A Thorny Subject

 

Thorns of Trifoliate Orange (Poncirus trifoliata).
Rowan County, North Carolina. 

It happens all the time.  Hiking through a field, I get pulled up short by a Blackberry cane and come away with a bloody scrape.  Plants that grab and slash are said to be armed and botanists have precise terms for these armaments; thorns, spines and prickles. 

Wounds from Blackberry (Rubus sp.) prickles.
Rowan County, North Carolina. 

Thorns are modified branches that come to a point.  These sharp structures defend the plant from the attention of herbivores.   Sweet Acacia, Vachellia faresiana, is a shrub in the bean family, Fabaceae.  It has a world-wide distribution and in the US it grows in the west and Florida.  We found Sweet Acacia flowering in the deserts of southeastern Arizona.  The thorns are arranged along the stem and protect the delicate leaves and bright yellow flower clusters. 

Sweet Acacia (Vachellia faresiana).
Cochise County, Arizona. 

Honey Locust (Gleditsia triacanthos) is a tree in the bean family.  It is native to the Mississippi valley but has been introduced to many areas around the world.  Honey Locust has impressive, 3 inch, multi-pointed thorns that probably evolved to protect the tree from giant ice age mammals that are now extinct.

 

Giant thorns of Honey Locust (Gleditsia triacanthos).
Rowan County, North Carolina. 

Another small tree with impressive thorns is Trifoliate Orange (Poncirus trifoliata).  Trifoliate Orange is a close relative of oranges and lemons.  It is native to northern China and Korea and has been naturalized in many countries.  Trifoliate Orange is cold tolerant and is used as root stock to graft  species of Citrus.  Because of its thorns Trifoliate Orange is planted as a natural fence.  

Leaves and thorns of Trifoliate Orange.
Rowan County, North Carolina. 

Members of the family Cactaceae have spines.  Cacti have reduced their leaves through evolutionary time to spines.  This change lowered the leaf surface area and cut down on water loss from the plant.  The spines have lost their photosynthetic ability and the cactus stem has taken on that function.  The stems also store water, and the spines protect that precious resource from thirsty desert creatures.   

 

The aptly named Fishhook Barrel Cactus (Ferocactus wislizeni)
has hooked spines..
Portal, Arizona.

Prickly Pear Cactus (Opuntia ficus-indica) with spines.
Arizona-Sonora Desert Museum, Arizona.

Saguaro (Carnegiea gigantea) with rows of spines.
Arizona-Sonora Desert Museum, Arizona. 

Some armed plants have structures that resemble thorns or spines but are extensions of the epidermis called prickles.  Both thorns and spines have vascular bundles running down their center, but prickles lack this tissue.  Blackberries (Rubus sp.) and Roses (Rosa sp.) have hooked prickles on their stems.  Greenbriar (Smilax sp.) is a vine that also bears prickles.  Besides protection the prickles help these viny, rambling plants to climb over other vegetation. 

Blackberry (Rubus sp.) armed with prickles.
Rowan County, North Carolina. 

Prickles on Multiflora Rose (Rosa multiflora).
Rowan County, North Carolina.

Greenbriar (Smilax sp.) showing its prickles. 
Rowan County, North Carolina. 

You often hear people talk about thorns of the rose.  This combination of beauty and pain have made roses a powerful symbol of love over the centuries.  But roses have prickles, not thorns. This misuse of terms is common. Thorn and spine are used interchangeably by most people and prickles are hardly mentioned at all.  But to botanists, thorns, spines and prickles have a precise meaning that the rest of the world ignores, at its peril.

The Bosque in Winter

 

Bosque and surrounding mountains. 
Pecha Dam State Park, New Mexico.

