Sooty Tern (Onychoprion fuscatus)

Sooty Tern


The sooty tern (Onychoprion fuscatus) is a seabird in the family Laridae. It is a bird of the tropical oceans, returning to land only to breed on islands throughout the equatorial zone. O. f. nubilosus flying on Rodrigues Island in the Indian Ocean

Distribution And Habitat

The Sooty Tern occurs through the tropical oceans of the world (Oberle 2018, Raffaele and others 1998). In the West Indies, it is generally a common breeding resident from May to August (Raffaele and others 1998). It is fairly abundant in Puerto Rico during the summer months (Biaggi 1997), and it can be seen on the nesting colonies in Mona, Monito, and Culebra, as well as the Cordillera Natural Reserve (Oberle 2018). It is also found on Vieques, where it is considered an extremely rare summer visitor (Gemmill 2015). It mostly occurs far offshore (Raffaele and others 1998), except when nesting (Oberle 2018). The atlas fieldwork yielded a total of 24 records within 14 hexagons or 3 percent of the 479 total hexagons (see map). Of the 14 hexagons where this species was founds, breeding met the atlas definition of confirmed in 43 percent (six) of the hexagons and possible in 7 percent (one), while the species was observed in 50 percent (seven) of hexagons but without evidence of breeding (see map).Sooty 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. 117Sooty Tern/Charrán Oscuro

Sooty Tern Distribution

Breeding Habits

Previously published reports indicate that the Sooty Tern breeds from April to August (Raffaele and others 1998). The nest is a scrape made on coral rubble or below overhanging vegetation, mostly in large and gregarious colonies (Raffaele and others 1998). Atlas results show that this species breeds from March to July (see chart). The breeding activity peaks in June and takes place in the subtropical dry forest life zone (see chart). Results show that this species breeds in coastal areas within the subtropical dry forest life zone (100 percent of the hexagons) (see table and map).


The current overall population trend of the Sooty Tern is described as unknown, as some of the populations are decreasing and others are increasing or have unknown trends (Delany and Scott 2006). This species is currently listed as a species of least concern by the IUCN (BirdLife International 2018). Locally, this species is not listed in any of the threatened categories of PRDNER and USFWS. In Puerto Rico, the Sooty Tern has a protected habitat in land of 2 percent or 3 km2 of the total area covered by the hexagons where evidence of breeding was found for this species (167 km2).