Breeding

Phenology

Pair Formation

Figure 7. In migratory population (NY State), older (after second year) males arrived on breeding marshes about 1 wk before females (WP). At Gulf Hammock, FL, males and females associated all year in or near breeding territory (WP). Males at latter site had cloacal protuberances as early as 9 Mar; first female brood patch seen 22 Mar.

First Brood

Date of first egg relatively constant among years. At Buzzard’s Bay, MA, first egg dates 25 May (1985) and 26 May (1986) (Marshall and Reinert 1990); at Narragansatt Bay, RI, about 23 May (DeRagon 1988). At Oak Beach, NY, average date of first egg 19 May, compared with 20 July for last clutches (Post et al. 1983). At Gulf Hammock, FL, first eggs found on 24 March (1979) and 23 March (1980) (WP). At Taylor Slough, Everglades, FL, clutches started as early as late February (Werner and Woolfenden 1983), and fledglings were found as early as 30 March (Howell 1937).

Second Brood

Repeatedly renests after nest failures. At Buzzard’s Bay, MA, 64% of pairs nested twice, 36% 3 times (n = 39 pairs; Marshall and Reinert 1990). At Oak Beach, NY, 54% of pairs nested twice, 21% 3 times, and 4% 4 times (n = 17 pairs; Post 1974). Two broods raised successfully by some pairs in New York (JSG), but apparently only 1 brood fledged in Massachusetts (Marshall and Reinert 1990).

Because of similar lengths of breeding cycle and lunar period, success higher when birds renest immediately after spring tide floods (DeRagon 1988). In Massachusetts, rapid renesting after large-scale flooding led to local synchrony; first eggs of replacement nests were an average of 6.3 d from date of destruction. Nests whose cycle extended as little as 1 d longer were flooded (Marshall and Reinert 1990).

In Connecticut, by contrast, Gjerdrum et al. (2005) found that although flooding was a major source of mortality, timing of nesting did not significantly affect reproductive success. Nesting success was improved by nesting in taller than average vegetation. At Oak Beach, NY timing of first nests was not synchronized with normal tidal cycle; in one instance, renesting immediately followed storm flooding. In New York, mean interval between nest failure and renesting was 5.5 d. Interval between fledging and start of second clutch was 17.5 d (WP, JSG). At Gulf Hammock, FL, clutch completion dates occurred in 2 peaks, one in late March–early April, the other in early May. Second peak was composed of females whose first attempt failed; interval between failure and renesting was 7.8 d (Post et al. 1983).

Brood overlap noted in Massachusetts: a female completed new 3-egg clutch on same day that single young from earlier nest fledged (Marshall and Reinert 1990). At Taylor Slough, FL, female mirabilis may initiate new nests before earlier broods have fledged (Werner and Woolfenden 1983).

Length of breeding season

New York: 76.8 d (67–88, n = 4 yr); fledglings appeared as early as late May, and nests contained young as late as 14 Aug (Greenlaw 1992). Breeding season 96 d at Gulf Hammock, Florida (Post et al. 1983); last clutch completed in third or fourth week of June. In each year, 90% of clutches completed by last week of May. Range of egg dates in Rhode Island: 27 May–31 August (DeRagon 1988); Massachusetts: 25 May–30 July (Marshall and Reinert 1990); Merritt Island, FL, (A. m. nigrescens): 17 April–11 August ([WFVZ), later than for salt-marsh population at same latitude (Gulf Hammock). Although range of confirmed egg dates is 29 Mar–7 Jul (Stimson 1968, Werner 1975), earliest A. m. mirabilis nest found 20 Mar 1997 (Lockwood et al. 2001). Nesting regularly extends into August w when rains are light and prairie not deeply flooded, (Dean and Morrison 1999). Nest starts decline as water depth approaches 25-30 cm (Werner 1975, Nott et al 1998),

Nest Site

Selection Process

Female selects nest site within male’s territory. No other information.

Microhabitat

In coastal marshes, spring tides determine lower point of nest placement. Upper point determined by availability of stable vegetation for nest support and by amount of cover above nest. In some years, appropriate substrates limited in spring because of destruction of grass by winter storms (Post 1974). Nest sites in New York could not be differentiated from randomly chosen sites, whereas those at Gulf Hammock, Florida could be. Main differences between Florida nest sites and random sites were lower height and lower density of vegetation around nests (Post et al. 1983). Taller and denser cover such as needlerush may be little used because of rodent predation (Post 1981a).

