Birds and the Border

Diane and I have visited the border between the US and Mexico a number of times in the last few years.  One reason we go to these areas is because a lot of interesting birds reach the northern end of their range in the borderlands and are hard to find in other parts of North America.

Plain Chachalaca (Ortalis vetula) is a tropical bird that reaches
the northern end of its range in South Texas.  Photographed
at Estero Llano Grande State Park.

South of San Diego, California is the busiest port of entry in the US.  This border crossing connects suburban San Diego and Tijuana, Mexico.  Millions of vehicles and many more millions of people cross there every year.  The border wall is very prominent in this area.  Metal slats, in some areas topped with razor wire, restrict the flow of people.  The barrier even runs into the Pacific Ocean.  Customs and Border Protection’s (CBP) white and green-striped trucks are common in the area and agents ride jet skis a half mile into the ocean to look for swimmers trying to go around the wall.  While birding along the Tijuana Slough just north of the border in California, we saw our first White-tailed Kite (Elanus leucurus) and Long-billed Curlew (Numenius americanus). 

Border wall between the US and Mexico extending
into the Pacific Ocean. Viewed from Tijuana, Mexico.

Some of the nation’s premier birding spots are in the mountains of southeastern Arizona.  These sky islands rise from the Sonoran and Chihuahuan deserts and host many bird species that are at the northern edge of their range.  Painted Restart (Myioborus pictus), Mexican Jay (Aphelocoma wollweberi) and Elegant Trogon (Trogon elegans) are all species that just reach the US in these mountains.  

Elegant Trogon (Trogon elegans) in Cave Creek Canyon, Arizona.

Painted Redstart (Myioborus pictus) in Maderia Canyon, Arizona.

The Huachuca Mountains lie just a few miles from Mexico and border security is ever-present.  The canyons of these mountains are renowned for their bird life.  One of these canyons also hosts Fort Huachuca, established in the 1870s as a cavalry outpost in the Indian Wars.  In addition to the ubiquitous CPB vehicles, this area has another interesting border security device. On most days, an aerostat, a blimp-shaped balloon, flies over the fort on a tether.  We met a couple of soldiers from the base while hiking and they told us the aerostat has radar and other sensors to watch the border.  

The Fort Huachuca aerostat, visible as a white dot
to the left of the pine. This blimp-like ship has sensors
to monitor the US-Mexico border. 
Carr Canyon, Arizona.

Closer view of the aerostat. 
Carr Canyon, Arizona. 

Mexican Jay (Apheolocoma wollweberi) in Ash Canyon, Arizona.

The Rio Grande valley in Texas is another area where rare birds abound at the border.  This fall we went with a group that birded from near the mouth of the river to the fabled cowboy town of Laredo.  The lower end of the Rio Grande valley is subtropical.  Native palms are abundant in the few remaining natural areas and the region is a major citrus producer.  The birds here also have a tropical flavor about them.  Of the 181 species of birds our group saw, I had previously seen 15 of them in the American tropics.  Some of these tropical birds were; Tropical Kingbird (Tyrannus melancholicus), Great Kiskadee (Pitangus sulfuratus), Neotropic Cormorant (Phalacrocorax brasilianus), Plain Chachalaca (Ortalis vetula) and Ringed Kingfisher (Megaceryle torquata).  The tropical affinity of the region extends to its insect life.  South Texas has its own leafcutter ants (Atta texana).  These ants march from their nests, cut sections of leaves from live plants and carry the leaf parts back to the nest.  At the nest, the ants chew up the leaves, inoculate the macerated plant tissue with a fungus and then eat the fungus.  These ants are farmers.  

Texas Leafcutter Ants (Atta texana) at Frontera Audubon, Texas.

Another Lower Rio Grande Valley location we visited was Sabal Palm Sanctuary in Brownsville, Texas.  The Sanctuary was actually located on the other side of the border wall.  Sabal Palm is in Texas so we did not need our passports and did not enter Mexico.  We drove over a dike and through a gap in the rusty slat wall to the Sanctuary.  At Sabal Palm, we got our first looks at the Altamira Oriole (Icterus gultaris) and Olive Sparrow (Arremonops rufivirgatus).  If the border wall at Sabal Palm became as impervious as the wall near San Diego, the Sabal Palm Sanctuary, homes, farms and cemeteries would be lost in a no man’s land between the border and the wall.  

