The Roseate Tern (Sterna dougallii) population in northeastern North America has decreased markedly over the last 100 yrs, and is presently around 3100 breeding pairs, of which 103-127 breed in Canada, almost exclusively in Nova Scotia. The number of Roseate Terns in eastern Canada has probably always been relatively small, but strong evidence suggests that the population has declined recently. Roseate Terns in Canada and the United States are still threatened by gulls and mainland predators on the breeding grounds, and human predators on the wintering grounds. The Roseate Terns' status in Canada is Threatened.

#57-28 Livingston Road Scarborough, Ontario M7E 4S5, Canada Canadian Wildlife Service Bedford Institute of Oceanography P.O. Box 1006 Dartmouth, Nova Scotia B2Y 4A2, Canada STATUS DE STERNA DOUGALLH EN CANADA Sinopsis.--Durante los filtimos 100 aftos las poblaciones de Sterna dougallii han ido mer- mando en nfimero en el noreste de Norte America. La poblaci6n se estima en unos 3100 pares de adultos de los cuales entre 103-127 se reproducen en Nova Scotia, Canada. La poblaci6n de estas aves en Canada probablemente nunca ha sido numerosa, sin embargo, hay evidencia que sugiere que ultimamente la misma se ha reducido. Estas gaviotas todavfa estan amenazadas en los Estados Unidos y el Canada por otras gaviotas y depredadores que se encuentran en sus areas de anidamiento, y ademas por humanos en aquellas areas en donde pasan el invierno. Se recomienda se considere el status del ave como amenazada en Canada. Our knowledge of population size and status of the Roseate Tern (Sterra dougallii) in eastern North America has increased dramatically since 1970, when a major effort to survey tern colonies in the northeastern United States and maritime Canada began. These data allow estimates of recent changes in population size and status in the three provinces where Roseate Terns breed in Canada. The present report reviews the breeding records and selected sight records of the Roseate Tern in eastern Canada. The Roseate Tern is a marine species that breeds mostly on tropical and subtropical islands, with only a very restricted breeding range in temperate and boreal zones. Its distribution within the Americas is limited to the Atlantic coast from maritime Canada to Long Island, New York, and from the Florida Keys to the Lesser Antilles (Fig. 1). The present distribution is concentrated in Massachusetts owing to declines at the edges of the breeding range. It formerly bred abundantly in New Jersey, but only a few pairs do so today (Burger in Kress et al. 1983, Nisbet 90 2 ?5 ų 45* NORTH ß AMERICA. 30 ų . -. ß ß .... ß ß ß ß ß ß . ß ß . . 60 ų A TI A N TIC OCEAN o ,o ?'"'"'"ii.: :.-:..-:'i. '" '' ,so "...:..:?:.(:.:.!:i.:.'..'.:.:? , ß : 0 ų 0 o 90 ų 75 ų 60 ų FIGURE 1. The current breeding distribution of the Roseate Tern in eastern North America and the Caribbean (after Nisbet 1980, Kress et al. 1983, Clapp and Buckley 1984, van Halewyn and Norton 1984, Sprunt 1984, this study)ß 1980). There was a single nesting record in North Carolina in 1973 (Soots and Parnell 1975). The Roseate Tern formerly bred also in Mary- land, Virginia (Nisbet 1980), and in Bermuda (Reid 1884), where it now occurs only as a rare migrant (Wingate 1959). Breeding populations of Roseate Terns in Massachusetts have de- creased, from 7500-8000 pairs in 1941, to 4800 pairs in 1952, where they remained until 1972, then rapidly dropped to a low of 2600 pairs in 1978 (Nisbet 1980). Numbers are now around 3100 pairs (Kress et al. 1983). Roseate Terns have never been common in eastern Canada. Tufts (1962) summarized the status of the Roseate Tern as rare and declining. Recently, there has been more effort to locate and census Ro- seate Terns in eastern Canada. Most Roseate Terns breeding in northeastern North America migrate to their wintering grounds during September. They spend the winter along the north shore of South America, especially northeastern Guyana, south to Brazil (Nisbet 1984). RESULTS Quebec.--The only location in Quebec where Roseate Terns have been recorded and suspected to breed is the Magdalen Islands, about 100 km north of Prince Edward Island, in the Gulf of St. Lawrence. Breeding is unconfirmed. Based on several sightings of adult Roseate Terns flying within two Common (Sterna hirundo) and Arctic tern (S. paradisaea) colonies, up to 16 pairs were reported possibly breeding there in 1972 (Finch 1972, A.D. Smith unpubl. CWS report, Chapdelaine in Kress et al. 1983, Nisbett 1980). In 1973, six adults were seen, and three nests were tentatively identified as those of Roseate Terns (N. David, pers. comm.). The putative breeding population on the Magdalen Islands has probably bred annually since at least 1972, but only in very small numbers (<5 pairs). New Brunswick.