Saltmarsh Sparrow

Ammospiza caudacuta

Order:
Passeriformes
Family:
Passerellidae
Sections

Behavior

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Saltmarsh Sparrow perching.

When perching, sparrow often clings to vertical side of tall stems, holding its body close to the stem with the upper foot and flexed leg and bracing its body with the lower foot and extended outer leg.

© Mark R Johnson , Maryland , United States , 4 November 2015
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Saltmarsh Sparrow perching.

Frequently supports itself straddled acrobatically between two erect, adjoining Phragmites culms, legs spread wide apart with feet grasping separate stems.

© Ryan Schain , Massachusetts , United States , 22 July 2011
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Saltmarsh Sparrow bathing.

Bathing involves dunking head and splashing water on feathers by fluttering wings rapidly, then standing and performing rapid wing-shuffling motions in crouched position that further wets body feathers.

© Taylor Abbott , South Carolina , United States , 22 December 2016
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Adult female Saltmarsh Sparrow starting molt with heavily worn plumage; note, nearly “tailless”.
© Chris Elphick , Connecticut , United States , 26 August 2003
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Three Saltmarsh Sparrows (right) with Nelson's Sparrow (left).

Foraging Saltmarsh Sparrows may form loose flocks with Nelson’s Sparrows and Marsh Wrens. When pursued, these birds follow each other to different patches of tall vegetation.

© Ernie Miller , Virginia , United States , 11 October 2015
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Saltmarsh Sparrows interacting.

During male-male encounters, an individual may settle 0.5 m or less from another male that was unidentified at a distance. They stand with sleeked plumage, bill tilted up, and stare for a few seconds until one of them turns and disappears into the grass or flies off. Contact seems rare, but one male frequently takes over a perch occupied by another.

© Chad Witko , New Jersey , United States , 23 May 2017

Locomotion

Walking, Hopping, Climbing, etc.

Mode of locomotion on the ground varies with circumstance and substrate. An undisturbed foraging bird in a vegetated site walks, intermittently pausing, as it inspects substrate (10; JSG). In more open sites, it runs in short spurts and pauses to scan. Unlike Woolfenden (10), JSG recorded instances of hopping locomotion (1–3 hops) during foraging, often when moving closer to some object of interest. Birds climb up vegetation column to reach prey items inaccessible from the ground. When not foraging, an individual will often run, stopping at intervals and climbing to top of vegetation from which it can survey neighborhood. When alarmed in grass cover or flushed from the nest, individuals run rodentlike in a low crouch with head lowered, parrying stems in its path as it goes (10); also during foraging.

When perching, sparrow often clings to vertical side of tall stems, holding its body close to the stem with the upper foot and flexed leg and bracing its body with the lower foot and extended outer leg; on such stems, agile and able to shift up or down or reverse its position. Also frequently supports itself straddled acrobatically between 2 erect, adjoining Phragmites culms, legs spread wide apart with feet grasping separate stems.

Flight

Characteristics of flight variable, depending on social context, associated behavior, or destination. Uninterrupted long flights are direct, relatively fast, and slightly jerky as bird periodically and momentarily interrupts wingbeats. Typical flight height about ≤ 1.5–2 m above vegetation (113; JSG). Most flights are relatively localized; bird leaves grass, flies a short distance then pitches back into grass. Males tend to fly in the open more often than females except when females are provisioning young. Away from the nest, females fly in a slow, jerky pattern, as posterior body is pumped up and down and wings opened and closed. Female also may perform lookout or “inspection” flights when disturbed near a nest, flying up vertically 1 to 1.5 m, stalling or hovering momentarily, or fluttering slowly forward for 2–3 m, then dropping back into cover (113; JSG). Males are capable of steady wingbeats and fast direct flights when they see a flying sparrow at a distance and seek to intercept or overtake it; when pursued, females exhibit a similar fast flight with uninterrupted wingbeats. See Sounds and Vocal Behavior: Vocalizations: Songs, for flight behavior associated with singing in flight.

