Conservation and Management

Shooting, Trapping, Egging

Before the twentieth century, humans took Roseate Tern eggs in U.S.; egging is still the main form of predation at Caribbean breeding colonies (Gochfeld et al. 1994). Egging has eliminated many colonies in Virgin Is. and elsewhere in Tropics. Capture onshore and offshore in Guyanese and w. African wintering grounds affects mainly first-winter birds, but also many adults (Nisbet 1984, Urban et al. 1986, Trull 1988), and may be most important source of mortality. In Guyana, birds are netted at night by use of jacklights (van Halewyn and Norton 1984, Trull 1988); caught by hand when they land on shrimp boats (Nisbet 1989); also caught on baited lines (w. Africa; Urban et al. 1986).

Pesticides And Other Contaminants/Toxics

In early 1970s, congenital defects in Roseate Terns at Great Gull I., NY, were attributed to organochlorines (Hays and Risebrough 1972). Organochlorine levels have declined generally since 1970s in many species, including Roseates (Custer et al. 1983), and number of abnormal tern chicks declined after 1971 (MG). In 1981, eggs from 5 northeastern colonies and 1 Caribbean colony were analyzed for organochlorines; maximum DDE ranged from undetectable to 0.9 ppm (wet weight); higher in Massachusetts than in Long Island Sound. PCBs ranged from 2.15 to 9.04 ppm, highest at Dead Neck, MA. No other organochlorines detected. In this sample, no correlation between shell characteristics and DDE or PCBs (Custer et al. 1983). Roseate Tern eggs from Ireland had DDE and PCB levels comparable to those in ne. U.S., but had higher dieldrin levels (0.03–0.12 ppm).

An experimental study involving trapping the same terns early and again late in incubation allowed comparison of metal levels in original feathers (grown in South America) and new feathers (grown in Northeast); latter had higher geometric mean values of lead, mercury, cadmium, and selenium (Burger et al. 1992). Concentrations of metals (ppb) in egg contents and eggshells from Cedar Beach, NY, in 1992 were: lead (2,300 in contents/1,200 in shell); cadmium (200/100); mercury (970/20); selenium (4,200/5); manganese (4,200/4,300); and chromium (2,800/1,200; Burger 1994).

Ten adult Roseates from Culebra, Puerto Rico (1989), had breast-feather mercury levels ranging from 700 to 3,000 ppb (geometric mean 2,230 ppb), and averaged 2,440 ppb lead and 55 ppb cadmium (Burger and Gochfeld 1991a).

Paralytic shellfish poisoning kills some terns that eat fish that have fed on red-tide dinoflagellates (primarily Gonyaulax spp.). One episode in Massachusetts in 1978 killed 1 of 600 Roseate Terns, compared with 78 of 6,000 Common Terns (Nisbet 1983). Overall impact of paralytic shellfish poisoning on Roseate Tern population unlikely to be significant at present.

Ingestion Of Plastics, Lead, Etc

No information.

Collisions With Stationary/Moving Structures Or Objects

No information.

Fishing Nets And Other Gear

No information.

Degradation Of Habitat

Some suitable islands and beach areas have been usurped by various human activities and are no longer available for nesting. Some suitable colony sites have been preempted by larger gulls. Availability of fish may also have been reduced; this requires study in Northeast and Caribbean, and on wintering grounds.

Disturbance At Nest And Roost Sites

In Northeast, most breeding sites are on protected islands and are under intensive study. Although human disturbance may have been important in the past, it is usually not significant at present. In some Caribbean colonies, human disturbance is very frequent and devastating. Sensitive to disturbance early in breeding cycle, when first occupying colony site, and may desert (Nisbet and Drury 1972). When disturbed, parents leave nest, circle, and weakly mob human intruders. With prolonged disturbance, may sit on nearby rocks or beach for duration of disturbance. Roseate chicks less likely to wander off territory than chicks of other species, and return to nest or shelter immediately after being handled (Burger et al. 1993).

Direct Human/Research Impacts

Roseates gradually habituate to researcher activity and are usually not significantly affected by well-controlled studies that limit disturbance at nest. Uncontrolled fieldwork, however, could cause damage by keeping adults off nests or preventing feeding of chicks. This is likely to be more serious in small, dense nesting areas than in large, dispersed areas.

Can be trapped and banded safely, if appropriate precautions are observed. Response to trapping depends on colony size and timing (Nisbet 1981b, Burger and Gochfeld 1991b, Burger et al. 1995a). Compared with Common Terns, Roseates take longer to return to nests and are more likely to desert after being trapped at nest (Nisbet 1981b, Burger and Gochfeld 1991b). Time for a trapped bird to return to nest after release varied among colonies; quicker returns at Cedar Beach, NY (average 41 min, n = 34), compared to Falkner I., CT (115 min, n = 134), and Bird I., MA (174 min; n = 178; Burger et al. 1995a); Great Gull I., NY, birds averaged 71 min (H. Hays pers. comm.). Differences in return time may be due to colony configuration, nest density, predator pressure, human disturbance, and distance to foraging grounds.

Conservation Status

USFWS listed Roseate Tern as Threatened in Caribbean and Endangered in Northeast, effective 2 Dec 1987 (USFWS 1987). Protection of Roseate Tern requires international cooperation. Management must be aimed at protecting Roseate breeding colonies, feeding areas, and wintering areas.

Measures Proposed And Taken; Effectiveness Of Measures

Recovery plans have been formulated for northeastern population (USFWS 1998), Canadian population (Lock et al. 1993), and Caribbean population (USFWS 1993), as well as in Europe. Wide variety of management practices are used to protect Roseate Tern colonies to foster recovery of population. These include fencing, control of vegetation and predators (mainly gulls and mammals), provision of nest shelters or other cover, sign-posting, wardening, and law enforcement (Spendelow 1982, Gochfeld et al. 1994, USFWS 1998). In Caribbean, new laws and enforcement of existing laws are necessary to prevent elimination of colonies by egging. Nest boxes and tires offer protection to chicks and have been used successfully at several colonies.

Successful management of Roseate Tern colonies requires management of Common Terns also. Since 1975, 12 former colony sites from Maine to Long I., NY, have been restored by removal of gulls. Common Terns have recolonized all of these sites; Roseates have nested at 11 and appear established at 3 (Petit Manan I. and Eastern Egg Rock in Maine, and Ram I., MA; see Appendix 1). By 1996, 24% of regional population was nesting at restored sites. However, most restored sites have been subject to predation; breeding success has been low at several. Long-term success of this management technique will require restoration of offshore sites that are more secure from predation (USFWS 1998).

If main impact on population is occurring on wintering grounds, these management efforts may be not be adequate. Public education and legal action or enforcement of existing laws are of paramount importance in Tropics. Judging from band recoveries in Guyana in 1970s, significant numbers of Roseate Terns were captured there in winter for food (Nisbet 1984, 1989). Thus local consumption on wintering grounds may have contributed to population declines in 1970s (Nisbet 1989). Reduced number of recent band reports indicate either that this harvest has declined or that band reporting has diminished. Major effort under way to protect wintering European terns on w. African coast (A. del Nevo pers. comm.).