Site Characteristics

At Oak Beach, NY, mean height of nest (eggs) above ground was 14.2 ± 5.8 cm; mean height of vegetation above nest rim: 54.4 ± 12.6 cm (n = 94). At Gulf Hammock, FL, height of nest above ground 27.7 ± 8.2 cm; height of vegetation, 71.9 ± 14.4 cm (n = 47). At Taylor Slough, FL, mean nest height above ground: 18 cm (n = 16, range 6–37 cm).

Throughout range, most often nests in graminoid vegetation (Spartina, Distichlis, Sporobolus, Paspalum, Muhlenbergia, Cladium, Typha, Phragmites) (Fig. 8). Also uses wide variety of other substrates, ranging from woody vegetation black mangrove, Avicennia, germinans), high-tide bush, marsh elder) to forbs (glasswort., , sea-puslane, sea-ox-eye). Also nests under tidal debris. Nests found from ground level to 4.3 m

At Merritt I., Florida, A. m. nigrescens nested mainly in sand cordgrass (50% of 36 nests), needle-rush (22%), saltgrass (14%), and saltwort (11%) (Western Foundation Vertebrate Zoology). At Gulf Hammock, FL, A. m. peninsulae nested in saltgrass 48% of time; (n = 114 nests), although saltgrass was only 24% of the cover. Glasswort was also used out of proportion to its coverage (25% use vs. 7% coverage). In contrast, needle-rush and smooth S. alterniflora were infrequently used for nesting, although they accounted for a majority of the vegetative cover (needle-rush: 15% use versus 37% coverage; alterniflora: 9% vs. 26%). Seaside Sparrows seldom nested in alterniflora because it grew at lower elevation, where there was increased probability of flooding at higher elevations, nest site selection may be affected by predators (Post 1981a).

In Everglades, A. m. mirabilis nests were placed where effective cover was twice as high, and perches were 3-4 cm higher, than in other parts of territory. Vegetative cover was moderately high (25% coverage by sawgrass, 75% by dead vegetation). Nests were placed where sawgrass was 1-1.5 m high. Sparrows avoided continuously flooded areas, where sawgrass was > 1.5 m, and too densely packed (Lockwood et al. 2001).

Nest

Construction Process

Female builds nest alone. Once nest is started, she continues building even when male is removed. Captive males observed placing nest material in vegetation (Post and Antonio 1981).

Structure And Composition Matter

Nest a cup of grass stems and blades, lined with finer grass blades. Nests usually covered to some degree, most often by a canopy that the female constructs by manipulating surrounding vegetation (Fig. 8). Some nests built under wrack or matted live vegetation. Mean cover above nest at Oak Beach, NY: 80.0% (n =100, range 15–100%; JSG); Gulf Hammock, FL: 76.9% (46, 10–100%; WP). In New York, most nest entrances oriented between south and east (54% of 65 openings; JSG). In Everglades, FL, 45% of 16 nests were domed, with openings usually to east. Orientation was related to vegetative support rather than to temperature regulation (Werner 1975).

Dimensions

At Taylor Slough, FL, nest dimensions: outside diameter of cup, 10 cm (15, 8–13 cm); inside diameter of cup, 6 cm (15, 4–7 cm); depth of nest cup, 5 cm (15, 2–7 cm); outside depth of nest cup without dome, 7 cm (15, 4–11 cm); outside depth of nest including dome, 13 cm (6, 7–19 cm); dry weight of nest, 16.2 g (15, 8.2–24.3 g) (Werner 1975, Werner and Woolfenden 1983).

Maintenance Or Reuse Of Nests, Alternate Nests

Not observed.

Non-breeding Nests

Not observed.

Eggs

Shape

Short ovate to ovate; elongation (length/diameter) 1.31.

Size

Mean diameter and length: Oak Beach, NY (A. m. maritimus), 15.51 mm (SD 0.79, n = 63, range 14.48–17.78) x 20.28 mm (0.64, 63, 19.02–22.56; JSG); Taylor Slough, FL (A. m. mirabilis), 14.7 mm (27, 14.1–15.2) x 19.3 mm (27, 17.6–20.6; Werner and Woolfenden 1983); Merritt I., FL (A. m. nigrescens), 15.11 mm (72, 14.50–16.25) x 19.84 mm (72, 19.02–20.92; WFVZ). Runt eggs not reported.

Wet Mass

Mean wet mass of fresh eggs, Oak Beach, NY, 2.6 g (SD 0.21, n = 58, range 2.3–3.2; JSG); Taylor Slough, FL, 2.3 g (n = 14; Werner 1975); Gulf Hammock, FL, 2.63 g (0.15, 24; Burroughs 1989).

Dry Mass

Mean dry mass of contents and eggshell, Gulf Hammock, FL, 0.38 g (0.03, n = 22). Lipid content 37% of dry mass, about same as in other altricial species (Burroughs 1989).

