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There is a season — Tern! Tern! Tern!

Submitted by admin on Wed, 02/08/2012 - 13:08
When it comes to breeding — or not — headgear is all important. The royal tern in the foreground displays readiness for breeding with a black cap of plumage covering the eyes, while the neighboring royal dons the winter (nonbreeding) outfit: a snowy cap with some black speckling toward the crest. ©2012 Judith Lea GarfieldTern style is facing the ocean, always a prudent pose when poised where land meets the unruly sea. The combined physical attributes and determined stance somehow make the terns look like they are fighting a headwind, though in reality they are comfortably stationary. ©2012 Judith Lea Garfield
  • When it comes to breeding — or not — headgear is all important. The royal tern in the foreground displays readiness for breeding with a black cap of plumage covering the eyes, while the neighboring royal dons the winter (nonbreeding) outfit: a snowy cap with some black speckling toward the crest. ©2012 Judith Lea Garfield
  • Tern style is facing the ocean, always a prudent pose when poised where land meets the unruly sea. The combined physical attributes and determined stance somehow make the terns look like they are fighting a headwind, though in reality they are comfortably stationary. ©2012 Judith Lea Garfield
Who doesn’t get excited when royalty comes to town? Presently holding court in our midst is the royal tern (Thalasseus maximus), a standout among shorebirds, always terrifically turned (dare I say) out in a sophisticated mix of neutrals and just a pop of color. Co-mingling with other species adjacent to the beach break at La Jolla Shores, the royal tern might be just another avian marked by black, gray and white plumage that hangs out here or passes through the area but for its dagger-like orange-red bill — talk about a snazzy accessory!
 
When it comes to breeding — or not — headgear is all important. The royal tern in the foreground displays readiness for breeding with a black cap of plumage covering the eyes, while the neighboring royal dons the winter (nonbreeding) outfit: a snowy cap with some black speckling toward the crest. ©2012 Judith Lea Garfield
A purely minimalist look can be striking, too, and this is true for the royal tern, who is typically decked out in a white forehead, wispy black crest, pale-gray back and wings, white under parts with just an edge of dark, and ebony legs and feet. Sizewise, a royal tern is crow-size, but lacks the gift of gab heard from the latter. Though usually taciturn from my experience, a verbalizing royal tern calls out in short, clear shrills, also communicating with a longer, rolling and more melodious whistle.
 

Seasonal locks

Seasons, breeding, and juveniles reveal slightly altered looks but in the same “color” palate. Winter is the only time I see royal terns on the sandy beach at La Jolla Shores, and during this time, the bird’s crown is almost entirely white with just some inconspicuous black spotting forward of the black crest. During February, the onset of breeding season, royala acquire a black skullcap of plumage that covers the rear half of the crown and extends forward to completely envelop the eye area. Breeding birds of both sexes share this inscrutable look.

Tern style is facing the ocean, always a prudent pose when poised where land meets the unruly sea. The combined physical attributes and determined stance somehow make the terns look like they are fighting a headwind, though in reality they are comfortably stationary. ©2012 Judith Lea GarfieldAs for nesting, it won’t happen in La Jolla because tern couples prefer an estuary to an open coast. Even so, they have no history of nesting in any significant numbers in San Diego’s inland waterways, preferring to deal with their broods in the southern latitudes of Mexico’s estuaries. Though out of my sight, by late June, the birds’ black caps have receded, revealing their typical white forehead with black stubble near the crest. Juvenile royal terns look similar to nonbreeding adults but youngsters have black-splotched wings and an orangey bill that may lean more toward yellow instead of red.

Flitting here and there

Sources suggest a royal tern does not have a strong seasonal pattern, being found along San Diego County’s coast year round. Maybe so, but whenever a royal is seen, count on it being near seawater, a commitment likely connected to its favored prey choice, small fish like anchovies and sardines. The mercurial movements (and booms and busts) of these fish species are one reason the status of royal terns has been poorly understood throughout the 20th century. We are only beginning to document changes in behavior of seabirds and correlate them with their prey (in terms of numbers and distribution fish).

The point now is to understand how changes in prey populations are linked to fishing pressure and global climate change. Since seabirds that nest with success can expect to be widely distributed across their range, decreases in their numbers or change in their expected range provide quick and visible proof of environmental impact. Though the royal tern is no canary and it lives by the ocean instead of in a coal mine, it is one of the seabird species on the front lines that is responding to global environmental change. In other words, the royal is more than an arbiter of sartorial taste.

In my speck of range that intersects with that of the royal tern, I will enjoy observing these birds as long as they choose to visit. Somehow, it always happens that one morning, just as I discover them at the water's edge of La Jolla Shores, I discover they’ve gone. Then after 9 or 10 months, they just as abruptly return from points south to again adorn our seashore.

— Judith Lea Garfield, naturalist and underwater photographer, has authored two natural history books about the underwater park off La Jolla Cove and La Jolla Shores. Send comments to jgarfield@ucsd.edu.

 

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