MOTUS Tower Provides a Whole New Look at Bird Migration

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Motus tower

Our MOTUS tower has been active for eight months now and I will admit to checking the data every day here.  Using radio towers to collect and distribute information is not new technology, but applying the methods to birds so we can learn more about where they go IS a relatively new approach. In this blog post (which includes our tower), Jen Tyrell of Audubon South Carolina describes the tower:

Radio telemetry uses radio signals and receivers to track birds. Small nanotag transmitters are temporarily attached to birds, bats, butterflies, or even dragonflies. These transmitters send out a signal a few times every minute that can be picked up by a receiver along the way, specifically a Motus tower. These towers have antennas that can pick up the signal from a tagged individual if they fly within a few kilometers of a tower. Staging these towers along migration routes creates a virtual net to capture the animals’ information. Imagine having check-points along migratory routes to see which path they’re taking. These towers connect to the internet and download tag ID numbers as they are detected in real-time, giving the researchers who deployed these tags the whereabouts of the bird as the individual migrates. The towers are the perfect blend of old and new technologies to make understanding the mysteries of migration more affordable, comprehensive, and collaborative with a wide range of hosts and partners deploying tags and hosting towers. The result is a better understanding of the full life cycles of imperiled migratory species in a cooperative scientific approach.

Migration has captured the imagination of naturalists and scientists for ages.   We have other means of studying them: we’ve been banding birds for a century (and Dewees participates in this occasionally, especially with painted buntings). But finding out information about a banded bird is largely contingent on recapturing the same bird.  Geolocators can also be placed on birds, but they also require the bird to be recaptured in order to read the data. Large migrations can be tracked on radar, but they don’t give us specifics about individual birds.

Recent applications of telemetry have given rise to some new ways to study this migration.  Here is an explanation of the whole system at (along with their infographic)

The Dewees Island Conservancy funded a tower, which we erected at the top of the landings building.   The “brains” of the tower are a machine called a sensorgnome, which records the data and sends it to the cloud network of researchers to compile the data.  Wildlife outfitted with nanotags fly within 15 km of the tower and register with a ping, so that the researchers can see where they go.  I think the most exciting part of all this is that it gives us the information to tell the story of an individual bird: where it winters and where it nests. Here are some interesting things we’ve learned thus far.

We’ve had a total of 40 different individuals with nanotags register on our tower.  Some of them have registered many times, others just send us a ping when they’ve passed by.  Of the 40 birds, 21, or just over half, were Red Knots, a species of concern that migrates from South America to Canada and back each year.  One of those birds stopped by on his way to Canada and then popped back in on the return journey. Another registered in Hampton Roads, Virginia on July 31, and here on August 1, flying 350 miles in a single day.

Including the Red Knots, we’ve had a total of 13 species register on our towers: Ruddy Turnstone, Semi-palmated Plover, Short-billed Dowitcher, Piping Plover, Common Nighthawk, Sora, American Kestrel, Clapper Rail, Chimney Swift, Common Tern, and a Rusty Blackbird.  The last one is pretty exciting~ it’s not a bird I’ve ever seen here. And now I know to get out there and look. One day I spotted a Kestrel outside my office window~ the next day one showed up in the data!

We have common nighthawks here, but when I started crunching the numbers on this guy, I was amazed.  A Common Nighthawk was first tagged in Canada in the fall of 2018.  In the fall, it left Canada and came past Maryland, and then FLEW to Central America~ 2052 miles over four days.  He spent the winter in the tropics and returned to the same towers for most of the summer, and when it flew south again, it came past Dewees.  I actually check his data every day to see if he registers on the same towers in Central America, but so far I’ve lost sight of the bird… or the transmitter battery died after the 18 months it’s been recording.  Carl Miller captured this photo of a nighthawk one summer on Dewees… It’s such fun to imagine where it might be right now.

I’m really excited about all the applications to understand more about where birds go, how they don’t really understand borders, and the dangers they face, as well as the incredible journeys they perform.  And each day, the network of towers grows~ we are now finding individuals that register both here and the Fort Moultrie tower. If the batteries last through the winter, it will be so interesting so see when they return.

Want to help?  Feel free to donate to the Dewees Island Conservancy.  Maybe we can fund some nanotags for nesting buntings or other migratory species.  Each nanotag is about $200.  And feel free to ask me about this any time… I get so excited!

