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This is the last chapter of our story about a great egret that we gave a GPS tracking device on the Outer Banks of North Carolina in spring 2013 (see photo). We followed his movements for about 8 months and reconstructed his story with his GPS and ACC data (see parts I, II, III and IV).
This was the first time that an egret’s migration has been recorded in such detail and, as you could see through this blog, we learned some quite amazing things about this bird.
Mr. Bisbing had spent his summer within the Outer Banks, breeding and raising chicks with a mate, then taking it easy in the wetlands south of Roanoke Island. As the days became shorter toward the end of September, he started becoming unsettled, and on October 24th he took off, flying south over the open ocean. He migrated all the way down to Colombia, stopping for a few days in the Bahamas, Cuba, and Jamaica.
Finally, when Mr. Bisbing arrived in Cesar Province, Colombia, our data show that he started foraging in the same routine manner detected while he was in North Carolina (Fig. 1).
Suddenly, on Dec. 8th his movements stopped. His tag was still sending data, so it must have been in a sunny location to keep powering the solar panel of our tag. It took us a few days to realize that the tag had completely stopped moving, and that Mr. Bisbing had probably died, or possibly dropped the harness off his back.
Our next challenge was to go to the site to see if there was a dead bird, and recover the tag, so that we could download the detailed data (the daily text messages from the tag to us just sent us a subset of the data) and analyze the results. We started asking around among colleagues and birders to find someone locally in Colombia who would be able to search for the tag at this the GPS location.
On March 3rd, Mr. Curtis Smalling (Director of Land Bird Conservation, Audubon North Carolina) sent a note to the group, ProAves, a Colombian bird group, asking if anyone would search for the radio-tagged egret for us. On March 20th, Dr. Matthew Godfrey (sea turtle program leader, NCWRC) informed us that he gave all the information we had provided to him to his Colombian colleague, who in turn, posted the request on the Colombian Bird Network.
On March 19th, we received an email from Magaly, who told us that she would search for the tagged bird! We found a biologist, who was willing to help us, far away in Colombia!!! She asked a few questions about the frequency of the tag and the exact GPS location, then started her search.
She found the tag exactly where we thought it was, and also the feathery remains of Mr. Bisbing in Plot No. 16 of the San Miguel, Vereda, The Navajo town of El Copey Cesar, Colombia. We are very grateful that Magaly volunteered to take her time to recover and send the tag back to the Museum of Natural Sciences in Raleigh.
But what caused Mr. Bisbing’s death? The area that he chose to forage in had been affected by an unusual summer with no rain in five months and the vegetation was very dry as evident in pictures from the area (Fig. 2).
The only water sources were man made wells for cattle. One of the farm workers (Fig. 3) reported to Magaly that he had seen the dead heron and its transmitter about two months before she arrived looking for it. He did not handle the dead bird but observed, that he “did not see any wounds on the bird”.
We assume that Mr. Bisbing died of starvation and exhaustion after the long migration. He chose a foraging area that didn’t provide enough food to recover from his depletion of reserves. Was he inexperienced in this area, or was it the unusual summer that turned his trip into a disaster? We will never know about this individual bird, but if we keep observing more egrets and follow their way through life, we will hopefully understand more about how and why they choose locations to spend the summer or winter, and what their preferred migration pathways are.
We have tagged other great egrets and found that they each have an individual schedule and have quite different preferences regarding foraging areas or migration routes. You can see their movements on movebank.org and find out in which areas Ms. Palma, Mrs. Newbern, Mrs. Kelly, Mrs. Heller, Mr. Norvell, and Mr. Meadows preferred to live and migrate.
With the detailed observation of Mr. Bisbing, for example, we found that at least this bird preferred migrating during the night. There are only a few observations of migrating great egrets reported prior to our study, and they stated that great egrets migrate during the night. We were pleased to find that these older reports were confirmed by our study.
This new, detailed knowledge about breeding behavior, foraging preferences, migration pathways and timing, etc. will help us protect great egrets and increase their survival in our more and more urbanized environment.
