Breeding

Pair Formation

Some Willets arrive apparently already paired and immediately take up territor-ies (Tomkins 1965, Sordahl 1979). Unpaired Willets engage in group displays that appear competitive (Howe 1982, Douglas 1996), and sometimes paired Willets join these displays. Such displays occur for 3 wk following arrival and prior to nesting (Tomkins 1965), and may continue at lower levels throughout nesting period, particularly when nest-loss rates high (CLG-T).

Nest-Building

No information.

First/Only Brood Per Season

Figure 4 . Western. In Cache Co., UT, copulations 19 Apr–3 Jun, egg dates 1 May–18 Jun (Sordahl 1981). In N. Dakota, period between first sighting of Willet and first egg laid averaged 20 d (range 15–29 d; Higgins et al. 1979). In N. Dakota, egg dates range 10 May–21 Jun (n = 24; Stewart 1975). In n.-central U.S. and s.-cen-tral Canada, median nest-initiation date, 20 May (range 7 May–10 Jun, n = 41; Kantrud and Higgins 1992). In s. Alberta, from 1995 to 2000, median date of first egg of all nests, 18 May (range 1 May–14 Jun, n = 206); median date of known renests only, 2 Jun (range 20 May–11 Jun, n = 9); median hatch date of all nests, 16 Jun (range 30 May–10 Jul, n = 97; CLG-T).

Eastern. Seasonal egg-laying distribution often bimodal. In S. Carolina, spring tides may wash out low-lying nests, and these pairs may renest (P. Wilkerson pers. comm.). In Chatham Co., GA, late Apr–Jun (Tomkins 1965); egg dates mostly May, earliest 24 Apr, latest 18 Jun (n = 75; Burleigh 1958). In N. Carolina, mid-May–mid-Jun (Pearson et al. 1942). On Wallops I., VA, early May–late Jun, peaking 5–15 May (Howe 1982). Maryland: egg dates 23 Apr–12 Jul (n = 67; 36 between 1–15 Jun; O’Brien 1996). Delaware egg-date range 7 May–1 Jul; median clutch-completion date 23 May (n = 78; Hess et al. 2000). On Long I., NY, most clutches completed 16–26 May (Wilcox 1980). Canadian Maritimes: eggs mid-May–mid-Jul (Erskine 1992).

Selection Process

Pairs fly to potential nest areas; during flight, both male and female may quiver wings below horizontal (as in aerial display) and raise wings and give PWW Calls as they descend to ground; pair wanders in grass performing nest-scraping behavior (Howe 1982). During nest-searching, male leads female, giving chittering call; steps into grassy tuft, makes small depression with bill (and possibly feet) and circles with breast in depression and sits; leaves tuft after few minutes, then female enters tuft, repeats “breast down turn” and sits; this sequence repeated 3 or 4 times (Hansen 1979).

Microhabitat

In N. Dakota, nests almost always in proximity to piece of wood, dried cattle dung, stone, etc. (Higgins et al. 1979). In n.-central U.S. and s.-central Canada, average vegetation height at nests 0.11 m (range 0.0–0.6, n = 43); average visual obstruction 0.04 m (range 0.0–0.2, n = 59); percent dead vegetation of total vegetation averaged 38% (range 0–99, n = 43; Kantrud and Higgins 1992).

Site Characteristics

On ground.

Western. Pond margins (Sugden 1933) and raised ground near water (Wolfe 1931). In s. Alberta, nests rarely very near wetland edges: In area of managed wetlands (i.e., wetland basins with water), median distance from wetland edges 240 m (range 33–1,700, n = 44); in area with natural (usually dry) or no wetland basins, median distance to any water (including dugouts) 960 m (range 60–2,840, n = 21; CLG-T). In U.S. Great Basin, often nest at edges of sagebrush near ponds (N. Warnock pers. comm.). In N. Dakota, nests usually in short, grassy cover (Higgins et al. 1979); similar in s. Alberta, although more likely to nest in taller planted grass than are Marbled Godwits (CLG-T). In n.-central U.S. and s.-central Canada, 51 nests found in native grasslands, 1 in seeded grass, 11 in cropland. Native grassland used most often, especially that which is idle during current growing season (Kantrud and Higgins 1992).

