Conservation and Management

Shooting, Trapping, And Egging

Formerly hunted for meat and skins by Native Americans in Gulf of California (Anderson and Keith 1980). Shot for feathers for millinery trade and by fishing industry in late nineteenth and early twentieth centuries in s. U.S. Shooting blamed for population decline in Texas in 1920s and 1930s (King et al. 1977b). Band returns indicate that shooting was major cause of human-induced mortality in se. U.S. prior to 1950 (Schreiber and Mock 1988). Shooting mortality decreased in second half of twentieth century, but isolated incidences still occur. Five shooting deaths reported between 1973 and 1980 in Florida Bay (Blus et al. 1977, Kushlan and Frohring 1985) and >50 reported in Aug and Sep 1997 along Texas coast (Texas Parks Wild. Dep. 1997). Over 100 pelicans killed or maimed in Brevard Co., FL, during Feb and Mar 1998; some had their necks broken, others had their bills snapped or wings pinned behind their backs (Howard and Van Boven 1998). Adults shot throughout Caribbean region, but extent unknown; egging and collection of young considered a more serious threat (van Halewyn and Norton 1984). In 1990, fishing concerns took eggs from all but 1 nest in newly established colony on Mud Lumps at mouth of Mississippi River, LA; no young fledged, and site was not used in 1991 (Anon. 1991). Commercial egging occurs in colonies along Pacific coast of Baja Mexico and in Gulf of California (Everett and Anderson 1991). In Costa Rica, those in fishing trade occasionally destroy nests and eggs, and sometimes kill nestlings for use as fish bait (Stiles 1984).

Pesticides And Other Contaminants/Toxins

Of avian species studied, most sensitive to organochlorine pesticides, particularly endrin and DDT (Blus 1982). Endrin toxicity suspected cause of rapid population decline in Texas in late 1950s and extirpation from Louisiana by 1963 (King et al. 1977b, Blus et al. 1979a). Endrin also probable cause of die-off in 1975 of 35–40% of 400–450 birds transplanted to Louisiana from Florida (Nesbitt et al. 1978). Low reproductive success of Louisiana population in 1975 correlated with peak endrin residues in eggs, but no cause-and-effect relationship established (Blus 1982).

DDE, a metabolite of DDT, implicated in several adult deaths in California (Keith et al. 1971), but main effect eggshell thinning, which led to breakage during incubation (see Breeding: eggs, above). Concentrations ≥3 µg DDE/g wet weight associated with 20% thinning and substantially impaired reproductive success (Blus 1982, 1984). Most severe DDE-related eggshell thinning occurred in S. California Bight; mainly responsible for population decline between mid-1950s and mid-1970s (Anderson and Anderson 1976) and nearly total reproductive failure in late 1960s and early 1970s (Keith et al. 1971, Risebrough et al. 1971, Jehl 1973). In Apr 1970, discharge of liquid wastes from DDT manufacturing plant into S. California Bight terminated; geometric mean DDE residues in intact pelican eggs declined rapidly from 30–34 µg/g wet weight in 1969 and 1970 to 4.6–12 µg/g in 1972–1975 (reviewed by Gress 1995). Concurrently, eggshell thickness increased (see Breeding: eggs, above), as did productivity (Anderson et al. 1975, 1977b). DDE residues continued to decline until mid-1980s, then stabilized at about 2 µg/g, a level producing no measurable impairment of reproduction (Gress 1995). In S. Carolina, apparent population decline in 1960s and low fledging success in late 1960s–early 1970s also attributed primarily to DDE-induced eggshell thinning (Blus et al. 1974a, 1974b, 1979b). Geometric mean DDE residues in eggs 2.48–5.24 µg/g wet weight between 1969 and 1972 (Blus at al. 1979b). Following implementation of ban on general use of DDT in U.S. on 31 Dec 1972 (Environmental Protection Agency 1972), level of DDE in eggs declined, with means falling below 2.0 µg/g by 1975, coincident with increases in eggshell thickness, productivity, and population size (Mendenhall and Prouty 1978, Blus 1982). DDE concentration in eggs in Florida, Texas, Louisiana, and Gulf of California in 1970s high enough to induce eggshell thinning, but not high enough to cause widespread reproductive failure or population declines (Schreiber and Risebrough 1972, King et al. 1977b, Keith 1978, Blus et al. 1979a). Low levels of DDE detected in eggs in Puerto Rico (0.001–1.85 µg/g wet weight) and U.S. Virgin Is. (0.01–0.11 µg/g wet weight) in 1980s and 1990s not associated with eggshell thinning or reduced reproductive success (Collazo et al. 1998).