You can participate and help us in these efforts, too, by using a new application called Movebank. With this app you can follow birds live in real-time, and go out in the field to find the tagged birds, take pictures and send them back via the application. So give it a try, check out the location of the closest bird, get into your car and enjoy the search.
This is the fourth chapter in the story about a great egret that we gave a GPS tracking device on the Outer Banks of North Carolina in spring 2013 (see photo). We followed his movements for about 8 months and reconstructed his story with his GPS and ACC data (see parts I, II and III).
On October 24th at 9 p.m., Mr. Bisbing took off for his last long trip. Up to that point he had spent his summer within the Outer Banks, breeding and raising chicks with a mate, then taking it easy in the wetlands south of Roanoke Island. Everything seemed to be orderly and his daily routine was relaxed and regular. As temperatures got colder toward the end of September, he started becoming a bit unsettled. He checked out new foraging areas, drifted farther and farther south, but still returned to his roost every night. Eventually, he overcame his inhibitions and took off flying south away from the Outer Banks, over the open ocean.
During his migration, Mr. Bisbing covered a total of about 3200 km (2000 miles) (Fig. 1). He started with an impressive 22.5-hour nonstop flight (from Oct. 24th, 9 p.m. until Oct. 25th, 7:30 p.m.) from his roost south of Roanoke Island straight across the ocean to the Bahamas, where he took his first break. During this first nonstop stage he covered more that 1200 km (about 755 miles)!
But why do egrets migrate at all? Bird migration is the regular seasonal movement, often like in our case, north and south along a flyway between breeding and wintering grounds. Migration carries high costs in predation and mortality but many species of birds have to risk it because of the availability of food. Great egrets like Mr. Bisbing feed on fish and other small vertebrates such as amphibians, reptiles and mice. During winter all these vertebrates appear less abundant, because many of them hibernate. So egrets need to find foraging areas with higher abundances of their preferred food.
Timing of migration is controlled primarily by changes in day length. For navigation birds often use celestial cues from the sun and stars, the earth’s magnetic field, and probably also mental maps. Mr. Bisbing flew across the ocean, during the night, so we can assume, that he had no visual orientation to navigate. Nevertheless he found his way back to a shore and foraging grounds to regain some strength. We were quite surprised to observe that when migrating, Mr. Bisbing was flying actively, flapping his wings nonstop, without soaring as birds of similar size and body shape like storks or cranes do (Fig 2).
After his first landing in the Bahamas, he rested for only 80 min before he flew farther south for another 35 min. Here, in the south of Greencastle, he found a wetland and rested for the rest of the night. He slept-in the next morning and took off at 9:40 a.m. to forage in the surroundings. But he took only one day to recover from the long and exhausting flight, spending his time resting and foraging (Fig. 3).
Why Mr. Bisbing didn’t stay in Bahamas longer we will never know, but in the evening of October 26th at 8:00 p.m., he flew another 435 km (270 miles) south over the Caribbean. It took him 6 hours, and by 2 a.m. he reached the northeast coast of Cuba. He rested there for a few days in a quite regular daily pattern, as he used to do before the migration: waking up at 7 a.m. and spending the day foraging until 8 p.m., when he went to bed at his roost (Figs. 4 and 5).
Our ACC data record ends on Nov. 2nd at 1 a.m.. We were not able to download any data from the memory card during Mr. Bisbing’s migration, so the ACC memory card filled up and stopped recording. From now on, we don’t have any more details about his body movements, but we could still follow his regional movements, because the GPS was still working. The resolution was lower, due to the memory limitation, but we received a few points every day to follow his large scale movements.
After 20 days in Cuba, Mr. Bisbing was on the move again, migrating 400 km (about 250 miles) farther south to Jamaica on November 15th. He found a roost south of Pamphret (Fig. 6) and stayed in this area for almost two weeks, until November 27th.
