Seaside Sparrow Ammospiza maritima Scientific name definitions

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

Movements and Migration


In the migratory populations of two nearby tidal marshes in the town of Babylon, New York, adults and juveniles after the breeding season moved from a broad zone of unditched, inner intertidal marsh (Oak Beach Marsh) or disturbed, ditched inner marsh (West Gilgo Marsh) where they nested to the outer fringes of their respective marshes where tall Spartina alterniflora was setting seed in late August. The seed crops kept most of them on their marshes until fall departures peaking in October. Once the seeds became available, both adults and juveniles completed a post-breeding switch from diets of marsh insects and other arthropods (insectivory or arthropodivory) to a chiefly granivore diet. This may not always happen on the natal marsh in northern areas where migration occurs unless areas of tall S. alterniflora are present in daily flooded marsh edges facing a bay as on Long Island's south-shore barrier islands. Estuarine marshes in the mouth of a river may not offer this local, within-marsh movement opportunity (WP, JSG), where other forms of local movement may occur to other areas of seeding tall Spartina during adult molt and before migration.

Near Charleston, South Carolina, breeding populations of A. m. macgillivraii nest several kilometers upstream on river islands and both adults and juveniles (later) abandon these breeding sites after nesting by end of July and spend the winter in tidal marshes elsewhere (125; A. Given, personal communication). A. T. Wayne, an ornithologist from the Charleston area, spent most of his adult life collecting wintering sparrows on the coast in that region but never knew where they nested until a population was discovered inland in the region (120, 132, 125). These later authors assumed that local breeding birds inland near Charleston spent the winter on the nearest islands on the coast, but so far this hypothesis is unsupported (70). See macgillivraii under subspecies.

In a winter study on the north coast of South Carolina, of 51 individuals banded and recaptured in two winters, only one was banded at one study site and recaptured at another site, which was 420 m distant from the banding site (133). In winter, other local movements were made between feeding areas and roosting sites on marsh islands, where shrubs growing there provided cover and were infrequently flooded (see Habitat; WP). Marsh-wide floods during spring or storm tides with strong onshore winds also cause sparrows in the marsh grassland to retreat to the landward edge of the marsh where sheltering shrubs or Phragmites cover above flooding waters are available (WP).

In contrast, in the Everglades, there is no evidence for migration or even mid-distance population movements between isolated breeding units within the region. Adults and banded juveniles that did not "disappear" tended to stay in their immediate breeding or natal area, thus exhibiting little movement (9). Yet, within this general pattern, one case of an extreme movement was documented by a juvenile that after leaving its natal territory moved about 7,000 m into a new home range within the same breeding population (9).

Dispersal and Site Fidelity

Natal Philopatry and Dispersal

As in other saltmarsh sparrows (134), natal dispersal is limited. In South Carolina (A. m. macgillivraii), there was no apparent difference between male and female post-fledging dispersal distances: males, 268 m (range 55–602, n = 8); females, 156 m (range 20–294, n = 4) (135). Post-fledging dispersal rates were also similar: males, 5.5 m/d (range 1.3–12.6, n = 8); females, 6.8 m/d (range 1.1–18.4, n = 4) (WP unpublished data). A. m. mirabilis in Florida on average were resighted or recaptured 577 ± 98 m SD (n = 15) from place of hatching (135), but see Movement for one case of extreme movement of a juvenile (9). Maximum natal as well as adult breeding dispersal distances of mirabilis were occasionally > 1 km (131). Later, radio-tagged juveniles of mirabilis often range widely in small flocks and exhibited a more even distribution of dispersal distances than younger fledglings until onset of adult molt in August and September (9). After breeding period, juveniles in New York wandered up to 2.5 km from natal site, usually to feeding sites in tall Spartina alterniflora (WP). A nestling banded at East Quogue, New York, was caught 70 d later, 65 km west (U.S.G.S. Bird Banding Laboratory data, WP).

In South Carolina, distance between fledging site and first year (breeding) site was limited, and the same for both sexes: males, 234.1 m ± 28.8 SE (range 4–552, n = 34); females, 242.4 m ± 12.7 SE (range 81–688, n = 26). In South Carolina, no indication of additional dispersal following first breeding period; distances, fledging to year 2: males, 304.5 m ± 50.5 SD (range 38–596, n = 13); females, 286 m ± 21.8 SD (range 55–724, n = 10) (WP, unpublished data). From 1997–1999, return rates for juvenile A. m. mirabilis ranged from 15% to 20% one to two years post-banding (9).

