Cape Sable seaside sparrows are a subspecies of the seaside sparrow. It is endemic to southern Florida and has been designated endangered under the Endangered Species Act. Young birds’ backs are dark olive-grey with their tails and wings olive-brown. Adult birds, on the other hand, are light grey on the belly to almost white with dark olive-gray streaks on the breast and sides. At full maturity, they are only 13 to 14 centimeters in length.
You will find them in prairie habitat and breeding in mixed marl prairie dominated by gulf hairawn muhly. Sparrows make cup-shaped nests attached to vegetation a few inches above the ground and will produce two clutches per season. If the conditions are favorable, there may be a third.
Being very territorial, males will claim a patch of prime breeding habitat and defend it. While calling loudly to defend his territory, he also is advertising to the females. Courtship includes males chasing females and offering them food and nesting materials. It’s not uncommon for the females to initiate the process by approaching males and begging. Both raise their clutch of young together. They may also remain together for the next clutch.
Since they are omnivorous, they glean plant and animal items from the ground, including seeds, insects, and marine invertebrates.
The largest populations of the Cape Sable seaside sparrow are found in the Big Cypress National Preserve and Taylor Slough in Everglades National Park. Their name comes from Cape Sable at the southernmost point of Florida’s mainland and part of the Everglades.
The Cape Sable seaside sparrow requires aquatic prairie with low water levels and open areas. Alterations in water flow, caused by water management practices in South Florida, sea level rise, and hurricanes have all caused reductions in available habitat. Increasing plant density and diversity in the area for fire suppression has also reduced the open habitat they require. These factors are contributing to their decline.
Rising water levels effectively halts their breeding activities since their nests are suspended just off the ground. With daily water level shifts are affecting the behavior of territorial males, by subduing his vocalizations. Consequently, with its sensitivity to environmental conditions, it has earned the nickname “Goldilocks bird” since, in order for it to succeed, conditions must be “just right.”
In 2016 after heavy rains, the floodgates were open inundating areas where water levels have been relatively low for decades. Immediately sparrows in these areas lost breeding habitat. Afterward, further conservation activities were announced with plans to better support the sparrow.
The Cape Sable seaside sparrow illustrates the umbrella species concept of conservation biology. By protecting this bird, the result would benefit many other species.