Our recent trip to New Mexico introduced us to a unique ecosystem, the bosque.  The bosque is an open woodland with scattered trees, shrubs and grasses found along rivers in the southwestern United States.  Bosque is the Spanish word for forest and reflects the influence of Mexican culture in that part of the country.  One of the best places to see the bosque is along the Rio Grande in New Mexico.  It is 400 miles long and a few miles wide, surrounded by desert. The bosque originally ran from near Albuquerque south to El Paso, Texas.  Before the arrival of Europeans, the river ran in a multitude of  braided channels. Frequent floods would change the route of the flow and create sandbars, ponds, sloughs and marshes.  These wetlands provided extensive habitat for wildlife.

Rio Grande and bosque.
Albuquerque, New Mexico.

Bosque del Apache National Wildlife Refuge.
 New Mexico.

The transition from bosque to desert can be abrupt.  Climbing a few feet above the floodplain, the forest disappears and the Chihuahuan desert scrub takes over. 

Desert at Bosque del Apache National Wildlife Refuge.
Socorro County, New Mexico.

The dominant tree in the bosque is the Rio Grande Cottonwood, Populus deltoides wislizeni.   Rio Grande Cottonwoods are large trees, reaching 80 feet in height and 9 feet in diameter.  The bark is dark gray with deep fissures. In the fall, the green leaves turn gold and during the winter many Cottonwoods retain their leaves. Cottonwood require the sub-surface water of the river floodplain. 

Rio Grande Cottonwood (Populus deltoides wislizeni).
Albuquerque, New Mexico.
Photo courtesy of Dr. Richard Pockat.

A multitude of mammals call the bosque home. We saw Mule Deer (Odocoileus hemionus) browsing the forest edges and Collared Peccaries or Javelinas (Dicotyles tajacu) rooting in the fields.  Javelinas are pig-like mammals with small tusks that feed on cacti, fruits, eggs and reptiles throughout the bosque.  Javelinas are found from South America through Central America and reach the northern end of their range in the Southwestern United States. 

Mule Deer (Odocoileus hemionus).
Bosque del Apache National Wildlife Refuge, New Mexico.
Photo courtesy of Dr. Richard Pockat.

Javelinas (Dicotyles tajacu).
Bosque del Apache National Wildlife Refuge, New Mexico. 
Photo courtesy of Dr. Richard Pockat. 

Perhaps the most interesting mammal in the winter bosque is the North American Porcupine (Erethizon dorsatum).  This large rodent is known for the quills that cover its coat.  The quills are actually hollow, barbed hairs that protect the slow moving porcupine from predators.  North American Porcupines are vegetarians and we found one high in a tree eating bark. 

North American Porcupine (Erethizon dorsatum).
Albuquerque, New Mexico. 

Bird life is diverse and abundant in the bosque.  I wrote about the Snow Geese (Anser caerulescens) of the bosque in the last blog but there is so much more to the avian life there.  Many species of ducks inhabit the ponds and streams of the bosque in winter.  Diving ducks like Ring-necked Ducks (Aythya collaris) and Canvasbacks (Aythya valisineria) frequent the deeper ponds.  

Ring-necked Ducks (Aythaya collaris).
Albuquerque, New Mexico. 

Male Canvasback (Aythya valisineria).
Albuquerque, New Mexico. 

Dabbling ducks like American Wigeons (Mareca americana), Northern Pintails (Anas acuta) and Northern Shovelers (Spatula clypeata) are abundant on shallow ponds.  

Male American Wigeon (Mareca americana).
Albuquerque, New Mexico.

Male Northern Pintail (Anas acuta).
Bosque del Apache National Wildlife Refuge, New Mexico. 

Male Northern Shoveler (Spatula clypeata).
Bosque del Apache National Wildlife Refuge, New Mexico. 

The most dazzling of the bosque ducks is the Wood Duck, Aix sponsa.  The males have bright red eyes, a black face with white stripes and an iridescent green cap with a dashing crest.  Female Wood Ducks are plainer than the males but have a lovely, tear-shaped eye ring.

Male Wood Duck (Aix sponsa).
Albuquerque, New Mexico. 

Female Wood Duck.
Albuquerque, New Mexico. 

