Carrying Capacity

Many visitors to the Island want to know where are the best places to see wildlife.  For variety and consistency I would have to say the Dungeness area on the south end of Cumberland, especially the quarter mile stretch between the Miller Greene cemetery and the beach.  Within this relatively short distance several Island eco-systems come together to create a bottleneck effect where animals from these converging habitats live together in close proximity.  At the center of this wildlife corridor is a boardwalk that borders a tidal creek and saltmarsh.  During high tides, Bottle nosed dolphins will sometimes move up this creek to feed.  In the warmer months, both alligators and manatees also frequent the waterway as well.  At low tide the creek is greatly reduced in size leaving a large area of exposed oyster beds and mud flats.  This is when wading birds and some shore birds move in to feed.  Raccoons find a buffet of things to eat here but are most often found digging fiddler crabs along the mud flats.  Occasionally river otters can be seen catching fish and blue crabs that congregate in the deeper areas of the creek at low tide.

Much of what happens in a saltmarsh eco-system can be observed from the south side of the boardwalk, but turning to the north side the vegetation of a maritime forest borders these wetlands.   Large live oak and red cedar trees grow here and are interspersed with a profusion of under growth that attracts a great variety of migratory song birds in the spring and autumn months.  Leaving the boardwalk on the east end, visitors are surprised to see the remnants of a maritime forest that was killed by migrating sand; here the twisted remains of dead live oak trees reach up through the sands of the large active dune that killed them.  This surreal landscape is a favorite location for photographers as a foot trail to the beach winds through the area.  A number of game trails also converge in this crossing zone between the habitats of saltmarsh, maritime forest, inter-dune meadows and the nearby beach.  The mostly night time activities of animals can be seen etched in the sand every morning.  This is an area we cover with our early morning birding tours that can quickly turn into tracking tours, depending on the amount of animal use the night before.  The easy to observe signs left here by wildlife tell a revealing and often dramatic story.  Signs of fighting, mating, searching for food and territorial marking with scat are just part of the story.  It’s easy to see which animals travel between habitats in this location and how often they pass through.  Understandably, reptiles such as lizards, snakes and alligators are only active during the warmer months.  But even then, their use of this cross over is infrequent.  Bobcats and coyotes hunt the area year round but may not be seen for intervals of up to a month.  However raccoons, opossums, armadillos and deer leave tracks almost every night:  especially raccoons.  This is one animal that really thrives on Cumberland because it can find food in all of the various habitats on the Island, while there are plenty of suitable den trees in the forest area as well.

In an area with s0 much wildlife I often think about the carrying capacity of the eco-systems they are a part of.  In other words, the number of species and the numbers within each species these areas can support.  This is an exercise for trained wildlife biologists but most people can understand that a natural area will only accommodate a certain number of animals.  If these numbers are exceeded; starvation, disease and damage to the habitat itself soon follows.  National Park lands such as Cumberland are managed to maintain a natural balance of native species.  This may include re-introducing native predators that were exterpated earlier in order to control prey species that can overpopulate.  Proper wildlands management also includes removing non-native species that upset the natural balance that developed over evolutionary time.  The Park Service also recognized the impact humans can have.  That is why they have a limit on the number of people allowed to visit the Island on a daily basis.

I wonder if scientists will ever identify the human carrying capacity for coastal eco-systems in relation to the heavy development that is occurring along the east coast, and will the government ever regulate these numbers?  One thing I know for sure, is that after talking with thousands of visitors to Cumberland over the years there is a growing awareness of what is being lost to development in other coastal areas.

Spring Thoughts and Encounters

Spring is well underway on Cumberland Island even though we have experienced some recent cold snaps over the last few weeks.  Temperatures have ranged from the low thirties to over eighty.  A couple warm days together managed to bring forth our first reptile sighting of the season; a six foot long Eastern Diamondback rattlesnake.  We watched as the snake slowly crossed the main road and disappeared into a nearby thicket of saw palmettos where it will be safe from snake predators such as hawks and owls,, but not from feral hogs.  One thing I have noticed over the years is when hog populations increase, I see fewer snakes.  Feral hogs are known for eating these important reptiles that help control the rodent populations and the diseases they carry.

On Cumberland the hog numbers are up, but that may change soon as the Park Service steps up their efforts to hunt them.  Also, there are some indications the coyotes that have recently found their way to the island are now feeding on pork among other things.  As temperatures rise alligators will become active and they too feed on hogs that often roam the wetland areas.  Over the years I have seen a number of hogs floating in the water that were killed by alligators; one was still in the reptile’s mouth.  Alligators don’t usually try to eat a large animal right after killing it because their teeth are not designed for chewing.  More often, they will let the carcass partially decompose in the water so it can be easily torn into bite size pieces and maybe it improves the flavor for them also, who knows?  It’s amazing how some animals can tolerate such extremes in the quality and condition of the foods they consume.  I often think of this when I drive by some fast food places on the mainland.

The breeding season for wild turkeys is getting started and there is a lot of this activity on the island now because we have a lot of turkeys.  I would have to say there are more turkeys on Cumberland today than I can remember at anytime in the past.  If anyone wants to photograph wild turkeys, this is certainly the time and place to to it.  The birds are not hunted here and therefore not afraid of people, making them much easier to observe and photograph. 

There are quite a few song birds visiting the island now as part of the spring migration.  Large flocks of Yellow Rumped warblers have already passed through.  While a number of other species will stay and nest here this time of year.  One bird in particular is not shy about it’s nesting intentions.  The Carolina wren is a true extrovert with a loud call that rings out through the forest.  This bird also nests where it pleases; meaning, it can be inside someones car or house if the windows are left open.

Winter shorebirds are still on the beach.  Many of these species will soon begin a migration northward to their nesting grounds in the arctic region.  However, the Oystercatchers are paired up now and will be nesting on Cumberland in a few weeks.  The nests of these beautiful birds is nothing more than a depression in the sand above the high tide line, usually closer to the foredunes.  Oystercatchers are a species of critical concern because they need wild undisturbed beaches for nesting and this type of habitat has become increasingly rare as so many beaches along the east coast have been developed.  Cumberland provides suitable conditions for ground nesting shore birds like Oystercatchers, while the park service  will also place signs near a nesting area warning people to stay away. 

Also on the beach are a few shells left over from winter northeast storms.  More recently though a number of Keyhole urchins, also known as sand dollars have been washing ashoree on the north end of the island to the delight of those visitors who collect them.  Sand dollars are related to both the Starfish and Sea urchins.  Most of the ones I’ve seen on Cumberland have been on the north end of the island.  This may be due to a shallow shoal area not far off shore which would be good habitat for this burrowing marine animal.

Spring is happening on Cumberland and it is a good time for visitors to experience the great variety of wildlife we have out here.