Skyline drive survey

Our survey vehicle on Skyline Drive in the Shenandoah National Park during our initial survey in the summer of 2005

By Keith L. Bildstein, Ph.D.
Sarkis Acopian Director of Conservation Science
Hawk Mountain Sanctuary

20 July 2016

I realize that I am running a risk with this column in talking about raptor monitoring. Indeed, when I begin to talk about monitoring, my audience often begins to doze off.  If I continue to talk long enough, some may even fall asleep.  Nevertheless, monitoring not only is a useful tool in raptor conservation; it is an essential tool.  When we in raptor conservation fail to monitor populations of birds of prey we often pay a steep and, in some instances, an irreversible cost.

Consider the current plight of the Indian Long-billed and Asian White-rumped Vultures, two species that 40 years ago ranked as the world’s most abundant large raptors.  Both species were then common and widespread throughout southeastern Asia.  When populations of both species crashed by more than 95% in Bharatpur, India in less than two decades in the late 1900s, the problem was thought to be pesticides.  But when similar reports were received for other populations elsewhere in these species wide ranges, a lack of earlier population monitoring made it difficult initially to ascertain the actual magnitude of the declines.

Two vultures that had once been so common that no one thought to monitor the sizes of their populations were now so uncommon that some conservationists were suggesting that they were in the “fast-lane” to extinction.  Half of a very large number is still a very large number, and by the time people were paying attention to these formerly species few knew what their once very large numbers had been.

Eventually conservationists learned the problem was an FDA approved drug, diclofenac, then in use on livestock.  Diclofenac, a non-steroidal anti-inflammatory substitute for aspirin that, while non-toxic to humans, turned out to be highly toxic to vultures in the genus Gyps.  But without proper population monitoring, we had reached a point where expensive captive breeding was necessary to reverse the trends.  Had we been monitoring these populations earlier, such extreme measures would not have been necessary.

Which brings me to my point.  Monitoring populations of raptors—even common and abundant species—is a critical component of practical and effective raptor conservation.  This is why Hawk Mountain decided to begin doing so with two species of common and widespread New World vultures in 2005.  As of late 2015, the Sanctuary has surveyed Black, Turkey, and other vultures in 23 locations throughout the Americas: from central western Canada in northcentral North America all the way south to Tierra del Fuego in southern South America and the Falkland islands in the South Atlantic.

Our surveys include both winter and summer counts totaling more than 24,000 miles of road counts across 14 United States, 4 Canadian provinces, and 6 central and South American countries.  Surveys are conducted by a driver and one official observer along secondary routes at 30 to 40 miles an hour on rain-less and fog-less days.  Counts begin at nine in the morning and end at four in the afternoon after and before most of the birds have roosted for the evening. In addition to Black and Turkey vultures, all other scavenging birds of prey are counted as well, including all other vultures, condors, and caracaras.

When we began the counts in 2005, the plan was to survey both Turkey Vultures and Black Vultures in representative areas across much of their geographic ranges and to redo the surveys once a decade in both winter and summer, so that populations of both migratory and resident populations of these common scavengers could be monitored routinely. Declines in numbers could be assessed in a timely fashion, and conservation action taken as necessary, before populations had declined catastrophically.

Black bear scvenging a road-killed deer

An unexpected “non-vulture” scavenger feasting on a road-killed deer along Skyline Drive during our second round survey in the summer of 2016.

Round two of our surveys began in early July 2016 when three Summer Field Experience Interns and I redid two day-long road counts in northern Virginia that were originally undertaken in the summer of 2005.  One of the routes was a mountainous 195-kilometer meander along Skyline Drive in the Park Service’s Shenandoah National Park and the northern-most section of the Blue Ridge Parkway.  The other was a 211-km route that followed the eastern shoulder of the upper Shenandoah Valley.  The numbers of vultures sighted were encouraging.  During two days of field work this summer, we counted a total of 253 Tukey Vultures and 14 Black Vultures, versus 124 TVs and 9 BVs seen on the summer 2005 counts.

Although this initial field effort was a modest one, we will ramp-up counts this winter to include 6 routes totaling 963 kilometers in western and central Panama, along with the two winter counts in northern Virgina.  Over the next five years, we plan to re-conduct all of our surveys from west-central Canada south to Tierra del Fuego.  We hope to find that all populations previously surveyed are stable of increasing.  However, if they are not, we plan to put conservation actions into play that will determine the cause or courses for the declines and begin work to reverse them.