Shell Mass

Mean dry mass of shell, A. m. maritimus, 0.149 g (n = 82, range 0.126–0.169; WFVZ); A. m. nigrescens, 0.128 g (69, 0.116–0.142; WFVZ); A. m. peninsulae, 0.163 g (0.014, 23; Burroughs 1989).

Color

Ground color bluish white to grayish white, speckled and blotched with shades of brown, often more heavily on larger end.

Surface Texture

Smooth, but not glossy.

Clutch Size

Two to 5 eggs. See Demography and Populations: measures of breeding activity, clutch.

Egg Laying

One egg/d; rarely, 1 day elapses between laying of eggs (JSG, WP).

Incubation

Only female incubates. Female has single brood patch on lower abdomen. In New York, brood patch first evident 2–10 d before first egg found. Incubation begins with laying of penultimate or last egg (JSG). Incubation period for A. m. maritimus 12.2–12.4 d (Worth 1972, Marshall and Reinert 1990, Greenlaw 1992); for A. m. mirabilis, 12d (Lockwood et al. 1997)

Hatching

Parents remove eggshells but leave unhatched eggs in nest. Hatching rates high: at Oak Beach, NY, in 1979, only 8% of eggs (9 of 115) failed to hatch (JSG).

Young Birds

Growth And Development

Mass increases logistically (Fig. 9). Growth rate constant (K) = 0.546. Time taken to grow from 10 to 90% of asymptotic weight = 8.04 d; ratio of nestling asymptotic weight to adult weight = 0.76 (Post and Greenlaw 1982).

Day 0. Series of white neossoptiles present on posterior part of ventral tract and on back near uropygium. White egg tooth present. Young give 1-note peep call on hatching day, also gape (Woolfenden 1956).

Day 1. Feather papillae visible on capital, humeral, and alar tracts and on cervical and dorsal regions of spinal tract. Occasionally, papillae visible on crural tract and cervical region of ventral tract. Thick ridge of tissue forms over eyeball, where eyelids delaminate. Young can maintain upright position when begging, by resting on tarsi (Werner and Woolfenden 1983) Can move short distances by using feet and wings (Woolfenden 1956). May give double peep call.

Day 2. Eyelids open slightly on some birds. Papillae visible on all regions of capital and spinal tracts. On some birds, papillae begin to appear on femoral tract.

Days 3–4. Papillae present on caudal tract and all regions of ventral tract. Papillae prominent on all pterylae. Eyelids partly open on most birds.

Day 5. Most individuals have eyes fully open. Egg tooth gone. Incoming feathers all remain sheathed. Buff color appears on spinal, femoral, crural, alar, and ventral tracts. Yellow tinge appears near alula on some birds. Reedy vocalization (“cedar call,” Werner and Woolfenden 1983) given during begging. Peep call no longer given. Young still beg when nest disturbed.

Day 6. Juvenal remiges still sheathed, but tips of body feathers unsheathed on all but capital tract. Cowering begins. Young begin to utter distress vocalizations when handled. Eyes fully open for all individuals. Some may utter scree call.

Day 7. Sheaths of remiges change from blue to gray and begin to slough off. Breast streaking begins to appear. When handled, young attempt to escape. Young first give tuck call (Werner and Woolfenden 1983).

Day 8. Birds well feathered except for coronal region of capital tract. Breast streaks distinct. Scapulars have light edges. When disturbed, young are first capable of leaving nest. May fledge prematurely when if nest disturbed.

Day 9. Young normally leave nest (Woolfenden 1956, JSG).

Parental Care

Brooding

Only females observed brooding (JSG, WP).

Feeding

Both parents feed young. Female feeds more often on hatching day; thereafter, delivery rates of sexes the same. Delivery rates (feedings/young/h): Oak Beach, NY: female 2.00, male 2.08; Gulf Hammock, FL: female 1.69, male 1.32 (Post et al. 1983). In FL Everglades, males delivered food 52% of time. (Lockwood et al 1997), In NY, sexes flew same average distance when foraging for nest (males, 35 m, females, 31 m; Post and Greenlaw 1982). Multiple items brought to nests in a single delivery. Prey often macerated, delivered in mucous-bound bolus. Mean volume of food delivered was 0.037–0.253 ml/h/nest (Merriam 1983). Frequency of large-sized items and total volume of food delivered to nest increased with nestling age (Merriam 1983). Females were able to adjust feeding rates to compensate for disappearance of males, and growth rates of male-orphaned young were the same as that of non-orphaned young (Greenlaw and Post 1985). Adults continue to feed fledged young for additional 20 d (DeRagon 1988, JSG).