Dieldrin apparently embryotoxic at concentrations >1 µg/g wet weight; may have contributed to low reproductive success of S. Carolina population in late 1960s and early 1970s (Blus et al. 1974a, Blus 1982). Impact of PCBs, chlordanes, and other organochlorines on reproductive success and adult survival negligible at concentrations observed (Nesbitt et al. 1981, King et al. 1985, Gress 1995). Organophosphate pesticide runoff from nearby golf course implicated in 127 deaths at Dorado Lagoons, Puerto Rico, between Feb and Aug 1982 (Collazo 1985). Trace elements (arsenic, cadmium, chromium, cobalt, copper, lead, mercury, nickel, selenium, silver, zinc) detected in body tissues and eggs not known to cause mortality (Connors et al. 1972; Blus et al. 1975, 1977; King et al. 1985; Wickliffe and Bickham 1998).

Oil Pollution

Highly susceptible to oil spills; breeding, roosting, and foraging sites often near shipping channels with heavy commercial traffic, harbors with refineries and oil-storage facilities, or offshore oil wells. California colonies near natural oil seeps in Santa Barbara Channel (U.S. Fish Wildl. Serv. 1983). Contamination with oil or tar listed as cause of mortality in 4 of 2,660 band returns (Bond 1942, Schreiber and Mock 1988). Death of 1 adult found floating in Corpus Christi Bay, TX, attributed to fouling with oil resuspended from sediments 6–7 wk after pipeline rupture in 1976 (King et al. 1979). Eight birds with oiled feathers observed in Texas following blowout of oil well in Bay of Campeche, Mexico, in 1979; none debilitated (King et al. 1985). Eggs in 24 of 98 nests on island in Cape Fear River, NC, oiled after spill of 300,000 l of no. 6 diesel oil in May 1982; hatching success reduced 28% relative to unoiled eggs (Parnell et al. 1984); no adult mortality observed (MAS). Pelicans and eggs fouled with oil often observed in S. California Bight and Gulf of California (U.S. Fish Wildl. Serv. 1983). Spills in S. California Bight in Feb 1990 and Apr 1991 oiled about 210 birds; 112 captured, rehabilitated, and released. Rehabilitated birds experienced lower survival than unoiled controls and exhibited no breeding activity 1–2 yr postrelease (Anderson et al. 1996). About 12% of adults in Tampa Bay, FL, colonies lightly oiled after tanker collision spilled 1.25 million l of fuel oil in Aug 1993 (Wamer 1994). Rehabilitation center cleaned and released 318 of 371 birds received (L. Fox pers. comm.). Spill of no. 2 diesel oil, stearate, and aldehydes in E. Pascagoula River, MS, in 1995 fouled 147 pelicans; 110 cleaned and released (Matthes 1996). About 750,000 l fuel oil spilled when tanker ran aground near San Cristobal I. in Galápagos Is. in Jan 2001; unknown number of pelicans oiled; several cleaned and released (Charles Darwin Foundation 2001).

Ingestion Of Plastics, Lead Etc

No reports.

Collisions With Stationary/Moving Structure Or Objects

Twenty-seven crippled or dead birds and 441 skulls found under power transmission line in ne. Venezuela on 27 Feb 1983. Pelicans collided with power line while flying between breeding colony in lagoon and foraging areas in Caribbean Sea (McNeil et al. 1985). Collision with vehicle listed as cause of death in 21 of 2,660 band returns; includes 1 bird hit by train (Bond 1942, Schreiber and Mock 1988). One bird killed after diving into boat in Everglades National Park (Kushlan and Frohring 1985). Seventeen reports of aircraft strikes by Brown and American White pelicans in U.S. between Jan 1991 and May 1998 (Dolbeer et al. 2000). Collisions with vehicles and power lines kill many Peruvian Pelicans when they enter cities in search of food during strong ENSO events (Leck 1973, CNN 1997).

