Monthly Archives: September 2016

Oahu hui works to protect urban-dwelling white terns

Published September 24, 2016 in the “Ocean Watch” column, Honolulu Star-Advertiser
©2016 Susan Scott
tern

A white tern chick lives on a concrete ledge on Tern Island, a tiny coral island in the French Frigate Shoals in the Northwestern Hawaiian Islands. ©2016 Susan Scott

If you love the white terns that flit around our trees and add joy to our city, join the club. Really. There is a club.

After my recent white tern column, I learned that several like-minded Oahu residents, researchers and conservation group members, both public and private, have formed a white tern fellowship called Hui Manu-o-Ku. The hui’s purpose is to make sure that this Tinker Bell of seabirds — Honolulu’s official bird — is protected, counted (in both numbers and importance) and continues to thrive.

No one knows why white terns have chosen urban Oahu to raise their kids, but our tall trees may be a factor. Because white terns lay their eggs and raise their chicks in the crooks of tree branches, tree trimming, a necessity in all cities, is a vital issue for the birds. The hui’s website has tree trimming tips for arborists and homeowners as well as a map of known “nests,” meaning an egg or chick on a branch. A Citizen Science tab explains how you can help record the city’s growing population, what to do if you find a fallen chick and how to volunteer for other activities.

Tree trimming also has a plus side for the terns. Cut branches form cups, forks and scars that can secure eggs, something that may attract the birds to Honolulu.

White terns can breed year-round but their peak egg-laying time is February through June. The female lays one egg. If it falls, she soon lays another, and another if necessary. The parents take turns sitting on the egg for about five weeks. As soon as the hatchling is fluffy and standing on its big clawed feet — useful for hanging onto a bare branch – the parents are off fishing for juvenile goatfish, flying fish and others.

A parent can hold up to eight fish (I have a photo of this amazing feat) crosswise in its small beak, feeding each one whole to its chick. About seven weeks later, the youngster can fly but, like most kids, sticks around home for the next two months for free meals.

Honolulu is the only city in the world that has white terns raising chicks in bustling built-up areas. To learn how to help keep our feathered friends safe and their population growing, or just to see some fabulous photos, check out Hui Manu-O-Ku’s excellent website, whiteterns.org.

And speaking of safe, our Kaena Point albatrosses will be returning there soon, but the vandals who last winter stole equipment, broke eggs and killed nesting parents have not yet been prosecuted.

You can help our albatrosses by asking the city prosecutor when legal action will begin. Send an email using the form at honoluluprosecutor.org/contact-us/ or call 768-7400.

Man-of-wars are 1 animal, not a mishmash of critters

Published September 17, 2016 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2016 Susan Scott

At the beach, I recently ran into my neighbor, Marya, who, as usual, had a thoughtful marine animal question. She wondered how it is that a Portuguese man-of-war is a colony of individuals rather than one animal.

“I can’t picture how that works,” Marya said.

I can’t picture it, either, but we don’t need to because it’s an old idea. Besides that, the confusing colony statement detracts from the fact that the Portuguese man-of-war is one of nature’s most exquisite masterpieces.

A man-of-war starts life when a drifting sperm meets a drifting egg and grows into a larva, a flat bean-shaped thing with swimming hairs.

As it matures, the front end of the larva transforms into a blue, air-filled bubble topped with a fleshy pink sail that the creature trims to move at an angle to the wind. When strong tradewinds and storms overpower the little sails, man-of-wars get shipwrecked on our beaches.

While forming its float, the larva also produces, from below, three types of tentacles. One type contains sperm and eggs (man-of-wars are hermaphrodites). Another kind has long tentacles with stinging cells. The third tentacle type consists of hollow eating tubes.

As the creature sails around the ocean surface, its stinging tentacles troll below for small crustaceans and fish. When it gets a catch, the retractable tentacles reel it in to the eating tentacles, which wrap around the food.

Normally having openings invisible to the naked eye, the mouths of man-of-war eating tentacles can expand to three quarters of an inch. After spitting enzymes on the prey to externally digest it, the food tubes suck up the meal.

Most animals function similarly, having a nerve-directed team of genetically identical, but specialized, organs dependent upon each other to live and reproduce. But because the man-of-war grows its float and tentacles by budding (pooching out) from its larva, some biologists in the past declared that each pooch was an individual animal, even though each does a different job and none can live alone. It’s like saying our stomach is one person, our gonads another and limbs another.

Although the statement that each man-of-war is a colony rather than an individual is pervasive, it’s not written in stone. My favorite invertebrate zoology textbook authors write “ … that it sometimes seems more appropriate to consider the colony (of siphonophores, man-of-war and their clan) as one complex individual.” And the authors of my Monterey Bay Aquarium go-to book on gelatinous animals write that although it’s still debated, “ … most specialists now prefer to think of (siphonophores) as individuals with many well-integrated parts.”

Now that we can picture. Thanks, Marya, for another great question.