Vulture perform important ecological services in the ecosystems they inhabit, not the least of which include nutrient recycling and reducing the likely spread of diseases including botulism, anthrax, and rabies.  Protecting their populations is a critical aspect of Hawk Mountain’s mission, and we plan to stay on top of this.  Our next surveys in Virginia are scheduled for December 2016.  We plan to redo our winter surveys in Panama in January 2017.  Once we have conducted them I will be in touch.

Between then and now let me know if you have any questions on this monitoring effort and how you can support the Sanctuary financially in carrying out this crucial part of our mission. Feel free to email me at Bildstein@hawkmtn.org or call me at 570 943 3411 ext. 108.

keith releasing vulture may 2016

Keith releasing “Calm Lady” at the Buckeye dairy-farm trap site.

By Keith L. Bildstein, Ph.D.
Sarkis Acopian Director of Conservation Science
Hawk Mountain Sanctuary

27 June 2016

We’ve all seen the Gary Larson cartoons of vultures perched or soaring above one or two desiccated cowboys insightfully expounding on something comical.  Truth be told however, vultures are rare inhabitants of most of the world’s deserts.  Fortunately, this is not so in the Sonoran Desert of the southwestern United States and northwestern Mexico.

The Sonoran, a fascinating and ecologically rich region, is an important go-to place for vacationing Canadian and US snow birds, as well as home to 10 species of amphibians, 100 or so reptiles, 60 mammals, and more than 350 species of birds, including the world’s most northern breeding populations of Cathartes aura aura, a largely Neotropical subspecies of Turkey Vultures.  Investigating raptors at the limits of their geographic ranges has been a fascination of mine for more than 40 years, and this explains why I traveled to Buckeye, Arizona, 30 minutes west of Phoenix on Interstate 10 just before midnight on the night of Tuesday 17 May 2016.

Hawk Mountain’s Senior Research Biologist Jean-Francois Therrien and I landed at Sky Harbor Airport in Phoenix with an ambitious agenda.  The following day I would travel two hours south to Tucson to give a talk on our vulture work at the world famous Arizona Sonora Desert Museum, while at the same time Jean-Francois would hook up with Rich Glinski, the editor of The Raptors of Arizona, and try to catch vultures at a dairy facility outside of Buckeye.  Dairy farms are large in Arizona, and still-born calves would be the bait at our desert trap site.

Both Black and Turkey Vultures occur in Buckeye, and although we had begun our studies in the state in 2014 focusing solely on the latter, we have recently expanded the work to both species, as both were feeding, interacting at, and fighting over at the same nutritional resources, and fully understanding the feeding ecology of two species was only possible if we studied both of these competitors.

My talk at the museum was set for noon and a group of 40-plus museum workers and volunteers were eager to what I had to say as the museum had open an exhibit featuring both Black and Turkey Vultures a few months earlier.  Half way through the talk my mobile phone vibrated in my pocket.  Unfortunately, I ignored it as I didn’t want to interrupt the presentation.  That was a mistake, as Jean-Francois was calling from Buckeye to let me know that he and Ron had just caught and placed a satellite tracking device on an adult Turkey Vulture they had decided to call “Moo Moo,” the name the young daughter of our host blurted out when she first laid eyes upon it.  (Most of our trapping sites are on private land, and we always make certain to engage the land owners in all aspects of our field work, including watching us place tracking devices on the birds we catch and tag and helping us name them.)  The next phone call came two hours thereafter when JF called to let me know that he and Rich caught and tagged a second Turkey Vulture named “Gash.”  Both individuals, while quite healthy, weighed less than 70% of the Turkey Vultures we catch in Pennsylvania, which were members of the considerably more massive septentrionalis subspecies.  Needless to say we celebrated the day over dinner at a “wings” restaurant close to our motel.  We had brought four tracking devices with us, and after just one day of the four that we had allotted to trapping and tagging birds, we were half way to our goal.  The pressure was still on, but reaching our goal certainly appeared doable, and we were pleased.

Keith and AZ bird May 2016

Keith with “Calm Lady” at the trapping site.

