Sterna hirundo
Silhouette: Sharon Wegner-Larsen · PhyloPic
In 3 days <5%
The common tern (Sterna hirundo) is a seabird in the family Laridae. This bird has a circumpolar distribution, its four subspecies breeding in temperate and subarctic regions of Europe, Asia and North America. It is strongly migratory, wintering in coastal tropical and subtropical regions. Breeding adults have light grey upperparts, white to very light grey underparts, a black cap, orange-red legs, and a narrow pointed bill. Depending on the subspecies, the bill may be mostly red with a black tip or all black. There are several similar species, including the partly sympatric Arctic tern, which can be separated on plumage details, leg and bill colour, or vocalisations.
Breeding in a wider range of habitats than any of its relatives, the common tern nests on any flat, poorly vegetated surface close to water, including beaches and islands, and it readily adapts to artificial substrates such as floating rafts. The nest may be a bare scrape in sand or gravel, but it is often lined or edged with whatever debris is available. Up to three eggs may be laid, their dull colours and blotchy patterns providing camouflage on the open beach. Incubation is by both sexes, and the eggs hatch in around 21–22 days, longer if the colony is disturbed by predators. The downy chicks fledge in 22–28 days. Like most terns, this species feeds by plunge-diving for fish, either in the sea or in freshwater, but molluscs, crustaceans and other invertebrate prey may form a significant part of the diet in some areas.
Eggs and young are vulnerable to predation by mammals such as rats, badgers and American mink, and large birds including gulls, owls and herons. Common terns may be infected by lice, parasitic worms, and mites, although blood parasites appear to be rare. Its large population and huge breeding range mean that this species is classed as being of least concern, although numbers in North America have declined sharply in recent decades. Despite international legislation protecting the common tern, in some areas, populations are threatened by habitat loss, pollution, or the disturbance of breeding colonies. Wikipedia →
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Dakar | 🇸🇳 Senegal | |
| 2 | Helsinki | 🇫🇮 Finland | |
| 3 | Liverpool | 🇬🇧 United Kingdom | |
| 4 | Minsk | 🇧🇾 Belarus | |
| 5 | Nizhny Novgorod | 🇷🇺 Russia | |
| 6 | Izmir | 🇹🇷 Turkey | |
| 7 | Ulaanbaatar | 🇲🇳 Mongolia | |
| 8 | Rostov-on-Don | 🇷🇺 Russia | |
| 9 | Rotterdam [The Hague] | 🇳🇱 Netherlands | |
| 10 | Padang | 🇮🇩 Indonesia |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | Bronx Zoo | 🇺🇸 United States | |
| 2 | Ralph Perkins II Wildlife Center and Woods Garden | 🇺🇸 United States | |
| 3 | New England Aquarium | 🇺🇸 United States | |
| 4 | Montreal Biodome | 🇨🇦 Canada |
Rare
Under 5% of wildlife watchers report a Common Tern sighting in Los Angeles on a given day, based on 192 verified sightings from GBIF citizen-science data. It is the 304th most-seen of the 426 birds we can rate there. Over three days the chance rises to under 5%, if each day is a fresh chance.
Any time of year
In every month with enough records, under 5% of wildlife watchers report a Common Tern in Los Angeles on a given day, so our monthly data shows no clear season.
Between 8 and 11 am
Across all the parks we cover, that three-hour window holds the most Common Tern sightings with a recorded time, and nearly all of them come between 6 am and 6 pm: it is a daytime animal.
94th of 105
Of the 105 cities where we can rate Common Tern sightings, Los Angeles ranks 94th at under 5%. The best odds are in Dakar (Senegal, about 40%), Helsinki (Finland, about 30%) and Liverpool (United Kingdom, about 20%).
GBIF citizen-science records
It is estimated from how often the Common Tern is recorded against all the birds logged in Los Angeles (192 verified sightings), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
