Acorns and Wildlife

October is when acorns ripen and fall from the trees; at times almost covering the forest floor.  On Cumberland there are eight species of oak trees that produce acorns.  However, the live oak, which is the predominant tree on the island, is also by far the largest producer of acorns.  Most people know that a tiny acorn can eventually become a huge oak tree, but fewer individuals understand how these oak seeds can effect wildlife populations.  A great number of animals depend on acorns as a food source; for some, their reproductive success is closely linked to the abundance of acorns.  For example:  White-tailed deer rely heavily on this nutritious autumn food, so when acorn production is high in the fall, chances are, there will also be a high number of fawns born the following spring.  If an animal eats well, they are more likely to reproduce well.  But this could ultimately lead to the future reduction in the number of oak trees; with a constant high number of browsing animals in the system there would be fewer acorns left for re-seeding the forest.  However, oaks have managed to survive by not producing a constant number of acorns each year.  During years of low acorn production, dependent animals adjust their numbers lower to match the food source.  If followed by a year of heavy acorn production, there will be a lot of food for the remaining wildlife plus plenty for re-seeding the forest.  It should be mentioned that large predators are also a regulating factor of plant consuming animals and complex relationships among all native plants and animals have been worked out over evolutionary time.  On Cumberland, however, this natural balance has been disrupted by non-native feral hogs.  Originally from Europe, hogs were first brought into North America and on to Cumberland in the 1500’s.  Hogs directly compete with native animals for the acorn crop but their population is not effected by acorn production because they have such a varied diet.  Also, while feeding, hogs root the ground plowing up the floor of the forest destroying the regeneration of new plant growth.  Left alone, hogs would eventually decimate a barrier island as they also impact other island Eco-systems with their rooting behaviour.  On Cumberland, predation on hogs from alligators and bobcats is hardly enough to keep their numbers under control.  These highly invasive swine can produce up to three large litters of young each year, so the National Park Service manages the hogs by hunting and trapping them.  The park service also sponsors six public hunts to help reduce the hog population.  The first hunt this year is in the third week of October and happens to coincide with the fall acorn crop which is much lower than what it was last year.  So competition for this important food source is much higher.  Removing the non-native hogs from this competition is a step towards achieving a more balanced natural system.

Fall Migration

October is the month when the fall migrations usually reach peak activity on Cumberland.  We already have peregrine falcons on the island following their food source:  other birds, south for the winter.  Peregrines, considered to be the fastest of all birds will also migrate long distances from the arctic regions to as far south as Argentina.  Of course, many of the small shore birds and song birds they feed on are in the area now.  Sanderlings, ruddy turnstones and semipalmated plovers frequent the beach this time of year while in the forest warblers are commonly seen.  Thirty two species of warblers have been recorded on Cumberland, so properly identifying these small birds in the thick vegetation can be a challenge.  American redstarts along with yellow throated and black and white warblers have been passing through for a couple weeks, while large flocks of yellow rumped warblers are just starting to arrive.

As for large numbers of birds though, nothing can compare with the huge flocks of tree swallows that usually show up in October.  Sometimes, thousands of these small dark colored birds swarm together over the inter-dune meadows and beach turning these areas black when they land in great numbers. 

A few bald eagles are on the island now, on their way to Florida for nesting season, but there were also two active eagle nests on Cumberland last year and once established, these birds may return to have their young.

The northern harrier or marsh hawk can be seen now flying low over the salt marsh and inter-dune meadows as flocks of cormorants fly higher over the island in V shaped formations.

Butterflies are also on the move.  Large numbers of sulfurs and gulf fritillaries have already passed through, being followed now by the monarchs.  Some years the monarch migration can be quite impressive.  I recall seeing great numbers of these large orange and black butterflies following the main duneline along the island as they work their way south toward a winter destination in Mexico.

Being located on the Atlantic flyway, Cumberland is both an important resting and feeding stop for many species of birds and butterflies during the migration.  This becomes apparent to anyone visiting the island during this active time of year.

Spanish Moss

Spanish moss is one of the most noticed and misunderstood plants on Cumberland.  Over the years, I have heard a number of unusual descriptions and interpretations of the ’strange stuff’ that hangs from the trees.  I remember a commercial photo shoot on the Island a few years ago, when one of the fashion models thought a set designer had “put that stuff in the trees” to enhance the photos.  More recently, a visitor said “the stuff in the trees” reminded him of women’s under garments and a walk through Victoria’s Secrets. 

Just the origin of the plants name sparks the imagination as it may have been compared to the long gray beards of early spanish explorers.  The truth is, spanish moss is neither spanish nor is it a moss.  Instead it’s a native sub-tropical air plant or epiphyte that draws nourishment from moisture in the air, as opposed to a parasite that would feed directly on the host tree it is attached to.  Some people are confused over this because they have seen trees killed by spanish moss.  This is due usually to large amounts of moss shading out the trees leaves rather than feeding on the tree itself; but this is seldom seen on Cumberland where frequent windy conditions prune back the buildup of moss on most trees.  On the other hand, spanish moss acts like a sponge during wet weather adding a great deal of weight to a tree.  If strong winds occur many limbs can be broken off, leaving the tree susceptible to insect damage.  But the reservoir of water held by this odd looking plant will benefit the surrounding forest as it is released slowly through evaporation, nourishing other moisture loving plants.  Wind and air quality play a key role in the distribution and survival of spanish moss.  Although it flowers and produces seeds, the plant spreads mostly by pieces that have been separated by the wind.  This air plant is also an indicator of air quality because it will not grow in a polluted environment.  Spanish moss hanging from a live oak, it’s main host tree, is the classic picture of the deep south.  This time of year especially, with our brilliant red and golden autumn sunsets, the moss stands out in the forest, back lit by a warm quality of light that can stir the imagination, but for some reason it just doesn’t remind me of Victoria’s Secrets.