We caught Turkey Vulture number three, “Calm Lady,” early afternoon the next day, and caught our fourth Turkey Vulture, “Early Bird,” before eight the following morning.  Four birds after a little more than two days in the field.  Not bad… not bad at all.  We took time off from the field the rest of day three while planning our work for the remaining two days we had scheduled to be in Arizona.  When we first started working in Arizona in May of 2014, our plan was trap and tag at least a dozen Turkey Vultures, and the four we caught in May of 2016 brought our total 15.  We also planned to conduct a series of six seasonal road surveys totaling 1,061 miles in southern and western Arizona.  The surveys would allow us to estimate the sizes of the wintering and summering populations there, providing us with critical information on regional numbers.

The next morning we set off a 166-mile road survey that began at Gila Bend and meandered through the towns of Ajo, Why, and Sells Arizona, while circling back toward Tucson.  We counted 63 Turkey Vultures and 3 Black Vultures along the way.  After overnighting in Tucson, we conducted a second, 152-mile survey that began at Three Points and continued south to Nogales on the border with Mexico, before turning north to Continental.  On that survey we counted 30 TVs and 1 BV along this route.  After finishing the survey we scurried back to Sky Harbor Airport in Phoenix to catch a red-eye flight back to Newark, New Jersey.  It was then onto Hawk Mountain by car, where we arrived mid-morning on Monday the 23rd.

Although we had spent but five days in the field, we had managed to catch and tag four new Turkey Vultures and had conducted two full-day roadside counts.  Our next trip to Arizona will be in January 2017, when we hope to catch and tag at least three Black Vultures and conduct as many as six road surveys.  Although the work—if you want to call it that—might seem tedious to some, for me and my colleagues it was as close to heaven as one comes in raptor biology…  a chance to catch up on all things “vulture” while trapping and tagging a few birds, surveying an important regional populations of two species, and getting the word out to the public about why we are studying Turkey and Black Vultures and what we are finding out about them.

In my next blog, which I hope to have out in several weeks, I will update you on our Arizona findings to date.

To learn how you can help support our studies, email me at Bildstein@hawkmtn.org or call me at 570 943 3411 ext. 108.

wingtagged vulture 70 by jeff dietschBy Keith L. Bildstein, Ph.D.
Sarkis Acopian Director of Conservation Science
Hawk Mountain Sanctuary

8 January 2016

Why are some species of birds of prey widespread and abundant whereas others are not?

It turns out that this critical ecological question, one that is fundamental to understanding biological diversity, along with many other aspects of ecology, is easy to ask, but not easy to answer.


Article in The Auk

Earlier this month two former Hawk Mountain trainees, Dr. Todd Katzner (now the head of the U.S. Bureau of Land Management’s Boise State University Raptor Research Center) and Julie Mallon (now a Ph.D. student at the University of Maryland) and I published an article in the ornithological journal The Auk that helps to explain why turkey vultures are one of the world’s most abundant and widespread avian scavengers. The field work was conducted while Julie was a Master’s degree student at West Virginia University.

The short answer to the question is that turkey vultures have evolved two so-called “key innovations” that, together, make them decidedly “above average” as avian scavengers. The long answer, which follows, is a bit more intriguing.

The turkey vulture’s first key innovation is their acute sense of olfaction. This is something that is quite handy when the food you are searching for is decaying carcasses and smells.  Turkey vultures have the largest nostrils of all New World vultures, including the far more massive California condor and Andean condor, as well as the largest olfactory bulbs in their brain–the next largest being those of the king vulture, a species that does not appear to use olfaction in its search for carcasses. Two other Central and South American species of vultures, the lesser yellow-headed vulture and greater yellow-headed vulture, are both close relatives of the turkey vulture and also locate carcasses by both smell and sight.

turkey vulture 03 03 15 bill moses, at french creek .jpg

Turkey vulture at carcass by Bill Moses

Intriguingly, although there is no evidence that black vultures are able to locate carcasses by smell directly, the species indirectly locates carcasses by smell. Indeed, black vultures routinely seek out turkey vultures and then follow them to carcasses, capitalizing on the latter’s olfactory capacity. Old World vultures, on the other hand, show no evidence of locating carcasses via their sense of smell.

