# Bridled Tern

Scientific name: Onychoprion anaethetus

Bird group: [gull](https://birdsofpuertorico.com/family/gull)

Canonical source: https://birdsofpuertorico.com/bird/128/Bridled-Tern

## Identification

The bridled tern (Onychoprion anaethetus)  is a seabird of the family Laridae. It is a bird of the tropical oceans. The scientific name is from Ancient Greek. The genus comes from onux meaning "claw" or "nail", and prion, meaning "saw". The specific anaethetus means "senseless, stupid".
This is a medium-sized tern, at 30–32 cm in length and with a 77–81 cm wingspan similar to the common tern in size, but more heavily built. The wings and deeply forked tail are long, and it has dark grey upperparts and white underparts. The forehead and eyebrows are white, as is a striking collar on the hindneck. It has black legs and bill. Juvenile bridled terns are scaly grey above and pale below.


## Distribution and habitat

The Bridled Tern occurs throughout the tropical and 
subtropical seas of the world 
(Raffaele and others 1998). It 
is a resident species in Puerto 
Rico (Raffaele and others 1998), 
regularly seen during breeding 
season in waters off Mona 
and Monito, as well as in the 
Cordillera Natural Reserve and 
Culebra (Kepler 1978, Oberle 
2018), but it is an extremely 
rare spring and summer visitor 
in Vieques (Gemmill 2015). 
However, during the breeding 
season it can also be seen 
commonly on the north coast 
of Puerto Rico between Isabela and Barceloneta (Oberle 2018). 
This species often occurs far 
offshore (Raffaele and others 
1998) or near islets where it 
breeds (Oberle 2018, Raffaele 
and others 1998). The atlas 
fieldwork yielded a total of 37 
records within 24 hexagons or 5 
percent of the 479 total hexagons 
(see map). Of the 24 hexagons 
where this species was found, 
breeding met the atlas definition 
of confirmed in 50 percent (12) 
of the hexagons and possible in 
17 percent (4), while the species 
was observed in 33 percent (8) 
of the hexagons but without 
evidence of breeding (see map).Bridled 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.      119Bridled Tern/Charrán Monja

## Breeding

The Bridled Tern nests in small colonies on a coral rubble 
beach or under the protection of 
vegetation and rocks on isolated 
islands or cays from April to 
July, according to previously 
published reports (Oberle 2018, 
Raffaele and others 1998). Atlas 
results indicate that this species 
mostly breeds in May, June, and 
July (see chart). Results show 
that breeding most commonly occurs in the subtropical dry 
and subtropical moist forest life 
zones (69 and 31 percent of the 
hexagons, respectively) (see 
table and map).

## Conservation

Although the overall population trend of the Bridled Tern is 
uncertain, it is listed as a species 
of least concern by the IUCN 
(BirdlLife International 2019), 
and locally it is not listed in any of the threatened categories 
used by PRDNER and USFWS. 
In Puerto Rico, the Bridled Tern 
has a protected habitat in land of 
6 percent or 23 km2 of the total area covered by the hexagons 
where evidence of breeding was 
found for this species (382 km2). 

Photo: https://birdsofpuertorico.com/static/images/webp/in_128_Im0.png.webp

Distribution map: https://birdsofpuertorico.com/static/images/webp/in_128_Im1.png.webp

Source note: Text is reproduced from this site's published record. Historical conservation statements and taxonomy have not been independently revalidated. See https://birdsofpuertorico.com/about for source credits and limitations.