Border wall, Sabal Palm Sanctuary, Texas.

For much of the length of the Rio Grande in Texas there is no wall.  A few hundred feet of water is all that separates Mexico from the United States.  Much of the border is rural with farms or scrub forest on either side of the river.  These areas still have a CBP presence.  Cleared riverbanks, dikes with roads on their tops, towers with floodlights and cameras are scattered along the US side of river.  

Altamira Oriole (Icterus gularis) at Salineno Preserve, Texas.

Altamira Orioles on Customs and Border Patrol
floodlights, San Ygnacio Sanctuary, Texas.

The Juarez-Lincoln Bridge links Laredo, Texas, USA to Nuevo Laredo, Tamaulipas, Mexico. As traffic waited on the bridge to enter the US, our birding group saw two Ringed Kingfishers, the largest kingfisher in the country in Laredo.  One of these birds flew across the river and it was no longer an American kingfisher but a Mexican one.  Birders are particular about where they see a bird.  Some go so far as keep lists for counties, states, countries and the world.  We could not count birds on the Mexican side of the Rio Grande for our Texas bird list.  

Ringed Kingfisher (Megaceryle torquata) at Zacate Creek, Laredo, Texas.

We saw dozens of birds cross the river between the two countries.  Green Jays (Cyanocorax yncas), White-tipped Doves (Leptotila verrauxi), Great Kiskadees and Gray Hawks (Buteo plagiatus).  All made the crossing at Laredo in seconds while drivers on the bridge waited an hour to cross.  

Great Kiskadee (Pitangus sulphuratus) at Quinta Mazatlan, McAllen, Texas.

Green Jay (Cyanocorax yncas)
 at Laguna Atascosa National Wildlife Refuge, Texas.

The southern border, like all international frontiers, is a political boundary imposed on an ecological landscape.  What a sharp contrast between the ease with which birds cross the border and the complications to people crossing.    

Iron and Water

Sometimes in a swamp or marsh, you can see a metallic sheen on the surface of the water.  It may look like an oil spill but it is usually a molecular scale layer of iron floating on the water’s surface.  You can tell oil on water from iron on water by touching the surface.  If the film breaks up into plates, it is metallic.  

Iridescent layer of iron produced by bacteria floating in a marsh in Clayton County, Georgia.

If the layer swirls and reforms, it is oil.  The basis for the sheen with both oil and iron is thin film iridescence.  This type of iridescence is found not only with oil on water and iron on water but also in soap bubbles.  The thickness of the film determines which colors are reflected, so oil spilled on a wet road or soap bubbles may show all the colors of the rainbow. 

Plates of iron bacterial film broken up by water movement. 

Oil on pavement showing thin film iridescence.

This iridescent layer is the signature of a bacterial ecosystem that runs on different ionic forms of iron.  The sheen appears in still water when there has been no rain for several days.  Rain or water current will break up the layer into plates and they will wash away.  In these swampy places, decomposition of plant material by bacteria and fungi deplete the oxygen in the water.  This anaerobic environment is where a several bacteria use iron in their metabolism.  Animals, plants and most fungi are aerobes and carry out their energy metabolism by removing electrons from organic molecules like sugars.  These electrons go through a bewilderingly complex set of chemical reactions to make cellular energy.  In the last step of this process, the electrons end up on oxygen.  Bacteria involved in making the iron sheen have a similar type of energy metabolism but rather than dumping their electrons on oxygen, they put their electrons on the oxidized form of iron.  This oxidized iron is abundant in the red clay soils of the southeastern Piedmont.  The iron that has gained those electrons is said to be reduced, an odd term since the atoms have actually gained something (electrons). 

Bacterial iron film.

Reduced iron is an energy source used by another group of bacteria, the iron oxidizers.  These bacteria remove the electrons from the reduced iron and regenerate the oxidized form while producing their energy.  Iron oxidizing bacteria live at the top few millimeters of the anaerobic swamp water where a small amount of oxygen is dissolved.  The bacteria deposit the iron produced by their metabolism as iron oxide, also known as rust, at the surface of the water and make the shining layer.  These two groups of bacteria depend on the metabolism of each other to fuel their survival.

