More Birding on the Dry Tortugas

The Dry Tortugas have a reputation for superb spring birding. In addition to the nesting colonies of tropical seabirds which I wrote about last week, these tiny spots of land in the Gulf of Mexico are a resting place for migrating birds.

Eventually I tore my gaze from the clouds of Sooty Terns over Bush Key, the perching Brown Noddies, and the whisper-like flight of the Magnificent Frigatebirds, and began exploring other parts of Garden Key and Fort Jefferson.

On the pilings of the old pier, Royal Terns perched regally, along with several Black-bellied Plovers, most still coming into the breeding plumage which gives them their name. A single Whimbrel briefly showed its long, down-curved bill before tucking it beneath a wing and dozing off in the warm mid-day sun. On the sandy shore, a pair of Ruddy Turnstones, like the plovers not yet into their variegated breeding plumage, turned over stones and seaweed in search of food. A single Spotted Sandpiper flew from the beach where a pair of Brown Pelicans were preening. A Sandwich Tern alighted briefly near the pelicans.

I turned from my vantage point and began walking through the campground. A woman came from around the copse of trees. “Did you see the owl?” she asked with quiet excitement. “It went this way.”

I fell in step beside her. A few yards on, we paused. Perched in the grass was a Short-eared Owl, the West Indian race of this wide-spread species that I have now seen from Massachusetts to the Hawaiian Islands to a remote speck of Florida. This time, however, I could clearly see the short feather tufts which are mis-named “ears,” and which give the owl its name. After a few minutes, it became tired of being stared at and flew off around the walls of the fort.

Inside the walls of Fort Jefferson, the old parade ground is now a grassy expanse with a scattering of trees and shrubs and the reputation for being a spring-time birding hotspot. Most of the visitors to the National Park missed this quiet attraction. There had been no strong weather fronts so there was no songbird fall-out with birds dripping from trees. As the majority of visitors wandered about the old gun emplacements and strolled the top of the fortress walls, they probably wondered about the couple dozen people skulking about with binoculars and spy glasses on tripods or stretched lazily on the grass staring at a tree.

When I first walked into the parade ground, two things caught my attention. Cattle Egrets stalked through the grass. Accustomed to following cattle and eating the insects which the hooves stir up, these long-legged waders were wading the short grass in search of scarce insects. There are few insects on the keys of the Dry Tortugas, and the Cattle Egrets which stop at Fort Jefferson find such slim sustenance that they sometimes take to chasing, and taking, songbirds instead. These Cattle Egrets stayed in the grass, were wary whenever someone began approaching them, and occasionally found something to eat. At least, I did not see them pursing songbirds. They were in breeding plumage with rusty orange patches on the head, back, and neck. Immigrants from Africa to the Western Hemisphere in the late 1800s, they are now widespread in North America and expanding in other parts of the world.

The Cattle Egrets were not stalking songbirds, but songbirds and shorebirds were not free of danger. A dark, fast moving, pointed wing silhouette swept over the walls, circled the parade ground rapidly, and landed on the top of a tree. At the Putney Mountain hawk watch a dark, fast moving, here-and-gone hawk which prompts a “What was that?” reflex ... is a Merlin. On the top a tree in the middle of the Fort Jefferson parade ground, I focused my scope on a Merlin, perched erect and alert. For the next couple of hours this small falcon flew about the fortress walls and returned to perch. It was an adult male, an experienced hunter, and sooner or later he would return with food in his talons.

The same pattern with intervals of hunting and rest was followed by the Short-eared Owl, which used a tree on the other side of the parade ground as its operational base. This past winter, I watched a Short-eared Owl on Plum Island as it defined, on its own, a day of good birding. The owl and the Merlin would have easily made this day at Dry Tortugas National Park a day of good birding. But remember, they came after the hordes of Sooty Terns, the perching Brown Noddies, and the whisper-like flight of the Magnificent Frigatebirds had already defined the day as a good birding day.

