Food Habits

Main Foods Taken

Broad diet. Aquatic and terrestrial invertebrates, including earthworms, flying insects, beetles and other insects, snails, crabs, crab eggs, crab larvae, fish, squid, garbage, offal, and berries such as mulberries (Morus) and blueberries (Vaccinium) (Bent 1921, Burger 1988, Patton 1988, Burger and Wagner 1995).

Microhabitat For Foraging

Normally feeds on coast at edge of water; goes inland during high winds and on high tides, and to find insects in grassy meadows and worms in plowed fields (Burger 1983, 1988; Burger and Wagner 1995). Feeds on variety of inland lakes and marshes, coastal marshes, impoundments and pools with different water depths (Burger et al. 1982, Burger 1988). Distribution on bays affected by tidal factors; on inland pools, by weather-related and seasonal factors (Burger 1983).

Food Capture And Consumption

Forages while walking by picking up food from surface of land or water; while swimming by picking up items on surface, just below surface, or emerging; while walking in water or by foot-paddling for invertebrates or horseshoe-crab eggs; while flying by seizing insects; by plunge-diving for fish; and by pirating food from conspecifics or other species (Hatch 1970, Burger 1988, Burger and Gochfeld 1991). Along beaches, will forage on carrion (Stone 1937), or will catch emerging 17-year cicadas (Magicicada septendecim, Forbush 1924). Under strong head winds, may skim surface of water by putting tip of lower mandible in water (Stone 1937, Hailman and Reed 1982). Engages in piracy at tern colonies, where multiple gulls chasing 1 tern are more successful at obtaining fish from terns than single gulls (Hatch 1970). Sometimes forages with Brown Pelicans (Pelecanus occidentalus) in North America and Puerto Rico by hovering overhead or sitting on back of pelican and seizing escaping prey (Bent 1921, Carroll and Cramer 1985, Saliva 1994, JB). Cooperative foraging on horseshoe-crab eggs: male foot-paddles to dislodge eggs from below sand for female (Sullivan 1984). Superabundance of horseshoe-crab eggs on Delaware Bay may reduce predation pressures on infaunal benthic invertebrates (Botton 1984).

Interfood interval, a measure of foraging difficulty and prey availability, varies (in increasing length of intervals) from snails in intertidal zone to garbage, small invertebrates in sand, insects from air or ground, worms in wet field, fish (Burger 1987, 1988). In general, surface-seizing, surface-dipping, and picking up items from ground or water surface have shorter interfood intervals than jump-plunging, aerial-dipping, or surface-plunging for food over bays or oceans (Burger 1988). Feeding in lakes, river mouths, bays, and oceans results in longer interfood intervals than feeding in wet fields, on calm pools, at sewage outfalls, or at garbage dumps.

Competes with Herring Gull for food and foraging space on sanitary landfills. Where Laughing Gull numbers are low, this species is less able to land on dumping surface; forced to suboptimal foraging sites and loses food to Herring Gull pirates (Burger 1981). Laughing Gulls may respond to competition for foraging space by hover-dipping for food rather than attempting to land on surface, and by waiting to feed when larger gulls are satiated (Burger 1981). Laughing Gulls are significantly less aggressive than Herring Gulls when foraging, and win fewer encounters (Burger 1981). Laughing Gulls can feed around moving bulldozers without injury (Burger and Gochfeld 1983b). In Texas, Laughing Gulls form dense foraging groups and prevent less numerous, larger Herring Gulls from locating foraging places to land (Burger and Gochfeld 1984).

Vigilance behavior, scanning for predators and humans, decreases with increasing density of foraging group (as is true for many birds), thus increasing foraging rates and decreasing aggression (Burger and Gochfeld 1991). Laughing Gulls foraging on edge of dense flock take fewer pecks at food items, take more steps, and devote more time to vigilance than those birds in intermediate or central parts of the flock (Burger and Gochfeld 1991). Aggression rates are higher in intermediate position in flock, where gulls are trying to avoid being on edge of flock and are not yet in center (Burger and Gochfeld 1991).

Age Effects

Many aspects of foraging behavior in Laughing Gulls show age-related differences (Burger 1987, 1988). In intraspecific encounters at sanitary landfills, adults won 75%, subadults 66%, young only 29% (Burger 1981). Similarly, at sanitary landfills in Florida, adults obtained more food in a shorter time period than young did (Burger and Gochfeld 1983b, 1984). When fishermen or scientists threw offal to flying Laughing Gulls, adults caught and ate 65% of food, young of year only 46%; young dropped 24%, adults only 13%; young were less able to obtain and keep large pieces (Burger and Gochfeld 1981).

On wintering grounds in Mexico, adults generally had higher capture success rates and shorter intervals between obtaining food items than young in a variety of feeding habitats using different methods (Burger and Gochfeld 1983a). Where food was most readily available, differences among age classes were smaller (Burger and Gochfeld 1983a). Young compensated for their deficiencies by concentrating on those situations where their interfood intervals and success rates most closely approached those of adults.

Few data. Items in 39 stomachs from coastal Massachusetts in diminishing order of occurrence: mollusks, fish, shrimp, insects, echinoderms, small crustaceans, and small lobsters (Palmer 1949). Of 32 stomachs collected in summer: gulls in Alabama contained crustaceans and insects, those along Atlantic Coast contained fish (43%), crabs or shrimp (46%), and beetles, grasshoppers, and moths (Howell 1932). Chicks at Stone Harbor, NJ, fed 60% horseshoe-crab eggs, beetles and other insects, fish, and fiddler crabs (Uca spp.) (Burger and Wagner 1995). Audubon (1840) reported Laughing Gulls eating eggs and small chicks of Sooty Terns (Sterna fuscata) and Brown Noddies (Anous stolidus) in Dry Tortugas, FL, and Bent (1921) recounted them eating eggs of Royal Terns (Sterna maxima); these are unusual events, however.

Very opportunistic; see Diet, above. Not known to store food.

No quantitative data for usual food items. Although horseshoe-crab eggs make up a significant proportion of the diet of adults and dependent young during the breeding season in coastal New Jersey, the birds cannot survive on crab eggs alone; they must supplement them with other foods such as fish, fiddler crabs, and other invertebrates (L. Wagner and JB unpubl. data).

No quantitative data, but both chicks and adults stand in shade of vegetation or rocks on hot and sunny days (JB). Adults and young gular-flutter when air temperatures reach >33°C. In Puerto Rico, nests on high rocky islands with maximum exposure to cooling winds, usually under tall or open vegetation that allows cooling while providing shade (Burger and Gochfeld 1985, JB).

Prefers drinking fresh water from small pools or ponds, but will drink salt water. On hot days, leaves nest to drink or wet belly feathers to transport water to eggs (Puerto Rico; JB). Casts pellets at nest; pellets sometimes contain vegetation, seeds, hair of rodents, horseshoe-crab eggs, diamondback terrapin (Malaclemys terrapin) eggshells, or bits of crustacean shells (JB). Adults fly from nest to defecate; chicks back to edge of nest to defecate over edge. Nest normally remains clean of defecation until early or middle chick phase when parents cease to add new material.

Laughing Gulls have salt glands; droplets of water often visible on bill of incubating adults (JB).