Food Habits

Feed day and night (Robert et al. 1989).

Main Foods Taken

Aquatic invertebrates, also fish (Hawaiian Stilt; Telfer 1973, 1976).

Microhabitat For Foraging

While wading, tend to feed in shallow water at any depth up to the height of the breast (approximately 130 mm for males, 110 mm for females; Hawaiian Stilt, Telfer 1973). Avoid getting the breast wet. Some evidence that depths used are slightly different for avocets and for male and female Black-necked Stilts (Hamilton 1975); difference is primarily related to longer legs of male stilt.

In Hawaii, stilts cluster to feed around delivery pipes carrying water runoff from sugar cane fields (Telfer 1973).

Food Capture And Consumption

Hamilton (1975) described 3 visual feeding methods: Pecking, Plunging, and Snatching. Pecking method consists of visual search for prey while standing still or walking slowly, followed by a quick jab of the bill to capture prey on mud or near water surface; head does not go under water. In Plunging method, head and upper breast enter water to capture food from within the water column. Snatching method involves capture of a flying insect with bill. Black-necked Stilts also feed using tactile methods, but these have only been observed in wintering areas (Robert and McNeil 1989, Cullen 1994).

In another food capture method, Scythe-like Sweeps, bird walks or runs and swipes the head and bill through water or liquid mud (compare to Single Scythe and Multiple Scythe described for American Avocets by Hamilton 1975). In Head Immersion behavior, bird immerses its head and a portion of its neck in the water while feeling in the soft mud. Hamilton’s (1975) Plunging and Robert’s and McNeil’s (1989) Head Immersion may not be completely distinct. Visually locates and pecks at brine shrimp (Artemia salina) on the surface of the water, and brine flies (Ephydridae, Ephedra spp.) along the shoreline.

Robert and McNeil (1989) quantified feeding behaviors at a wintering site in ne. Venezuela. During nighttime, visual and scything methods were used equally (n = 38 and 33 observations respectively; unknown number of individuals). During daytime, feeding predominantly visual when winds were calm; switched to tactile plunging when winds >30 km/h. In a separate sampling study (Robert et al. 1989), stilts were seen foraging in 66.7% of nighttime observations, but only on 1.9% of daytime observations (day n = 54, night n = 102).

At least for some prey items, greater foraging success has been observed in groups than solitarily (Burger 1980). Hatch-year Black-necked Stilts in Texas spent more time foraging than adults, and foraged later in the day than did adults (Burger 1980).

Hawaiian Stilt feeds using Scythe-like Sweeps and Plunging (Ohashi and Burr 1977, Telfer and Burr 1978). Also trap fish by concentrating them in shallow water (Telfer 1975, 1976).

Major Food Items

On salt ponds: brine shrimp, brine flies, and terrestrial insects (Hamilton 1975). In freshwater wetlands (Wetmore 1925): crawfish (Cambarus sp.); water-boatmen (Hemiptera, Corixidae); adult and larval beetles (Coleoptera), especially crawling water-beetles (Haliplidae), predaceous diving beetles (Dysticidae), water-scavenger beetles (Hydrophilidae), and aquatic species of weevils (Curculionidae); fly larvae (Diptera), especially soldier flies (Stratiomyiidae) and brine flies (Ephydridae); snails (Gastropoda); small fish (carp [Cyprinus carpio] and sunfish [Centrarchidae]); and frogs (Anura).

Vertebrate prey are an important part of the diet of Hawaiian Stilts (70% of foraging time spent pursuing fish; Telfer 1975); including fish (Mozambique tilapia [Tilapia mossambica] and mosquito fish [Gambusia affinis]) and tadpoles (Bufo spp.; Telfer and Woodside 1977). Also consume invertebrates such as water boatmen, beetles, and possibly brine fly larvae (Ohashi and Telfer 1977, Telfer 1973, 1975, 1976, Telfer and Burr 1978, 1979).

Quantitative Analysis

From analysis of 80 stomachs from stilts in California, Utah, Florida, and Puerto Rico (details in Wetmore 1925): 35% true bugs (Hemiptera), 32.4% beetles, 9.7% flies, 7.9% snails, 3.3% caddisflies (Trichoptera), 3.2% fish, 2.7% miscellaneous animals (grasshoppers and crickets [Orthoptera] and a frog [Anura]), 2.9% dragonfly nymphs (Odonata), 1.3% mayflies (Ephemeroptera), 1.1% seeds and vegetative matter, 0.5% crawfish (by weight).

Information on food selection not available. Food storage not observed.

Two cycles of fattening and loss occur each year: fattening periods are prebreeding and postbreeding (premigratory), and occur in both migrant and resident stilt populations (McNeil 1971).

Under hot conditions, pants while incubating and wets belly to cool eggs (see Breeding: incubation, below).

Hamilton (1975) did not observe stilts drinking in his thorough behavioral studies. Moved from aquatic feeding area to land to defecate in 73.8% of 62 cases (Hamilton 1975).