The next data we received are from November 29th, and at this time, Mr. Bisbing is already in 960 km (about 600 miles) farther south in Colombia, south of Momil in Cordoba Province, where he stayed for another day. From there he flew another 212 km (133 miles) farther northeast, to Cesar Province. The GPS tells us that he arrived here on December 2nd and he stayed and foraged in this area for another couple of days – until his movements stopped on December 8th. This was the last step of his migration, indeed, the last flight of Mr. Bisbing. What happened next to our tragic hero, and how we got the tracking tag back from South America to North Carolina will be the subject of our final blog post about Mr. Bisbing the great egret.
This is the third chapter in the story about a great egret that we gave a GPS tracking device on the Outer Banks of North Carolina in spring 2013 (see photo). We followed his movements for about 8 months and reconstructed his story with his GPS and ACC data (see parts I and II).
On July 17th Mr. Bisbing got up before dawn (5:05 am to be precise) and took off for a major change in his life. Breeding season was over, his offspring were on their own by now, so he could have some fun in a maybe more diverse environment.
So he took off, flying south, along the coastline (Fig. 1). After 45 min he took his first break right behind the city of Duck at the beautiful sound. During this first stage of his trip south he covered about 32 km (20 miles). But the new area seemed not to be very interesting, at least we couldn’t observe any foraging behavior in the Accelerometer (ACC) data (Fig. 2), so he took off again at 6 am and flew for another 12 min, 9 km (5.6 miles) further south. He rested again, maybe checking for some food, and as nothing interesting showed up, he kept going south. On the whole Mr. Bisbing took 6 stages to cover a distance of about 71 km (44 miles) which took him about 70 min flight time and a little over 4 hours all together.
Eventually he arrived at 9:20 am at his new home for the rest of the summer: a small island between Hog and Cedar Island in the south of Roanoke Sound.
After this long and strenuous flight Mr. Bisbing was certainly hungry and needed a meal, so he started foraging and spent the rest of the day island hopping around his new roost site, searching for food (Fig. 2). The first night was a little rough, and it took him until midnight to finally settle down and sleep calmly (Fig. 3), but from the next day on, he fell into a regular and relaxed routine.
Mr. Bisbing usually woke up around 5:40 a.m. and left his roost around 5:50 a.m., quite punctually every day. From the roost, he first flew south to the wetlands of an island west of the Oregon inlet (Island C). He spent most of the day there, but sometimes checked the wetlands east of the Bodie Island Lighthouse or east of Tommy Hammock, before he went back to his roost for the night between 5:30 and 8:30 p.m. (Fig. 4).
He stayed in the area south of Roanoke Island until October 24th, but decided that another change was necessary on Sept. 27th. From that day on, he roosted 5 km (3.1 miles) farther south on Island C, west of Oregon Inlet. This was the island where he used to go foraging every day. He also changed his foraging preferences. From now on, he chose more and more often to forage south of the Inlet, an area, that he didn’t use before at all (Fig. 5).
As autumn wore on and temperatures got chilly, his daily schedule became more and more irregular, and his foraging trips took him farther and farther south. He flew up to 19 km (12 miles) south from his roost to forage – a long distance for a daily routine. Perhaps this was training to get prepared for his next big adventure – a huge migration south of the Outer Banks, heading out over open ocean. Read more about it in our next post in a couple of days!
This is part two out of five of our story about a great egret that we tagged at the Outer Banks in Spring 2013. We followed his movements for about 8 months and reconstructed his story with his GPS and ACC data (see part I).
The exact position of the lines in the ACC graph are the result of totally different behaviors, giving us clues about important events in Mr. Bisbing’s life. While the motion of the bird is recorded by changes in lines on an ACC graph, the relative position of the lines to each other show the position of the bird relative to gravity. Leading up to May 19th, Mr. Bisbing would occasionally rest at night in a horizontal position, motionless, with the blue line above the green line, different from his roosting position, which was green line over blue, over red (Fig. 1).
So we concluded that this horizontal posture was actually Mr. Bisbing incubating eggs, sitting all the way down on his nest to keep them warm. This was exciting news! Our tagged bird was going to have babies!
We observed this incubation position only until May 19th, presumably the hatching date. Prior to this date, he incubated every other day or so, sometimes up to 52 hours in a row (May 13th)! Egrets take turns incubating eggs, and we could observe that Mr. Bisbing took turns with his partner because he roosted at places other than the nest.