In New York, none of the nestlings banded between 1977 and 1980 returned to the natal marshes during two studies (136, JSG). In Massachusetts, none of 35 nestlings banded in first year were known to have returned to the natal marsh the following year (117). In comparison, as noted above in the resident population of mirabilis, young birds mostly banded in the nest were often detected in their natal area in the following couple years, but at a rate lower than adults.

Adult Fidelity to Breeding Site and Dispersal

Breeding fidelity (philopatry) across years may be regarded as a species-specific tendency present in all northern, migratory populations where examined. In Massachusetts (117), 34% (4 of 13) of breeding adults returned to the same marsh the following year. Three of four returning adults occupied territories that overlapped with those of the previous season while the fourth defended a territory about 100 m from the one it occupied the precious year. However, little information exists on post-breeding movements in most northern, migratory populations, while strong quantitative results are available on nonbreeding period dispersal of adults and yearlings based on radio-telemetry and resightings of marked individuals of A. m. mirabilis, which is sedentary in the Everglades ecosystem complex of south Florida (137, 9; see Natal Philopatry and Dispersal above).

In a migratory population in New York, surviving males reoccupied the same or overlapping territories in succeeding years. When insufficient cover remained after a severe winter, they nested near previous territories. The mean distance between 1970 and 1971 nests of 9 males was 13.6 m ± 9.4 SD (range 1–28) (116). After nest destruction, both sexes renested within same territory (24 cases in New York) (116). Nonmigratory (northern Florida) birds stayed in or near breeding territory all year (WP). From 1994–1999, 28% to 48% of adult A. m. mirabilis returned to the same breeding territory one year after banding and 20% to 37% returned two years post banding (9). Over 5 years (1994–1998), return rates of adult mirabilis to breeding areas varied from 29% to 45%; 2 years post-banding, it was 20–37%; only 5% returned 4 years after banding. Average between-year distance of territories: 212 m (n = 30) (135). Occasionally adults undertake lengthy movements on their breeding grounds and typically return to their home ranges. But rarely they undertake longer movements: 3 radio-tagged individuals vacated their breeding territories and moved 450 to 7,000 m (7 km) into a new home range (9).

During breeding period, male A. m. nigrescens on Merritt Island, Florida, moved 1.6 km from original banding site, then returned, both movements apparently in response to variation in feeding conditions in marsh impoundments (138). Six of 13 A. m. nigrescens on Merritt Island, Florida, moved 1.2 km from one marsh impoundment to another. Two later returned to original capture point. Not known if such long-range movements were regular (138).

Adult males of A. m. mirabilis defended territories an average of 212 m ± 131 SD (n = 30) from the breeding territory location established within two previous breeding periods, indicating that adult of this subspecies are sedentary with low adult immigration and emigration rates (9). Distribution of dispersal distances of adults resembled an exponential decay in which most individuals moved less than 300 m from previous nestings (9). Post-breeding movements of adults were mostly short and concentrated < 400 m from breeding or banding sites (137). Researchers have found no movement between 5 isolated breeding populations of A. m. mirabilis in Everglades, Florida (139, 131, 135, 140).

Fidelity to Overwintering Home Range

Recaptures of an individual adult banded on both breeding grounds and wintering grounds has been reported only once—one individual banded as a nesting bird in Connecticut in 2010 (returning twice to that location) was found on its wintering grounds in South Carolina, where it was recaptured repeatedly at the same location over three successive overwintering periods. This observation supports breeding and nonbreeding inter-seasonal fidelity (philopatry) and within-season site tenacity in both seasons (110). Strong site fidelity was reported in North Carolina populations during overwintering periods (141, 142). During the nonbreeding period of 2006–2010 in North Carolina, 23% (173 returned out of 736 banded) of the adults returned to the same sites in following winters (142). In South Carolina, the winter return rate of birds assumed to be wintering non-residents was about 30% in one report and migrants about 30% in a second report (143) and 43% in the northern part of the state (133).

Migration Overview

Northeastern populations are short-distance migrants, although in mild winters some birds in New York are sedentary (WP). In northern migratory populations, older males males arrive before older females (see Timing and Routes of Migration), but there is broad overlap of sex and age classes. Southeastern Atlantic, Florida, and Gulf coast populations are nonmigratory. Populations near Charleston, South Carolina (A. m. macgillivraii) make short-distance movements (ca. 23 km) between coastal wintering marshes and brackish breeding marshes that apparently experience less nest flooding (109). Only three long-range banding recoveries (two as stopover migrants) have been reported: of 3,184 individuals banded by 1980, one individual banded in New York was recaptured in Rhode Island and another also banded in New York was recaptured about 64 km west in the same region (50); a third individual banded in Connecticut was recovered in South Carolina in three successive winters (110; see Dispersal and Site Fidelity: Fidelity to Overwintering Home Range). The overwintering range of northeastern birds (A. m. maritima) extends to Florida (WP).