Flight speeds (clocked by stopwatch over known distances on gridded marsh) of females on provisioning flights to or from the nest vary with distance. Flights to feeding sites < 140 m from nest averaged 5.2 m/s ± 1.18 SD (range 3.0–6.3, n = 14). Flights > 140 m from nest averaged 10.2 m/s ± 0.82 SD (range 8.9–11.7, n = 18) (JSG, unpublished data).

Females may fly directly to nest or drop into grass near nest, covering last few meters on ground. They usually walk from nest for a short distance before flying up, unless surprised at nest, when they fly off directly. Disturbed or alarm-calling birds (uttering Tic or Tuc calls) on perch perform wing and tail-flicking movements that may be flight-intention signals (156).

Self-Maintenance

Preening, Head-Scratching, Stretching, Bathing, Anting

During preening, bird mandibulates smaller feathers, probes into plumage to skin, and draws flight feathers through beak. Body stance during this activity typically relaxed, sitting or crouching on a perch, plumage usually fluffed or erected.

Plumage becomes wet during early morning in dew-laden grasses. Perched bird frequently fluffs and shakes feathers and shuffles folded but partially fanned wings held loosely over rump and flanks. Preening especially evident at this time. Scratches head by turning head toward foot and extending leg and foot over partly lowered, folded wing (i.e., indirect scratching) (165). Unilateral stretch (wing and leg on same side extended, tail partly fanned toward stretching side) and bilateral stretch (both wings raised and partly unfolded over back, both legs extended) maneuvers used, often first preceding second, typically when terminating a period of inactivity (JSG).

After feeding, preening, or bathing, bird bill-wipes on perch with stropping motions from base to tip or tip to base of bill, first on one side of perch then on other. Bathing involves dunking head and splashing water on feathers by fluttering wings rapidly, then standing and performing rapid wing-shuffling motions in crouched position that further wets body feathers. After period of splashing, bird moves to nearby perch where it preens actively, accompanied by ruffling feathers and shaking body vigorously.

No reports of anting or dust-bathing.

Sleeping, Roosting, Sunbathing, Perching

Female spends night on nest while incubating or brooding. Full-grown birds during post-breeding period roost in large areas of tall cordgrass on outer salt marsh in New York. In South Carolina, winter home ranges center on communal roost sites, located in tall vegetation such as Black Needlerush. Roosts are occupied at night and in the day during high tides; most birds forage within 300 m of roosts. During the day, when disturbed, foraging Saltmarsh Sparrow fly into nearest patches of Black Needlerush or tall Smooth Cordgrass, and form loose flocks with Nelson’s Sparrow and Marsh Wren (Cistothorus palustris). When pursued, these birds follow each other to different patches of tall vegetation (WP). Thus, post-breeding and wintering behavior exhibits an element of sociality that is not seen during the breeding season.

Sunbathing is unknown but likely.

Daily Time Budget

Little published information. Singing by males is concentrated in morning and evening periods (see Sounds and Vocal Behavior: Vocalizations: Songs). Male activity budget during the breeding season, at least during mornings, is dominated by local reconnoitering as males seek contact with females, alternated with singing and foraging; foraging seems to predominate during midday. Based on frequency data collected during 30-min observation periods (0600–1000) from blinds in a 2-yr study in New York, males spent 20% of their time singing (perched and aerial), 38% “lookout” behavior from perches (see Behavior: Sexual Behavior), 17% foraging, 10% silent, transit flying, 8% sexual interactions, 6% agonistic interactions, 1% self-maintenance, and resting. Female time budgets were dominated by foraging and parental care, including nest building, incubation, brooding, and provisioning dependent young.