The turkey vulture’s ability to locate carcasses by smell is a key innovation because it allows individuals to search over forested as well as more open habitats for dead animals, thereby considerably expanding their feeding habitat. This key innovation explains–at least in part–why turkey vultures are the most wide-ranging of all vultures.

The turkey vulture’s second key innovation and the focus of our recent publication in The Auk provides the rest of the story. This innovation is the species dihedral wing posture, which allows it to engage in what my coauthors and I call “contorted soaring” while flying close to the ground in search of carcasses. What atmospheric scientists call “small-scale, shear-induced atmospheric turbulence” routinely occurs close to the ground. It happens anywhere the topographic features such as mountains and valleys, forest edges, and small-scale thermal mosaics, disrupt the flow of wind near the earth’s surface. This creates small pockets or eddies of swirling air that alternately push and pull on objects flying through them. Many of us have experienced this kind of turbulence during bumpy take-offs and landings at airports.

Turkey vultures are lightly-wing loaded (i.e., they have big wings for their body mass), making it easy for them to soar in large packets of warm, rising air called thermals. Other vultures, too, are able to do this. Close-to-the-ground, contorted soaring, however, is another matter entirely. It is close to the ground where the dihedral (“V” shaped) configuration of the species’ wing profile comes into play.

DSC_9244 turkey vulture 10 14 18 bill moses

In addition to a relatively long, rudder-like tail that allows them to turn in tight circles while soaring in small-scale turbulence, turkey vultures have long, narrow wings that they hold above their backs in a dihedral. The latter is a key innovation that serves as an “aerodynamic self-righting (or stabilizing) mechanism.” This allows the bird to continue to soar in turbulent air even when its two wings are exposed simultaneously to different up- and down-drafts.

The unusual wing profile functions whenever one wing (either the left or the right) experiences more lift than the other. When this happens the wing experiencing greater lift tilts upward making it less parallel to the ground and reducing its aerodynamic surface and, hence, lift while the opposite occurs to the other wing. The side-to-side rocking, which at first suggests instability, actually is an energy-efficient, soaring flight that allows the birds to stay aloft. It also allows them to continue soaring without having to flap its wings to right itself, which is usually what happens when “flat-profile-wing” soaring birds encounter small-scale turbulence.


Other lightly wing-loaded soaring birds that regularly scavenge for food close to the ground, including greater and lesser yellow-head vultures, Egyptian vultures, black kites, bateleurs, and zone-tailed hawks, all have slight to strong dihedral wing configurations, as do more predatory harriers, which also forage close to the ground. Intriguingly, turkey vultures soaring at greater heights tend to do so in a less pronounced dihedral, whereas black vultures flying close to the ground frequently adopt a slight dihedral rather than their more typical flat-wing profile.

That they are able to extract useful updraft energy while soaring in small-scale turbulence near the ground means that turkey vultures can soar closer to the carcasses they are both looking and smelling for, which makes them easier to locate before turbulent winds jumble and disperse odors associated with them.

Low soaring flight has a second benefit as well. Contorted soaring allows low-flying turkey vultures to stay below the radar screen of potential competitors. This is important when a located carcass is squirrel-sized rather than deer-sized and there might not being enough food to share with others.


Ornithologists speak in awe of just how high vultures can fly while searching for prey. The world record, for example, is held by a Rüppell’s vulture that was sucked into a jet engine while soaring 37,000 feet, an altitude high enough to require special hemoglobin to capture oxygen sufficient for metabolism. But the ability to soar close to the ground also has benefits, particularly if you are searching by smell and want to keep a carcass to yourself. A keen sense of smell, coupled with a wing dihedral help makes turkey vultures what they are today, one of the most abundant and widespread of all raptors.

But of course the question then becomes “why don’t other vultures do the same?” The short answer is because they have not evolved these two key innovations. The long answer requires another blog.

You can find our paper on turkey vultures, “In-flight turbulence benefits soaring birds” on the Sanctuary’s website under “Numbered Publications” on our Science tab. Look for contribution to conservation science number 258.

Finally, if this work interests you, or any of our other research projects that better conserve raptors, please consider making a gift now. Just click here to donate now, writing “research” in the comments.

