail structure and foraging habits hold for other long-tailed members of this large family of flycatchers (Tyrannidae), like the Scissor-tailed Flycatcher of the southwestern U.S. and the Streamer-tailed Tyrant of the Brazilian Pantanal.

Scissor-tailed Flycatcher

Streamer-tailed Tyrant

 

[R. Åke Norberg, 1994.  Swallow-tailed streamer is a mechanical device for self-deflection of tail leading edge, enhancing aerodynamic efficiency and flight manoeuverability.  Proceeding of the Royal Society B. Vol 257, 22 September 1994.]

Jabiru – a giant stork

The last in this series of the very large animals of South America is the Jabiru Stork, the tallest flying bird of the continent (equal to the flightless Rhea) with the second largest wingspan (after the Andean Condor).

Males are about 25% heavier (about 15 pounds) than females (about 11 pounds) and may reach 5 feet in height.  Their wingspan ranges from 7 to 9.5 feet across their body.

A stork with a wingspan so long it doesn’t even fit in the frame of the camera. (Photo by Debbie Reynolds)

These large-bodied wading birds feed near streams, ponds, or rivers, but are not at all picky eaters, taking whatever crosses their path: mollusks, amphibians, snakes, mice, small birds or bird eggs.  They probe with that enormous bill into mud for invertebrates which they can detect with the tip of the bill, grab, and throw it up and back into their gaping maw,

The bill is wide and thick and slightly upturned.  When they stand around in swampy water, they are likely to be besieged with biting flies that are attracted to the naked black skin of the stork’s head. (Photo by Debbie Reynolds)

Although usually seen in pairs, Jabirus respond to high densities of food (e.g. small mammal population explosion) by congregating there in large numbers.

Jabiru parents build an enormous stick nest which is used for multiple years, and may end up being 3 feet wide and 6 feet deep.

Their nests are easy to spot from far off. Usually one parent stands guard to protect the chicks from predation by raccoons or other storks.

They rear their 2 to 5 chicks to fledging for almost 4 months and then continue to feed their young for another 3 months.  Consequently, Jabirus usually breed every other year; only 25% of the pairs may be successful raising another clutch of chicks in a successive year.  But since they are long-lived birds (35 years), they will undoubtedly replace themselves many times over.

One parent shields the chicks from the heat of the afternoon sun. It’s amazing how much just a little shade lowers the heat load in this tropical environment.

Jabiru Storks are truly an iconic bird of tropical South America.

Giant rodent of Brazil

Continuing the discussion of “giant” animals of Brazil, how about the Capybara, the largest rodent (think rats and mice) in the world?

Capybara and its youngster strolling along the Pantaneiro (road through the Pantanal).  Female capybara usually have 1-4 young at a time, but we usually saw only one youngster at a time — probably due to predation.

These giant rodents stand 2 feet tall at the shoulder, are 3.5 to 5 feet long, and can weigh 80-150 pounds.  They are highly social, congregating in herds of 30 to 40 animals, but also travel in small family groups.

A herd of capybara settled onto the bank of the lagoon we were walking around at sunset one evening.

When the vegetation dries up on land Capybara switch to eating aquatic vegetation, like the water hyacinths that border rivers and streams.

Being a large, stocky, heavily furred rodent in a hot, tropical climate would be really disadvantageous, if not for the capybara’s love of swimming.  They dine on aquatic plants, soak in water during the heat of the day, and can cross rivers when they want to move to other areas to forage.

But danger lurks in the waters of the Pantanal…

Jaguar are also excellent swimmers, and are much faster and more powerful than Capybara, one of their primary prey.

Although Capybara are superb swimmers and can hold their breath under water for several minutes at a time, there may not be many places to hide from a Jaguar under water.

And Caiman also inhabit the shores of ponds, lagoons, and small streams in the Pantanal and would relish a meal of Capybara.

Life is fraught with danger if you’re a Capybara living in the Pantanal, which is why their life expectancy is just a few short years.

the flower picker

I remember sitting in the dark before dawn near some feeders in southeastern Arizona two years ago, just to catch a glimpse of a rare visitor to the area, the Streak-backed Oriole.  After 3 hours we did catch just a brief glimpse of “the bird” (there was only one).  Now two years later, I find they are common in this part of Mexico, and seem to like to enrich their fruit diet with a few flowers (perhaps containing nectar) plucked from various vegetation.

Streak-backed Oriole, Jalisco, Mexico

This bird was exploring the purple Jacaranda flowers, pulling them off the tree at random. Note the streaks along its back behind its head. Well-named bird!

Streak-backed Oriole, Jalisco, Mexico

Another oriole attacked the much larger flower of a banana plant. Perhaps it was attracted to the large red sheath at the base of the banana bunches.

Streak-backed Oriole, Jalisco, Mexico

The bird pecked at several places on the flower, but didn’t seem to find much.

Streak-backed Oriole, Jalisco, Mexico

And off he went…with some part of the plant grasped in his toes.

Like most Orioles, males of the Streak-backed variety are the most colorful, with females being considerably duller and less orange.  However, the species ranges from northern Mexico (occasionally venturing into southern Arizona) where the two sexes are completely different in color, through most of Central America, where the two sexes become more and more similar in coloration going south.

Why would there be such a difference between coloration of females from the northern vs southern extent of their range?

Apparently, Streak-backed Orioles maintain permanent territories year-round in the southern part of their range, where the bright coloration of the females helps territory defense.  In more northerly areas, the orioles maintain only a breeding territory, and may undergo short migrations away during the non-breeding season!