Agonistic Behavior

Physical Interactions

Most agonistic encounters between males in New York involve supplanting (in which one male actively forces another off a perch, or defends its perch from an approaching male by “Head-Forward threat” – see visual displays in Communicative Interactions) or displacement (male simply withdraws or gives-way as another male approaches with apparent intent to settle in same position). Evidence of dominance between males in sexual contexts is most often expressed in the field as displacements, but status cues seem subtle and are poorly understood. Loose dominance hierarchy evident in mixed-species (with Seaside Sparrow) captive flock (WP, unpublished data). Of 27 “win-lose” encounters witnessed between Saltmarsh Sparrow, 5 (18.5%) involved reversals. The most dominant bird (male) accounted for 13 encounter records (48.1% of all encounters, including 3 reversals). Countersinging between males is unknown. Female commonly fight with male or supplants male in sexual contexts (see Behavior: Sexual Behavior), and sometimes chases male from vicinity of nests. Implied dominance among males in the field is evident during forced mounting behavior when, often, the active male seeking to suppress female’s resistance is watched by other males that approach, but do not interfere (134). Female–female agonistic behavior is rarely observed (WP; 1 case in New York study).

Communicative Interactions

Female’s Tuc call (see Sounds and Vocal Behavior: Vocalizations: Calls) primarily used in agonistic contexts during encounters with males; seems to function chiefly as defensive threat. We witnessed cases in which flying females leaving a nest began Tuc calling as a male approached in an overtaking flight; he swerved off when she began calling. Other times, a female will give the Tuc call routinely, as she flies toward or away from the nest on provisioning flights, and an overtaking male will continue his sexual interaction with the calling female (134). Scream is given during intense agonistic interactions when subordinate is attacked in a net-holding bag by another Saltmarsh Sparrow; in this context, it may be strong appeasement display. Of 7 visual displays known in the Saltmarsh Sparrow, 3 serve “threat” function (Head Forward, Wing-wave, Gaping), 1 (Wing/Tail-flicking) is a flee signal, and 2 are submissive (Body Fluff, Bill-up; JSG).

Spacing

Space Use

In contrast to close relatives that are territorial, non-territorial male Saltmarsh Sparrows localize their daily activities in large, overlapping home ranges (10, 163, 166, 49, 127, 129, 134). Flight paths of different males crisscross one another, and perches are often used in common by several males at different times (10, 134). Extreme overlap indicated by up to 40 marked males observed within 50 m of single observation blinds during a single season of timed watches in New York. Home range sizes have been estimated by mapping locations of color-banded individuals and by radiotelemetry. Based on maximum area polygons, male home ranges in New Jersey were between 1.2 and 1.6 ha (10). New York male home range size averaged 4.3 ha, ranging from 3.0 to 5.7 ha 150). Based on radiotelemetry in Maine, Shriver et al. (129) found male home ranges averaged 52.9 ha, while female home range was 27.8 ha. Population density of males in New York averaged 45 males per ha in 1976–1980 (150). Based on a study of food resources in New York (141), it is probable that small home range sizes there compared to those in Maine are primarily related to differences in population density and in food resource availability. In Maine, males’ core area comprised 42% of their home range, compared with 35% in New York. Some males in both Maine and New York used 2 core areas in their home ranges during a single season. In Maine, each core area was associated with different spring tidal cycles (129), while in New York, the shift was seasonal and unrelated to tides. In Connecticut, distances between the banding site of males and nests where the male was known to have fertilized eggs varied from within 1 ha to as far as 1.4 km away. The distances covered by males represent those fathering chicks within a core area containing both the banding site and nest or apparent shifts to new home ranges over 1 km away, which was close to the longest possible distance a male could be in the same marsh among those sampled (167). See Demography and Populations: Range.

Although average distance between closest neighboring, contemporaneous nests was 44 m (n = 135) in New York, 2 to 3 females nested 2–3 m from each other, with no aggression evident. Females react aggressively to approaches of males to nests, both during nest building, when sexually receptive away from nest, or later when young were present. Female aggression is expressed by supplants and perfunctory chases, accompanied by Tuc calling. Males appear to show little or no interest in nests, and mostly seem not to know where they are located (10; JSG).

In New York, male dispersion was found to be related to distribution of nest-building females (134). The positive relationship between multiple paternity rate at nests and number of males in vicinity of nests (167) may be weak in part because, at any given time, not all nearby nests are in an early stage when females are receptive to sexual advances of males. Absence of birds from potentially suitable nesting patches may reflect chance associated with low population density and limited local recruitment. Patchy local distributions have led to accounts of species as being “colonial” (see 163).

