Breeding

Pair Formation

Males begin advertising in Feb in Arizona; pair formation begins shortly thereafter (WRE). Pairs begin to form in late Mar in Texas (Simmons 1914). Adults arrive in New Jersey and Virginia in early Apr; pair formation begins almost immediately (Mangold 1974, Meanley 1985). Timing unknown for other populations.

Nest-Building

Nesting in San Francisco Bay, CA, begins in late Mar; peaks in late Apr–mid-May (DeGroot 1927, Harvey 1988). First nests in Arizona recorded 13 Mar; peak initiation mid-May (Eddleman 1989). In Trinidad, breeds Apr–Dec (mostly May–Jun; Hilty and Brown 1986). First nests in e. Florida in Mar (Nicholson 1927). Initiates first nests in Louisiana the last week in Mar; peak mid-Apr–mid-May (Sharp 1976). Earliest nest in N. Carolina 1 Apr; peak late Apr (Adams and Quay 1958). Nest initiation begins in Virginia in latter half of May to early Jun (Stewart 1951, Meanley 1985). First nests initiated in New Jersey in early Apr; peaks 27 Apr–1 Jun and 1–20 Jul (Mangold 1974). Peak in New York in second week of May (MacNamara and Udell 1970).

First Brood Per Season

Figure 4 . Peak based on egg dates varies with subspecies and location (Western Foundation of Vertebrate Zoology [WFVZ] records, nest card records from Cornell Laboratory of Ornithology; WRE); from earliest to latest (subspecies, location—mean date [SD], n): levipes, s. California—20 Apr ± 18.4, 209; obsoletus, San Francisco Bay, CA—1 May ± 24.8, 275; yumanensis, sw. Arizona and se. California—11 May ± 29.8, 11; scotti, Florida—4 May ± 25.1, 35; waynei, s. Atlantic Coast of U.S.—17 May ± 19.3, 120; crepitans, n. Atlantic Coast of U.S.—23 Jun ± 24.3, 579.

Second Brood Per Season

Second nests in San Francisco Bay, CA, initiated late Jun–early Jul; eggs begin to hatch in Jul (DeGroot 1927, Harvey 1988). Hatching date for second brood of 1 pair in New Jersey on 20–29 Jul (after first nest hatched between 10 and 19 Jun; Ferrigno 1990). Small numbers of nests occur into Aug in most locations (WRE).

Selection Process

Nests placed to avoid flooding by tides, yet in dense enough cover to be hidden from predators and to support the relatively large nest (Storey et al. 1988). Nest-site selection thus involves a compromise between sites at higher elevation with less dense cover and sites at lower elevation with denser cover.

Microhabitat

Nests placed in clumps of vegetation or forks of shrubs from just above ground surface in marsh habitat to 1.5 m above substrate in mangroves. Nests in se. California and sw. Arizona placed in clumps of emergent plants, in base of shrubs, or in clumps of downed dead vegetation near uplands (Eddleman 1989). Clapper Rails nesting in mangroves in Mexico and the Caribbean placed nests an average of 73.6 cm ± 28.1 SD above ground (range 30–150, n = 19; WFVZ records). In San Francisco Bay, CA, places nests on raised ground near tidal sloughs in low marsh (Harvey 1988, Shuford 1993). Early nests placed under dense vegetation, under wrack or debris, or under gum plant bushes. Vegetation recorded at 45 nests in San Francisco Bay, CA, was pickleweed (at 96% of nests), Pacific cordgrass (45%), and salt grass (Distichlis spicata, 18%; Harvey 1988). Most nests in New Jersey placed on ground among plant stems (Kozicky and Schmidt 1949). Vegetational type at 56 nests was salt marsh cordgrass >61 cm tall (73.2%), high-tide bush (Iva frutescens; 14.3%), salt marsh cordgrass–salt meadow cordgrass mix (7.1%), salt marsh cordgrass <61 cm tall (3.6%), and black rush (Juncus gerardi; 1.8%).