Fishing Gear

Entanglement in sport-fishing gear a major cause of mortality in se. U.S. (Schreiber and Mock 1988). Over 700 adults and immatures die each year in Florida alone (Schreiber 1980b), and 80% of live birds examined there showed signs of past en-counters with fishing gear (Schreiber 1975a). Hundreds treated for hook-and-line injuries each year; most hooked accidentally, some intentionally (Mackey 1982). Hook may tear hole in gular pouch, impairing ability to capture fish, resulting in starvation; mono-filament line may entangle wings or legs, making flight difficult or impossible, or wrap tightly around limbs, causing necrosis and infection (U.S. Fish Wildl. Serv. 1983). Trailing line frequently becomes entangled in vegetation when bird returns to roosting or breeding site; panicked bird often falls from perch while struggling to free itself; dies of shock, stress, or starvation while hanging in branches (Mackey 1982). Line also may ensnare other birds; as many as 6 dead pelicans have been found on a single 30-m length of line (Nesbitt 1996). Mortality caused by sport-fishing gear not considered a significant threat to population in California (U.S. Fish Wildl. Serv. 1983, Jehl 1984). Incidental drowning in seine nets occurs in Galápagos Is. (Cepeda and Cruz 1994). Several hundred Peruvian Pelicans annually caught on longlines in n. Peru (Jahncke et al. 2001).

Degradation Of Habitat

Amount of mangrove habitat in Caribbean reduced by fuel-wood cutting and deterioration from pollution (van Halewyn and Norton 1984). Breeding and roosting habitat in Puerto Rico destroyed by expansion of recreational facilities, but birds apparently relocated to suitable alternative sites (Collazo et al. 1998).

Disturbance At Nest And Roost Sites

Flushes from nest or roost when disturbed; flush distance varies with type and frequency of disturbance, season (breeding vs. nonbreeding), security of site, and population. In Florida, mean flush distance for walking approach directly toward nest, 19.2 m (n = 63); for motor-boat approach directly toward nest, 9.4 m (n = 14; Rodgers and Smith 1995). Flush distance progressively shortens as adults become habituated to regular visits (Schreiber 1979, MAS). During nonbreeding season, pelicans flushed at significantly greater distances: 27.4 m (n = 21) for approach of walking human and 34.4 m (n = 22) for approach of motor boat (Rodgers and Smith 1997). At Ding Darling National Wildlife Refuge (NWR), FL, pelicans loafing or foraging near road became attentive when approached by vehicles, but seldom flushed unless approached by human on foot (Klein 1993). Flush distance of breeders in California, Baja California, and Gulf of California much greater than in Florida (Schreiber 1979, Anderson and Keith 1980), but not quantified. In California, birds roosting in shallow inland ponds at Elkhorn Slough flushed at mean distance of 220 m (range 110–600, n = 15) when approached by human on foot; approach to within 50 m tolerated at island roosts surrounded by deep water (Jaques 1994). Birds roosting at Mugu Lagoon, CA, flushed on average once every 2.5 h. Gunshots from waterfowl hunters and approach of humans on foot main sources of disturbance; frequent overflights of military aircraft from Naval Air Weapons Station, Point Mugu, elicited little response (Jaques et al. 1996). Apparent habituation to frequent overflights also noted at Conejo Cay, Puerto Rico, located about 1 km from U.S. Navy bombing range on Vieques I. (Schreiber et al. 1981, Collazo 1985). Elsewhere, low-flying aircraft (especially helicopters) often flush loafing or roosting birds, but rarely birds on nests (Schreiber 1977a, U.S. Fish Wildl. Serv. 1983). Roosting birds flushed by aircraft usually return quickly to same site; those flushed by gunshots or humans on foot usually relocate (Jaques et al. 1996). Energetic cost of flushing and its impact on survival and fecundity unknown.

