Roseate Tern (Sterna dougallii)

Roseate Tern

Description

The roseate tern (Sterna dougallii) is a tern in the family Laridae. The genus name Sterna is derived from Old English "stearn", "tern", and the specific dougallii refers to Scottish physician and collector Dr Peter McDougall (1777–1814). "Roseate" refers to the bird's pink breast in breeding plumage. This is a small-medium tern, 33–36 cm (13–14 in) long with a 67–76 cm (26–30 in) wingspan, which can be confused with the common tern, Arctic tern, and the larger, but similarly plumaged, Sandwich tern. The roseate tern's thin sharp bill is black, with a red base which develops through the breeding season, and is more extensive in the tropical and southern hemisphere races. It is shorter-winged and has faster wing beats than common or Arctic tern. The upper wings are pale grey and its under parts white, and this tern looks very pale in flight, like a small Sandwich tern, although the outermost primary flight feathers darken during the summer. The adults have very long, flexible tail streamers and orange-red legs. In summer, the underparts of adults take on the pinkish tinge which gives this bird its name.

Distribution And Habitat

The Roseate Tern occurs throughout the worlds tropical and subtropical oceans, and it is generally uncommon to rare in the West Indies (Raffaele and others 1998). Small breeding colonies can be found from The Bahamas through the Greater Antilles, especially in the Virgin Islands and cays off southwestern Puerto Rico (Oberle 2018), which support the largest population of Roseate Terns in the tropical Atlantic Ocean (Raffaele and others 1998). It is described as fairly abundant during the summer in coastal areas of Puerto Rico (Biaggi 1997) and is a regular breeder off Culebra and cays south of La Parguera in the municipality of Lajas (Oberle 2018), as well as other cays near Puerto Rico (Biaggi 1997). On Vieques, it is a fairly common breeding visitor in summer (Gemmill 2015, Johnson 1988), extremely rare in fall, and rare in spring (Gemmill 2015). It usually inhabits coastal areas, harbors, and lagoons (Raffaele and others 1998). The atlas fieldwork yielded a total of 42 records within 27 hexagons or 6 percent of the 479 total hexagons (see map). Of the 27 hexagons where this tern was found, breeding met the atlas definition of confirmed in 30 percent (8) of the hexagons and probable in 4 percent (1), while the species was observed in 67 percent (18) of the hexagons but without evidence of breeding (see map). Roseate Tern distribution. The map shows the highest breeding code by hexagon and overlaying the ecological life zones in Puerto Rico. Note: percentages may not total 100 due to rounding. 123Roseate Tern/Palometa

Breeding Habits

Previously published reports indicate that the Roseate Tern breeds from May to July (Raffaele and others 1998). Nesting is usually colonial on offshore cays, and the nest consists of a scrape in the sand or a rocky depression (Raffaele and others 1998). On Culebra, the terns nest on cliffs between boulders (Oberle 2018). Breeding colonies are very local, but birds are regularly observed along coastal waters during the breeding season (see map). Atlas results show that this species breeds from May to July (see chart). Overall, the breeding activity peaks in June, and it mostly takes place within the subtropical dry forest life zone (see chart). Results show that this species breeds mostly in coastal areas within the subtropical dry forest life zone (67 percent of the hexagons) and the subtropical moist forest life zone (33 percent of the hexagons) (see table and map).

Conservation

The current overall population trend of the Roseate Tern is described as uncertain or unknown as some populations are decreasing, while others are stable or increasing (Wetlands International 2012). This species is currently listed as a species of least concern by the IUCN (BirdLife International 2018). However, it is locally listed as a threatened species by Federal laws (Oberle 2018, USFWS 1973). In Puerto Rico, the Roseate Tern has a protected habitat in land of 16 percent or 35 km2 of the total area covered by the hexagons where evidence of breeding was found for this species (214 km2).