During these first 3 weeks, from April 21st until May 19th, Mr. Bisbing foraged in two different areas. After waking up and doing his morning grooming, he flew either north, towards Swan and Johnson Islands and spent the day there foraging in the surrounding wetlands, or he flew south to forage in the wetlands west of Corolla. Once in a while he made his way along the coastline, probably searching for new foraging grounds, but always returning to his two favorite wetlands where he spent most of the daytime (see Fig.2).
Then, during the night of May 17th, something exciting seemed to happen. The GPS data show that Mr. Bisbing stayed on the nest for almost 60 hours in a row, until 6:20a.m. on May 19th. The ACC lines tell us little more details about what happened during this time (Fig. 1).
On May 17th Mr. Bisbing flew back to his nest in the evening and settled down in the incubating position. He stood up once in the middle of the night (the switch from blue over green to green over blue), probably to stretch his legs and neck. During the next day he stayed in the incubating position, but moved around quite a bit, more than during other incubating periods– was he nervous? Something seemed to bother him – was there something going on with his eggs?
But he calmed down again in the late afternoon, the lines are flat again. During the following night he switches into the roosting position, still at the nest site. Maybe he took a turn in incubating with his partner. The next morning, he incubated for another 3 hours – the last time that we observed this behavior. When he stood up again he started moving around but stayed close to his nest as the GPS data tell us. Great Egret young usually hatch one at a time, so we assume that those days were probably the time when Mr. Bisbing’s chicks were hatching.
After May 19th, Mr. Bisbing changed his daily schedule. Before that day his routine was rather irregular, including long periods of rest in different places, long periods of incubating and foraging in many different areas. After May 19th, Mr. Bisbing chose the wetlands west of Corolla as his absolutely favorite foraging site. He went there in more than 90 % of the time during the next two months and he flew north only twice, towards Johnson and Swan Islands (see fig. 3).
We assume that the wetlands west of Corolla became the new preferred foraging area, because it’s only half the distance compared to Swan and Johnson Islands. By choosing the closer food source, Mr. Bisbing could save time and energy, which he urgently needed to feed his offspring.
Surprisingly he left the nest all day and came back only in the evenings to help feed the chicks. Typically he took off early in the mornings, around 5:30 a.m. and came back before dusk, between 6 and 8 p.m.. This behavior is likely caused by the remote location of Monkey Island and long commuting time to get there. Long flights cost time and energy, and as Mr. Bisbing was raising his chicks he needed to budget these factors.
Another interesting fact was that he slept on Monkey Island, but at a roost away from the nest, for 12 nights in a row. Furthermore, on three occasions he didn’t come back to Monkey Island for 48 hours. For a new dad, he certainly was avoiding the nursery. However, after these initial days of fatherhood, he slept at the nest in his roosting posture except for three nights. It’s not quite clear to us, why he behaved this way. Maybe his wife took good care of the chicks during the night, so that he could rest and get ready for the next day’s foraging trip.
Other studies have found that great egrets feed their offspring at the nest for 20-30 days, depending on the local food supply. Egret chicks start clambering from the nest after about three weeks and fly away from the colony after 1-2 months. We cannot tell from our data, when Mr. Bisbing’s chicks left the nest. But we do know, exactly when he left the colony – [July 17th, 5:05am] – never to return. Find out where he went in our next blog in a few days.
How often do you see a bird flying high in the sky and wonder where it’s going? Some birds make amazing migrations of many 1000s of miles – how long has that bird already been flying? How much farther does it have to go? Migratory birds must have amazing stories to tell, but we are left to imagine the details as we watch them fly overhead.
Modern technology is now revealing these stories in amazing detail – new tracking tags use GPS to record location and a 3-axis accelerometer (ACC) to record their behavior. These solar powered units work 24/7, anywhere on the globe, for the entire lifetime of an animal. Here I want to show you one example through the life and death of Mr. Bisbing.