Site Characteristics

Grass height is a major proximate cue used in site selection, because of need for nest concealment (Adams and Quay 1958, Sharp 1976, Storey et al. 1988). Nest sites vary depending on stage of nesting season; earlier nests placed on higher sites because of shorter available grasses at lower sites. Substrate height above mean high water (MHW) 1.9 cm ± 1.8 SD at 16 early nests, 3.7 cm ± 1.8 SD at 16 late nests; grass height 72.8 cm ± 3.2 SD at early nests, 91.6 cm ± 6.1 SD at late nests; grass height above MHW 75.0 cm ± 2.8 SD at early nests, 87.6 cm ± 5.0 SD at late nests (Storey et al. 1988). Implies that later nests are placed at lower sites, but in taller grass to avoid flooding and take advantage of denser cover. Similarly, first nests in N. Carolina placed in needlerush (higher sites) in early Apr, later in needlerush-cordgrass mix, then in cordgrass (lower sites) by late Apr (Adams and Quay 1958).

Nests on East and West Coasts often placed near edges of tidal sloughs; 60% of 50 nests in s. California were within 7.8 m of a slough edge, 80% of 79 nests in Virginia were within 4.6 m, and 71% of 63 nests in New Jersey were within 3.7 m (Kozicky and Schmidt 1949, Stewart 1951, Massey et al. 1984). No such relationship found in Alabama or Louisiana, where nests were dispersed in large patches of tall salt marsh cordgrass (Holliman 1978, Sharp 1976).

Construction Process

Male performs most nest-building (Meanley 1985). Process of nest construction not described. Egg-laying often begins before nest is completed.

Structure And Composition Matter

Nests tall and cryptic to avoid tidal flooding and protect eggs from predation (Storey et al. 1988). Nest is a bulky platform of dry cordgrass, pickleweed, salt grass, or other marsh vegetation built up 8–15 cm from substrate (Shuford 1993). In San Francisco Bay, CA, early nests consist of layer of pickleweed twigs over broken bits of dead Pacific cordgrass stems; later nests are constructed entirely of dead cordgrass, often attached to living stems (DeGroot 1927). Dome over top of nest may or may not be present; function is probably concealment or to hold eggs during tidal inundation (Kosten 1984). In response to experimental destruction of dome in 15 nests, adults rebuilt dome in 12 nests within 24 h. Dome present in 90.5% of 63 nests in New Jersey (Kozicky and Schmidt 1949). Dome absent in many Arizona nests, probably because overhead cover is dense (WRE). Nests may have ramp from water surface or substrate to rim; 68.4% of 63 nests in New Jersey had ramps, but 50% of 6 nests in Arizona lacked these ramps (Eddleman 1989). Ramps probably more common in habitats with high or fluctuating water levels.

Dimensions

Eighteen nests in New Jersey averaged 26.7 cm (range 10–50) from rim to substrate (Kosten 1982). Dimensions of 63 nests in New Jersey (mean [cm] ± SD): inside diameter 14.2 ± 1.8, outside diameter 23.6 ± 3.2, inside depth 5.3 ± 1.4, nest height above substrate 22.9 ± 8.0, nest rim to top of dome 18.3 ± 3.5 (Kozicky and Schmidt 1949). Measurements at 45 nests in San Francisco Bay, CA, (mean [cm] ± SD): outside diameter 21.1 ± 2.8, nest height above substrate 17.9 ± 6.3, height of dome 57.1 ± 15.2 (Harvey 1988). Dimensions of nests and nest bowls in Arizona (mean [cm] ± SD): inside diameter 14.7 ± 4.1 (n = 15), outside diameter 26.5 ± 3.0 (n = 12), inside depth 4.3 ± 2.6 (n = 16), nest height above substrate 19.3 ± 20.8 (n = 18), width of ramp 10.7 ± 3.2 (n = 3), length of ramp 37.7 ± 26.5 (n = 3; Eddleman 1989).

Microclimate

No information.

Maintenance Or Reuse Of Nests, Alternate Nests

Builds up nest during periods of high water (Jackson 1983). Male adds material to nest while female continues to incubate; female tucks material under eggs and into nest. Such augmented nests may measure up to 31 cm in diameter, 19.5 cm from rim to bottom, and 41 cm from mean water level. Egg nest may be used to brood young, but it is not used for second clutch (Blandin 1963).

Nonbreeding Nests

Up to 6 brood platforms constructed after hatching for brooding chicks (Adams and Quay 1958). Differ from primary nest in lacking a dome and being capable of floating at high tide. One pair in Florida constructed crude roost platform each evening to brood chicks (Duhsé 1988). Often uses dead mats of emergent vegetation for loafing and casting pellets after feeding; these sites may appear similar to nests (WRE).

Shape

Subelliptical to long subelliptical or ovate.

