- Seaside Sparrow (Atlantic)
 - Seaside Sparrow
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 - Seaside Sparrow (Gulf of Mexico)
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Seaside Sparrow Ammospiza maritima Scientific name definitions

Jon S. Greenlaw, W. Gregory Shriver, and William Post
Version: 2.0 — Published July 1, 2022
Revision Notes

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Introduction

The Seaside Sparrow is a habitat specialist of salt and brackish marshes, and rarely freshwater marshes (subspecies A. m. mirabilis), along the Atlantic and Gulf coasts of the United States. First described in 1811 by Alexander Wilson (1), the species has attracted the interest of systematists since the late 1800s. It occurs in relatively small, localized populations that have been divided into several morphologically distinct subspecies, with weakly differentiated forms subsumed by some authorities. The population near Corpus Christi, Texas, south to the Rio Grande is an isolated and genetically distinct subspecies (A. m. sennetti) that appears to have a small population and is potentially at risk.

Nesting begins in May in northern populations and as early as March in the Florida Everglades. The Seaside Sparrow is socially monogamous, though extrapair matings have been reported. The species is territorial, but often feeds at long distances from the defended space around its nest, a response to the wide separation of nesting and feeding areas in tidal zones. In the Everglades, defended territories are typically all-purpose spaces that include the nest and areas to forage around bases of grass stems. Under ideal conditions it occurs at high population density, a reflection of the high productivity of some salt marshes. Optimal nesting habitat is found in tidal marshes with expanses of medium-high cordgrass (most commonly, Spartina alterniflora) with patches of residual (dead) stems. Nests are elevated above the marsh substrate in herbaceous vegetation and especially suitable sites are those that are not subject to extreme flooding and have open muddy areas for feeding. Nest mortality is caused mainly by flooding from storm-driven and spring high tides and by nest predation. Flooding is a significant mortality factor for populations in New England, whereas predation becomes more important regionally and locally south of New England and along the Gulf of Mexico. The relative importance of these sources of nest failure can vary from year to year at a single locality.

As a maritime wetland specialist, the Seaside Sparrow is an “indicator” of ecological integrity for certain types of coastal marshes and has proven sensitive to habitat modification in Florida. For example, of the seven subspecies recognized in this account, the Dusky Seaside Sparrow (A. m. nigrescens) of east-central Florida is now extinct, and the Cape Sable Seaside Sparrow (A. m. mirabilis) of the Florida Everglades is endangered. Other populations are likely also susceptible to disturbance and habitat loss. The Seaside Sparrow has been studied in detail in the northeastern United States (2, 3, 4, 5, 6), Georgia (5, 6), Florida (3, 7, 8, 9, 10), and Mississippi (11). Information is available on the genetic structure of all subspecies and multiple populations along the Atlantic coast (12).

Distribution of the Seaside Sparrow - Range Map
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  • Year-round
  • Migration
  • Breeding
  • Non-Breeding
Distribution of the Seaside Sparrow

Recommended Citation

Greenlaw, J. S., W. G. Shriver, and W. Post (2022). Seaside Sparrow (Ammospiza maritima), version 2.0. In Birds of the World (P. G. Rodewald and B. K. Keeney, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.seaspa.02