Bathing With Frigatebirds

I am going to speak my mind, because I have nothing to lose – S.I. Hayakawa

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A dry adult male Magificent Frigatebird before the bathing regimen begins.


Frigatebirds have, as far as I can tell, a unique method of bathing. Before we delve into their personal habits, a brief introduction would be appropriate. Frigatebirds consist of five species of tropical/subtropical seabirds in the genus Fregata that are close relatives of pelicans and boobies. All five species are imbued with an aura of speed and power. Indeed, these attributes inspired their English name as well as their Latin name (Fregata). These birds reminded Linnaeus and his crowd of the dreaded era-of-sail warship, the frigate. Like their naval namesake, Frigatebirds are not petite. The wingspan of the aptly named Magnificent Frigatebird, North America’s predominant species, is more than seven feet (88 inches on average). Despite their size, frigatebirds manage to embody aerodynamic elegance: Those long, narrow, angular wings are attached to a slim bullet-shaped body and deeply forked tail. Befitting this gracile build is a lengthy and relatively thin bill. The business end of that beak, however, looks (and is) lethal, rather like a grappling hook. Indeed, it is used in this manner to snatch fish from the water. 

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As seen in these three images, even getting a drink poses a challenge for a frigatebird.


Frigatebirds, for all of their magnificence, have a problem. They are rather large birds with narrow wings and itsy-bitsy feet. Thus they cannot leap into the air like a pelican or run along the water/ground like a swan. A frigatebird on the water or the beach is a frigatebird that will never fly again,  thus bathing is a challenge. Landing in the water and shimmying about, spreading droplets hither and yon amongst your plumage like a joyful gull is not an option. Well, it is an option, but for a frigatebird, it is the final option, the last bath. When they do land, it is on trees, cliff edges, or since the advent of sailing, masts.

To solve this challenge, frigatebirds use their strength, speed, and maneuverability. Watching frigatebirds bathing is one of the World’s most unappreciated wonders, comparable with breaching whales and leaping manta-rays. I have had the pleasure of enjoying this spectacle a number of times, often in solitude and amid peaceful surroundings, giving the experience even more luster. Typically, a small group of frigates will approach in leisurely fashion, soaring in lazy circles over some lagoon or large freshwater pond (which, amazingly, includes sewage ponds) near saltwater. They come in as if they have nothing particular in mind. “Don’t mind us, we’re just enjoying some especially nice updrafts in the neighborhood.” My guess is that this initial period is one of inspection, during which the frigates are assessing the safety of their chosen bathtub. Then, one or two will suddenly fold their wings and tail and angle sharply downwards towards the water, the change in direction and action is so abrupt as to startle. The stoop earthwards is not dissimilar to that of a diving Peregrine, and likewise the frigate accelerates with an amazing burst of speed. A few feet above the water, this downward bullet abruptly flares its wings, translating much of the downward speed into horizontal velocity, paralleling the water’s surface, with the bird now flashing along a foot or so above the agua infirma. Before too much of this momentum is stolen by drag, the frigate bounces itself once or twice across the water’s surface, and after splashing satisfactorily, labors to become airborne once again. This is done with great effort and a certain air of desperation. As one frigatebird is taking back to the air, another is typically impacting the water. 

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The Dive

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Wings open up as the vertical dive transitions to a horizontal approach towards the water's surface.

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The final approach.

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Splashdown and recovery.

Once safely airborne, the now semi-waterlogged bather shakes itself grandly. Frigatebirds shed excess water much like a Labrador retriever after a good swim. It all starts with a slight sideways movement of the head, the side-to-side wave gaining amplitude as it travels tailward, resulting in a substantial shimmy of the body followed by a vigorous wag of the tail. The process is often repeated several times. The difference between a Lab and a frigatebird drying itself is that the frigatebird rarely sprays nearby humans with water of dubious origin, and of course, the frigatebirds are shaking and rattling in mid-air, suspended like a marionette during the process. It is nearly impossible to impart the wonderment of watching this simple maneuver with mere words.

Drying Off:  The Shimmy and Tail Waggle 

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Indeed, I was once so inspired that I wantonly shed my clothes and waded enthusiastically into the reservoir, blissfully ignorant of my legs sinking nearly knee-deep into oozing muck. After a bit of splashing around in the cool smelly waters, I struggled back to shore, trying to maintain my momentum and avoid becoming immobilized by mud – much like a frigate trying to gain altitude after its dip. Finally, upon reaching terra firma, I attempted to dry off with a good shake but only managed to hurt my back and achieve an unpleasant sense of vertigo while panicking the nearby stilts and avocets. Just kidding. Or …

The impact of witnessing these huge birds maneuver so skillfully while traveling at great speeds is beyond my skill as an author. However, some of the birds’ beautiful lines, and the humor of the dunk-and-wag, are not beyond the capabilities of my camera. For these, see the five images above of an adult female Magnificent Frigatebird shaking herself dry. All photos were taken on a glorious afternoon in March 2009 at “El Tanque,” a reservoir that is part of the wastewater system of La Paz, Baja California Sur, Mexico.

All photos taken by Steven Mlodinow using a Nikon D300 with a 400mm lens and a 1.4 teleconverter.

1

Neat photos and story. I would take issue with the description of high wing-loading. In fact frigatebirds have very low wing-loading which I believe is the weight divided by the wing area. A frigatebird has a wing span of about 8 feet but a weight of only about four lbs. Compare that to a White Pelican with a similar wing span but a weight of 30 lbs. Frigatebirds are particularly agile fliers precisely because of their low wing loading.

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Very cool. Agreed with Mr. Morlan, though that frigatebirds have the lightest avian wing loading.

3

Greetings All

I guess I was incorrect about wing-loading. To define terms: Wing-loading is body weight divided by wing area. Wing-aspect is wing area divided by wing span. Using the weights and wingspans in Sibley’s book and some photos, I arrive at a wing-load for frigatebirds that is about half that of either Brown or Am White Pelicans. So, the trouble that frigates have in taking off must be mostly due to their small feet.

As to maneuverability, this is probably best related to the wing aspect ratio, which is wing-span squared divided by wing area. Birds with long, narrow wings will tend to have the highest aspect ration, and most of our most maneuverable birds (jaegers, terns, Peregrines) have long narrow wings. My best estimate shows frigatebirds with an aspect ratio about 50% greater than that of a pelican. For those interested (per Newton’s Migration Ecology of Birds), the highest wing aspect-ratio is in albatrosses (>20) and the lowest is in grouse (~5).

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We appreciate the comments posted by Joe Morlan and Jim Gilbert, which correctly pointed out that Magnificent Frigatebirds do not have a heavy wing-load. This article has been modified in light of their comments, which now appear to be out of context. We want to make it clear to those who are just seeing this piece for the first time, that their comments made perfect sense when they wrote them even though they reference terminology that no longer appears in the article.

One of the real upsides to this medium (compared to the printed page) is that we can readily correct errors or statements that are written in a way that might mislead the reader.

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