Disturbance of breeding colony may result in greatly reduced reproductive success. Eggs or small nestlings sometimes crushed or knocked from nest when parent flushes in panic (Schreiber and Risebrough 1972, Kushlan and Frohring 1985). Unattended eggs and small nestlings susceptible to predators and hyperthermia (Anderson and Keith 1980). Larger, more mobile young displaced from nests may starve if unable to return or become entangled in vegetation and die (Schreiber 1979, Anderson and Keith 1980); sometimes killed by conspecifics (MAS). Regurgitation by nestlings may decrease subsequent growth and survival (Anderson and Keith 1980). On islands in the Gulf of California, subcolonies disturbed by tourists and recreationists produced 0.0–0.6 fledglings/nest compared with 1.2–1.5 fledglings/nest in undisturbed subcolonies (Anderson and Keith 1980). On Islas Los Coronados, Mexico, mean productivity between 1974 and 1979 (0.9 fledglings/nest attempt) was triple that between 1980 and 1987, when increased use of islands for fishing caused many nest abandonments. Presence of humans <600 m from colonies associated with reduced productivity; rate of abandonment negatively correlated with distance from human activity (Anderson 1988).

Human disturbance caused abandonment of colony on Isla Guayabo, Costa Rica, in 1982 (Stiles 1984). Island with colony of 20,000–30,000 pairs of Peruvian Pelicans and Guanay Cormorants deserted following single visit by egg collectors in 1977 (Duffy et al. 1984). Repeated visits may result in permanent abandonment of colony site, as occurred at Isla San Martin, Mexico (Anderson and Keith 1980). Many islands and sand bars used for loafing and roosting on Florida Gulf coast abandoned as result of increased boat traffic and recreational use (Schreiber and Schreiber 1982). Once-important roost site at Elkhorn Slough, CA, abandoned in 1989 after elimination of water buffer increased access by humans and terrestrial predators (Jaques et al. 1996).

Direct Human/Research Impacts

Competition with commercial anchovy fishery reduced numbers and productivity of Peruvian Pelican in 1960s and 1970s (Duffy 1983b, 1994). Researcher visits to subcolonies in Gulf of California reduced productivity 67–100% relative to undisturbed subcolonies (Anderson and Keith 1980). In Florida, nests visited weekly had larger clutches and greater hatching success and productivity than nests visited more frequently, but number of fledglings/successful nest did not differ (Schreiber 1979). In N. Carolina, no difference detected in clutch size or hatching success between nests visited 2–5 times/wk and nests visited once every 2–4 wk; adults at frequently visited nests became habituated to researcher presence; often had to be pushed off their nests by hand to gain access to eggs or nestlings (MAS). In Florida and N. Carolina, and perhaps elsewhere along Atlantic and Gulf coasts, adverse impacts of frequent intrusions into colony can be minimized if visits are made in a routine manner. Researcher should crouch to maintain low profile, approach slowly and in clear view, walk along same route at same time of day, avoid entering colony during heat of the day, move tangentially rather than directly toward nests, wear same-color clothing, and avoid making eye contact (Schreiber 1979, MAS). In California and Mexico, where adults more sensitive to disturbance, researcher intrusion into colonies should be minimized, especially early in nesting season (U.S. Fish Wildl. Serv. 1983).

Conservation Status

Listed as Endangered throughout range in 1970 because of pesticide-induced reproductive failures and population declines in U.S. and nw. Mexico and uncertain status elsewhere (U.S. Code of Federal Regulations 1970). Removed from Endangered Species List in Alabama, Florida, Georgia, S. Carolina, N. Carolina, and points northward along Atlantic coast in 1985; Endangered status retained throughout remainder of range (U.S. Fish Wildl. Serv. 1985).

