Long-Term Hydrology

Long-Term Hydrology The Cape Sable seaside sparrow only breeds during the dry season when the water table can be as much as one meter below the surface. The dry season in the Everglades typically lasts from mid-March to mid-June. The hydrological data used to drive SIMSPAR (western sub-population only) consists of a set of long-term data from hydrological station, NP205. The water level versus year for NP205 is plotted at right. The red line signifies the mean sea level (MSL) height of NP205 (~ 180 cm). Cape Sable seaside sparrows traditionally build their nests at a height of 10 to 20 cm above the base of grass tussocks or at ~ 200cm MSL. When water rises above nesting height, sparrow's will delay breeding and if nests currently exist they will be abandoned due to nest inundation and their subsequent failure.

In order to successfully complete one brood, Cape Sable seaside sparrows need between 33 and 40 days when water levels do not rise above nest level. If there are less than 40 days where water levels do not drop below the nesting height then sparrows will be unable to breed during that season. If there are 60 days where the tussocks stay dry, the sparrow will be able to complete two broods. If there is greater than 90 days in the dry season, sparrows may be able to complete an additional third brood.

In the late 1970's there were a number of years where the water table was well below the surface. These years provided periods of greater than sixty days for the sparrow to breed. In the years between 1988 to 1992, the number of dry days for breeding was comparable to the late 1970's. The years 1994 and 1996 were some of the wettest on record. During these years most nests in the western sub-population were unsuccessful.


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