Size

Largest eggs laid by subspecies on West Coast of North America. Mean measurements (mm) of 165 eggs from 20 clutches of obsoletus collected at San Francisco Bay, CA, in WFVZ collection: length 44.30 (range 41.71–45.80), breadth 31.58 (range 30.69–32.50). Smallest eggs laid by yumanensis; mean measurements (mm) of 30 eggs from 6 clutches collected in se. California in WFVZ collection: length 40.26 (range 37.91–41.86), breadth 28.87 (range 28.26–29.76). Size of eggs of other subspecies intermediate (WFVZ data).

Mass

Little information. One fresh egg from Arizona weighed 19.0 g (WRE). Eggs from n. Atlantic Coast of U.S. may weigh 18–20 g at laying, and lose 2–2.5 g during incubation (Ripley 1977).

Color

Ground color creamy white, dull cream, pinkish, very pale buff, pinkish buff, yellowish buff, greenish buff, glossy buff, clay, or pale olive buff (Forbush 1925, Bent 1926, Oberholser 1974). Blotched or spotted irregularly with shades of brown, reddish brown, drab, lavender, gray, or lilac; spots may be concentrated at larger end. Degree of spotting highly variable.

Surface Texture

Smooth and glossy (Bent 1926).

Eggshell Thickness

Mean eggshell thickness in clutches collected in 1863–1947 averaged 0.241–0.244 mm from N. Carolina to Florida (n = 156 clutches), and 0.258–0.260 mm from New Jersey and Virginia (n = 82 clutches; Klaas et al. 1980). Similar measurements on clutches collected after 1947 were 0.242–0.257 mm for 16 clutches collected from N. Carolina to Florida and 0.255–0.262 mm for 40 clutches collected from New Jersey and Virginia. No difference in eggshell thickness between time periods, but shells of New Jersey and Virginia eggs were thicker than those of N. Carolina to Florida (Klaas et al. 1980). Mean empty shell weight of 165 eggs from 20 clutches of obsoletus from San Francisco Bay, CA, in WFVZ collection 1.832 g (range 1.658–2.013); mean empty shell weight of 30 eggs from 6 clutches of yumanensis from se. California in WFVZ collection 1.332 g (range 1.142–1.507).

Clutch Size

See Demography and populations: measures of breeding activity, below.

Egg-Laying

Little information. Birds at 4 New Jersey nests laid average of 0.9 egg/d (Kozicky and Schmidt 1949). Egg-laying rate at 1 nest in Louisiana 7/8 d (Bateman 1965). Eggs are laid before 08:00 in New Jersey (Schmidt and McLain 1951).

Onset Of Broodiness And Incubation In Relation To Laying

In many nests, incubation begins before end of egg-laying, resulting in asynchronous hatching (Meanley 1985).

Incubation Patch

No information.

Incubation Period

Averages 20 d in New Jersey (range 18–22, n = 6; Kozicky and Schmidt 1949). Averages 21 d in N. Carolina (Adams and Quay 1958). Extremes of 23 and 29 d reported in San Francisco Bay, CA (Applegarth 1938, Zucca 1954, Johnston 1956b). Incubation period at 7 nests in Arizona 23–28 d (Eddleman 1989); varies because incubation begins before last egg is laid.

Parental Behavior

Incubation by both sexes, on basis of marking and radiotelemetry data (Oney 1954, Eddleman 1989). Male incubates at night and sporadically during day; female does most diurnal incubation, and relieves male after sunrise. Dis-turbance of incubating adults produces responses including aimless flight, “broken wing” displays, aggressive distraction displays, and bewilderment (Nicholson 1927, MacNamara and Udell 1970). These displays reach peak during hatching (Kozicky and Schmidt 1949). Incubating adult retrieves eggs displaced from nest using bill (Pettengill 1938, Kosten 1982). Experimental displacement of eggs 1 m from nest showed that adults retrieved eggs in 15 out of 18 trials; stage of nesting cycle made no difference in behavior (Kosten 1982). Rare individuals (4 of 200) had to be lifted off nest to examine eggs (Zembal and Massey 1983).

Hardiness Of Eggs Against Temperature Stress; Effect Of Egg Neglect

Eggs in 1 nest in New Jersey hatched successfully after submersion during high tide (Kozicky and Schmidt 1949). Eggs submersed up to 45 cm deep during high tide are still capable of hatching (Oney 1954).