The birding wasn’t over, but it did mellow down. I was finally able to turn my attention to the trees and shrubs harboring the songbirds. The numbers and variety were not great, but each different species was something of a surprise, a discovery, often a welcome anticipation what would be awaiting me when I returned to Vermont: Black-and-white and Yellow-rumped Warblers, Northern Parula, Ruby-throated Hummingbird, Eastern Kingbird.

In our northern climes, we don’t pay much attention to doves or pigeons. They are all Mourning Doves or Rock Pigeons. But in southern Florida there are at least three other doves and pigeons, plus tropical vagrants that might show up at any time. The dove atop a tree in the parade ground warranted a closer look, and gave me my first White-winged Dove since my last visit near a southern border.

As the sun climbed high and the day wore on, I adopted a different birding tactic. Instead of wandering around looking for birds, I found a shady spot beneath a tree with a good view of the bird fountain. I sat and let the birds come to me. It is an effective tactic, maybe more effective than barging about and disturbing the birds.

It worked. A Black-and-white Warbler foraged along a tree branch in its upside-down, nuthatch-like manner. A Palm Warbler wagged his tail in Palm Warbler fashion, causing me to mentally reminisce about the tail-wagging Eastern Phoebe which had begun singing outside my bedroom window just before I left for Florida.

Blackpolls came close. I know them as denizens of the high elevation spruce forests, one of the last migrants to pass through the Connecticut River valley where I usually do my birding. Here they were on a tropical island a few feet above sea level. I had to look twice to be sure I was identifying them correctly.

Seabirds, shorebirds, songbirds, raptors - all capped off with a period of lazy semi-somnolent birding - the Dry Tortugas provided a day of excellent spring birding.

The Short-eared Owl Show

I attended a Short-eared Owl show. I was told that the show began in the early morning, but I did not join the show until two in the afternoon. I watched it until sunset.

When I pulled into the parking area, four people were staring across the barren salt marsh. Short-eared Owl, they told me. Across the ice and snow and broken grasses of the marsh, I saw a dark anomaly. With binoculars I saw the owl’s flat round facial disk. It was still there when I set up my scope and brought it closer with the long lens. It was eating. Then it took flight. In its beak it carried something limp and gray, probably a vole.

The flight was short and when it landed, it resumed its meal. The final remains of its prey disappeared in a single gulp. Then it flew to a stake and perched. From there it surveyed the lifeless looking marsh. Soon it would hunt again.

I wandered slowly, back and forth, along a mile and a half of the Parker River refuge road on Plum Island. Three Short-eared Owls were active along this short stretch. They provided a textbook study of this particular owl, and of life in a winter salt-marsh.

The winter salt-marsh never ceases to amaze me. It is a stark, forbidding landscape. The ponds are frozen. The tidal channels are rimmed with jagged chunks of ice. The reeds and grasses are battered, broken, flattened. Nothing breaks the wind as it sweeps across the open marsh, and the wind, laden with ocean moisture, penetrates. The heavy dampness chills. The winter salt-marsh is not a welcoming place. Forbidding is an appropriate adjective.

And yet ... there is life that goes on about the business of earning its living. In the tidal channels, Red-breasted and Hooded Mergansers dove. The drakes displayed for the hens. Gulls were in constant movement; often one could be seen dropping a mussel, using the hard ice to crack open the shell. Black ducks and geese grazed among the grasses. Robins went from berry bush to berry bush, feeding on the fermented fruit. A mockingbird, his mimicking song still silenced by winter, eyed me with interest and curiosity.

I could easily understand where these birds were finding their food, although I wondered why they might not find a more temperate place to winter.

But consider the birds of prey. In addition to the three Short-eared Owls, I saw at least six Northern Harriers hunting over the marshes and dunes. Somewhere in the large expanse of the refuge, there were wintering Rough-legged and Red-tailed Hawks and at least one Snowy Owl. I did not see them, but there were almost daily reports of their presence. Small rodents make up most of the winter diet of these predators. These raptors may be adapted and accustomed to frigid conditions, but their survival still requires many calories every day. Each of these predators must hunt successfully several times each day.

