Temperature: Max 23o C
Day three largely consisted of travelling from Kissimmee to the Vester Field station in Bonita Beach which gave us an opportunity to spot wildlife on the journey. In particular we saw large numbers of turkey vultures (Cathartes aura) and black vultures (Coragyps atratus) catching thermals by the side of roads likely looking for roadkill. The black vultures which I had previously thought were turkey vultures, I learned could be identified by different white sections on the underwing when flying above (which I sketched).
The drive also took us alongside Lake Okeechbee, the largest freshwater lake in Florida being 1,900 km 2 yet having an average depth of 2.7 metres.
We had the opportunity to visit to the Arthur R.
Marshall Loxahatchee National Wildlife Refuge home to LILA (Loxahatchee Impoundment Landscape Assessment) an 80-acre model of the Everglades ecosystem. The model is used with the goal of restoration of the Everglades.
The Everglades system has been altered over the years by humans, in particular by draining, building levees, canals and floodgates for land development. This has resulted in the loss of much of the natural hydrology with little being known about the original hydrology.
Much research at LILA is into how water management can alter conditions within the Everglades ecosystem. This is used to test models prior to altering the Everglades system.
Water can be managed in three ways; depth, flow and timing. These are altered at LILA and the effect of this is recorded.
An example we were given of this was the effect of water availability on bird breeding:
- 1-2 years after a drought event breeding of wading birds is known to increase.
- This was thought to be as a result of reduced aquatic predation by predatory fish on crayfish. Therefore increasing crayfish populations and so influencing wading bird breeding.
- A drought was staged and 25,000 predatory fish were removed.
- Compared to a year without drought crayfish numbers increased fourfold which was as a result of reductions in crayfish predation due to removal and death of predatory fish. Whereas crayfish are able to burrow and survive periods of drought. As a result, a year after a drought there is an increase in crayfish populations explaining why there was an increase in bird breeding. (Dorn & Cook, 2015)
We came across a wide variety of species at the refuge, in particular many invasive species. An interesting find was the brightly coloured apple snail eggs attached to bulrush and the empty shells including that of the island apple snail (Pomacea maculate), native to South America. Apple snails are the primary food source of the snail kite (Rostrhamus sociabilis) and also the Limpkin (Aramus guarauna), likely culprits of the empty shells.
We also had the first chance to witness a swamp area along a boardwalk . This meant that we came across many fern species, which I am particularly interested in. Below are a few of the species that we came across, a species that I wasn’t expecting to see was the water fern (Salvinia minima) which is an invasive aquatic fern from South America and the West Indies.
Having had time to explore LILA we piled back into the minibuses and continued with our journey to the field station. We travelled along alligator alley which gave us an opportunity take in the sheer scale of the Everglades while travelling through the Big Cypress National Preserve (although the lack of alligators was more than a little disappointing).
Reference DORN, N.J. and COOK, M.I., 2015. Hydrological disturbance diminishes predator control in wetlands. Ecology, 96(11), pp. 2984-2993.