Eastern. Along edge of salt marshes in cordgrass (Spartina alterniflora and S. patens) or in sand-dune areas utilizing American beachgrass (Ammophila breviligulata; Bent 1929, Burger and Shisler 1978, Howe 1982). At Bombay Hook NWR, DE, nest always in cordgrass (Spartina patens) and/or saltgrass (Distichlis spicata); cover type considered more important than proximity to water (Munro 1969). In Nova Scotia, Willets nest in great diversity of sites, from Spartina marshes to upland meadows (Douglas 1996). In N. Carolina (Douglas 1996), S. Carolina, and Georgia (Tomkins 1965), nests behind barrier dunes in short vegetation or on bare ground. In Caribbean islands, nests in coral cobble (Phelps 1975). In Maine, 1 nest of presumed small colony found in spaghnum bog (Wells and Vickery 1990), the only record of Willets nesting in this habitat.

Construction Process

In N. Dakota, male typically made several scrapes with female nearby. Male would stand after scraping with head low and bill pointed toward scrape. Eventually female would settle on scrape and pull at nearby vegetation with bill, tossing it over shoulders; only female seen to add pebbles or vegetation to scrapes (M. Ryan pers. comm.).

Structure And Composition Matter

Comprised of grass stems bent down to form floor or grass gathered from distance (Erichsen 1921, Tomkins 1965, Phelps 1975); in grass clump lined with finer grasses (Bailey 1876). Nest in peat bog set in sphagnum and “lined with small twigs, dried leaves (mostly Vaccinium sp.) and sphagnum” (Wells and Vickery 1990: 74).

Dimensions

Average inside diameter in Alberta 160 mm ± 14 SD (range 110–195) × 140 mm ± 15 SD (range 110–180); depth 55 mm ± 12 SD (range 32–102, n = 56; CLG-T).

Microclimate

No information.

Maintenance Or Reuse Of Nests

Tomkins (1965) described 1 instance of reuse: first clutch destroyed by mower after 11 d incubation, second clutch started at same site 8 d later. Only 1 definite case of reuse noted in 6 yr in Alberta: same pair reused scrape of successful nest in subsequent year. Pair of Willets rescraped nest used by Marbled Godwits in previous year, but laid eggs in another scrape nearby (CLG-T).

Nonbreeding Nests

No information.

Shape

Usually ovate or ovate pyriform (Bent 1929).

Size

Western. From s. Alberta: mean 53.7 mm ± 1.9 SD (range 49.3–62.0) × 37.2 mm ± 0.9 SD (range 34.4–39.5, n = 46, CLG-T). From throughout range, mean 54.2 mm (range 50.5–58.1) × 37.6 mm (range 35.0–39.7, n = 56; Bent 1929).

Eastern. From Long I., NY, mean 38.0 mm (range 36.5–40.0) × 53.5 mm (range 49.5–57.0, n = 66; Wilcox 1980). From throughout range, mean 52.5 mm (range 49.0–60.5) × 38.0 mm (range 36.0–40.0, n = 56; Bent 1929).

Mass

Western. S. Alberta: mean mass of unincubated eggs 37.4 g ± 2.6 SD (range 33.0–43.0, n = 40 eggs of 14 clutches; CLG-T). Total mass of clutch of 4 eggs 51–62% of female mass (CLG-T).

Eastern. Averaged 38.5 g (range 31.5–44.4, n = 66; Wilcox 1980). Eggs lose approximately 0.2 g/d during incubation (Wilcox 1980); for 1 clutch of 4 eggs, mean egg mass changed from 39.2 g at laying to 34.7 g at hatching (Tomkins 1965). Total mass of clutch about 58–74% of female mass (based on 12 sets; Wilcox 1980).

Color

Ground color varies “from ‘deep olive-buff’ to ‘olive-buff,’ rarely ‘yellowish glaucous’” (“greenish types”) to “‘avellaneous’ to ‘tilluel bluff [sic],’ rarely pale ‘Isabella color’” (“buffy or brownish types”) with numerous shades in between. Bold and irregular spots (various sizes) and blotches of dark browns (burnt umber, bister, sepia, clove brown, sometimes lighter olive-browns), sometimes evenly covered with small spots (Bent 1929: 30). In s. Alberta, 4-egg clutches often consisted of eggs of 2 colors: greenish and white (CLG-T).

Surface Texture

Slightly glossy (Bent 1929).

Eggshell Thickness

For s. Alberta, 1995–1998; n = 10 (6 clutches), mean 0.19 ± 0.01 SD (range 0.18–0.21; CLG-T).

