Elegant Terns (Jim Kenney 4/29/15)

“Elegant Terns are…well, they’re just so elegant!,” founding chapter member Abigail King used to say. They certainly are.

More Elegant Terns (J. Kenney 4/29/15)

We were recently treated to the sight of thousands of Elegant Terns dropping into Malibu Lagoon, and on April 29 Jim Kenney caught them in action. Often starting off slow, such gatherings can build over several hours, until suddenly you realize you’re in the storm-center of a swirling mass of wings, bills and cries.

Even more Elegant Terns (J. Kenney 4/29/15)

Some of us have been looking at Elegant Tern – and its disconcertingly similar conspecific Royal Tern – for decades, and we still have trouble telling them apart. Here are some tips.

Some of the Elegants get spooked (J. Kenney 4/29/15)

Bill shape and size is one of the best field marks.
Elegant: Very long and slender. Lower bill lacks any gonydeal angle (bump on lower bill, common among gulls and terns); bottom of lower bill curves slightly downward to tip.

Elegant Terns: bill long & decurved, yellow-orange, black legs and cap, pink breast on right bird (J. Kenney 4/3/10)

Royal: Lower bill has small gonydeal angle near middle; bottom of bill appears either straight or curving slightly upward to tip. Bill is stouter than on Elegant.

Royal Terns: stout orange bill, small gonydeal angle on lower bill, non-breeding dark cap barely reaches dark eye (J. Kenney 11/15/06)

The juveniles of  both species will have shorter bills for a while. Species with large bills take longer to develop a full-sized bill.

Size ranges of Caspian (rear) & Royal (front) Terns overlap (J. Kenney 4/14/10)

Bill color in both species range from pale yellow to bright orange, almost red. Juveniles have the palest bills; adults tend towards darker orange and near-red; colors are brighter during breeding. Royal tends towards orange, Elegant tends towards yellow, but colors vary and overlap so greatly, it is more misleading than useful.

Elegant Terns have a variety of bill colors (J. Kenney 4/29/15)

Black Cap: In non-breeding birds, this is the best field mark. In breeding season both have black caps from bill to shaggy nape; the Elegant has a slightly shaggier nape-crest. After breeding, black caps are gradually and partially lost, beginning at the bill. The Royal loses a bit more of the black cap than does the Elegant, and in winter, the black eye of the Royal stands out noticeably from the black crest, whereas the black eye of the Elegant remains ‘buried’ within, or at the very edge, of the black cap.

Elegant Tern with non-breeding cap, note black plumage in front of eye. Note decurved lower bill and pale yellow to deep orange bill.
(Joyce Waterman 6/14/14)

Elegant Tern with non-breeding cap; note orange legs (J. Waterman (9/22/13)

Calls are similar: The Elegant perpetually utters a “kreeeeek!” screech, and when the flock is large, it can be extremely noisy. Royals have a lower “koorrick” call, but at the lagoon seem to remain quiet. Maybe they can’t get a word in edgewise when Elegants are around.

Noticeably bulkier Royal Tern (left) before developing breeding crest which Elegant already has. Elegant with fully extended neck seems as tall as Royal.
(J. Kenney Apr’07 Playa del Rey, CA)

Dimensions: Elegant and Royal almost, but not quite, overlap. Royal and Caspian (world’s largest tern) overlap in size, not in weight. Royal and Caspian Terns overlap in all dimensions with Ring-billed Gull.^[1]

Legs and feet: About 90% of adult Elegant have black legs & feet; 10% have orange legs & feet. Adult Royal have black legs & feet. Juveniles of both species often have yellow-to-orange legs & feet.

Royal Tern juvenile has spotty back & yellow-orange legs. The bill may also be shorter. (J. Kenney 8/4/09)

Breast: White, but breeding Elegant often has a pale pinkish cast. This comes from carotenoids (as in carrot) – specifically astaxanthin – from fish and crustaceans in their diet, is in the feathers themselves, and does not occur on the plumage surface or in preen oil, as some have previously speculated. Carotenoids color the plumage of many other birds, including Flamingos and House Finches. (See above photo of Elegant Tern bill shape.)

Anxiety spreads (J. Kenney 4/29/15)

Wings are long, slender and pale underneath with limited dark in the primaries; tails are noticeably forked.

Waves of flight (J. Kenney 4/29/15)

Still confused? Join the club. Confusion is the proper attitude. The best way to differentiate them is to get them to stand side-by-side. Then – usually! – the differences in bulk, crest, size, bill shape and length, and eye location in the black cap become obvious. Sort of.

All terns are plunge divers, feeding on small fish. Most gulls will eat nearly anything, plucking their food from the surface of the water or ground, robbing other birds (especially terns) or hanging around pelicans, hoping for a freebie.

Royal Terns are not globally threatened. They nest along both coasts of North & South America, the Caribbean, and the west coast of Africa, totaling over 70,000 pairs. Our west coast populations have suffered crashes in the past 40 years due to the virtual disappearance of their staple food, the pacific sardine. The relatively large size of their prey also makes them especially susceptible to pesticides working their way up the food chain.

They’re very noisy (J. Kenney 4/29/15)

Elegant Terns are considered near-threatened, numbering 30,000-50,000 pairs, about 90% of which nest on Isla Rasa, 1/3rd way down the sea of Cortez. [See map.] Such concentration on a particular breeding location makes them highly susceptible to local dangers, and gathering of eggs by local fishermen, before the island was declared a sanctuary in 1964, nearly wiped them out. Isla Rasa is also the primary breeding location of Heermann’s Gull, commonly seen at Malibu Lagoon.

Elegant and Royal Terns are not always at the lagoon. Our records show:

The single Elegant Tern present in Feb. 2010 was an anomaly. Normally they are completely absent from SoCal December through February. As the above table shows, while both species are present nearly equally often, Elegant, absent in winter, still outnumbers Royal 13-to-1.

Chaos reigns (J. Kenney 4/29/15)

Birders visiting from the East Coast and around the world often have Elegant Tern high on their ‘want list.’ Although it ranges from southern Washington State to Peru, SoCal is probably the most easily accessible place in the world to find it. Something to think about the next time you see this truly elegant bird on the sand.     [Chuck Almdale]

Notes:
[1] Handbook of Birds of the World (HBW), Vol. 3; Lynx Edicions, 1996; del Hoyo, Elliot & Sargatal
[2] There is wide disagreement on Ring-billed Gull length. Sibley’s & NGS field guides both give 17.5″; HBW 18.1-21.3″, Cornell Lab of Ornithology 16.9-21.3″, BeautyOfBirds.com gave averages of female 18.5″ male 20″, other web sources gave 16″, 17″, 18″, or 19″. I chose to use the Cornell lab length dimension as most inclusive.