Archive for February, 2013

Wind in the Woods

Saturday, February 23rd, 2013

snow-in-tree-fissures

The morning wind blows cold.  But deep in the woods, I find refuge from it.

High above, scraps of cloud hurry eastward at a purposeful clip.

Long-dead trees, leaning against their living cousins, groan slowly as they rub back and forth, pushed by an unseen hand.

Treetops creak as they bend, yielding to every gust.

And below, the trunks of trees are scoured bare of snow, save for a few dots and stripes of white, driven into the bark’s fissures by an untiring wind.–April Moore

Good News: Nature Rebounds on Pacific Islands Atoll

Friday, February 15th, 2013
the coconut crab, the world's largest land-dwelling arthropod

the coconut crab, the world's largest land-dwelling arthropod

I love reporting good news.  Even more, I love finding examples that illustrate the tremendous resilience of life.

So here is a brief summary of a very encouraging report I came across recently:

On Palmyra, a Pacific atoll of about 25 small islands about 1,000 miles south of Hawaii, many species of animals and plants that, just a few years ago, were endangered, are making a strong comeback.  Migratory shorebirds, nesting seabirds, coconut crabs, native trees, and other native species are all increasing in number.

And what is the cause of this welcome turnaround?  The eradication of rats from the entire atoll.

Thought to have been introduced to these islands during World War II, rats thrived in the tropical environment, reproducing three or four times a year.  By 2011, they numbered in the tens of thousands and did serious damage to island flora and fauna.

The invasive rodents ate land crabs, the eggs and chicks of ground- and tree-nesting birds, and the seeds and seedlings of native tree species.  But in 2011, the U.S. Fish and Wildlife Service and the Nature Conservancy, which cooperatively manage the Palmyra Atoll as a National Wildlife Refuge and a scientific research station, initiated a rat eradication program.

Thanks to a rodenticide that had proven successful on other islands, the Palmyra Atoll has recently been declared rat-free!  A year after the eradication program began, team members visited their 286 rat detection stations throughout the atoll four times in a month, and scoured the islands for signs of rats’ presence.  Not a trace could they find!  Instead, they found many signs that native species were recovering.

Evidence of recovery included a 130 percent increase in the number of seedlings of 10 native tree species, and the first record of seedlings of pisonia grandis, a rare flowering tree of the bougainvillea family.  (No seedlings at all had been found on the atoll in 2007, before the rat eradication effort began).  The team also found a 367 percent increase in such native arthropods as insects, spiders, and crabs.

“This wonderful atoll is again able to thrive the way nature intended–without rats,” says Susan White, refuge project leader.  ”Palmyra had been infested with rats for so long, there will be benefits to wildlife we didn’t even fully anticipate–such as the explosion of the fiddler crab population that we’re seeing.”

Indeed, “staff and visitors to the atoll have seen a large increase in the numbers of crabs, insects, seedlings, and seabirds,” adds Suzanne Case, executive director of the Nature Conservancy’s Hawaii program.

The blossoming of native species on Palmyra is an encouraging example of collaboration between government and non-profit organizations, of using science to solve a problem that then allows nature to thrive.  ”The collaborators did an outstanding job,” says Dr. George Wallace, vice president for ocean and islands at the American Bird Conservancy.  ”The science on these efforts has been evolving, and while there have been some learning experiences along the way, the Palmyra effort stands out as a great example of how to do it right and get rid of destructive invasive species while still protecting the native wildlife,” he explains.

In addition to its status as a national wildlife refuge, the Palmyra Atoll is also part of the Pacific Remote Islands Marine National Monument.–April Moore








The Woods At Dusk

Thursday, February 7th, 2013
a chestnut oak in our forest

a chestnut oak in our forest

The day is aging, and color drains from the sky.

Trunks of the tall trees lose their daytime hues of light and golden brown and grey.

Against the colorless sky, leafless oaks and hickories darken into silhouettes.

April Moore


How Do Birds Keep Warm in Winter?

Saturday, February 2nd, 2013

chickadee-d300-20091228-00331

On a very cold, snowy walk one recent morning, I wondered where the birds were.

Just the day before, I’d seen all the usual suspects–chickadees, titmice, nuthatches, and juncoes.  They’d eaten from the feeder, flitted in and out of  bushes, and hopped about on the ground.  But this day was much colder, and they were  nowhere to be seen.  Except for an occasional crow.

I assumed these little birds were keeping warm somewhere, taking the day off from their usual foraging.  But where were they?

And were they going without food?  I had to wonder–if  birds must eat voraciously every day in order to maintain their body weight, did the day’s extreme cold mean they had to sacrifice nourishment in order to keep warm?

And while I didn’t know the answers to my questions, I was not worried.   Birds have been navigating harsh winter weather for a very long time.  Still, I was curious. Where do birds go on the coldest days?

So I decided to do a little research.

I learned, not surprisingly, that small birds are more vulnerable to cold than large ones. Hence, the spotting of crows on that cold day, but not little guys.  Because of small birds’ proportionally larger surface area compared to their heat-generating core, keeping warm is more challenging for them.

Fortunately, small birds have many strategies for keeping warm on the coldest winter days. They do what they do on winter nights.  Chickadees, titmice, nuthatches, and woodpeckers, for example, gather together in a tight space, like a cavity in a tree, the dense branches of an evergreen tree, an old nest, a chimney, a birdhouse, or even in the space between a building and close-growing bushes.  In such close quarters, birds huddle together and share body heat.

Packing into a small space with their fellows is not the only tool small birds have for staying warm. Chickadees, for instance, can significantly slow their metabolism, so that their bodies burn fewer calories.  Their body temperature can drop by as much as 14 degrees F during very cold spells! Many birds can even control the temperature of their legs and feet separately from the rest of their body!  By constricting the flow of blood to their extremities, birds can maintain more heat in their core.

Feathers also play a key role in small birds’ winter survival.  Their oily surface is insulating, and some species even grow additional feathers during the fall to add greater warmth in winter.

And birds use their feathers in ways that increase the warmth they provide.  For example, many birds fluff out their feathers, creating tiny air pockets that hold warm air close to the body, like a down jacket.  On sunny days, birds turn their back to the sun and spread their wings and tail, maximizing the feathered surface area that receives the sun’s rays.  And birds crouch, covering–and warming–their feet and legs with their feathers.

Many birds fatten themselves up for the winter, building fat reserves by gorging during the fall.  During extreme cold, a last-ditch mechanism–that we share with birds–may kick in–shivering. Shivering occurs when the metabolic rate is elevated, generating more body heat.  But shivering is only a short-term solution, since it uses up a great many calories.

And I learned that, indeed, many birds do go without food on the coldest days.  Apparently, the energy little birds would expend in foraging on such cold days exceeds the energy they would derive from the food itself.  So, even though their nutritional needs are greater in colder weather, on the coldest days it makes sense for them to hunker down until the temperature rises.–April Moore






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