“Mr. Bisbing” was a male Great Egret. He was a slender, good-looking guy of average size and, as we found out later, he was in a productive relationship. We met our protagonist at the Whalehead Club in Corolla, North Carolina, where we lured him into our traps with bird decoys and a bucket of fish (more in this Untamed Science video).
Once we had him in our hands we gave him a high-tech backpack a GPS and ACC tag (Figure 2). We released him on April 21st , 2013 at 11:40am, in front of the Outer Banks Center for Wildlife Education, and followed his every movement for the next seven and a half months, until his untimely death.
We immediately learned an important part of Mr. Bisbing’s story: he had a nest on Monkey Island. The GPS data showed us that he went there every night. There’s a known egret colony there, and our tagged bird was obviously a member of this group. Looking very carefully at the GPS data we realized that he used two different parts of this small island: one spot on the south that was his nest and another spot to the north where he must have gone when he needed to get out of the house (Figure 4).
The ACC sensor records 3 dimensional movement of the bird that we can use to learn about the behavior of the bird. The graph below (figure 5) shows three lines describing the bird’s movements in three dimensions: up and down (blue), forward and backward (green) and right-left sway (red). Different behaviors of the bird create patterns that we can identify. In the resting position, all lines are flat. When an animal is walking, each foot-step creates a similar, but slightly delayed pattern in the blue and green. The wing-beats of a flying bird show the strongest peaks in blue. The ACC data are recorded in high resolution every 4 minutes, for 4 seconds at a time.
The following graph shows you what Mr. Bisbing’s typical day looked like (Figure 6). Early in the morning, before dawn, he freshens up and goes for breakfast. In this example (May 24th) the GPS shows that he flies from his nest on Monkey Island 3.7 km (2.3 miles) to the wetlands west of Corolla. In the ACC data you can see from the width of the blue high amplitude peaks that the early morning flight away from Monkey Island and the evening flight back to Monkey Island take longer than the short flights around the wetlands during his foraging behavior. The sleeping position during the night is also easy to recognize because the bird is motionless.
Now you have met our main character and know the cool things this technology can tell us about his life. In my next post I’ll dive into the details of family life on the Outer Banks.
Things are heating up this month at the North Carolina Museum of Natural Sciences. On June 22, we will participate in the first annual International Sun-Day, complete with presentations on current solar research, Sun-focused activities, and solar observing with special telescopes available to visitors throughout the day.
The Sun is our star. It warms our solar system, as we probably most clearly notice in the more tropical summer months when our part of the Earth is tilted toward the Sun. While the Sun is a relatively average-sized star compared to all the stars in the Galaxy, it is critical for our existence, and for life as we know it to thrive on this planet. Nearly 99.9 percent of the mass of the solar system is wrapped up in the Sun, making it one of the most important components of our solar system for astronomers to understand as part of a complete picture of how our solar system formed and evolved.
The Sun has been our star for roughly 4.6 billion years, and in about 5 billion more years it will expand to become a Red Giant, swallowing the Earth and other bodies in its radius, and eventually fade away.
In the meantime, as scientists are exploring far-away planets, moons and icy bodies at the edge of the solar system, we still have many unanswered questions related to our Sun, the precise details on how the solar system formed from a cloud of gas and dust, why Earth continues to be a habitable planet, while life is absent on the other rocky planets, including Earth’s “twin”, Venus, and how life on a planet will be affected in the long-term by its parent star.
Toward answering these and many other related questions, several missions are now studying the Sun from low-Earth orbit (altitudes between 100 and 1200 miles overhead). Solar astronomers (or, heliophysicists) are using these missions to study the Sun’s magnetic field and surface details, including plasma eruptions, flares, sunspots and solar wind that can bring high-energy radiation toward the Earth, leading to space weather, potentially influencing communication satellites and astronauts on the International Space Station, with possible negative impact on human life and health.