Another water bird of the bosque is the magnificent Sandhill Crane (Antigone canadensis).  These birds stand over four feet tall, with a gray body and a red cap.  Sandhill Cranes winter in southern states and northern Mexico then migrate north to breed.  Their ringing call sounds across the ponds and sloughs throughout the day.  

Sandhill Cranes (Antigone canadensis).
Bosque del Apache National Wildlife Refuge, New Mexico.

Sandhill Crane in flight.
Bosque del Apache National Wildlife Refuge, New Mexico.

Raptors abound in the bosque.  We saw American Kestrels (Falco sparverius) perching on wires and treetops.  They would turn into the wind, hover, then dive on unsuspecting rodents.  Another small predator we found was a Western Screech Owl (Megascops kennicottii) dozing in the mouth of a nest box. 

Male American Kestrel (Falco sparverius).
Bosque del Apache National Wildlife Refuge, New Mexico. 

Western Screech Owl (Megascops kennicottii). 
Albuquerque, New Mexico. 

There are many land birds in the bosque too.  Coveys of Gambel’s Quail (Callipepla gambelii) with their jaunty topknots and rufous caps scamper through the brush giving their plaintive calls.  Overhead, flycatchers like the subdued Says Phobe (Sayornis saya) and the dazzling Vermillion Flycatcher (Pyrocephalus obscurus) snap up insects on the wing. 

 

Gambel's Quail (Callipepla gambelii).
Bosque del Apache National Wildlife Refuge, New Mexico. 

Say's Phoebe (Sayornis saya).
Bosque del Apache National Wildlife Refuge, New Mexico. 

Male Vermillion Flycatcher (Pyrocephalus obscurus).
Pecha Dam State Park, New Mexico.  

Three different species of bluebirds live in the bosque.  The most impressive is the bluest of the bluebirds, the Mountain Bluebird (Sialia currucoides).  The males of this lovely species are turquoise on the head and back, sky blue on the breast and fade to light blue on the belly. 

 

Male Mountain Bluebird (Sialia currucoides). 
Bernardo Wildlife Management Area, New Mexico.  

Blackbirds (Family Icteridae) are well represented in the bosque.  Western Meadowlarks (Sturnella neglecta) can be found singing, even in winter.  Brewer’s Blackbirds, (Euphagus cyanocephalus) gather in large flocks to feed in fields and perch in the tops of trees.  Male Brewer’s Blackbirds are iridescent black with yellow eyes and the females are brown with dark eyes.  We also found a single Yellow-headed Blackbird (Xanthocephalus xanthocephalus).  With its black body, bold white wing patches and bright yellow head, the Yellow-headed Blackbird stands out among the other blackbirds.  

Western Meadowlark (Sturnella neglecta) singing to the sunrise.
Mesilla Valley Bosque Wildlife Refuge, New Mexico. 

Male Brewer's Blackbird (Euphagus cyanocephalus).
Bosque del Apache National Wildlife Refuge, New Mexico. 

Female Brewer's Blackbird.
Bosque del Apache National Wildlife Refuge, New Mexico. 

Male Yellow-headed Blackbird (Xanthocephalus xanthocephalus). 
Bosque del Apache National Wildlife Refuge, New Mexico. 

The bosque was once a continuous forest following the Rio Grande through New Mexico.  The same environmental conditions that make this area so biologically rich; fertile soil, mild climate and a steady water supply, have also made it desirable to people.  Large swaths of the bosque have been converted to agriculture, the river has been channelized and irrigation systems put into place.  Cities, large and small, have grown up on the bosque, but natural areas remain that give us a glimpse of this unique ecosystem. 

 

Bosque with hot air balloon.
Albuquerque, New Mexico

 Thanks to Dr. Richard Pockat for providing excellent photographs for this blog. 

The Flight of the Snow Geese

 

Snow Geese (Anser caerulescens) rising with the sun
at Bosque del Apache National Wildlife Refuge, New Mexico.

One of the world's great wildlife spectacles takes place each winter along the Rio Grande in New Mexico. Over 50,000 Snow Geese (Anser caerulescens) that breed in the North American Arctic during the summer, spend the cold months on the ponds and fields along the river.  