Clutch Size

Four eggs (Kantrud and Higgins 1992, CLG-T); sets with <4 eggs often attributed to egg loss, sets with >4 eggs sometimes attributed to >1 female laying (see Colwell 1986) but no genetic or physiological studies. See Demography and populations: measures of breeding activity, below, for details.

Egg-Laying

Clutch of 4 eggs usually laid in 6 d (Tomkins 1955); intervals between laying range from 1 to 4 d (Tomkins 1965, Hansen 1979). Three females collected in ne. Venezuela with 2 ovaries and 1 (left) oviduct (McNeil 1969).

Onset Of Broodiness And Incubation In Relation To Laying

Male often flushed from incomplete (1–3 eggs) clutches, but extent of incubation before clutch completion unknown (CLG-T).

Incubation Patch

Both sexes have typical shorebird incubation patches consisting of large oval patch on each side of sternum (CLG-T). Tomkins (1965) claimed neither male nor female with vascularized brood patch; Wilcox (1980) stated brood patches not found on either sex.

Incubation Period

Mean 25.2 d ± 1.2 SD (n = 8; Howe 1982), 25.2 d ± 0.4 SD (range 25–26, n = 5; CLG-T), and 22–29 d (Tomkins 1965). Discrepancies in incubation period noted by Tomkins may be related to parental inattentiveness, perhaps due to frequent disturbance of adults at nest (Tomkins 1965, Wilcox 1980).

Parental Behavior

Both parents share incubation duties (Tomkins 1955, Howe 1982). Incubating adults during day very likely to be females; only males found to incubate at night (Howe 1982). Close to 100% incubation after clutch complete; exact proportion of time/sex unknown. Time of day individuals on nest when first captured in s. Alberta: 96% females during day (09:00–19:30; 24 of 25 different females), 69% males during night (17:30–23:00; 18 of 26 males). Males more likely to be captured during day than females are in late evening; no information from 23:00–09:00 (CLG-T). In N. Dakota, incubation exchanges observed in early morning (06:00) with male replacing female; females again on nest at least occasionally during midday, males in early evening and females on nest near dusk (after 19:00; M. Ryan pers. comm.). Incubation may begin prior to clutch completion, causing hatching asynchrony and possible abandonment of viable, unhatched eggs (Tomkins 1965), but desertion of viable eggs unusual in s. Alberta (CLG-T). In N. Dakota, egg hatchability 93% (63 of 68 eggs) in 17 successful clutches (Higgins et al. 1979).

Hardiness Of Eggs Against Temperature Stress; Effect Of Egg Neglect

Recorded incubation periods of 29 d (Tomkins 1955) and 32 d (latter apparently due to frequent disturbance of adults by observers to measure eggs; Wilcox 1980).

Preliminary Events And Vocalizations

Little information. Chick makes pip hole in shell at large end of egg, then—with bill in hole to provide leverage—convulsive movements of chick slits shell in longitudinal lines (from pip hole to head at egg’s equator) along shell’s contact with chick’s spinal process; manner of hatching similar to that of American Woodcock (Scolopax minor; observations of 1 clutch by D. K. Wetherbee in Wetherbee and Bartlett 1962). Behavior of parent changes (more vocal and defensive, as in other species of shorebirds) when chicks start peeping shortly before hatch (CLG-T).

Shell-Breaking And Emergence

Usually 3 eggs of clutch hatch within several hours and fourth hatches about half-day later (Howe 1982). Two days required for chicks to break through shell, and they consistently chip through larger end of egg (Tomkins 1965). In s. Alberta, from first cracks in egg (star pip) to hatch usually 3–5 d. May hatch at any time of day; normally all eggs in clutch hatch in 1 d (12 of 16), occasionally 2 d (4 of 16). Once chick breaks through egg (hole pip), normally hatches that day (CLG-T).

Parental Assistance And Disposal Of Eggshells

Parents remove eggshells to some distance (Tomkins 1965), but in s. Alberta, shells not removed as quickly as in most shorebird species; sometimes left in nest after chicks leave (CLG-T).