If you run across iridescence in a marsh, it probably does not signal a petroleum release but rather a sign of an iron-based microbial ecosystem. 

The Birds and (wait for it) the Bees

One of our favorite places to visit in South Florida is a tiny park in the beach town of Lantana.  The Lantana Nature Preserve is a 6.5-acre piece of old Florida.  The Preserve is located between Lake Worth and the Atlantic Ocean and is a reconstructed Florida maritime hammock. The Preserve was constructed on the site of the old Lantana town dump.  The dump was cleaned up, fill was added to make an artificial dune and exotic plants were removed.  Red Mangroves (Rhizopora mangle) and Sea Grapes (Coccoloba uvifera} fringe the Preserve while Cabbage Palms (Sabal palmetto), Wild Coffee plants (Psychotria nervosa), Gumbo Limbo trees (Bursera simaruba) and a giant fig (Ficus sp) grow in the interior.  A quarter mile trail winds through the Preserve giving intimate views of the plant life, butterflies, birds and bees.

Giant Ficus in Lantana Nature Preserve

Male Red-bellied Woodpecker at nest in Cabbage Palm

During a visit in May, we found Red-bellied Woodpeckers (Melanerpes carolinus) with a nest in a live Cabbage Palm. In most of their range, Red-bellied Woodpeckers nest in dead trees or at least in dead branches. Where Cabbage Palms are available, these woodpeckers will make nests in the soft, fibrous trunks of the live palm.  Red-bellied Woodpeckers drill a round hole about two inches in diameter in the tree trunk, then burrow down about a foot to make the next cavity.   We watched the nest as the adult birds would regularly visit bringing food to the nearly fledged young peeking out of the hole. Red-bellied Woodpeckers usually lay about four eggs.  We could see two young woodpeckers peeking from the hole waiting to be fed.  Woodpeckers typically use a nest hole only once. 

Male Red-bellied Woodpecker bringing food to young woodpecker

Immature Red-bellied Woodpecker looking out of the nest

In September, we returned to the Preserve and found the nest again.  To our surprise, the nest no longer hosted woodpeckers but instead hosted Honey Bees (Apis mellifera).  After the woodpeckers left the nest, bees must have come from an already established hive whose population had grown too large. Large hives produce new queen bees that will fly off with about half the hive’s population of worker bees in a process called swarming.  The swarm will stay in a compact group and send out scouts to look for a new hive location.  When the scouts agree on a new nest site, they lead the swarm to it and the new hive is established.  The bees will then make hexagonal cells of wax to grow the next generation of bees.  The bees will fill other waxy cells with honey they made from nectar.  Honey is the food to fuel the members of the hive. 

Honey Bees using the old Red-bellied Woodpecker nest

This cabbage palm tree in Florida hosted two different species of vastly different size, behavior and ecological needs in the same year.  A scarce resource like a good nest tree can have many different users, even birds and bees. 

Bug Stories

An adult Large Milkweed Bug (Onopeltus fasiciatus) on
Tropical Milkweed (Asclepias curassavica) 

Two brightly colored species of bugs are conspicuous in the fall and they are not even trying to hide.  They are the Large Milkweed Bug (Oncopeltus fasiciatus) and the Boxelder Bug (Boisea trivittata).  These two are true bugs in the Order Hemiptera, a group that also contains aphids, leafhoppers and stinkbugs. Hemiptera go through incomplete metamorphosis.  When a true bug hatches, it enters a larval stage called a nymph.  Nymphs look like miniature adults but lack wings.  The nymphs eat and grow.  As they grow, the nymphs molt their exoskeletons several times. With each molt they becomes larger nymphs. After going through several nymphal stages, they undergo a final molt to make the winged adult.  This type of development contrasts with complete metamorphosis where a worm-like larva emerges from the egg.  After several molts, the larva makes a cocoon or chrysalis where a complete rearrangement of the body plan produces the adult.  Moths and butterflies are typical insects with complete metamorphosis.  The larvae are the caterpillars and the adults are flyers.     