Because closest relatives of Saltmarsh and Nelson’s sparrows are territorial, it is reasonable to assume that absence of territoriality in these sister species is a derived condition (49). Murray (163, 168, 169) proposed an interspecific aggression model to explain loss of territoriality based on subordinate relationship of late-arriving Nelson’s Sparrow with early-arriving LeConte’s Sparrow in the same habitats on interior breeding grounds. But, we now know that the sister relationship to sharp-tailed sparrows is with the Seaside Sparrow. The critical comparison must be with that territorial species, which exhibits a minimal arrival differential (earliest arrivals) with the Saltmarsh Sparrow in co-occupied habitats (28, 101). Thus, the essential assumption of Murray’s proposal (that a substantial arrival differential occurs with a syntopic relative) is unsupported. Alternative models for loss of territoriality in sharp-tailed sparrows need to be considered, which must encompass the social systems of both sharp-tailed sparrows in relation to the innovation of uniparental care and promiscuity and the abundance of food in nesting habitat.

Even though Saltmarsh Sparrow does not compete for space with Seaside Sparrow, one-way interspecific aggression initiated by Seaside Sparrow is persistent between the 2 species. But, characteristics of aggressive responses within Seaside Sparrow are different from those toward Saltmarsh Sparrow. Aggression by Seaside Sparrow toward conspecific intruders is more persistent than the perfunctory, short chases or supplants of Saltmarsh Sparrow intruders. Such aggression may be related to defense of personal space (“individual distance,” see below), or simply defense of localized resources within a territory (e.g., nest sites, song perches).

Individual Distance

No quantitative information. JSG and WP frequently saw a male approach another male perhaps because it could not determine sex or species, or it observed another male interacting with a female (134). During male–male encounters, an individual may settle 0.5 m or less from another male that was unidentified at a distance. They stand with sleeked plumage, bill tilted up, they stare for a few seconds until one of them turns and disappears into the grass or flies off; we never witnessed contact between them. However, as noted males frequently took over a perch occupied by another male. A male flying from a distance may seek to supplant another male perched in the open on a frequently used perch. The perched male either gives way without contest, or holds its perch, crouches, and performs a Head Forward Threat, which is often enough to thwart the other male’s landing. Again, JSG and WP witnessed no fighting in such circumstances. The outcome of these interactions was possibly determined by established dominance relationships of males occupying overlapping home ranges.

Sexual Behavior

Mating System and Sex Ratio

Most details and descriptions here are from Greenlaw and Post (134); some are elaborations on the previously published account introduced below. Evidence best supports the notion that “scramble competition” in the species (150, 127) involves a specialized form of communicating male dominance to females through a search-and-pounce system that involves suppressing female resistance followed by ritualized copulatory mounting (without an attempt to achieve cloacal contact), and ending in flight singing during male departure. Thus, this system may be an unusual, non-lekking form of female access if mating in the species is a female choice system based on sexual dominance of males that are able to subdue active resistance of females to force mount her without copulating; this hypothesis proposes that females allow assertive, persistent males to mate with her without resistance when she is sexually receptive, but not otherwise (167). How these males may be recognized is unknown. A male (possibly only experienced birds) expresses dominance over females during seek-and-mount behavior at any time during a female’s nest cycle. This behavior involves locating females, intercepting them in the air or meeting them in the grass, immediately attempting to mount onto her back while feather pulling. The female vigorously fights back and often drives off less persistent, perhaps less dominant (evidence lacking), males; some males simply watch the struggle between a female without interfering with a male fighting for the ability to mount. After an active male subdues a female, he flies off uttering a flight song (see details below). If this interpretation is correct, the female’s resistance may be viewed as a test of male quality. An alternative hypothesis suggests that males practice sperm competition by force mating with a female after mounting her (134), although there is no evidence supporting this view (see below).