Timing and Routes of Migration

Dates of spring departure from overwintering sites where the species does not breed are 12 April (Ft. Myers, Florida) and 15 May (Lucie County, Florida) (144). Schedule of arrival in northeastern United States varies geographically. Significant spring movement occurs as early as 20 April in Maryland (145). In New England, first arrivals vary from 14 April (Monomoy Island, Massachusetts) to 28 April (New Haven, Connecticut) (143). First arrivals in New York were 21–26 April in most years, with tenth percentile of males arriving by 30 April and by 5 May for females; median arrival dates were 12 May for males and 20 May for females (JSG, unpublished data). Some spring migrants overshoot breeding range, as indicated by specimen collected at Reading, Pennsylvania, 30 April 1887, and sight reports from coastal Maine from May to early June (50; see eBird).

Fall movement may begin as early as mid-August, based on records of birds that hit lighthouses in New York on 7 and 20 August (50). A nestling banded at East Quogue, New York, 21 June 1978 was recaptured 29 August at Oak Beach, 65 km west (WP). In New York, 95% of population has left breeding area by 1 November (WP). Fitted and smoothed capture patterns of banded adults in late summer and fall in Connecticut suggested a similar post-breeding pattern—early disappearance from breeding marshes small to nil—in which males exhibit a seemingly flat curve from August into October, while females exhibit a small decline (disappearance) in early August followed by flattening into October when most leave (35).

Most birds appear to migrate near and along the Atlantic coast in a narrow corridor (see Migratory Behavior); some overland, subcoastal migration is indicated by birds killed at TV towers in Raleigh, North Carolina, 180 km from Atlantic coast (146), and in Bladen County, North Carolina, 68 km from the coast (147). None were documented to have collided with a TV tower in northwestern Florida, where 42,384 bird specimens were collected over 25 years (148), suggesting that Atlantic coast birds seldom migrate to Gulf of Mexico. Stopover locations of two individuals migrating southbound from marshes bordering the Delaware Bay in New Jersey to overwintering marshes on Kiawah Island, South Carolina, confirmed stopover sites were distributed along the Atlantic coast in tidal marshes (70; see Habitat in Migration).

Specimen records from areas north of the typical breeding range suggest northward movement after nesting season: Ossining, New York, 2 October 1885; Muscongus Bay, Maine, 18 August 1884; Halifax County, Nova Scotia, 5 February 1962 (50). This is supported by observations from early August to October from Canadian Maritime Provinces and Maine (50, eBird). A bird banded near Fire Island Inlet, New York, 24 July 1977, was recovered 20 days later in Washington County, Rhode Island (50).

Migratory Behavior

A nocturnal migrant that mostly migrates near the coast as evidenced by birds hitting lighthouses at Fire Island and Little Gull Island, New York (50), and at Cape Island, South Carolina (Charleston Museum, unpublished data). There are over 20 records of TV tower fatalities near the coast, several of which indicated that some migrate somewhat farther inland (towers in Wake and Bladen counties) (146, 109, 136; see also eBird). Virtually nothing is known about migratory connectivity. Bowowske (110) found no evidence of sex- or size-based geographical trends in wintering individuals. Two individuals marked with GPS dataloggers when overwintering on Kiawah Island, South Carolina migrated north to summer in tidal marshes of the Delaware Bay in New Jersey, then used coastal tidal marshes as stopover sites during fall migration back to South Carolina (70). This study, together with observations on the rarity of inland records and evidence of migration fluxes at banding stations (WP, JSG), support the view that northern, migratory sparrows tend to migrate in a narrow corridor along the Atlantic coast and use coastal marshes as stopover sites (see Habitat in Nonbreeding Range).

Control and Physiology of Migration

Little information. Birds accumulate fat reserves before fall and spring migrations. Of 222 birds examined in New York during fall (15 September–15 November), 49% had moderate or larger fat deposits in furculum (fat class ≥ 2) (WP, unpublished data). By contrast, of 120 resident individuals examined on Gulf coast of Florida in fall (30 September–30 November), only 2 birds had moderate or larger fat deposits (WP, unpublished data).

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Seaside Sparrow

Ammospiza maritima


Estimates of relative abundance for every week of the year animated to show movement patterns. Relative abundance is the estimated average count of individuals detected by an eBirder during a 1 hour, 1 kilometer traveling checklist at the optimal time of day for each species.   Learn more about this data

Relative abundance
Week of the year

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