Large Milkweed Bugs spend much of their life on milkweeds (Asclepias sp).  Like Monarch Butterfly larvae, Large Milkweed Bugs consume their host milkweed and incorporate cardiac glycoside toxins into their bodies. Like Monarch Butterflies, Large Milkweed Bugs have a bold pattern of orange and black to warn predators.  

Large Milkweed Bugs on a fruit of Asclepias sp.

Large Milkweed Bugs have four nymph stages and at each stage, the nymphs are bright orange.  The adults have wings that are black with an orange “X” pattern.  Both nymph and adult Large Milkweed Bugs use a mouthpart called the proboscis to suck nutrients from their host milkweed plant.  Adult Large Milkweed Bugs survive the winter in this area by burrowing in leaf litter and entering a hibernation-like state called diapause. 

Large Milkweed Bugs mating on a Milkweed

Eggs of Large Milkweed Bugs on the underside
of a Tropical Milkweed leaf. 

A mixed group of adult and nymph Large Milkweed Bugs on the leaf of
Common Milkweed (Asclepias syriaca). The large nymphs have small, black,
non-functional wings.  

Large Milkweed Bugs nymphs feeding on seeds of Common Milkweed. 

It is no surprise that Boxelder Bugs live on Boxelder trees (Acer negundo).  Boxelders are not elders at all, they are maples.  Boxelders are interesting for a couple of reasons.  First, they are the only North American maple with compound leaves.  Boxelder leaves typically have 3-7 leaflets.  Second, Boxelder is the only North American maple with separate male and female trees.

A single compound leaf with three leaflets
of Boxelder (Acer negundo).

Winged fruits with seeds of Boxelder.

Boxelder Bugs have a wider range of hosts than the milkweed bugs, laying their eggs on Boxelder, other species of maple and ash trees.  The eggs hatch and bright orange nymphs emerge.  The nymphs feed on their host plant, particularly the seeds, grow and molt.  Like the Large Milkweed Bug, Boxelder Bugs have four nymphal stages and then molt into the winged adult. 

Boxelder Bug nymphs (Boisea trivittata) on the bark of
a Boxelder tree (Acer negundo).  The large nymphs have
non-functional wings. 

A group of Boxelder Bugs with both adults and nymphs. Adult
Boxelder Bugs have dark brown wings with orange stripes.

Adult and nymph Boxelder Bugs.

The adult Boxelder Bugs are dark brown to black with deep orange stripes on the wings.  The colors are warning signals to predators not to eat these bugs.  Indeed, Boxelder Bugs are protected by chemical defenses.  Unlike Large Milkweed Bugs and Monarch Butterflies, Boxelder Bugs do not ingest toxic chemicals from their host plants but make them from scratch.  Boxelder Bugs have glands in their abdomen that release noxious smelling (and tasting) compounds if attacked by a predator.  Because the nymphs feed on the Boxelder seeds large groups of Boxelder Bugs of different developmental stages are found on the female Boxelder trees during the fall.     

Boxelder Bug nymph feeding on a Boxelder seed.

Be on the lookout for these bright bugs as the bug season winds down.

Advice from a Caterpillar

While Alice was adventuring in Wonderland, she met a hookah-smoking caterpillar who asked her unpleasant questions and gave her advice.  The caterpillars we run into can give us advice too. 

Monarch Butterflies (Danaus plexipus) feeding on Aster sp. in the
North Carolina mountains

Two common butterflies in the Southeastern United States advise their predators, and us, how dangerous they are.  Monarch Butterflies (Danaus plexipus) are the most charismatic of our butterflies.  They are large, brightly colored and undertake epic migrations from Mexico to Canada and back.  If you plant milkweed in your garden you will probably have Monarchs.  They lay their eggs on the milkweed (Asclepius sp.) leaves.  

Butterfly Weed (Asclepius tuberosa), a species of
Milkweed

The eggs hatch into caterpillars with alternating white, yellow and black stripes.  Monarch caterpillars are not trying to hide.  That is because the milkweed upon which they feed is laced with cardiac glycosides, a potent toxin.  