Condition At Hatching

Precocial and nidifugous. Chicks covered in buff or gray down (Tomkins 1965). On Long I., NY, newly hatched chicks averaged 28.0 g (range 23.6–30.6, n = 25), or 70.9% of fresh egg mass (Wilcox 1980). Chick measurements at hatch in s. Alberta (n = 12 chicks of 5 clutches): wing 22.9 mm ± 0.8 SD (range 22–24), culmen 15.9 mm ± 1.0 SD (range 14.1–17.4), tarsus 35.7 mm ± 1.9 SD (range 31.9–39.2), mass (n = 9 fluffy chicks of 3 clutches) 26.4 g ± 3.0 SD (range 22.0–30.0). Per-cent of adult measurements (average of sexes): mass 9.8%, wing 10.4%, culmen 26.2%, tarsus 53.1%. Egg teeth in upper and lower bill, normally lost 1–2 d after hatch (CLG-T).

Growth And Development

Legs grow more rapidly than wings; tarsi nearly adult length at 1 wk (Tomkins 1965). Period from hatching to first flight approximately 4 wk (Howe 1982); in s. Alberta, fledge in 27–31 d (usually 28 d; n = 13; CLG-T).

Both adults share in chick-rearing duties: adults lead, follow, and gather young; brood young; per-form antipredator behavior/respond to predators with alarm calls/mobbing and vigilance (Douglas 1996). Brood territories defended by adults against other adults and young (Douglas 1996). Females abandon chicks approximately 2 wk after hatching but males continue their presence with broods for at least 2 wk after females depart (Howe 1982). In s. Alberta, males remained longest with brood in 87% of pairs, females remained longest in 8%, and both remained in 6% (n = 52). Departure of females from brood, as in most other biparental sandpipers, varies with date of hatch: females stay longer with early-hatching broods, sometimes to fledging. Males may desert when young fledge, some protect young for up to 1 wk after fledging (CLG-T).

Brooding

Adults brood young at night in New Jersey and apparently also in Nova Scotia (Douglas 1996); no evidence found in Georgia study (Tomkins 1965).

Feeding

Chicks peck and jab at vegetation from day of hatch, presumably for insect and other invertebrate prey. Not fed by parents. In s. Alberta, broods usually found at edge or within shallow wetlands, especially those vegetated with spikerush (CLG-T).

Nest Sanitation

Chicks leave nest 1–2 d after hatch. In s. Alberta, sometimes feather lice (Insecta: Mallophaga) on eggs but never fleas (Insecta: Siphonaptera) as in feather-lined waterfowl nests in same area (CLG-T).

Carrying Of Young

One report from S. Carolina of adult carrying young: “I found a nest in an oat field [on 29 May 1899], which contained one young bird just hatched and three eggs on the point of hatching. I remained near the place until the eggs were hatched, and the Willets were greatly alarmed all the time. Presently I saw one of the old birds remove a young one and fly with it across three creeks and marsh land to an island a quarter of a mile [0.4 km] away. This was repeated until all the young were removed” (Wayne 1910: 54; quoted also in Bent 1929: 31).

This single instance often reported, with impression that such behavior might well be common. Never observed in 6 yr in s. Alberta, with considerable observations of parents with broods (CLG-T), nor in 3 yr in N. Dakota (M. Ryan pers. comm.).

Only to extent that groups of adults often join in aerial mobbing of potential predators, especially in defense of young (CLG-T).

Interspecific brood parasitism never recorded. Specific explanatory details unknown for 1 nest found with 2 Wilson’s Plover and 4 Willet eggs (Tomkins 1965); probably Willet takeover of plover nest.

Departure From Nest

Chicks depart nest within a few hours to 2 d after hatching (Tomkins 1965, Wilcox 1980, CLG-T). Young of 1 brood moved 23 m from nest in 1 h (Wilcox 1980).

Growth

No information once young leave nest. Fully fledged young (>30 d old) may retain some downy feathers, particularly at back of neck and base of bill (CLG-T).

Association With Parents Or Other Young

See Parental care, above.

Ability To Get Around, Feed, And Care For Self

In s. Nova Scotia, recently hatched chicks hike up to several kilometers with their parents from upland meadows and fields to Spartina patens meadows (Douglas 1996). In s. Alberta, N. Dakota and U.S. Great Basin, chicks normally moved to nearest suitable wetland (shallow water and emergent vegetation), and as wetlands were flooded or dried up, broods moved to next suitable wetland. Distances moved often several kilometers in total; sometimes involved crossing paved or unpaved well-used roads (M. Ryan pers. comm., N. Warnock pers. comm., CLG-T).

No information.