Breeding

Arrival On Breeding Grounds; Pair Formation

Arrives unpaired at Hudson Bay in late May–early Jun (JRJ), n. Quebec in mid-May (Harris 1989). Unlike shorebird species that continue farther north, arrivals at Churchill, Manitoba, rarely seen in flocks, except in late years when breeding localities were unavailable; then concentrate in thawed areas along Churchill River. At Schefferville, Quebec, often in flocks (≥25) until late May, although sightings usually involved 1 or 2 individuals. Males arrive a few days earlier than females. If conditions allow, move directly to habitat, where birds associate as pairs as soon as both sexes present. Pairing occurs even if nesting habitat not suitable on arrival; laying delayed until snow, runoff conditions allow (JRJ).

Nest-Building

Never observed. Scrapes made by male crouching and twisting chest against substrate (JRJ).

First/Only Brood Per Season

Figure 5 . Raise only 1 brood/yr. Egg dates for nests with complete first clutches at Churchill 2 Jun–10 Jul. Mean date of clutch initiation about 8 Jun (n = 13 yr of observations), average a few days earlier in warm years (Jehl and Smith 1970, JRJ). In British Columbia, 7–29 Jun (Campbell et al. 1990); Alberta, 22 May (Western Foundation of Vertebrate Zoology; WFVZ); Quebec, 3 Jun (Harris 1989); Alaska, 16 May (WFVZ).

Laying Of First To Last Egg In Clutch

Four to 5 d; eggs probably laid at 26- to 28-h intervals (Harris 1989).

Hatching Of First Chicks

At Churchill, Manitoba, chicks from first nesting attempts hatch 23 Jun–12 Jul, depending on season, with majority 30 Jun–6 Jul. Clutches hatching after about 15 Jul almost surely renesting. Usually all eggs hatch in 10–12 h. In population, hatching synchrony high; in any year; 80% of nests hatch within 7-d span (JRJ).

Selection Process

Pair may investigate several scrapes (as do other shorebirds) before female selects one (JRJ).

Microhabitat; Site Characteristics

At Churchill, Manitoba, nests in wet meadows at treeline, dominated by sedge, cotton grass, small willows; also in muskegs within coniferous forest. Meadow sites typically within 3–4 m of standing water (range 0–40), usually 15–20 cm above water level atop sedge (Carex aquatilis) hummock, whose dry area covers 1.8 m²; a few nests found on flat ground. Muskeg sites tend to be 30–45 cm above water level on sides of frost-heaved hummocks. Nests and incubating bird well concealed by dead (previous year’s) overhanging sedge leaves (Fig. 6, contra photo in del Hoyo et al. 1996: 474, where cover obliterated by photographer). Nests almost always in proximity (average 14 cm, range 0–33 cm) to woody plants (birch, rose-bay [Rhododendron lapponicum], dead spruce stump) and sometimes under or partly concealed by branches. In Alberta muskegs, nests usually adjacent to stump and well concealed; 3 reported in atypically dry area covered with moss and lichen, unprotected from above (Randall 1961).

Construction Process

Never observed.

Structure And Composition Matter

Consists of a simple bowl in thick vegetation, usually atop clumps of sedge (Carex aquatilis). Well lined with dried grass 8–20 cm long, leaves of local plants (e.g., Arctostaphylos sp.), tamarack twigs, willow ptarmigan (Lagopus lagopus) feathers (JRJ). Nest cups at Churchill, Manitoba, have dense cover of sedge all around nest about 10 cm high, highest blades 30–40 cm tall.

Dimensions

Across breeding range, nests average 4.5 cm deep and 10–13 cm across (data courtesy of WFVZ, Gabrielson and Lincoln 1959, JRJ), whereas in 6 sedge meadow nests at Churchill, mean diameter was 8.1 cm, depth 1.9 cm (C. Macdonald pers. comm.). Differences probably result from a different perception in what to measure.

Microclimate

No indication that nest site selected with regard to microclimate. Nests at Churchill not aligned with respect to prominent vegetation, hillocks, prevailing wind; simply sheltered by dry sedge, which inevitably provides some protection from elements, but mainly concealment.

Maintenance Or Reuse Of Nests, Alternate Nests

Incubating dowitcher will fiddle with lining, add leaves or bits of grass, pull sedge over head for concealment. Old nests at Churchill not reused, likely because they are destroyed by snow overburden in winter and melt waters in spring (JRJ).