--The Roseate Tern is listed as hypothetical for main- land New Brunswick (Squires 1976) and as a rare visitor in the Grand Manan Archipelago (Pettingill 1939). At Machias Seal Island, in the mouth of the Bay of Fundy, the Roseate Tern is an uncommon summer visitor. Pettingill (1939) reported details of two sightings on or near Machias Seal Island in the 1930s. Later, two adults were seen by J. Hatch in 1968 (Drury 1973-1974). Since then, Roseate Terns have been recorded in the Grand Manan Channel in August 1970 (Squires 1976), at Machias Seal Island during the summer of 1971 (D. H. Baldwin, unpubl. report to CFN), and again in 1979 when a single pair was discovered breeding by R. Newell (A.D. Smith, unpubl. CWS report). This represented the first confirmed (but unsuccessful) breeding record in New Brunswick. Breeding was not detected in 1980 or 1981, but in 1982 one pair bred, laying two eggs which produced one fledgling (S. Daniel, pers. comm.). No Roseate Terns were found breeding in 1983, 1984, or 1985 (GWS files). Nova Scotia.--Roseate Terns were first reported breeding in Nova 508] I. R. Kirkham and D. N. Nettleship d od 6 j. Field Ornithol. Autumn 1987 Vol. 58, No. 4 Status of Roseate Terns [509 510] I.R. Kirkham and D. N. Nettleship J. Field Ornithol. Autumn 1987 Scotia on Sable Island in the late 1800s (Dwight 1895). Even though precise estimates of bird numbers do not exist for the population on Sable Island, it seems clear that numbers have declined since the turn of the century. Apparently a further decline occurred between 1971 and 1976; since that time the number of breeding Roseate Terns has fluctuated only slightly. The history of Roseate Terns elsewhere in Nova Scotia is unclear owing to the scarcity of estimates of their numbers. Details of known numbers and recent changes of Roseate Terns breeding in coastal Nova Scotia are presented in Table 1. The vast majority of past and present Roseate Tern colonies are situated along the Atlantic coast of Nova Scotia between Sheet Harbour and Yarmouth (Fig. 2). With one exception (see Kirkham 1983), Roseate Terns have not been recorded breeding on the Nova Scotian shore of the Bay of Fundy, or on Cape Breton Island (Godfrey 1958, Tufts 1962, A. R. Lock, unpubl. CWS report, A.D. Smith, unpubl. CWS report, A. R. Lock et al., unpubl. CWS report; see also Fig. 2). A total of 23 sites in Nova Scotia have been confirmed as breeding locations for Roseate Terns at one time or another. During a survey of these and other sites between 1982 and 1985, Roseate Terns were found breeding at eight sites, two of which were new (Table 1). Doubtless not all Roseate Tern breeding sites in Nova Scotia have been found, but it seems likely that those comprising the bulk of the population have been discovered and censused. Consequently, the present size of the Roseate Tern population in Nova Scotia is estimated as between 102 and 122 breeding pairs (Table 1). Total population size.--In a summary of Roseate Tern breeding records in Canada, A.D. Smith (unpubl. CWS report) estimated the size of the population to have been around 315 pairs between 1962 and 1978, with virtually all the birds breeding in Nova Scotia. However, because Ro- seates, like many other tern species, often relocate their breeding sites, that estimate could include individuals that bred at one site one year and at another site later during the 17-yr period. Our conservative estimate of between 102 and 122 pairs (Table 1) for the total population in Nova Scotia is probably more realistic, as well as up-to-date. If some estimates were low and some colonies were not found, there may be as many as 140 pairs, as A. R. Lock et al. (unpubl. CWS report) have estimated, or even slightly more. We do not know the absolute size of the total pop- ulation, but it seems certain that the error associated with the present estimates for Nova Scotia is greater than the total number breeding elsewhere in Canada: 1-5 pairs in Quebec. In summary, the total size of the breeding population of Roseate Terns in Canada is between 103 and 127 pairs, or 3-4% of the total population in northeastern North America. DISCUSSION Predation and human exploitation have been the most important factors limiting the distribution and abundance of Roseate Terns in eastern Canada and the United States (Nisbet 1973, 1981). Other limiting factors 48 c 4.6 = 64 ų 62 ų Magdalen Islands Mochios Seal island .. 21- 20' 18 F 16 -I 5 .. 14 ATLANTIC OCEAN 60* 48 ų 46* 2. 