White birds ‘having a blast’ likely honeymooning terns

Published September 10, 2016 in the “Ocean Watch” column, Honolulu Star-Advertiser
©2016 Susan Scott
The white tern, or manu-o-Ku, is abundant in the Northwestern Hawaiian islands, but in the main Hawaiian Islands they breed only on Oahu. ©2016 Susan Scott

The white tern, or manu-o-Ku, is abundant in the Northwestern Hawaiian islands, but in the main Hawaiian Islands they breed only on Oahu. ©2016 Susan Scott

Nuuanu resident Robert emailed, “For the last few years we have been blessed by beautiful white birds cavorting in the sky, swooping all over our valley at great speed. They never seem to go to ground, although they have settled for a few minutes in some tall trees around our home. They seem to be having a blast! Do you know what they are and why they swoop back and forth?”

Any Oahu resident who writes about being blessed with beautiful, white birds that race about and land in trees can mean only one species: the white tern or manu-o-Ku, formerly known as the fairy tern. White terns are foot-long seabirds with 30-inch wingspans which can hover over the ocean’s surface while plucking out fish. The birds also helicopter close overhead to check out a person and soar like Captain America’s buddy Falcon.

Fairy terns have a circle of black feathers around their eyes, giving them a mild-mannered and lovable look. Usually they are. But threaten them and the charming terns become the original angry birds.

At Midway Atoll last year, I saw hundreds of white terns gang up on a peregrine falcon that got blown to the atoll. In a raucous mob high above the trees, the sweet-looking terns shrieked, pecked and dive-bombed the poor peregrine until it flew off. Having nowhere else to go, however, the little raptor later returned to the island, once again unleashing the fury of the white angels.

Although white terns are abundant in the Northwestern Hawaiian islands, in the main islands they breed only on Oahu. In 1971 the first pairs were seen in Kapiolani Park and Fort DeRussy. The birds continued to branch out in the 1980s, raising chicks in downtown Honolulu, Pearl City and Nuuanu Valley. In 2002 a researcher counted 500 breeding terns in the city and suburbs. (They don’t seem to like the countryside.) Today estimates of white terns on Oahu are around 1,600.

The cavorting that Robert describes could be mating displays or prospective parents looking for a place to raise a chick.

White terns make no nest whatsoever. The female lays her egg in the crook of a tree branch or on a bare rocky ledge. If the parents choose a site that holds their egg through incubation and hatching, and the chick balances there well enough to fledge, that family wins the natural selection award.

Robert sent two pictures of his birds in flight, confirming my guess that his swoopers are white terns. How lucky we are that the fairylike birds have chosen our island to enchant. You can find white terns at Kapiolani Park, Fort DeRussy, Iolani Palace, Thomas Square, Foster Botanical Garden and some Windward communities as the birds continue expanding their range.

Reproduction is laborious for certain marine worms

Published September 3, 2016 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2016 Susan Scott
web1_Ocean-Watch-green-paddle-worms

These palolo worm relatives are called green paddle worms, common in eastern and northern Australia. Green paddle worms keep their sex cells to themselves, each segment making and shedding its own gametes. ©2016 Susan Scott

Labor Day marks the unofficial end of summer, the beginning of school, the kickoff of the football season and, where I grew up, the last day of the year that it was acceptable to wear white (go figure).

Those associations with the holiday became secondary to me when I was 11 years old because my mother went into labor on Labor Day, turning our picnic into pandemonium and resulting in a baby brother. Since then Labor Day has symbolized the production of offspring.

In mammals, reproducing is pretty straightforward, but for some marine invertebrates, getting eggs and sperm hooked up is more complicated.

Take a type of bristle worm called palolo worm. (Fijians call them “mbalolo,” hence the common name, palolo.) Palolo worm bodies can have up to 1,000 segments, totaling 16 inches in length. Each segment has two feet, and each foot bears gills, meaning the worms breathe though their feet.

with-toes-for-scale

With toes for scale. ©2016 Susan Scott

Sensory tentacles around the worm’s head help it find tiny living animals to eat. But don’t look for palolo worms hunting during a morning or afternoon snorkel. The creatures hate bright light and come out of their coral rock homes only at night. If you’re in the right place at the right time, though, you might see these worms have sex.

Each year palolo worms grow from their tail ends tubelike sacks filled with eggs in females and sperm in males. In Fiji and Samoa, on the seventh night after the full moon that follows the autumnal equinox (Sept. 22 this year), the worms cast off their packages of precious cells.

The released sex packs have paddle feet on the sides. Light-sensitive eyes running along the midlines guide the paddlers toward the starlit surface. Once there, the gamete tubes twist and twirl until dawn. Sunlight causes the packets to burst open like a milkweed pod, releasing the eggs and sperm to do their job of making more worms.

At least 14 species of palolo worms live throughout the world’s warm oceans, including Hawaii. The sex cell sacks of our worms, however, don’t all rise in one day, but swim up throughout the summer. I’ve seen them under the nighttime dock lights in Kaunakakai Harbor.

Some residents in Fiji and Samoa consider the green gonads a delicacy. People wade out with nets to catch the wigglers near the surface before they explode, and then prepare an annual feast. Some Indonesians also collect and cook palolo worms’ procreative packets.

Because one way or another, moms and dads work their rear ends off for their young, my Labor Day thoughts are with parents. I hope your picnics are peaceful.