Nonbreeding Nests

None.

Shape

Ovate pyriform.

Size And Mass

Measurements (mm): In Churchill, Manitoba, mean length 42.3 (range 39.9–45.7) and mean breadth 29.3 (range 27.9–31.2, n = 28; JRJ). In n. Quebec, mean length 40.5 (range 39.1–41.7) and mean breadth 29.4 (range 28.3–30.5, n = 12; Harris 1989); in Alberta, mean length 40.8 (range 38.2–44.0) and mean breadth 29.2 (range 27.2–30.3, n = 18; Bent 1927). Mass of fresh eggs from n. Quebec: mean 17.7 g (range 16.7–18.3, n = 4; Harris 1989).

Color

Ground color light greenish-brown or olive green; spotting brown, dark umber, and sepia of various intensity, ranging from light to very heavy, always denser at large end (Randall 1961).

Surface Texture

Smooth.

Eggshell Thickness

No evidence of thinning or surface abnormalities in nests found near Churchill in 1960s and 1990s (JRJ).

Clutch Size

Typically 4. Of 54 clutches from Churchill thought to be complete, 3 had 3 eggs, 49 had 4, and 2 had 5 (mean 3.98). Of 43 in central Alberta, 42 had 4, 1 had 5 (Randall 1961).

Egg-Laying

No data, as nests are almost invariably found only after clutch is complete (JRJ). Presumably eggs laid every 24–30 h, as in other shorebirds, so that clutch is completed in 4–5 d.

Replacement Of Individual Eggs Or Clutches

Timing of late hatches indicates that dowitchers, like other shorebirds, will re-lay in new nest if first clutch is lost early in season. At Schefferville, Quebec, 1 nest hatched 17 Jul, indicating laying 23–26 Jun, that period coming after 13–15 Jun blizzard (usual hatch third week of Jun; REH; see Gonadal development, below).

Gonadal Development

From JRJ. Males at Churchill capable of breeding as soon as they arrive, although testes less than maximum size; majority have free spermatozoa in the lumina of some tubules (stage 5b of Selander and Hauser 1965; Fig. 7). Testicular size maintained into third week of Jun (still stage 5b), then decreases sharply (maximum length 4 mm by the time they depart). By mid-Jul on coast of New Jersey, maximum length 2–3.5 mm, as in immatures.

In females, ova not fully developed until a week or so after arrival at Churchill and regress quickly after clutch is laid. Rapid regression makes it unlikely that females can re-lay much more than a week or so after original clutch lost.

Onset Of Broodiness And Incubation In Relation To Laying

Adults attend eggs sporadically or in evening as early as after first egg, continuously after fourth (sometimes third) egg. More prone to desert in response to bad weather, disturbance, early than late in incubation (JRJ).

Incubation Patches

Well defined in both sexes.

Incubation Period

Averages 21 d (Jehl and Hussell 1966a).

Parental Behavior

Both parents incubate and care for young, although female’s role in chick-rearing is minor (Harris 1989, JRJ). Among color-marked Short-billed Dowitchers at Churchill, Manitoba, females incubated mainly during day (07:00–20:00), males mainly, but not only, at night. Periods of changeover vary with pairs. In all nests closely watched (n > 20), female did at least half of incubation. However, when hatching nears, male takes an increasing role; in n. Quebec, some shifts lasted at least 19 h (REH). No daily pattern of incubation detected in 3 nests in Quebec; pairs share incubating duties in different proportions, with females taking 9–33% of load (Harris 1989).

Changeover is simple. Mate lands near nest and incubator departs; no interactions.

Incoming bird walks quietly to nest, settles, pulls sedge cover over back and head. Relieved bird apparently departs from territory (JRJ). In Quebec, males observed to sing during changeover (Harris 1989). See Behavior: predation, and Nest site, above.

Hardiness Of Eggs

Eggs covered with snow during laying period still hatch (JRJ). In 1 yr, just prior to hatch, adults incubated successfully through 5 d of continuous rain, snow, with temperature near 0°C (Jehl and Hussell 1966b).

Preliminary Events And Vocalizations

Egg star 2–3 days, pip 1 d before hatching. At that time, incubating bird becomes increasingly anxious; frequently preens, shifts direction on nest, stands and resettles, and gives various short calls. Also increasingly prone to give distraction display. Start of hatching and presence of chicks signaled by Alarm Calls, and adults flying toward intruder; most of all, by landing atop small bushes and screaming (see Fig. 3).

