Nordmann's Greenshank Tringa guttifer
Version: 2.0 — Published February 19, 2021
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Diet and Foraging
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Main Foods Taken
Breeding Range. Diet consists of small fish and various invertebrates.
Nonbreeding Range. Feeds primarily on crabs, as well as a wide variety of prey items including vertebrates, mollusks, and crustaceans.
Microhabitat for Foraging
Breeding Range. Forages on coastal meadows, lowlands, and intertidal flats. During low tide they feed on exposed algal patches, and sand or mud flats (18). During high tide they forage within the coastal meadows and lowlands, feeding along the edges of shallow lakes, ponds, and streams usually at a depth of 5–15 cm (18, 43, 41, 116). During all tides, the species can be found foraging at river mouths and deltas (18, 75).
Nonbreeding Range. Forages along flats of a pure mud or mixed sand-mud substrate, algal shores, sandy beaches and bars, rocky outcrops, shallow tide pools or pools of standing water, aquaculture ponds, and within shallow sea grasses (Halophila spp., Thalassia spp., Enhalus spp., and Cymodocea spp.). In tidal areas they often follow the incoming or outgoing tide and forage on freshly exposed areas along the water’s edge, avoiding deep water or flats that have been exposed for a long time (18, 8, 22, 70, 19, 131, 90, 73). The species is seldom found in water deeper than its belly.
Food Capture and Consumption
Breeding Range. On the breeding grounds, the species most often employ the swift lunging technique described above, although typical probing is also common (18). They also chase down prey exposed by outgoing water, similar to the foraging behavior of a Sanderling (Calidris alba) (18). If fish are hidden in the thick vegetation of a coastal meadow, they manipulate the vegetation until the fish is exposed or until it leaves cover. If their foraging areas are partially frozen, the species picks off sticklebacks underneath the ice (66). To swallow a stickleback, the species carries it to a dry section of the coastal meadow or mudflat, vigorously shake and briefly re-submerge it (presumably to wash off the grit and mud), then places the fish on a dry substrate to reposition it so the head is swallowed first and the spines do not interfere (18; VVP). Processing and swallowing a fish can be a lengthy ordeal; the species frequently drops and recaptures, and partially swallows and regurgitates the fish multiple times before finally succeeding to consume it (18, VVP).
Other foraging behaviors include the species hovering 5–10 m (but also as high as 20 m and as low as one m) above the surface of a mudflat and diving to catch prey items, similar to a tern (Sterna spp.) or kingfisher (Alcedines spp.) (132, 133, 73). They may stand motionless in an alert stance for 3–4 minutes near a crab burrow to ambush crabs with an “explosive movement” once it appears (134). Greenshanks occasionally employ kleptoparasitism to steal food from godwits (Limosa spp.), plovers (Pluvialis spp.), other Tringa species, and even terns (10, 101, 109). They can also be active foragers at night (116).
Nonbreeding Range. On the nonbreeding grounds, the species employs a variety of foraging behaviors and techniques. It is often a solitary forager (but sometimes in small dispersed groups), locating prey while walking or running in irregular patterns, collecting prey items with a series of pecks (bill partially inserted), jabs (bill inserted half way), and probes (bill fully inserted) and often moving its head rhythmically from side to side (135, 8, 70, 131). When consuming a crab, the species either swallows the crab whole or re-submerge and shake it vigorously until the legs fall off, subsequently swallowing the body and legs separately (135, 8, 3, 132, 131, 134). They also lunge at prey items that were located visually (10, 3, 132, 136). This lunging technique is considered a diagnostic characteristic when comparing to a Common Greenshank (Tringa nebularia), although may cause confusion when observing a distant Terek Sandpiper (Xenus cinereus) which employs a similar foraging technique (137, 12, 73). The overall foraging behavior of the Nordmann’s Greenshank is considered diagnostic when comparing to a Common Greenshank, as the former is often more calm and patient than the latter (116).
Major Food Items
Breeding Range. On the breeding grounds, their diet consists of small fish and various invertebrates. Small fish include Amur (Pungitius sinensis) and ninespine sticklebacks (P. pungitius) with a mean mass of 1.29 g ± 0.24, and a mean length of 59.22 mm ± 5.12 (VVP, KM). The invertebrate array includes polychaete and oligochaete worms, small crustaceans and mollusks, as well as aquatic and terrestrial insects (32, 18, 108, 116, 70). Undigested Pacific herring (Clupea pallasii) roe 2–3 mm in diameter has also been found in the species’ feces (60). Chicks forage on small fish, terrestrial and aquatic invertebrates, polychaete worms, and various amphipods (43).
Nonbreeding Range. On the nonbreeding grounds, the species feeds on a wide variety of prey items including small fish and mollusks, various crustaceans and larvae, shrimp or prawn, and larger prey items such as mud skippers (Periophthalmus spp.) and, most notably, crabs (6, 70, 134, 73, 112). Species of consumed crabs include swimming crabs (Portunidae sanduirolentus, P. pelagicus, and Scylla olivacea) and intertidal mud crabs (Macrophthalmus japonicus) with carapace widths ranging between 5–50 mm, and carapace lengths between 5-60 mm (135, 8, 22, 70, 131). The species may also consume gastropods, bivalves, amphipods, decapods, brachiopods, and Acanthogobius fish (i.e., gobies) (132, 24).
Food Selection and Storage
Considered a crab specialist on the overwintering grounds and a fish specialist on the breeding grounds. Not known to store food.
Nutrition and Energetics
The time needed to acquire and consume food likely depends on prey abundance and the skill, dexterity, or experience of a bird. One individual foraging in northeastern Sakhalin Island, captured and consumed 5 fish in 3 minutes (1.7 fish/min), making 3–4 attempts to process and swallow each fish; while another bird processed a fish in only 2–3 attempts and doubled its intake (116). During 27 minutes of active feeding in Singapore, a bird caught 15 prey items (1.8 prey/min): 10 crabs, a prawn, and 4 unidentified items at intervals ranging from every 7 seconds to 5 minutes (131). In South Korea, one individual took 1.2 crabs every 5 minutes (132).
The only study that calculated the energetics of foraging concluded that the species consumes 0.13 g of ash-free dry weight per minute of foraging activity (132).
Metabolism and Temperature Regulation
No information regarding metabolism.
May dissipate the intense tropical heat of their wintering grounds by keeping their feet and legs submerged in water (92).
Drinking, Pellet-Casting, and Defecation