Demography and Populations

Age At First Breeding; Intervals Between Breeding

No definite information. Based on banding data, youngest breeders were 3-yr-olds found incubating in New Jersey colonies; some 2-yr-olds shot near Jamaica Bay, NY, breeding colony, but not known if they were incubating (JB). Breeds every year in New Jersey (marked adults; JB).

Clutch

Modal clutch size of 3 for temperate populations, range 2–4; tropical populations usually 2. In Tobago, mean clutch 1.6–1.9 depending on season (Morris 1984). In Florida, mean clutch 2.8 (Dinsmore and Schreiber 1974, Schreiber et al. 1979). In New Jersey, mean clutch 2.51 (SE 0.03; Montevecchi 1978) and 2.80 (JB). Four-egg clutches rare: 0.2% in Florida (Dinsmore and Schreiber 1974), 0.1% in New Jersey (JB). Supernormal clutches reported from museum collections rare (<2% are 5- and 6-egg clutches; Conover 1984) and may be due to selective collecting and floods (JB). Laughing Gulls will retrieve eggs, including neighbor’s eggs, lost from nests during flood tides (JB). No 5- and 6-egg clutches reported for Florida (Dinsmore and Schreiber 1974) or New Jersey except following flooding (n = 1,500+ over 10 yr; JB).

Annual Reproductive Success

Appendix 2 . Hatching success: in Tobago 29.3–37.6% (Morris 1984); in Florida, 74 and 86% in 1972 and 1973, respectively (Dinsmore and Schreiber 1974), 79 and 81% in 1975 and 1976 (Schreiber et al. 1979).

Fledging success: in Florida, 1.32/nest for 3-egg clutches, 0.71/nest for 2-egg clutches (Schreiber et al. 1979); in Tobago, 0.16/nest, probably owing to predation (Morris 1984).

No data on lifetime reproductive success.

Proportion Of Total Females That Rear At Least One Brood To Nest-Leaving

Few quantitative data; in Barnegat Bay, NJ, varies from 0% (due to high flood tides) to 80%; varies in most years from 55 to 70% (JB). In Florida on dry land, 88% of 3-egg clutches raised at least 1 chick; 65% of 2-egg clutches raised at least 1 chick (Schreiber et al. 1979).

Parents with equitable distribution of total parental investment between members had a significantly higher breeding success than pairs with an unequal distribution of investment (Wagner and Burger 1992).

Maximum recorded longevity (from banding data): 19 yr 0 mo (M. K. Klimkiewicz pers. comm.); presumably older birds exist. Differential band wear on males and females should be taken into account in survivorship estimates based on banding; females wearing size 4A bands suffer more band wear than males (Dolbeer and Belant 1994). No population models available.

Botulism reported at landfill near a breeding colony in Virgin Is., Greater Antilles; 174 dead Laughing Gulls (Norton 1986). Of 1,800 chicks handled in Barnegat Bay, NJ (1976–1995; JB), 7 had crippled legs, 29 (2%) had broken wings, 1 born with anophthalma (no eyes).

Egg mortality includes embryonic death, hatching death, disappearance due to predation, disappearance due to washovers and floods, and eggs rolled out of nest during attempts by intruding conspecifics to steal nest material. Mortality of eggs greatest during egg-laying period when nests sometimes unguarded (JB), or during flood tides when all eggs can be washed out of nests, both on dry land colonies (White et al. 1983a) and in salt marshes (Burger 1978, 1979a, 1979b, Montevecchi 1978). Floods early in season (when marsh grass short) destroy greater proportion of nests than later floods (Montevecchi 1978). Tidal floods that destroy 70–100% of nests in New Jersey salt-marsh colony can occur once every 2–10 yr (Montevecchi 1978). Complete destruction of all nests occurred once in 20 yr in Barnegat Bay, NJ, salt-marsh colonies (1976–1995; JB).

Adaptations to avoid flooding include construction of substantial nests, nest maintenance before and during flood tides (Burger 1977a, 1978), construction of nests following high tides when highest sites can be selected (Montevecchi 1978), and attachment of nests to vegetation to prevent floating away during high tides. See Breeding: colony/nest site, above.

Mortality of chicks greatest during first week of life in Florida and New Jersey (Schreiber and Schreiber 1980, JB), during heavy flood tides, and during fledging period when young are separated from parents (JB). During heavy rains, storms, and hurricanes, when cold weather and rain are prolonged, mortality high for all ages, especially for chicks (7–14 d old) too big to be adequately brooded (Burger and Shisler 1980, JB). In Puerto Rico, chick mortality may be high during first few days of life when young are vulnerable to crab predation (Burger and Gochfeld 1985).

Cannibalism relatively rare, but does occur in dense colonies or in colonies with little vegetation to provide cover for very young chicks (JB). Seems to involve a few individuals that learn to eat nearby chicks, judging from banded legs found discarded at gull nests (JB). Some chicks killed by territorial encounters, pecked extensively on head and back of neck.