Preliminary Events And Vocalizations

Head tucked under right wing in egg; egg tooth by side of flank under section of egg covered with wreath of spots (larger end; Simmons 1914). Pipping begins about 48 h before hatching (Kozicky and Schmidt 1949).

Shell-Breaking And Emergence

Hatching lasts 24–48 h; duration may depend on whether incubation begins before egg-laying is completed (Kozicky and Schmidt 1949, Johnston 1956b). One clutch in Virginia hatched during 37-h period. A few young die during hatching; young from 0.8% of 513 eggs died during this time in New Jersey (Kozicky and Schmidt 1949).

Parental Assistance And Disposal Of Eggshells

Eggshells left in nest, eaten by adult, ground into small pieces, or dropped up to 6 m from nest (Simmons 1914, Meanley 1985).

Condition At Hatching

Covered with wet, long, black down; bill color pied, ranging from pinkish white with black base to blackish with pinkish white area around nostrils and tip; irides dark brown (Simmons 1914, Adams and Quay 1958, Meanley 1985). Stomach and cloaca rich orange pink or salmon (Simmons 1914). Eyes open, and emit faint cheeps. Length 75–80 mm (Adams and Quay 1958). Semiprecocial; incapable of moving from nest for at least 1 h after hatching and brooded by adult for several days (Meanley 1985).

Growth And Development

Egg tooth shed 4–6 d after hatching (Meanley 1985). Most growth in first 3 wk, but young able to swim and dive for short periods (Adams and Quay 1958). Bill coloration darkens in basal half by third week; still covered with black down at this time. Feathers appear in all except capital, caudal, and alar tracts by week 5; bill becoming uniformly light gray. All tracts have growing feathers by week 6, and irides become olive drab. See Appearance: molts and plumages, below.

Chick Behavior

Chicks flushed from egg nest in Louisiana ran a short distance to cover, then gave faint peeping sounds (Bateman 1965). Young follow adults during foraging bouts (Zembal and Fancher 1988). Forage independently on small prey soon after hatching. Begin to feed farther from adults as fledging age approaches (Meanley 1985).

Brooding

First-hatched chicks are led from nest by one parent while other parent continues incubating newly hatched chicks and remaining eggs (Kozicky and Schmidt 1949, Adams and Quay 1958). Brooded continually for first few days, on original nest, brood nest, or floating debris. One brood brooded by both parents for first 7 d in Florida; only 1 chick seen with 1 parent thereafter (Duhsé 1988). Adult covered chicks each night on newly constructed brood nest. Adults divided brood after first week, each parent tending half the brood (Duhsé 1988).

Feeding

See Food habits: diet, above. Chicks eat fragments of prey broken up by adults; foods do not differ from those eaten by adults (Adams and Quay 1958, Zembal and Fancher 1988). Adults sight prey, become motionless, and young race in to eat prey the adult has sighted (Zembal and Fancher 1988). Parental care usually extends until fifth or sixth week after hatching (Adams and Quay 1958, Zembal and Fancher 1988), but brooding may continue until eighth to tenth week (MacNamara and Udell 1970). At high tide, broods forage along narrow ditches with water 15–20 cm deep (Meanley 1969). Chicks stay in edge of vegetation during this time. Family groups forage in loosely organized unit, often dispersed over an area 15 m across (Adams and Quay 1958). Family unit maintained by peeps of chicks and subdued clucks of adult.

Carrying Of Young

Adults carry chicks <2 wk old during high water or across open water or to move away from human intrusion (Tomkins 1937, Pettengill 1938).

Little studied; not known to occur (WRE).

No information.

Growth

Independent of adult by week 6 after hatching (Adams and Quay 1958). Primaries about half grown by age 7 wk, three-fourths by age 8 wk. Bill and legs uniformly gray at 8 wk. Sheaths on primaries still visible on basal 1 cm, legs beginning to show orange at joint of tarsus and tibiotarsus; bill shows slight orange color at base, flank markings indistinct; some individuals capable of flight at 9 wk. All individuals can fly at age 10 wk; no sheaths remain on primaries, orange color expanding on bill and legs, flank barring becoming more distinct, iris becoming orange brown. After age 10 wk, individuals becoming indistinguishable from adults, but fleshy parts are somewhat duller in juvenile.

Association With Parents Or Other Young

Apparently not associated with parents or broodmates after fledging (WRE).

Ability To Get Around, Feed, And Care For Self

Tidal sloughs important for escape from predators (Harvey 1988).