The owls I watched were consistently successful. The Short-eared Owl is a bird of open spaces - tundra, marshes, grasslands. It is also the owl most likely to be seen hunting in daylight. Owls rely heavily on sound to find their prey. The circular facial disc of the Short-eared Owl acts like a dish receiver, capturing sound and funneling it to the ears. The ear openings are asymmetrical, allowing the owl to triangulate sound and locate its prey. The “short ears” of the Short-eared Owl are not ears, but small feather tufts which are not usually visible.

During the afternoon I watched the Short-eared Owl show. I saw it perch on the ground, camouflaged among the marsh grasses until suddenly it spread its wings for a short flight, landing on prey. Other times it perched on a stake, quite prominent on its elevated position. Its head turned one way, and the other. Then it was still, focused; it took flight - a short flight - landing on prey hidden beneath the snow and matted grasses.

More commonly the Short-eared Owls hunted in flight, climbing and descending, floating nimbly over the marsh. At times they resembled the Northern Harrier , their wings held in a droopy dihedral, but quicker than the harrier. The harrier is a somewhat owl-like hawk with a facial disk to help it hunt by sound; in flight the harrier long and rangy. By contrast, the Short-eared Owl looks like a blunt battering ram, or as Pete Dunne puts it: “a pale beer keg on wings.”

The owls and the harriers did not share the air space willingly. There were frequent aerial dogfights between the Short-eared Owl and the Northern Harrier. Sometimes it looked to me as though the owl was the aggressor, as though it was protecting its exclusive hunting preserve. Other times the harrier made the first aggressive maneuver.

The owl, flying above the harrier, dove and swirled. The harrier rolled on its back, talons up as though protecting itself. But such aerial maneuvers are quick and the purpose not always apparent. I spoke with a photographer who had been watching and photographing the birds all day. He showed me an image where the harrier had rolled in flight onto its back. Visible also was the vole which the harrier had dislodged from the owl’s talons. He described the harrier following the vole to the ground, grabbing it, and flying off. One predator had stolen from another. It is no wonder that predators are often aggressive toward one another.

Hawks usually sit in the open and consume their prey slowly. Owls, on the other hand, try to avoid thieving competitors by swallowing their prey whole. Their digestive system then compacts the indigestible materials (fur and bones) into a pellet. An owl ejects one or two pellets each day. Beneath an owl’s favorite roosting spot there may be a pile of pellets. These pellets have been used by biologists to study diet and foraging patterns.

Like all predators, the Short-eared Owl will take what is available, and this may include a variety of small birds. But its distinct preference is for small mammals. Generally non-migratory, they nevertheless wander, usually in winter, to where the food sources are. When rodent populations explode, the Short-eared Owls somehow get the message and congregate. They have been credited with preventing significant agricultural losses from rodents.

Short-eared Owls are found on every continent except Australia. They have even found their way to the most remote islands on the planet, the Hawaiian Islands, where “Pueo” was worshiped as a god and guardian spirit. On a couple of occasions, I saw a Short-eared Owl hunting on the grassy slopes near the summit of Haleakala on Maui.

It is a curiosity to me that the diurnal raptors, the day-hunting hawks, eagles, and falcons, are often elusive and difficult to study. I see lots of hawks during the Fall migration on Putney mountain, but most are here-and-gone observations. On the other hand, the nocturnal owls have provided a number of extended and rewarding occasions. One of these was the show put on by three Short-eared Owls. They hunted from the ground, a perch, or in the air. They competed with harriers. They swallowed their prey in a single gulp.

The owls reminded me that the winter marsh may appear cold and lifeless. But it is alive with the struggles for survival - with the rhythm of death and of life. At fading light, I was cold, yet conscious that sometimes harsh conditions are necessary for good birding.