Measures Proposed And Taken

Recovery plans prepared for P. o. carolinensis in U.S., P. o. californicus in S. California Bight, and P. o. occidentalis in Puerto Rico and U.S. Virgin Is. (U.S. Fish Wildl. Serv. 1980, 1983, 1986). Actions recommended included habitat protection, reduction of human disturbance, monitoring of contaminants and other potential threats, public education, and long-term population monitoring. Most significant management action taken in U.S. was reducing pesticide levels in marine environment. Discharge of DDT into Los Angeles Co. sewage system terminated in 1970; general use of DDT in U.S. banned effective 31 Dec 1972; use of endrin restricted in late 1970s. Louisiana Department of Wildlife and Fisheries (LDWF) and Florida Game and Fresh Water Fish Commission (now Florida Fish and Wildlife Conservation Commission) cooperated in effort to re-establish population in Louisiana following extirpation in 1963. Between 1968 and 1980, 1,276 nestlings (8–11 wk old) transplanted from Florida to 4 release sites in Louisiana (McNease et al. 1984). LDWF also attempted to expand breeding range in Louisiana by transplanting 149 fledglings from Queen Bess I. in Barataria Bay to Last I., Isle Dernieres between 1984 and 1986 (McNease et al. 1992). Legal protection of colony sites began in 1903 when Pelican I., FL, was set aside as a federal preserve (now a national wildlife refuge) to protect pelicans from hunters. Most breeding sites in U.S. protected under jurisdiction of federal or state agencies or private conservation groups, such as National Audubon Society. Public access to W. Anacapa I., CA, prohibited by National Park Service to protect pelicans from disturbance. Area extending from shoreline to 20 fathoms’ (36.6 m) depth offshore from colony designated a “Brown Pelican Fledging Area” by California Fish and Game Commission; closed to public between 1 Jan and 31 Oct to reduce disturbance to colony and young that congregate offshore after fledging (U.S. Fish Wildl. Serv. 1983). In Florida, buffer zones around colonies recommended to prevent disturbance; 76 m width for humans on foot, 65 m for motor boats (Rodgers and Smith 1995). Many seabird breeding islands in Gulf of California declared wildlife refuges by Mexican government in 1978 (Velarde and Anderson 1994); these islands, as well as Isla Contoy on Caribbean coast, later designated Special Biosphere Reserves. Many colonies in Central America and Galápagos Is. protected within boundaries of national parks, wildlife refuges, biological reserves, or marine reserves. Peruvian government has managed nesting areas of Peruvian Pelican and other seabirds for guano production since 1909; actions have included posting guards on each island, restricting boat and aircraft operations and closing fishery areas near islands, excluding terrestrial predators from coastal headlands, and increasing nesting space by clearing rocks and leveling slopes (Duffy 1994). Dredge spoil used to rebuild nesting islands destroyed or damaged by erosion in N. Carolina (Wilkinson et al. 1994), S. Carolina (T. Murphy pers. comm.), and Louisiana (McNease et al. 1992). Wildlife hospital built in 1997 at Sonny Bono Salton Sea NWR to treat pelicans sickened by regular botulism outbreaks (U.S. Fish Wildl. Serv.: http://pacific.fws.gov/salton/SaltonSea_hospital.htm).

Effectiveness Of Measures

Population size and productivity in U.S. increased as pesticide residues in marine environment declined during 1970s. Recovery and expansion of population in se. U.S. led to delisting in 1985. In S. California Bight, number of breeding pairs, but not productivity, has exceeded delisting criteria since 1985 (F. Gress pers. comm.).

Breeding population successfully re-established in Louisiana through restocking of nestlings from Florida. Colonies formed near 2 of 4 release sites; breeding first recorded at Queen Bess/Camp I. in 1971 and North I. in 1979 (McNease et al. 1984). Intra-state transplantation successfully established breeding colony on Last I. in 1987. Subsequent natural colony expansion and growth restored population to historical range by 1990 (McNease et al. 1992).

Numbers of breeding pairs in most states stable or increasing; total U.S. populations of P. o. californicus and P. o. carolinensis now exceed historical levels (see Demography and populations: population status, above). Management of Peruvian guano islands resulted in dramatic increases in guano-bird populations; numbers doubled between 1910s and 1930s, then doubled again to their highest levels in 1950s; subsequent declines related to collapse of prey base due to combined effects of overfishing and ENSO events (Duffy 1994).