As we are in a period of high solar activity, these missions are revealing previously unseen details related to the Sun’s influence on our planet. Below is a video showing a solar eruption called a coronal mass ejection, as seen by the current space observatories: NASA’s Solar Dynamics Observatory (SDO), NASA’s Solar Terrestrial Relations Observatory (STEREO), and the joint ESA/NASA Solar Heliospheric Observatory (SOHO):
Join us on June 22, 2014, for a fun-filled day of solar presentations, solar observing (weather permitting), and activities for all ages. This is also the first Sunday following our Summer Solstice — the day where the Northern Hemisphere is maximally inclined toward the Sun, marking the first day of Summer!
Remember! NEVER look at the Sun with your unprotected eyes, or with equipment that is not specifically made for observing the Sun.
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Dr. Rachel Smith is an observational astronomer. She uses the Keck Observatory in infrared wavelengths to study the detailed chemistry of protoplanetary systems in our Galaxy; these are exoplanetary systems before the planets form. Her work focuses on the gas surrounding protostars — forming stars before they start burning hydrogen and helium like our Sun, and other stars far beyond our solar system. Dr. Smith uses the data from these exoplanetary systems to help fill gaps in our knowledge on how our solar system and other planetary systems form and evolve. Read more about Dr. Smith’s research here.
By Roland Kays
North Carolina Museum of Natural Sciences & NC State University
Following the paw prints of their larger carnivore cousins, coyotes, fishers are now returning to New York City. A new photograph confirms that at least one animal has found its way to the Bronx, after a scattering of records across Westchester County in recent years. These oversized weasels (females are 4lbs, males weigh up to 13lbs) are adaptable predators recently found to climb trees to hunt the squirrels that typically overrun suburban areas.
Their long skinny build also makes fishers keen tunnel users, which helps them crawl through drainage culverts to cross under roads and avoid becoming road-kill. Their love of tubes and rodents should also make them keen ratters, although no fisher has ever lived so close to so many rats as our recent Bronx visitor.
Fishers lived in Manhattan when the island was first settled, but were one of the first to disappear due to the high prices fetched by their fur. Trapping pressure only increased over the centuries, leaving a handful of fishers surviving in the Adirondacks and other wilderness areas when trapping was banned in the 1930′s. Their population recovered, slowly at first, but is now booming across the Northeast, even with trapping seasons reinstated. After repopulating wild and rural forests, they began colonizing upstate suburban forests about a decade ago, and seem to be doing quite well there. Camera trap surveys suggest they may be more common suburban Albany than nearby wildlands, possibly because of the abundant squirrel populations. Our GPS tracking study showed how suburban animals use movement corridors to move between favorite hunting grounds, skirting around neighborhoods to find the next small patch of woods.
The recent Bronx fisher was photographed at dawn by Derek Lenart, a NYC Police officer who works the night shift. He saw it cross the road in front of him and run underneath parked cars and along the sidewalk on Hennessey Place, just south of Bronx Community College, and three blocks east of the Harlem River. The fisher then turned up a driveway, ran into a back yard and out of sight.
Although they can be active during the day in wild areas, fishers living near people are nocturnal. This fisher was probably looking for a place to hide for the day, either down a hole or up a big tree. Judging from the picture this a male fisher, likely a dispersing animal looking for a female and a new place to settle down. If he can find a place to sleep and something to eat he might stick around. Bronx squirrels would make good fisher prey, but things could get really interesting if fishers start hunting rats in New York.
Officer Lenart says he sees rats everywhere on his nightly patrols, some places in huge numbers. The other animals he sees at night – raccoons, possums and skunks -are not rat predators. Coyotes can certainly dispatch a rat, but their large size makes it difficult for them to move around the metro area outside of parkland, and Officer Lenart has never seen one in his five years working the night shift in the Bronx. No predator keeps a lower profile than fishers; if they can use their tunnel-running to hunt rats, and tree-climbing to get squirrels, they could make a nice living in New York City. Fishers pose little threat to people. Although they are rumored to kill cats, there is little evidence to support this idea.
But lets not get ahead of ourselves here – one brief glimpse of one male fisher in the Bronx does not mean the end of your local rat problem. It does, however, put an exclamation point on the recovery of fishers in the region, and highlights the adaptability of wildlife if given a chance.
For more on this story check out the video below where I discuss the Bronx fisher with Brian Malow.