Shell-Breaking And Emergence

At about 90% of nests, only male present at hatching. Adults do not assist chicks in emerging. First chicks start to wander from nest when dry. Time for whole clutch to hatch usually <12 h. Adults abandon eggs that do not hatch by the time first chicks are ready to leave, even if egg is well pipped and chick vocalizes (JRJ).

Parental Assistance And Disposal Of Eggshells

Adult removes eggshells and carries them 10–15 m before dropping; no attempt to conceal, then immediately returns to brood. Male heard to call oo-it repeatedly when disposing of shell, chick answered each time. May also toss shell to edge of nest and leave it there for 10 min or so before removing (JRJ). One female seen to eat a small piece of shell (Harris 1989). Occasionally shell from last chick not discarded.

Condition At Hatching

Chicks <12 h old at Churchill, Manitoba: mean mass 11.4 g (range 10.0–12.2, n = 6); bill 16 mm (JRJ). At Schefferville, Quebec: mean mass 12.3 g (range 11.9–12.9, n = 7); mean bill length 14.8 mm (range 14.1–15.7, n = 4); mean tarsus length 27.4 mm (range 26.7–28.2, n = 7; Harris 1989). Chicks precocial, covered with down; able to walk immediately, swim as soon as dry. Egg tooth present on tip of maxilla and mandible; falls off before chick is dry and leaves nest (Jehl 1968a).

Growth And Development

At about 16–17 d old able to fly short distance; mass 71 g, culmen 42 mm, wing 86 mm, tarsus 39.4 mm. Well flying, independent juvenile (age about 21 d) weighed 86 g, and was starting to lay on premigratory fat (JRJ).

Consists of brooding, leading to feeding areas and alerting chicks, and deterring predators; broods always observed in wetland habitat. Nearly all parental care by male. Most females take little interest; may desert brood just before hatching or remain for several (1–3) d (Jehl and Smith 1970, JRJ), then migrate (see Migration: timing and routes of migration, above). Rarely both mates defend brood together during first day or 2 after hatch. Males remain until chicks able to fly, usually about third week of Jul, but start flocking before; depart before end of month (Jehl and Smith 1970, JRJ).

Brooding

Males brood chicks for several days, and at night and in wet, cold weather. Females never observed to brood out of nest, though probably do so occasionally during first day or 2. Female observed to brood on nest on day of hatching, while male moved off a short distance to feed (JRJ). Chicks attain homeothermy at 18–19 g, or about 18% of adult body mass and 67% above hatch mass (Visser and Ricklefs 1993).

Feeding

Adults do not feed young. Small chicks feed at surface, mainly on mosquitoes, spiders, and other insects gleaned from vegetation. By time of fledging, probing like adults (JRJ).

Carrying Of Young

Never observed nor suspected.

Never observed.

Unreported.

Departure From Nest

Broods leave nest as soon as last chick is dry and active or, if that happens at night, the following morning. Early-hatching chicks wander a few meters from nest. Parent encourages them to return by clucking softly. When all chicks dry, adult (usually male) leaves nest and calls wit-wit, usually from ground, but also from small tree (see Fig. 3). If chicks do not follow, he may do some displacement probing or other activity, then return to brood several times. Male may return to nest once or twice to make sure all chicks have left. Female usually not present and may not be seen again (see Parental care, above); if present, may stay in vicinity, though not closely with brood, for a day or 2 before disappearing; rarely pays attention to male’s Alarm Calls or gives any of her own. See also Sounds: vocalizations, above. In inclement weather, chicks can remain in nest for ≥24 h. Large yolk sac of newly hatched chicks (0.7–1.1 g, or 6–9% of total body mass) probably adequate to sustain them for at least 2 d (JRJ).

Association With Parents

Male remains with young for 12–14 d (once 17 d), then joins flock and disappears. Rarely seen in nesting areas at Churchill after 20 Jul (JRJ). Flocking males do not challenge intruders (unlike those attending young) and show minimal curiosity to alarm calls of others.

Juveniles independent at 12–14 d, and can fly well, though for short distances, at 16–17 d (i.e., 15–18 Jul in most years).

If water conditions suitable, remain in marshes at Churchill until last third of Jul, then move toward coast and leave in early to mid-Aug.