Birds and Birding


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pelicansSometimes I think Pelicans are the clowns of the bird world, and sometimes I am awed by their grace. The bird featured below caught a huge red drum, and I wasn’t at all confident he was going to be able to eat it!

The pelican we are most likely to see on Dewees is the Eastern Brown Pelican. (Although we have seen White Pelicans on nearby Capers Island). It is the only pelican that feeds by plunge diving, and they can drop from great heights. According to Birdscope at the Cornell Lab of Ornithology, Pelicans have several adaptations to diving, including air sacs beneath the skin on their breast that serve as cushions and floats. While diving, they also rotate their body to the left, probably to avoid injury to their trachea and esophagus, which are on the right side of neck.

The eastern brown pelican was listed as an endangered species in 1970, when their population plummeted to less than 100. Widespread use of pesticides such as DDT caused thinning of eggshells, which subsequently broke during incubation. The United States ban on DDT in 1972 and similar pesticides spurred the pelican’s recovery to much of its former range. The implementation of the Brown Pelican Recovery Plan of 1979 also contributed to the restoration of brown pelican populations. (SCDNR) Now they’ve had such a spectacular comeback that they’ve become a symbol of wildlife conservation, and they’ve been delisted from the endangered species list.

The pelicans we see on the island probably nested at nearby Crab Bankpelicans, with large colonies of other pelicans and other colonial nesters, like terns and black skimmers.

They are strong swimmers, with webbing between all four toes. Their colors are brighter in breeding season, when they have one monogamous partner for the whole of the breeding season. Juveniles are brown with a white belly, and it takes three years for them to change to adult plumage.

In addition to plunging, they can also seize food from the surface of the water. Pelicans have a gular pouch that helps them catch food, and a hook on the upper mandible to help hold slippery fish. I came across this explanation for how it works at a website called How Stuff Works:

Another unique feature is the hook at the tip of the pelican’s upper mandible (the top half of its bill), which helps grab onto particularly slippery or wiggly fish. After locating and scooping up its prey, the pelican opens its bill and slowly contracts its pouch to empty out the water and keep the fish inside. Then, with a jerk of the bird’s head, the fish slides down the ­hatch. If a fish is particularly large, the pelican might manipulate it so that the fish goes down head first, which helps keep it from getting stuck. A pelican can’t eat or fly away if its pouch is still full of water, so the draining process is very important. By bending its neck, it can even turn its pouch inside out.

They can also soar right above the surface of the water, using the slight updrafts from the wave troughs in a process called dynamic soaring. This allows them to save energy as they fly.

This juvenile clown was fishing from slightly above the surface in Chapel Pond.
when he caught a fish that must have been bigger than he expected:pelican
and even though he tried to keep it to himself,
his friends swooped in and clamped down on his beakpelican
After shaking them off, he retreated to a spot where he could regroup

and try to wash the fish down with water.
and he finally moves on after somehow washing the fish down.

Here is a related post about releasing a Pelican after rehabilitation.

At a workshop at the South Carolina Aquarium, I told the story of watching this pelican, and wondering if the pouch could withstand all that action. The bird rehabilitation specialists told me that the bird was lucky– if he (or one of his exuberant friends) had punctured the gular pouch, there is almost nothing that can be done for them– sutures won’t hold, and trying to repair a tear actually makes the situation worse. Most birds with gular pouch punctures have to be euthanized. So I was glad to see this guy finally move along!

Birds and Birding

Some Books to think about giving for the Holidays

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Last weekend, when the Pro-Birder conference took place on Dewees, I was delighted to receive a gift from Instructor Drew Lanham. I had been admiring this field guide all day, because it is entirely photographic, and does a lot to show birds from a variety of angles in a variety of settings. The Crossley field guide to Eastern Birds is a great new sort of reference book. The photographer/author uses lots of pictures of each species, photoshopped against a natural habitat, to give you a clear picture of each bird.


Another fascinating field guide, this time about butterflies, was introduced to me by Lori Sheridan Wilson, island ecologist. Butterflies through Binoculars has more than just identification tips: it shows you what the host plants are for different butterflies, and explains when and where you are likely to find them.

And the third great find is Living Beaches of the Carolinas. This book has a treasure trove of information about the creatures you are likely to find in our tidepools. It’s a great reference for anyone who loves beachcombing and wonders about the shells and animals you find there!