The mating system practiced by this species is very unusual among birds and features an obligate, promiscuous, bond-free relationship between males and females (10, 167, 150, 127, 117, 134). Hill et al. (167) provided genetic evidence that confirmed observational evidence of promiscuity in species (see below), and discovered one of the highest levels of non-bond-related mating reported in any bird. See Multiple Paternity in Broods, below.

Receptive females solicit matings from males in the vicinity of their nests in a manner typical of other emberizids, but apparently without a pre-mating vocalization (170; JSG). The female’s hypothesized role (above) of allowing only dominant males to mount her needs to be tested. A male mounts the back of crouching female without feather pulling. Female raises tail, exposing cloaca for 1–3 s (10, 127, 117). After female solicits a mount, male may perform wing flutter before and during mounting (10).

Sexual chases, in which males intercept flying females, occur frequently, and at any time in a female’s nesting cycle. These chases are not directly related to invited copulations (contra 129: 343). Males search for females as they patrol their home ranges, and approach other males they see flying nearby or at a distance. This behavior often results in a meeting of two males, which may be joined by others (27). Woolfenden (10) observed these non-agonistic male–male aggregations, but did not comment on their function. When males encounter flying females, they force them to the ground, and attempt to mount them against their resistance, often while feather-pulling (127, 117). Males on occasion abort chases if the flying female begins Tuc-calling. Most often, only one male chases a female, but the chase may attract the attention of other males that converge on the location. Usually these additional males remain close to the interacting pair, but do not interfere. If two or three males compete to mount a female, they usually do not fight , although physical contact may occur as they get in one another’s way. Females attempt to escape at any opportunity, so any fighting between males would provide a distraction allowing the female to escape.

The coercion behavior exhibited during sexual encounters, in which a female typically resists aggressively (134), resembles behavior described as “forced mating” in other species (171, 172), including during extrapair matings (e.g., 173, 174). Based on appearance, the behavior was initially and incorrectly described as “scramble-competition polygyny” (150, 127), but the mate-seeking behavior of males is a form of scramble-competition only if it contributes to a level of sperm competition, and no evidence exists that sperm is transferred during the forced mountings. Since most females encountered by a male are non-receptive, sperm-transfer after forced-mounting (assuming it is possible without the cooperation of the female) may represent a significant waste of sperm (if not mitigated by sperm storage in the female tract) beyond that occurring in solicited matings (175). JSG and WP witnessed Saltmarsh Sparrows held in a spacious holding bag during banding in New York mount passive females; such males crouched on the female’s back and grasped nape feathers, but made no effort to bring their cloaca into contact with the unexposed cloaca of the females. Evidence indicates that the male either suppresses female resistance and mounts her, or the female thwarts the male, the latter occurring about 57% of the time (134). Many male mountings are hidden by vegetation and is difficult to determine if they are solicited or forced. But no matter their motivation, male-female interactions may be important in relation to female choice during her receptive window (contra 127, 117, 129). This too requires confirmation (134).

Males chase and pounce on females at all stages of the nest cycle, sometimes concentrating their activity in the general vicinity of a receptive female's nest (134), but their behavior suggests they do not know the locations of most nests. Some nests appear to be encountered accidentally. Females usually chase males that approach their nests.

No information on primary (fertilization) sex ratios. Adult sex ratios estimated from banding indicate a surplus of males varying from 1.6 to 2.8 (n = 6 estimates; 10, 150, 176, Gjerdrum et al. 2008). Because male home ranges are larger than those of females, probability of encountering males at any one banding site is greater for males (10, 150). Correction for sexual difference in average home range sizes suggested that adjusted sex ratio of adults was indistinguishable from unity (150; but see 177). Hill et al. (177) reported skewed prefledging sex ratio among nestlings sampled over two years in Connecticut, amounting to 59% more males (1.45 males to 1 female), based on 157 nestlings from 52 nests. A more recent study, however, found no evidence for a sex ratio bias in a much larger sample of birds (990 sexed individuals from 338 nests) from several sites at the northern end of the breeding range (178). This second study found that sex ratio varied considerably by year at one site, but was balanced elsewhere and overall for the five-year period. Ratio of sexually active males to receptive females, or operational (effective) sex ratio, has not been reported; this ratio influences degree of sexual selection and extreme of polygamy in breeding system (179, 180). Capture sex ratios of birds on non-breeding grounds (South Carolina, northern Florida) that were adequately sampled (n ≥ 50, 3 locations) varied from 0.32 to 0.66 males and averaged 0.52; no winter relationship evident between sex ratio and latitude from North Carolina to Florida (26).