A caterpillar of the Monarch Butterfly
on Tropical Milkweed (Asclepius curassavica)

Cardiac glycosides, as the name suggests, interferes with heart function that can result in heart failure. Cardiac glycosides also interfere with the digestive tract and muscular system of mammals that ingest them.  Not only that, these molecules taste bad.  The target of cardiac glycoside is a protein pump found in the membranes of all animal cells called the sodium-potassium ATPase.  This large protein maintains the proper balance of sodium and potassium ions in cells.  This is particularly important in muscle and nerve cells.  Monarch caterpillars take in the toxin when they eat milkweed leaves and store it in their bodies.  This makes them less palatable to predators like birds or mice.  The adult Monarchs retain cardiac glycosides after metamorphosis and this protects them from their bird predators.  A good question is; Why don’t the cardiac glycosides kill the monarchs?  It turns out the Monarchs carry a mutated version of the gene for the sodium-potassium ATPase that imparts  resistance to the effects of cardiac glycoside.  So the caterpillars can eat toxic milkweed with impunity, retain the toxin, advertise their toxicity with bright colors and patterns and pass this protection on to the adults. 

A Gulf Fritillary butterfly feeding on Lantana camara.

Another caterpillar giving advice is that of the Gulf Fritillary (Agralus vanilla).  The Gulf Fritillary butterfly, like the Monarch is large with a distinctive pattern of vivid colors.  When seen from above the Gulf Fritillary butterfly is bright orange with bold black spots.  The underside of the butterfly wings are brown and orange with large white spots.  

A Gulf Fritillary seen from below showing large white
spots on an orange and brown background.

Gulf Fritillaries lay their eggs on leaves of Passionflower vines.  The caterpillars hatch and eat the Passionflower leaves. Passionfllowers have chemical defense molecules called cyanogenic glycosides that protect the plant by releasing cyanide.  When a herbivore eats a Passionflower leaf they are poisoned by the cyanogenic glycosides.  But even cyanide cannot deter Gulf Fritillary larvae from eating the leaves.  The caterpillars are bright orange with black spines as if they are daring a bird to eat them.  Like the Monarch, its caterpillar is conspicuous and downright threatening.

Yellow Passionflower (Passiflora lutea) a host plant for
Gulf Fritillaries

Gulf Fritillary caterpillar on Passaflora sp.

Both the caterpillar and butterfly are protected by toxins from the Passionflower.  The adult butterfly also releases noxious chemicals from a gland in the abdomen to further deter predators.    

As a rule, boldly colored insects are toxic and should not be eaten.  I knew a young man that wanted to taste everything he could in the woods.  One day he found a Lady Bug and popped it in his mouth.  He immediately spit it out and spent the next half hour trying to get the horrible taste from his mouth.  The Lady Bug, with its red color and black spots was giving advice.  So are some of the caterpillars. 

An Asian Lady Beetle (Harmonia axyridis) aka Lady Bug
warning us not to eat it.

Basal Angiosperms II

 I wrote earlier this year about a group of plants called basal angiosperms.  These are flowering plants that branched off the evolutionary line that led to the eudicots and monocots.  Basal angiosperms have some characteristics of both monocots, like flower parts in multiples of three, and eudicots, with net veined leaves. 

Waterlilies are basal angiosperms classified in the family Nyphaeacea and grow on all continents except Antarctica.  These familiar plants grow in lakes, ponds and slow-moving streams.  They have floating leaves and brightly colored flowers that emerge from the water.  The largest waterlily in the world is from South America.  This waterlily, Victoria amazonica, has leaves that are ten feet in diameter and can support the weight of a person.  A famous nineteenth century lithograph shows young Annie Paxton standing on a leaf of V. amazonica at the English estate Chatsworth.  Annie’s father, Joseph Paxton, was the head gardener at Chatsworth and the first to get V. amazonica to flower in England.  Paxton noted the ribbed supports on the underside of the leaves of V. amazonica and used these as inspiration to design a large greenhouse at Chatsworth.  Later Paxton became the lead architect of the Crystal Palace that housed the Great Exhibition of London in 1851. 

Annie Paxton standing on a Victoria amazonica leaf at the
English estate of Chatsworth in 1849.
https://en.wikipedia.org/wiki/Victoria_amazonica
 

We could not visit the Amazon Basin to see these lilies but Fairchild Tropical Botanic Garden in Miami, Florida has Victoria sp. growing in a pond.  The Miami Victorias are not as large as those growing in the Amazon but the Florida plants sport 2-3 foot leaves that have the characteristic upturned edges.