Birds and Birding

18 Spoonbills!

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An occasional Roseate Spoonbill visit to the island is not a new thing; Ed Conradi recorded one in 1996. My first sighting was in 2005, and there have been one or two occasionally, and one year we spied 13. But every year it seems the numbers are bigger, and yesterday we counted 18 at my favorite birding corner. One observer driving by wondered if those pink birds were flamingoes, and with those big numbers and the characteristic pink color, I can see how they might guess that.

Roseate Spoonbill (Platalea Ajaja) adults and juveniles can look markedly different. In the past, we have seen almost exclusively juveniles– pale pink in color with darker pink wings, and some of which are almost white. Second year juveniles get a little darker, and adults have a bald greenish head and a much darker pink color. Their distinctive bill looks a bit like an ophthalmologist’s diopter, and they have a characteristic feeding behavior of sweeping their bills back and forth. They are tactile, feeding by a combination of sight and feel. They are social, and feed and nest both in groups and solitarily.

These probably nest in the Florida Bay, and disperse northward after hatching in search of food. They share rookeries with other birds and may have ranged this far north before the egret trade for hats damaged many of of those rookeries in the last century. The ones we watched yesterday were preening and bathing, with an occasional break to grab a snack. You can spend a minute with them in this quick video, and also get occasional glimpses of Reddish Egrets feeding, Laughing Gulls, and some shorebirds. Feel free to comment with shorebird ID’s– it’s a little bird quiz.

More on Spoonbills:

Birds and Birding

Killdeer with chicks: Video

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One shorebird that nests on Dewees Island and all over the lowcountry is the Killdeer.  Charadrius vociferus. It is a larger ringed plover, and on Dewees, they nest on grassy areas (the helicopter landing pad, the Moser’s yard) as well as in the dunes. The nest is just a shallow scrape in the sandy soil.

Killdeer get their name from their loud, persistent call. Adults can fake a broken wing to lure predators away from their nests.

The Killdeer is by far the most wide-spread and familiar of North American plovers because of the habitats it frequents, its tolerance of humans, its easily observed and often anthropomorphized parental care, and its killdeer vocalizations. Earlier common names, such as Chattering Plover (Catesby 1731) and Noisy Plover (Latham 1785), described the very vocal nature of this species. Once the target of market hunters and in serious decline, the Killdeer is probably more common today than at any time in its history as a result of habitat changes wrought by humans. At the same time, the species is vulnerable to twentieth-century problems such as pesticides, oil pollution, lawnmowers, and automobiles. (Birds of North America).

They eat earthworms, grasshoppers, beetles, and snails. Ginny saw this one nesting in her yard in late March. Like many other ground nesting birds, the Killdeer can stay very still and blend in with the surroundings.

When approached, she flares her tail, but does not try to lure us away from the nest on this day; perhaps she is already hiding chicks:

We were surprised to find the mother gone from the nest, but because they are so noisy, we were able to locate her on the other side of the yard. The chicks really blend in with their surroundings, and the easiest way to see them is to watch carefully for movement:

I was able to set up my tripod and grab some video footage, because the bobbing gait of these little guys is really fun to watch. Island buddy Walter Mashman provided the great music. You can even watch as one tucks under his mother’s wing! The video should autoplay below, but if you can’t see it, click this link.

Birds and Birding

Winter Birding brings different species

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Our winter birds are back, providing birders with new glimpses of birds we haven’t seen since last winter. While on the ferry, watch for loons feeding and diving in the waterway. Loons have a similar silhouette to cormorants– they sit low in the water, but they have a sharper beak and white underparts.
Another similar bird that fished the water near the dock is a Horned Grebe. We have also seen them at the north end of the island, fishing the surf. They sit much higher in the water and have a much shorter bill than a loon does.
Also on the ferry, look for American Oystercatchers, especially at high tide. We have a great population of these every winter, and it is fun to see them fly in large flocks on the shell islands that flank the waterway.
Winter ducks are returning: Hooded Mergansers, and Bufflehead have both been seen in the impoundment, and we are keeping watch for American Coot, Scaup, Teal, Widgeons, and Gadwall; all of which have been part of our winter counts before.

Birds and Birding

This is a great time to see migrating birds: especially Redstarts

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It is spectacular on the island at this time of year!  The wax myrtles along the roads are covered with tiny, flitting warblers on their way south, and it’s well worth the time to just park your cart and get out the binoculars:  you never know what you are going to find.  Yesterday’s bird count yielded yellow warblers, returning pied billed grebes, migrating cliff swallows, and a brief glimpse of a Merlin.