The issue of reproduction costs related to promiscuity and female-only parental care in this species’ breeding system was raised by Borowske (26) and Borowske et al. (101). A concern is whether multiple nestings extending into August (134, 118) impose investment costs on promiscuous females that may affect other annual processes after breeding (181). Relative to male Saltmarsh Sparrows, unshared parental care by female Saltmarsh Sparrows was associated with apparent carry-over effects of later molt initiation, shorter molt duration of flight feathers, and later fall departures by some females (101). Females also exhibit extreme feather wear by late July and August, when body feathers are heavily frayed and tails can be worn to their bases, thus causing some females to appear “tailless” (26; JSG). Still, by winter, Borowske (26) did not detect continued carry-over of poor, late-summer body condition or of predicted flight feather fragility (excessive wear) related to summer breeding and molt. Females in winter appeared to have compensated for any late summer or autumnal carry-over effects to the extent that winter feather wear and body condition were indistinguishable from that found in males. Perhaps, somatic effort costs were accrued during breeding that do not represent parental effort costs (182).

Pair Bond

No pair bond formed; see Mating System and Sex Ratio.

Multiple Paternity in Broods

Because the breeding system features a promiscuous relationship between sexes, the notion of extra-pair copulations not applicable. Still, sexual chases and forced mountings occur in the system (see Mating System above). As noted, these are not directly related to solicited copulations and they suggest a possible secondary mating strategy in males, or simply a non-lekking method employed by some males that provides male quality information (dominance capacity) directly to females. The result either way is an extreme incidence of multiple matings, at least during the female’s receptive period (167; Connecticut). All fully sampled broods for genetic genotyping had multiple fathers, averaging ≥ 2.5 fathers per brood. Every chick had a different father in one-third of broods. The probability that any 2 chicks in the same nest were sired by different fathers was 0.77. In 67 of 396 cases, 17% of genotyped males fathered 53% (109 of 206) of genotyped chicks. Most of the males sired 1 chick per sampled nest, but 26 males sired chicks in more than 1 nest. One of these males fathered chicks in 3 nests.

As noted, these rates of multiple mating are among the highest ever reported in birds (183, 167) and were positively related (albeit weakly) to number of males in vicinity of nests, but unrelated to nesting synchrony (variation in number of nests initiated per day during season).

Social and Interspecific Behavior

Degree of Sociality

Largely an asocial species during breeding season except for brief male-female contacts during solicited matings. No cooperative behavior known during care of dependent young or at any other time. The extreme breeding season asociality in Saltmarsh Sparrow appears to be in contrast to occasional biparental care (166) in Nelson’s Sparrow, its sister relative, and may represent a uniquely derived condition among passerines.

Post-breeding individuals on breeding grounds, and migratory individuals in route to winter quarters and on wintering grounds assemble in loose groups. These groups at times may be aggregations brought together by circumstance, but evidence for social cohesion is also evident when mixed species groups are disturbed in cover and remain together as they move to other patches of tall vegetation (WP).

Play

None known.