In unaltered marsh at Oak Beach, NY (maritimus), sparrows took relatively few arthropod groups. Ten most important taxa fed to nestlings comprised 94% of total volume delivered. Fourteen percent of 1,203 nestling food items could be classified as strictly mud-inhabiting organisms, e.g., immature flies. Food volume brought to nests was 28% immature (papal and larval) flies (21% Tabanidae; 7% Stratiomyidae) and 21% immature moths (Noctuidae); Nestlings were fed large numbers of plant bugs (Trigonotylus tarsallis), although these comprised relatively little bulk ((Merriam, 1979, 1983, Post et al. 1983)). Nestling diet changed seasonally, reflecting changes in availability of invertebrate stocks. Grasshoppers increased in importance, whereas flies, moths, and spiders decreased (Post and Greenlaw 2006). The diet reflected random choice of available prey, and did not differ from that of nestling Saltmarsh Sparrows in same marsh (Post and Greenlaw 2006)

At Gulf Hammock, FL, 10 most important groups fed to nestlings comprised 85% of 552 items; remaining 15% were distributed among 47 groups. Most important (by volume): long-horned grasshoppers (Conocephalus spp., Orchelimum sp.), spiders (mainly Lycosidae), and moths (Noctuidae and Pyralidae). Among smaller insects, many homopterans, mainly Delphacidae, delivered. Except for several fiddler crabs (Uca spp.), Florida birds took few mud-inhabiting invertebrates. Nestling diets significantly more diverse in Florida than in New York; in New York, average trophic diversity (Brillouin’s Hpop) was 1.08; corresponding value in Florida 1.14. (Post et al. 1983).

In altered (mosquito-ditched) marsh at West Gilgo, NY, food was about equally divided between prey inhabiting ground and vegetation (53% and 47%, respectively). Tabanid flies made up 71% of volume ( 47% immature and 24% adult), followed by soldier flies, 10% (equally divided between adults and immatures).

In comparison to other regions, nestling diet in S. Carolina (n = 280 items; 20 samples from 9 nests; WP, unpubl. data) was most similar to that in NY, in that a large proportion of ground-inhabiting forms were delivered, primarily wolf spiders, which composed 16% of items, followed by larvae and pupae of flies (Stratiomyidae, Tabanidae, 10%). Among prey that was presumed to occupy vegetation, the most important were leaf hoppers (Cicadellidae and Cercopidae (51 % of items) and spiders (10%). In terms of volume, however, crickets (Gryllidae) were most important (25% of volume); followed by grasshoppers (Conocephalus), 24%: wolf spiders, 9%; amphipods, 8%.

Nest Sanitation

Both sexes remove fecal sacs from cup and rim usually dropping them > 10 m from nest. On one occasion in S. Carolina, a female ate fecal sac at nest (WP). Parents do not defecate in vicinity of nest.

Cooperative Breeding

Not known to occur.

Brood Parasitism

Although a Seaside Sparrow was seen feeding a fledgling Brown-headed Cowbird (Molothrus ater) on Martha’s Vineyard, MA (Bagg and Eliot 1937), this does not confirm parasitism, as sparrows have fed fledgling Red-winged Blackbirds (Rakestraw and Baker 1981) and nestling Sharp-tailed Sparrows (WP). Cowbirds rarely seen in salt marshes, perhaps owing to shortage of high perches. Intraspecific brood parasitism not known.

Fledgling Stage

Young normally leave nest 9–11 d after hatching. If nest disturbed, leave on day 8. All brood mates usually leave within several hours of each other. Immediately after fledging, able to hop on ground, climb vegetation and swim short distances using wings. In Everglades, FL, fledglings “barely able to fly” 17-18 d post-hatching (Werner 1975). Fed by both adults up to 20 d after fledging (DeRagon 1988). When approached by predator (human), freezes until human is 10–20 cm away, flees by running on ground (Werner 1975). See Demography and Populations: Initial dispersal from natal site.

Immature Stage

In Everglades, FL, juveniles formed groups of 2–7 individuals, initially near nest. Adults occasionally accompanied parties of juveniles (Werner 1975). Group members gradually moved farther from nest sites; winter home ranges sometimes larger than area used in breeding season. Seaside Sparrow social groups appear to be oriented to taller vegetation, either roosting or feeding areas (Werner 1975, WP). Group members mob predators together. Membership of social groups apparently changes over short periods, but little known about composition or stability of groups. By 7 wk after fledging, one individual had moved 600 m from its nest (Werner 1975). Adult males may chase juveniles that enter their territories (Werner 1975, WP). See Behavior: social and interspecific/ degree of sociality.

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