I noticed a female redstart feeding through the window last week, and was surprised to see a flock of 5 or so of them out near six pipes.  I checked and double checked, because I only saw females and juveniles… no males!  (and I wanted to be sure I had the id correct!)  It turns out that males have also been seen all over the island.  The talk at coffee this week was of how many redstarts people have been seeing. This is a quick moving bird, and I wasn’t lucky enough to get a shot of them, so I asked our friends Carl and Cathy Miller (Technical advisors, bloggers of Pluff Mud Perspectives, and photograpers) if they had gotten any pics lately.  They sent me these, and you can clearly see the differences between males and females.  According to the Cornell Lab of Ornithology:

  • A young male American Redstart resembles a female in plumage until its second fall. Males in the gray and yellow yearling plumage will try to hold territories and attract mates, singing vigorously. Some succeed in breeding in this plumage, but most do not breed successfully until they are two years old.
  • The male American Redstart occasionally is polygynous, having two mates at the same time. Unlike many other polygynous species of birds that have two females nesting in the same territory, the redstart holds two separate territories up to 500 m (1,640 ft) apart. The male starts to attract a second female after the first has completed her clutch and is incubating the eggs.

They are on their way to winter in the tropics, foraging for small insects and fruits on their way.  Cathy saw a female fly off a nest in the mountains and took a photo of it:  nests are a tight cup, about 5-10 feet up, in the fork of a sapling. Grasses and twigs are tightly bound with spider silk and decorated with lichens.  They don’t nest here, but I loved the photo.

They flash wings and tails to show the yellow plumage, presumably to attract insects.  This week, they have been seen on every road on the island, foraging at the edges.


If you’d like to read more about this bird, there is an interesting article from the Smithsonian’s Migratory Bird Center.  In the tropics it is known as “The Christmas Bird” because that’s when it arrives for the winter, OR as “the latrine bird,” for its tendency to hang around latrines and garbage dumps in search of flies. The article also has details of how males (who help with feeding young) manage to maintain two separate mates, nests, and territories.


All photos courtesy of Cathy and Carl Miller.

Featured Creature

Spring Full Moons, Horseshoe Crabs, and Migratory birds

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Talented Island Photographer Bubber McAlhany sent this photo today, of two crabs embedded in sand.

During the week this week, there was a full moon, with high tide falling right at dusk. The full moons in April, May, and June are spawning times for Horseshoe crabs, Limulus polyphemus. For millenia, these prehistoric arachnids have been coming ashore to lay eggs on a full moon tide. The eggs are buried in the sand, and within them, the crab molts 4-5 times in the next two weeks. Two weeks later, the new moon again creates an above average tide, and the tiny crabs hatch out and take residence in the sea. Turtle watchers and beachcombers are encouraged to interfere with crabs that appear stranded ONLY if they are flipped upside down. (The information campaign encourages you to “just flip ’em,” turning them over and pointing them to the sea.) If, for some reason, they do not have a telsun (tail) strong enough to flip themselves over, you can help them out.

If you look up some evening and the moon is full, think about an ancient creature stirring on the ocean floor or a small bird flying through the night.  (PBS special, A Tale of Two Species)

Horseshoe crabs provide slow moving real estate for other organisms, like this slipper limpet.
Horseshoe crabs provide slow moving real estate for other organisms, like this slipper limpet.

Horseshoe crab eggs are a really important source of food for some migratory predators, like the red knot, a tiny shorebird that winters in Chile and nests in the arctic. Birds time their stopover resting in places where horseshoe crabs are spawning. (We saw a few red knots in Copahee sound over mother’s day weekend, and you can see ruddy turnstones flipping over the sand in search of eggs on many area beaches.) My Master Naturalist class took a trip to the ACE basin last week, and found out that there is a migrating population of red knots that has been banded there, who were NOT recaptured in Delaware Bay. This would mean that rather than hopscotching their way up the coast, red knots fly thousands of miles with very few stopovers. Which makes the time they spend here and in the ACE Basin even more important to the survival of the species.

Here is a link to a very interesting video on PBS
about red knots and horseshoe crabs… from the way we harvest and test horseshoe crab blood right here in Charleston, to the people who tag red knots on their journey, to the massive impact each species has on the survival of the other, it is a comprehensive look at a whole ecosystem. I enjoyed the video, and highly recommend it.

Here’s a link to a post about Horseshoe crabs and a lecture by intern Erica a few years back.