Victoria sp leaves at Fairchild Tropical Botanic Garden
Miami, Fl

Two common waterlilies in the Southeast are the alliterative Nymphaea and Nuphar.  One is Nymphaea odorata or the fragrant waterlily.  The scientific name of the fragrant waterlily is a wealth of information.  The genus Nymphaea gets its name from the nymphs of Greek mythology.  These minor female deities were associated with natural sites, particularly water.  The species name, odorata, tells that the flowers are fragrant and help attract its beetle pollinators. Fragrant waterlily leaves are large, bright green and oval shaped with deep cleft that runs to near the center of the leaf.  The flowers are white with dozens of petals and numerous stamens. 

Fragrant Waterlily (Nymphaea odorata) in Salisbury, NC

Nuphar advena, the yellow pond lily or spatterdock, has floating leaves and a yellow flower that emerges above the surface of the water.  The petals of the flower are inconspicuous while the sepals give the flower its yellow color.  Spatterdock is widely used in traditional medicine to treat diarrhea and skin disorders. 

Spatterdock (Nuphar advena) in Palm Beach County, FL 

 Magnolias are a large group of highly successful basal angiosperms.  The family Magnoliaceae contains more than 200 species and they are found in North, Central and South America as well as East Asia. Two important members of this family in the Southeastern United States are Tulip Poplars and Southern Magnolias. 

Liriodendron tulipifera goes by a number of names Tulip Poplar, Tulip Tree or Yellow Poplar and is among the tallest eastern trees.   Tulip Poplars in the Joyce Kilmer Memorial Forest in western North Carolina tower to heights of more than 160 feet with circumferences of greater than 20 feet.  Tulip Poplars are fast growing, long lived trees that are valuable for timber.  Tulip poplar leaves are large with four lobes and its yellow-green flowers are tulip-shaped.  The flowers have 3 sepals, 6 petals with orange at their bases and multiple stamens and carpels. 

Tulip Poplar (Lirodendron
tulipfera) flowering in April, Salisbury, NC
The flowers are shaped like tulips.

Close up of Tulip Poplar flowers showing six petals, numerous stamens and carpels.

Southern Magnolia, Magnolia grandiflora, is a forest tree with large shiny green leaves and in late spring produces large, white, fragrant flowers.  One of the primitive characteristics of magnolias is their stamens and carpels are arranged in a spiral pattern rather than a whorl.  As the petals fall from the flower the spiral-pattern of stamen scars are apparent.   The carpels that produce the seeds are in a cone that also has a spiral pattern. 

Bud of Southern Magnolia (Magnolia
grandiflora) in Salisbury, NC

Flower of Southern Magnolia with multiple petals. 

Mature flower of Southern Magnolia.  It has multiple petals, many stamens
some of which have fallen on one of the petals and numerous carpels, 

Details of a Southern Magnolia flower.  Petals are inserted at the bottom of the flower.
Next come the yellow stamens and at the top are the many carpels that will produce seeds. 

A dying Southern Magnolia flower.  In the center is the carpel that will develop into
the seed bearing cone.  The purple column below the carpels has the spirally arranged
purple scars where the stamens were attached. 

An immature cone of Southern Magnolia
with its carpels and a few stamens
still attached.

Southern Magnolia cone.  Below the cone are
scars from the stamens and below them
are the spiral scars of the petals.

A nearly ripe cone of Southern Magnolia.  Seeds are developing
inside the cone.

A mature cone of Southern Magnolia.  The bright red seeds
are being released. 

By early fall, the cones split and show bright red seeds.  The seeds remain attached for a time attached to the cone by strong, silky threads that smell, oddly enough, like Juicy Fruit gum.  

Mature cone of Southern Magnolia with red seeds.

Southern Magnolia seeds are attached to the cone by threads
that smell like Juicy Fruit gum. 

These basal angiosperms are relics of deep time.  They remind us of a world long past.  So next time you see a magnolia or a water lily or a pawpaw, think dinosaurs.