Sunrise over the Bosque del Apache
National Wildlife Refuge, New Mexico. 

Diane and I traveled with a group of birders to New Mexico this January.  We started in Albuquerque and followed the river south.  Our group arrived at the Bosque del Apache National Wildlife Refuge in the pre-dawn glow.  As we stumbled from the van, we could hear a giant flock of geese honking on the pond before us.  As the eastern horizon lightened it revealed the gabbling geese. Before the sun was up, some signal went out and the geese took flight with a mighty roar of wings.  They circled over the water and our heads with a cacophony of calls.  Their numbers were so vast they blocked out the rising sun behind them.  The geese flew for a few minutes then returned to land on the pond.  They repeated this action several times, then after the sun was well up, they flew off to their daily feeding grounds.   

Snow Geese resting before dawn.

Snow Geese in flight.

Snow Geese are joined in the Rio Grande valley by thousands of Sandhill Cranes (Antigone canadensis) and tens of thousands of ducks.  There are also Canada Geese (Branta canadensis) mixed in and a smaller number of Ross’s Geese (Anser rossii) that look like miniature Snow Geese.

Video of Snow Geese flying at sunrise.

Snow Geese have two color forms or morphs, the white Snow Goose and the darker Blue Goose.  Both morphs have black primary feathers and a white head, but the Blue Goose has a dark gray body.  Snow Geese and Blue Geese have dark pink legs and bright pink beaks that bear a black “grin patch”.  The grin patch, or smile, is the serrated edge of both the upper and lower mandibles.  The geese use this feature to graze on the rough plant material that makes up much of their diet.  The color of Snow Geese is controlled a single gene and in New Mexico the white form predominates. 

White morph Snow Goose.

Dark morph Snow Goose (Blue Goose).

White and dark morph Snow Geese in flight. 

A Ross’s Goose is about three quarters the size of a Snow Goose with a shorter neck and a pink beak that lacks the black smile.   Ross’s Geese also come in the white and blue morphs but we did not see any of the darker form in New Mexico. 

 

A Ross's Goose (Anser rossii), left of center,
among Snow Geese. The Ross's Goose is smaller with a shorter beak 
shorter neck, and no grin patch. 

Our group made a second visit to Bosque del Apache, this time in the afternoon.  The white Snow Geese were shining on the pond and an adjacent dike.  Blue forms were mixed in and with careful observation we could pick out the smaller Ross’s Geese.  The geese were placidly feeding making their honking calls when suddenly the whole flock went silent.  Every goose, on land and water raised their heads and then geese at the edge of the pond took off.  The flight became a wave sweeping across the water toward us.  As closest geese passed over our heads we were pelted with goose poop.  Like many birds, the Snow Geese lighten their load for flight and we got spattered.  They say getting hit is good luck.  We were indeed a lucky group. 

 

White and dark forms of Snow Geese resting on a dike. 

Snow Geese in flight. 

While this spectacular flight of Snow Geese can inspire awe, there is a downside. Unlike many species of birds, Snow Geese numbers are increasing.  The last century has seen their population grow from a few hundred thousand in the early 1900s to over 5 million today.  This increase in population was driven by drainage of wetlands and the conversion of forest and prairie to agriculture.  The geese found waste grain left in the fields and their numbers boomed.  The large population of Snow Geese is an environmental problem on their breeding grounds in the high Arctic.  The geese are overgrazing the tundra and this is having a negative impact on other species that live and breed in the Arctic.  One attempt to lower the Snow Goose population is a longer hunting season and increased bag limits.  So far this has not solved the problem. The Snow Goose population problem was, of course, caused by a species that currently numbers 8 billion.

Snow Geese rising.

Despite the clouds on the ecological horizon caused by the large Snow Goose population, the wintering  geese are an amazing sight that ranks with the Monarch butterflies in Mexico and the Wildebeest migration in East Africa.   If you get a chance, go to New Mexico in winter and experience the flight of the Snow Geese.

Snow Geese overhead.