Few data on adult mortality; rarely, adults are killed by Herring and Great Black-backed gulls (see Behavior: predation, above). Adults and juveniles killed in fishing lines, by plastic six-pack holders, by kite strings, by overhead power lines, and by aircraft. Few adults killed by moving bulldozers at garbage dumps, or by entanglement in vegetation (JB). Population control (shooting) at Kennedy International Airport (New York City) is a significant cause of mortality (see Conservation and Management: effects of human activities, below).

Adult mortality at colony rare; occasionally killed by Great Horned Owl, Northern Harrier, Herring and Great Black-backed gulls, and mink. Adult mortality away from breeding colonies seldom reported, but of 220 adults brought to “hospital” in s. Florida, 57% died from broken wing, 29% were sick, 2% hit by car, 6% in monofilament line, 1% oiled (Schreiber and Schreiber 1979). Aspergillosis more common in young birds (54%) than in adults (24%), but not a cause of death.

Initial Dispersal From Natal Colony

Fall dispersal of hatching-year birds characterized by northward movements before migration (Belant and Dolbeer 1993b).

Fidelity To Natal Colony Site

In U.S., 64% of adult recoveries during subsequent breeding seasons were within 50 km of natal banding location (n = 386); significantly more recoveries north of natal banding location than south during subsequent breeding seasons (Belant and Dolbeer 1993b).

Fidelity To Breeding Site Once Established

No data.

Home Range

May fly at least 40 km in search of food during breeding season (JB, L. Wagner pers. comm.).

Numbers

Estimates for breeding pairs in U.S. in 1990: Maine 716; Massachusetts 1,285; New York 7,629; New Jersey 58,722; Delaware >2,000; Maryland 25; Virginia 31,104; N. Carolina 20,676; S. Carolina 6,563; Florida 24,000–48,000; Alabama >250; Louisiana 28,975; Texas 64,595; total U.S. population 258,851 pairs (Belant and Dolbeer 1993a). Number of colonies varies; >10 colonies each in Maine, Massachusetts, New York, Delaware, Maryland, S. Carolina, and Alabama; 13 in N. Carolina, 19 in Louisiana, 63 in Virginia, 65 in Texas, and 92 in New Jersey (Belant and Dolbeer 1993a). Numbers can change rapidly; see Distribution: historical changes, above.

West Indies population about 7,000 breeding pairs in 40 colonies in the late 1980s (Gochfeld et al. 1994). Currently no population in w. U.S. (Small 1994) and very small population in w. Mexico (Howell and Webb 1995).

Trends

Ne. U.S. colonies almost extirpated in late nineteenth century by eggers and plume-hunters, but recovered with help of protection, increasing until 1940 (Nisbet 1971). After 1940s, decreased until mid-1970s, but have increased since then (see Fig. 2). In New Jersey, only 2 colonies at turn of nineteenth–twentieth centuries (Stone 1909), now nearly 100 colonies (Jenkins et al. 1989). Population from New Jersey to Maine increased from about 60,000 adults in late 1970s to 120,000 adults by late 1980s (Dolbeer et al. 1989). From 1977 to 1991, U.S. population essentially stable at about 249,001 to 258,851 nesting pairs (Belant and Dolbeer 1993a). This estimate does not include subadults or nonbreeding adults.

Trends vary by region. Species is capable of natural, rapid increases, particularly in Northeast; between 1880 and 1940, numbers doubled at Muskeget, MA, colony about every 4 yr, and doubled every 2.9 yr between 1890 and 1910 (Nisbet 1971); between 1977 and 1985, number of pairs rose from 30,940 to 58,550 in New Jersey (Dolbeer et al. 1989, Jenkins et al. 1989). At Jamaica Bay, NY, 15 pairs nested in 1979 and 2,665 in 1988 (Dolbeer et al. 1989). Such increases likely due to immigration, since many of Jamaica Bay birds were banded as chicks in New Jersey.

S. Florida (Florida Bay) population relatively recent, resulting from repeated colonization by birds from farther north, supported by availability of sanitary landfills and agricultural fields (Kushlan and White 1977, Frohring and Kushlan 1986); smaller than populations farther north in Tampa Bay, FL (Patton and Hanners 1984).

Main factors appear to be sufficient and suitable nesting habitat, adequate food resources during the breeding season, and competition with larger gulls (Herring and Great Black-backed gulls). Laughing Gull cannot compete effectively with these larger gulls for nest sites, and so in the Northeast it is being forced to nest on lower parts of salt marshes, where it faces losses due to tidal flooding (see Breeding: colony/nest site, above). In Caribbean, it has been forced from some nesting places by dense colonies of terns.

The larger gulls also eat Laughing Gull eggs and chicks, forcing this species to abandon some nesting colonies completely (see Behavior: social and interspecific behavior, nonpredatory interspecific interactions). Some evidence of adverse effects from chemicals (White et al. 1983a). See also Conservation and Management: effects of human activities, below.