Conservation and Management

Shooting And Trapping

During late 1800s, this species was decimated by feather trade; directly from collecting, but also indirectly from disturbance of nesting colonies for highly prized plumes of other species (Allen 1942). Probably not harvested for food, as Yellow-crowned Night-Heron and White Ibis are today (Anderson 1978, Martin 1991). Hunting is a problem in Central and South America; 9 of 16 band recoveries originating in Texas were shot birds (Telfair and Swepston 1987, R. Ridgely pers. comm.). In Louisiana, cannot obtain permission to shoot nuisance Roseates i.e. with a Federal Depredation Permit (W. Vermilion pers. comm.).

Pesticide And Other Contaminants/Toxics

See Appendix 3 . During 1987–1991, organochlorides not detected in nestlings from e. Florida Bay, but low levels of DDE found in nestlings from western portions of bay (Spalding et al. 1997). Heavy metals found in greater concentration; highest liver and cadmium concentrations for all species sampled were found in same individuals of Tricolored Heron and 1 spoonbill about 2 wk old from e. Florida Bay: 2.8 ppm lead, 0.40 ppm cadmium. Lead may have been responsible for nestling’s death; cadmium probably below toxic level (10–40 ppm). Otherwise, mean cadmium level for all Roseate specimens is similar to background level; significance of copper values unknown. In s. Florida, Roseates had lower concentration of mercury in feathers than did Great Egrets and Great White and Blue herons (1987–1990; Beyer et al. 1997), as well as lower liver concentrations of mercury than those of Great Egrets and Great Blue Herons (1987–1991; Sundlof et al. 1994). This difference probably is related to diet of smaller fish and arthropods of Roseates (Sundlof et al. 1994). Toxic concentration level undetermined.

Along Gulf Coast of U.S., 1972–1973, a higher percentage of Roseate eggs contained organochlorides (DDT, DDD, dieldrin) compared to other species, but DDE, cis-chlordane, and PCBs occurred at similar frequency (Ohlendorf et al. 1979). All spoonbill eggs sampled contained DDE (n = 24). Average concentration of DDE from eggs collected in Florida Bay in 1972–1973 was higher than that in brain samples from 1987–1991; this difference suggests drop in level over time, or difference in absorption and excretion between egg and brain tissues, respectively. Levels of DDE and other contaminants apparently are not enough to cause eggshell-thinning; eggs collected before and after widespread use of organochloride pesticides have similar thicknesses, ranging from mean of 426 µm pre-1947 (n = 47 clutches) to 423 µm in 1947–1973 (n = 29 clutches, FL, TX, LA combined; Ohlendorf et al. 1979). Sublethal effects unknown (Spalding et al. 1997).

Collisions With Stationary/Moving Structures Or Objects

Few data; 1 radio-tagged juvenile died as result of collision with power line (Powell and Bjork 1990).

Degradation Of Habitat

Degradation and destruction of coastal foraging habitat probably are the most important conservation problems for this species, at least in U.S. (Powell and Bjork 1989, Martin 1991, Bjork and Powell 1996, Gawlik et al. 1998). In Florida, many nesting sites in several counties are already protected as part of Everglades National Park, National Audubon Society’s Tampa Bay Sanctuaries, and Kennedy Space Center/Merritt I. National Wildlife Refuge, but foraging habitat remains vulnerable to human impacts (Bjork and Powell 1996). Foraging habitat must be near colony site (see Food habits: feeding, above); in Florida Keys, loss of principal foraging habitat to development (1955–1985) probably caused shift in breeding sites from adjacent southeastern region of bay to northern sections as mangrove estuary of southern mainland became principal foraging habitat (Powell et al. 1989, Bjork and Powell 1994; see Distribution: historical changes, above). Estuarine production and availability of prey have likely been degraded by water management, since the estuary no longer supports large historical colonies of wading birds (Ogden 1994). Major threats to production and availability of prey include reduced fresh-water inflow and hypersalinity that can exceed physiological tolerance of prey; decreases in primary production from reduced inflow of nutrients; and altered timing, length, and spatial extent of drying and flooding cycles (Powell et al. 1989, Ogden 1994, Lorenz 1999). In Texas, significant population decline of nesting Roseates in Galveston Bay Estuary was concurrent with losses of coastal marsh foraging habitat (Gawlik et al. 1998). In Louisiana, coastal marsh is destroyed or degraded by oil and gas industry (contamination of water, salinization, alteration of natural hydrology from discharge waters and canals) and by dams along Mississippi River (reduced freshwater flow, increased salinity, reduced sediment load preventing accretion of marsh sediments; Martin 1991).

Disturbance At Nest And Roost Sites

Can have significant impacts, especially during nesting.

