The apex alligator in photo #6436 described in the Alligator post is the Keystone animal for the Bird Island lake. Its behavior allows all of this balanced ecosystem to survive. Alligators are very territorial. There are only one or two and rarely three alligators that patrol the Bird Island lake. They feast on the other animals which attempt crossing the lake. The size of Apex Allie reflects the size, diversity and health of the system. The mass of the alligator pales in comparison to the mass of all of the birds, secondary predator animals and vegetation.
There are three potential access points that could allow an invasion of the predator animals onto the islands. The shallow areas close to the mainland which are overgrown with vegetation make two islands vulnerable. These are indicated at points listed on the map as A., B., and C. Human intervention is necessary to maintain the security of these vulnerable points. They need to be cut back on a regular schedule to prevent crossing by land or arboreal bridges through the overhanging vegetation. Note that Apex Allie is resting at a promontory of the mainland (See GPS location) that provides easy access to three sides of the South Island. It is a really big, well fed monster of an animal.
The birds seek out the areas that are protected by the alligators. Bird droppings are rich in nitrogen and other plant nutrients, therefore these areas have lush growth of native plants. The plants provide shelter for the birds. The secondary predators are attracted to the birds like a magnet, the alligators are attracted to the secondary predators. The alligators which eat the second level predators grow to substantial size.
If one of the layers such as the bird population collapses then the system is unsustainable. The isolation of the islands provided by the alligator shows their Keystone role in this collaborative circular economy.
In this schematic are four environments which are interconnected by bridges. These include air, water mainland and island. The two bridges shown here are soil and trees which support the bird populations. The water environment is dominated by the alligator. The alligator cannot climb the trees to threaten the wetland bird population. So they are safe if an alligator enters the island because the reptiles can’t climb trees. The aquatic birds are threatened by the alligator if they stay in close proximity to the island shore. If they move inland or from the shore to the undergrowth then they are at less risk. If a land bridge (shown in dotted amber line in the schematic) becomes available to the raccoon or other land based predators then the ecosystem will collapse. If the rats, snakes and especially the raccoons gain land access to the islands the birds and eggs will be eaten or the birds will abandon the islands. Raccoons are especially dangerous because they are prehensile and clever.
Characterizing the population of the Bird Islands. The island is populated by water birds many of which are moderate to large, big winged, long legged, migratory birds that roost and nest in the trees. There are many others. They typically feed on fish, insects, seeds, frogs, and anole. The overgrowth of trees provides perches and nesting areas for the birds. The interior has nests for the lower dwelling birds and some of the larger birds. There is nothing on the islands to feed on except for smaller birds. The population may be self limiting as determined by space.
| Organism | Takes | Gives | Relationship |
| Alligator | Food | Controls aqua population | Predator |
| Bird | Shelter and food | Nitrogen and nutrients | Predator |
| Raccoon | Food | Controls terra population | Predator |
| Tree | Nitrogen and nutrients | Shelter, Food | Mutualist |
The combination of these predators results in a stable system controlled by limitations imposed mostly by the animal niche behavior. This mutualist system is characterized by the cross predatory behavior.
If you look at the Bird Island apex alligator and compare it to this alligator you can see that it is at best one third of the size of the Bird Island lake alligator. True to the concept, the pond in which it resides is approximately one third of the size of the other lake. The pond also has no island. The iguana is a herbivore and the alligator is a carnivore. Mr. Iguana is very fast, climbs trees and is a very capable swimmer. He walked to the screen right. Thanks to Mr. Alligator my hibiscus survives for another day.
Naturally we can appreciate the beauty of the birds of the islands. Here are some busy birds on the island.
People provide the ultimate ecologic advantage to the species which satisfy their interests at the time. Human intervention provides an ecologic advantage to the birds by controlling the bridges to the islands, thus favoring the birds. Sometimes intervention can have unintended consequences.
References:
Florida water bird Colony locator
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