0,4 ų Sable Island FIGURE 2. The locations of Roseate Tern breeding stations in eastern Canada showing: O, sites occupied at the time of the most recent census from 1970 onward; (c), recently extinct sites or those occupied at the time of the most recent census prior to 1970; and O, extinct sites. Numbered sites correspond to those given in Table 1. include the loss of breeding habitat through encroachment by Larus gulls and the effects of toxic chemicals on reproduction (Nisbet 1980, 1981). During the 18th and 19th centuries there was significant exploitation of Roseate Terns, along with many other seabird species, by humans seeking eggs for food and the adults' feathers for the millinery trade. In both Dwight's (1895) and Saunders' (1902) accounts of the terns on Sable Island, they made reference to the collection of large numbers of eggs by the life-station keepers. Human exploitation largely ended early in this century when legislation (Migratory Bird Treaty [1916], Migratory Bird Convention Act [ 1918]) was introduced to protect migratory birds in North America. The collection of tern eggs in Nova Scotia still occurs today, albeit on a very small scale. Roseate Terns, along with most other seabirds, increased in numbers as a result of the protective legislation. However, by the late 1940s, Herring Gulls (Larus argentatus) and Great Black-backed Gulls (L. ma- rinus) had increased so that they began to displace Roseate and Common terns from many traditional colonies throughout northeastern North America (Nisbet 1980, 1981). In Canada, the increase of Herring and Great Black-backed gulls has probably been the most important factor influencing Roseate Tern numbers this century, perhaps most evident at Sable Island where the gulls have virtually displaced the terns. In 1894, Dwight (1895) reported very large numbers of terns breeding on Sable Island, but no gulls. In 1921, terns were still nesting "everywhere" and Larus gulls were uncommon (T. Raddall in litt. to A. R. Lock, pers. comm.). By 1971, A. R. Lock (unpubl. CWS report) estimated that only about 2600 terns were nesting on Sable Island. Eleven years later there were 1100 terns, a further decrease of 58% (I. R. Kirkham and I. A. McLaren, unpubl. obs.). In 1984, 1800 adult terns were counted at colonies on Sable Island (A. R. Lock, pers. comm.). Predation and physical displacement by gulls are probably the major determinants of the reduction of terns on Sable Island and elsewhere in Nova Scotia (Lock in Kress et al. 1983, and unpubl. CWS reports). Although predation and interference by Larus gulls at the breeding sites remain significant as factors limiting population size of Roseate Terns in Canada, the single most important factor may have been human pre- dation in the wintering quarters in Guyana (Hamilton 1981, Nisbet 1981, 1984). Since 1968, about 1% of juveniles and 2% of adults banded at North American sites between 1965 and 1977 have been recovered in northeast Guyana, mostly by a single market trapper operating over a small area (Hamilton 1981, Nisbet 1984). The terns were captured on beaches at night (Hamilton 1981), and were rarely seen near the shore during the day (Nisbet 1984, P. Trull, pers. comm., see also Dunn 1981). However, the intensive trapping of Roseate Terns in Guyana does not account for the 30-40% decline in the North American breeding popu- lation recorded since the mid-1960s. Moreover, the commercial trapping of Roseate Terns in Guyana is reported to have stopped (Nisbet 1984, P. Trull, pers. comm.) and an extensive search by P. Trull in 1980 and 1982 failed to reveal any evidence of other intensive trapping along the coasts of Guyana and Suriname (Blokpoel et al. 1982, Nisbet 1984, P. Trull, pers. comm.). Roseate Terns breeding in Britain overwinter in West Africa where they too are vulnerable to human predation. The recent decline of the British breeding population appears correlated with intensive trapping in Ghana (Dunn 1981, Dunn and Mead 1982, Hepburn 1986). This raises the question whether North American Roseate Terns are also being trapped on a large scale while in their wintering quarters, perhaps in areas not located by Trull or others? Thus, factors responsible for the rapid decline in numbers of Roseate Terns from the 1930s until 1978 remain unclear. Buckley and Buckley (1981 ) recommended that Roseate Terns in north- east North America be designated an Endangered Species. However, Ro- seate Tern numbers have stabilized since 1980 (Kress et al. 1983), and Nisbet (1980) recommended a classification of Threatened. In 1986, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) proposed (based on I. R. Kirkham and D. N. Nettleship, unpubl. rep. to COSEWIC 1985) that the Canadian population of Roseate Terns should be considered Threatened. ACKNOWLEDGMENTS We are grateful to many people for providing us with unpublished information on sightings and breeding records of Roseate Terns in Canada and northeastern United States: C. R. K. Allen, S. Daniel, N. David, R. and R. Denton, A. R. Lock, I. A. McLaren, E. L. Mills, R. Newell, I. C. T. Nisbet, H. Ross, P. Trull, and C. E. Tull. We also thank H. Boyd, W. 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