Investigator Bias. In Nueces Bay, TX, no significant differences in annual reproductive success, estimated as number of fledglings per total nests, at sites visited weekly from onset of egg-laying or as often as every other day during peak hatching versus control site visited only twice during entire season (White et al. 1982; see Appendix 1). In Florida Bay, colony visitation was not initiated until late in incubation (1–2 wk); birds deemed too sensitive to disturbance earlier but specifics not reported (Bjork and Powell 1994). Colony was visited at 4- to 6-d intervals thereafter. No control site, but researchers report no sign of negative impact to their presence. The Nueces Bay, TX, colony sites colony sites are located in industrial area; perhaps birds there are less sensitive than in Florida Bay. In Texas, paths used for accessing nests had trampled vegetation; fire ants built mounds here, indicating a researcher link to fire ant problem (Chaney et al. 1978).

Recreational. Boat traffic adjacent to Florida Bay colonies and inside via small channels caused significant declines in number of nesting spoonbills, low nest success during incubation period, or colony abandonment (Bjork and Powell 1994, 1996).

Conservation Status

Since 1979, listed by the state of Florida as Species of Special Concern; formerly (1972) listed as Endangered, but moved to Species of Special Concern when that category was created (1979; Bjork and Powell 1996). Designation in Florida recognizes vulnerability to habitat alteration and human disturbance, thereby providing species with special protection and consideration (Bjork and Powell 1996). Also classified as Rare by Florida Committee on Rare and Endangered Birds and Animals (Ogden 1978b, Bjork and Powell 1996). In Louisiana, designated as Species of Special Concern, but no special protection other than from disturbance at nesting colonies (W. Vermilion pers. comm.). No special designation in Texas; ranked as a fairly common breeder since 1994 (D. Scott pers. comm.). Florida breeding population probably is the most vulnerable because of its relatively small size, fluctuation in breeding numbers and annual reproductive success, relative geographic isolation compared to western populations, potentially low immigration rates, and dependence on Florida Bay and adjacent mangrove estuary of southern mainland for reproduction (Allen 1942, Robertson et al. 1983, Powell et al. 1989, Bjork and Powell 1996; see Effects of human activity, above).

Measures Proposed And Taken

In s. Florida (Bjork and Powell 1994, 1996, Smith and Breininger 1995, Beyer et al. 1997), proposed measures include the following: (1) protect mangrove estuary east of U.S. Highway 1 on southern mainland because of importance as foraging grounds for spoonbills nesting in Florida Bay; (2) restore ecosystem of coastal mangrove estuary; (3) continue to monitor spoonbills in Florida Bay; (4) identify and monitor sources of mercury contamination and determine minimum toxic concentration. At Kennedy Space Center, proposal is to manage mosquito impoundments to maintain favorable open-water foraging areas for wading birds (Smith and Breininger 1995). In Louisiana, proposed measure is regional protection of watershed: local, state, and federal agencies are working on a coastal restoration program that involves the release of Mississippi River water into marshes and estuaries (Martin 1991). General proposed measures include the following: (1) post buffer zones (100–125 m) around nesting colonies to limit close approach of boats during nesting season (Bjork and Powell 1994); (2) make sure that spoil islands do not connect mainland to nesting islands, to prevent access by terrestrial predators; and (3) remove predators when justified (Anderson 1978). A habitat suitability index model is available for evaluating potential of a site as nesting and roosting space for spoonbills (Lewis 1983, see also Anderson 1978).

In s. Florida (J. Ogden pers. comm.): entire mainland mangrove estuary east of U.S. Highway 1 is scheduled for purchase by South Florida Water Management District and Miami-Dade Co.; ongoing acquisitions are about 50% completed. The Comprehensive Everglades Restoration Plan was delivered to Congress in July 1999. The plan includes restoring hydrology of all major estuaries from Caloosahatchee River on the Gulf Coast to St. Lucie Estuary on the Atlantic Coast, based on a hydrology model that mimics predrainage conditions for salinity, freshwater flow volumes and timing, duration of flooding, and depth of water. Estuarine monitoring will ensue; spoonbills in Florida Bay will continue to be monitored and probably be approved for use as an indicator species for the regional restoration program. Congress has not authorized plan yet. In Louisiana, human activity is prohibited within 300 m of colony beginning 2 wk before colony initiation; in Florida Bay, a 100-m buffer zone is posted at vulnerable sites (Martin 1991, Bjork and Powell 1994).

Effectiveness Of Measures

In s. Florida, determining the effect of ecosystem restoration will require long-term monitoring of spoonbill population size, annual reproductive success, colony site distribution patterns in Florida Bay, and production of prey populations. This species has benefited from protection and management of nesting sites (Anderson 1978). Response to posting of buffer zone at Florida Bay colony was rapid: Nesting numbers more than doubled the following year (Bjork and Powell 1994). Predator removal is effective: Roseate Spoonbill recolonized former breeding site after raccoons were removed (Cedar Lakes, TX; M. Lange pers. comm.).