Nonpredatory Interspecific Interactions

No agonistic chasing of other species known. Males evidently misidentify other sparrows (Seaside Sparrow in New York) flying at a distance in the neighborhood and may initiate a meeting, but they abort interaction as they draw close (JSG, WP). Attempted interspecific matings between Saltmarsh Sparrow and Seaside Sparrow have been reported (76, 113; see Sexual Behavior). Some male sharp-tailed sparrows occasionally mount cowering female Seaside Sparrow held temporarily in mixed-species groups in holding bags for band processing (156, 127). In a captive flock of Saltmarsh and Seaside sparrows, all Seaside Sparrows (8 males, 3 females) were dominant over nearly all Saltmarsh Sparrows (4 males, 3 females). Occasional interspecific reversals in “win-lose” encounters occurred, in which a female Saltmarsh Sparrow won nearly as many encounters (8) as she lost (9) to Seaside Sparrows (WP, unpublished data). Saltmarsh Sparrow is sometimes chased or supplanted by syntopic Seaside Sparrow (10; JSG), and by Song Sparrow (JSG) in scrub at landward edge of a marsh. Events that appear to elicit interspecific aggression by Seaside Sparrows seem related to intrusion near their active nests and use of their favored song posts. In New York, a nest of a Saltmarsh Sparrow and that of a Seaside Sparrow only 1.5 m apart had young about the same age at the same time; the male Seaside Sparrow fed chicks in both nests, while the female Saltmarsh Sparrow provisioned only her own young. The male Seaside Sparrow briefly chased the female sparrow when both appeared together at the latter’s nest, but after retreating nearby, she returned as soon as the male Seaside Sparrow left.

A Meadow Vole (Microtus pennsylvanicus) that approached an active nest was chased off by the attendant female who interrupted incubation and ran at the mammal in front of nest entrance (WP).

Postbreeding feeding aggregations of juvenile and adult Saltmarsh Sparrow are joined by Seaside and Nelson’s sparrows, and rarely LeConte’s Sparrow. Few or no interactions are evident between the 2 species in these groups (JSG, WP).

Predation

Kinds of Predators and Manner of Predation

Known predators on adults and nest contents include Northern Harrier (113, 184), Short-eared Owl (Asio flammeus) (Hill 1968), Fish Crow (Corvus ossifragus) (JSG, WP), Norway Rat (Rattus norvegicus) (JSG, WP), and Garter Snake (Thamnophis sirtalis) (JSG). Suspected predators along northern mid-Atlantic Coast include herons, egrets, Glossy Ibis (Plegadis falcinellus), American Crow (Corvus brachyrhynchos), and North American Racer (Coluber constrictor) (10; JSG). The Meadow Vole is known to take over abandoned sparrow nests for their use in New York, but there is no evidence that they depredate nests (WP).

In New York, a Northern Harrier flying low over a salt marsh may hover momentarily, then drop vertically onto a nest visible from above. In one case, a Northern Harrier stooped on an empty nest, stood over it after displacing nest lining, then left. Nests in grass cover along edges of large marsh pools may be subject to predation by long-legged waders. Nests situated along landward marsh edges near Phragmites suffer predation from Garter Snake and Norway Rat (which also kill incubating or brooding females during night raids) (JSG, WP). Predation rates on nests containing eggs or young varied annually in New York (1977–1980) from 20% to 52% of all active nests found (JSG, unpublished data). No difference detected in mean seasonal rates of nest predation between an unditched marsh (mean 36.5%, n = 249 nests) versus a ditched marsh in New York (mean 32.8%, n = 64) (JSG). Generally, predators remove all contents of a nest and parent survives, but 29% of predation events caused only partial losses in one study (116).

Response to Predators

Female generally sits tightly on nest as a potential ground predator (human) approaches and flushes at the last moment. She remains silent and hidden nearby until predator leaves immediate area. Only when dependent young are present does she become vocal, uttering Tuc and Tic calls and performing short flights within 10–15 m of nest, and near the potential predator. When a snake approached a nest containing young, the female circled the snake closely while giving alarm calls (JSG). No nest distraction displays recorded in species. Tic-twitter alarm may be employed by male when an aerial predator approaches, but often bird simply dives silently into cover.

Recommended Citation

Greenlaw, J. S., C. S. Elphick, W. Post, and J. D. Rising (2018). Saltmarsh Sparrow (Ammospiza caudacuta), version 2.1. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.sstspa.02.1