Continuation of radio-tracking of hatchling crocodiles to enhance the replication of these data. The spatial structure of the model consists of several spatially disjunct habitat areas, which we will refer to as wetland habitat sites. A fifteenth habitat area was added to the model, representing the scattered pieces of peripheral habitat in the agricultural areas. This aggregate of peripheral habitat, while not suitable for nesting, can act as a refugium for the kites during a system-wide drought. The hydrology of individual wetland habitat sites in particular years is critically important to whether that site can be used for nesting by snail kites.
Apple snails die or estivate, becoming unavailable, when a site becomes dry.
After a drydown a particular site may not be good habitat for a few years, until the apple snail population recovers. For purposes of modeling, the water levels in each wetland habitat site can be given by a historical record estimated from a single watergauge near the core habitat of the snail kites on the wetland site, or these water levels can be produced from hydrologic models applied to forecast future water levels under different water regulation conditions. Weekly water levels are entered in the model. Both in the simulations involving the historical record of water levels as well as for forecasts of water levels produced by hydrologic models, these levels are transformed into standardized levels by subtraction of the long term average and division by the long term standard deviation in historical water levels. Each modeled kite goes through a fixed set of life stages.