Summer Terns in the Dry Tortugas

Terns are certainly one of the amazing wonders of the bird world.  Most stunning is the migration of the Arctic Tern yearly from the Arctic to Antarctic and back.  This summer while catching lots of King Salmon at a remote fish camp on the Nushagak River (this river drains to Bristol Bay – Alaska’s premier sockeye salmon fishery)  I was mesmerized by Arctic Terns.  Both eye- and ear-catching, busy, always busy guarding their young and catching fish to fatten the chicks for the long flight south.  Bills, legs and feet turn blood red during breeding season making them striking in appearance and sharp in call.

Arctic Terns

Arctic Terns

Arctic Terns

Arctic Terns

The Dry Tortugas has four species of oceanic (open ocean home) terns that utilize these remote islands for summer nesting.  Some terns reside along our shorelines – like Royal Terns in the Tortugas.  All terns feed on fish and sea life but some choose to live far out to sea, coming to shore only to breed.  Fortunately for bird watchers and nature enjoyers the Dry Tortugas offer a unique opportunity to observe these 4 species of oceanic terns on land: Sooty, Noddy, Bridled and Roseate Tern.

Sooty Tern

Sooty Tern

Noddy Tern

Noddy Tern

Bridled Tern

Bridled Tern

Sootys on Nesting Site

Sootys on Nesting Site

Most famous in the Tortugas is the Sooty Tern – mariners, naturalists and explorers have been captivated by the Sooty Colony since the islands were discovered by Ponce de Leon.  The Sooty Tern is simply a magnificent flying machine.  The chicks after just a few month of life choose to leave Mom and Dad behind and embark on a journey to the waters off South Africa where upwelling produces large numbers of fish for food.  The young Sootys will spend 3-5 years here meeting Sootys from other tropical colonies around the world.  This species has no natural weatherproofing in its feathers and can’t sit on the water – thus it spends most of its life aloft – even sleeping while flying.  Living over 20 – 30 years, these birds will reach sexual maturity at about 5 years and then return to a life over seas closer to breeding areas in remote islands throughout the tropics.  Here they lay a single egg in a scrape in the sand.  Males and females alternate sitting on the egg with feeding out to sea in about 12 hour shifts, later regurgitating fish for the chicks.  It is not uncommon for these birds to travel 100 or more miles on a feeding trip to sea.

Audubon described the Sooty colony at the Dry Tortugas at 250,000 birds in the 1830s, a striking sight in spring and summer.  Now the population stands around 30,000 – 50,000.  Hurricanes in recent years have significantly declined the population.  Enjoy these Terns on Bush Key in the Tortugas from February to late July or early August.

Sooty with Chicks

Sooty with Chicks

Amazing – Sooty flying while looking upwards

Amazing – Sooty flying while looking upwards

Sootys on Bush Key

Sootys on Bush Key

Noddy Terns will join the Sooty Terns on Bush Key in springtime for nesting.  Noddys however build a stick nest decorated with seashells and seaweed.  These birds tend to stay in groups especially out to sea and feed by diving or picking fish from the surface.

Noddy Terns

Noddy Terns

Noddy Terns

Noddy Terns

Noddys are named for nodding at each other both in courtship and in nesting.  Noddys can be seen in spring and early summer along the shoreline of Bush Key collecting sticks, seaweed and shells for their nests.  Elaborate nodding occurs at the nest site and in courtship and is fascinating to watch.

Roseate Terns feed by plunge diving – more typical of Terns overall – but unique among the four nesting Tortugas Terns.  Roseate Terns were known to nest in the Tortugas in the past but the colony wasabandoned.  They also nested in coral rubble along the reefline south of Key West but this area was left submerged by hurricanes.  Five years ago a combined effort by National Park Service and Florida Fish and Wildlife Conservation biologists produced a plan to use decoys and a sound recording of a Roseate Tern colony in New England to try to reestablish the breeding colony in the Dry Tortugas.  The program has been successful and 30 to 40 pair have nested the last several summers in the Dry Tortugas.  These birds prefer the coral rubble on the east end of Bush Key and in the north side of Long Key.

Roseate Terns

Roseate Terns

Roseate Terns

Roseate Terns

Roseate Terns were hunted heavily by plume hunters and their eggs are considered to be and aphrodisiac in the Bahamas and Caribbean.  This species is also waning in population.  Today Roseate Terns nest in the Tortugas and also on the roof of the government center in Marathon in summer.  They also nest along the shoreline of New England and Nova Scotia.  The yound are quickly fledged – first flight occurs in 27 to 30 days but the young can leave the nest after just a few days.

Roseate Terns

Roseate Terns

Roseate Terns

Roseate Terns

Two year ago biologists observing the Roseate Tern colony were surprised and pleased to learn that several pairs of Bridled Tern were nesting in coral rubble near the Roseate colony.  These Terns are commonly sighed in Gulf Stream waters but were not known to breed in the Tortugas.  Bridled Terns look similar to Sooty Terns but are lighter in the back and longer.

Bridled Tern – note charcoal back

Bridled Tern – note charcoal back

Bridled Tern

Bridled Tern

Unlike Sootys who like to stay aloft, Bridled Terns are frequently spotted sitting on sticks and flotsam.  Neither Sooty, Noddy, nor Bridled Terns plunge dive for fish like the Roseate Tern.  With the modern development of many offshore islands a lot of pelagic Terns have lost nesting habitat.  The Tortugas remain a very viable breeding opportunity for these four tern species and more pelagic birds.

Watch for Sooty and Noddy Terns on Bush Key from February to late July or early August.  The Roseates nest at the east end of Bus Key and the north side of Long Key in June through August.  Bridled Terns were spotted in late April and stay until chicks are fledged in late July or early August.  Flyovers by all these species will occur on Garden Key (home of the majestic Fort Jefferson) during the summer months.

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