It’s Hawk Migration Season: Here’s a Beautiful Hawk with a Tricky ID

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it was the tail that gave the hawk away

The other day I was zooming along Old House Lane on my golf cart, and I caught this unusual silhouette in the pine tree overlooking the impoundment.  Whirling around for a second look, I spied a juvenile hawk. The stripes on the tail pointed to either a Cooper’s Hawk or a Sharpshinned Hawk.

Both Cooper’s Hawks and Sharpshinned Hawks prey on songbirds, and have been known to hang around bird feeders regularly.

I snapped a bunch of photos for later identification– I can usually tell them apart if they are flying– in my experience, Sharpshinned hawks tend to careen wildly, flapping quickly, while Cooper’s are more focused with fewer flaps.  The Sharpshinned is generally smaller than a Cooper’s, but the male Cooper’s and the female Sharpshinned are about the same size.

note the rounded feathers on the tail

Still unsure, I sent the pictures to our friend Cathy Miller, a birding volunteer on the island and (the one who shot these great photos of dolphins strand-feeding).  Cathy and Carl often volunteer to count Hawks during migration season.  They head to Caesar’s Head state park each fall.  She says,

Carl and I are headed to Caesars Head to participate in the Hawk Watch.  We hope this weekend will be a peak time for the Broad-wings!  Yesterday they got 1114!  Here’s a video from a couple of years ago on the count and the website which gives the daily count numbers.

She also sent me this fabulous site from Project Feederwatch, which has wonderful details on sorting out these two similar accipiters.  Based on the site (and Cathy’s help), I am pretty sure that this is a juvenile Cooper’s Hawk, probably male due to the size.  The neck is fairly tall, the tail feathers are rounded, the streaks on the chest  fade to white at the lower belly.

Juvenile Cooper's Hawk

Interestingly, Project Feederwatch states that fewer of these Hawks seem to be migrating each year,

FeederWatch data shows that accipiters, especially Cooper’s Hawks, are becoming more common around feeder areas. Other researchers have found that fewer Sharp-shinned and Cooper’s hawks are migrating based on lower counts at various hawk watches. It appears that fewer of these hawks are migrating, which could be related to climate change or because they have learned that they can survive year round if they find a good feeder area to patrol. See trend graphs for the Sharp-shinned Hawk and the Cooper’s Hawk, which show the changes reported by FeederWatchers over time. If you have not participated in Project FeederWatch, join today and report the birds that visit your feeders in winter.

Additional info (July 2016). I came across some notes from a raptor class I took, and here are some more ways to tell:
On the Cooper’s Hawk, the leading edge of the wing is straighter, whereas it’s curved on the sharpshin, with the wing hunching forward more.
The Cooper’s has more of a crested head, and relatively longer tail. The short wings let them zip through the woods. The Sharpshin


The Anhinga

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The female's mouth is red or pinkThe Anhinga, Meleagris gallapavo, (literally “water turkey” because of its feathers) is also known as the snake bird.  It is generally found in fresh water, and needs fresh water for nesting.  They inhabit shallow wetlands, and can be seen in the water or on overhanging branches. In order to be more hydrodynamic, they have dense bones and plumage that doesn’t store air (like goosedown does).

Unlike most diving birds, the feathers can get completely wet while they are under water.  They therefore lose a lot of body heat while swimming, which they make up for by soaking in the sun’s warmth for thermal regulation.  Anhingas are equipped with very strong neck vertebrae, which they use for stabbing prey (spearing) and then tossing it strongly enough to release it off the bill and catch it in their mouths.  They can fly long distances without flapping their wings, soaring the way a vulture might.  In the sky, you’ll see them flying with their necks outstretched in a sort of cross shape.

When you see an anhinga swimming in the water, you will only see the top of the head and neck

aka: snakebird

— (usually you will see the top of the back on a cormorant.) If you go to the Huyler House area behind the oyster shed, you will find a small log with a tiny tree on it.  The anhinga commonly found at this site may growl and bob his head at you to tell you to go away.  Here’s a video of an anhinga at Huyler House pond.

Anhingas may need more fresh water for nesting, because we have not identified a nesting pair on the island.  They do, however nest at nearby Magnolia Plantation in the spring.  I went there for a field trip in May, and was delighted to see large fluffy babies in nests leaning out over the pond.

Anhinga nesting colony with chicks, Magnolia Plantation
when an anhinga swims, most of it is underwater