By Keith L. Bildstein, Ph.D.
Sarkis Acopian Director of Conservation Science
Hawk Mountain Sanctuary
9 December 2015

Together with African colleagues and Hawk Mountain research associates, I have been studying the “Critically Endangered” hooded vulture for going on three years. The work is beginning to pay off. I have just returned from 10 days in the field in and around Kruger National Park in northeastern South Africa where temperatures soared to 108 °F, and I have much to report.

As of early December 2015 we have placed satellite tracking devices on four “hoodies” in The Gambia, four units on birds in Ethiopia, and nine units on birds in South Africa. We also have placed “camera traps” at a number of hoodie nests in South Africa, as well as at several “vulture restaurants” there. Initial results at the latter are fascinating. But first some background…

hooded vulture nestling with tag

Fitting a tracking unit on a young hoodie

This summer, a second round of roadside counts in The Gambia indicated that hoodie populations there continue to do well, with numbers in the western part of the tiny African nation hovering at an astounding 15 birds per square kilometer, a density that makes the region home to the highest population of hooded vultures anywhere. Unfortunately, things are not nearly so good in South Africa where roadside counts in Kruger National Park, a supposed stronghold, indicate a population of far less than a single bird per square kilometer. My field work in South Africa earlier this mont

olifants river, kruger national park

Olifants River in Kruger National Park, South Africa

h also produced close-up looks at more than 10 active nests in private game reserves immediately west of “The Kruger,” where nests along some sections of the Olifants River are sometimes as close as 100 meters or less.


As in any collaborative endeavor, working with the right people makes all the difference and the Sanctuary’s hooded vulture studies in South Africa are not exception. Kerri Wolter at VulPro (a vulture NGO outside of Pretoria), consistently offers up exciting results and insights regarding hoodies breeding in the Olifants River Private Game Reserve. And Andre Botha at the Endangered Wildlife Trust (an NGO in Johannesburg) is doing likewise for birds breeding and feeding in The Kruger, as well as several adjacent private reserves. Dr. Marc Bechard at Boise State University continues to help with trapping and harnessing hoodies with satellite tracking devices, as well as helping on road counts within The Kruger.

Lindy, Marc, and Andre at the Selati Vulture Restaurant

Lindy, Marc and Andre at the Selati “vulture restaurant”

The newest addition to the South African team, Dr. Lindy Thompson, a Post-Doc in the Department of Biology in at the University of Kwa-Zulu Natal, adds an additional level of excitement and expertise to the team. On the job for less than a year, Lindy is following the nesting successes and failures (baboons and a hail storm appear to be responsible for at least some of the latter) of a number of hoodie nesting pairs in private reserves west of The Kruger.


Lindy also has initiated studies at several “vulture restaurants” in the region, where human provisioning of hoodies and other vultures with offal and assorted body parts of domestic animals slaughtered at local abattoirs, is helping the birds meet their daily caloric needs. Although such provisioning can disrupt the normal behavior of avian scavengers, human “nutritional assistance” at vulture restaurants provides “clean” food to birds in areas where poachers have been known to purposely lace with poison the carcasses of rhinos and elephants they kill for their horns and tusks. Their intent is to kill the vultures, whose flocking behavior often alerts game rangers of poachers’ activities.


Having spent considerable time in the field at a vulture restaurant last week, I now have a much better understanding of how hoodies and other vultures use the restaurants, as well as of the benefits of such sites in providing close-up looks at several of our satellite- and wing-tagged individuals. The vulture restaurant at the Selati Game Reserve, for example, routinely attracts dozens of hoodies, with attendance on some feeding days reaching 25% or more the regional breeding population. And indeed, I managed to visually locate two of our satellite-tracked birds at the site–both of which appeared healthy. (Actually, our tracking records indicate that four of the nine birds we are tracking visited the site while I was there.) Later this month Lindy and Andre plan to trap and measure up to three additional hoodies at this important site and place satellite tracking units on them.

Lindy and Marc at the Selati trap sitre

Marc and Lindy at the Selati trapping site

Trapping birds at the Selati site and, possibly, at other restaurants will help speed our wing-tagging and satellite-tagging efforts and also will provide us with much needed information on the health of individuals captured and examined there. Given the precarious nature of the species in South Africa, the restaurant work may make all the difference in helping us offer solutions for better managing this declining population.


Lindy will visit the Acopian Center this spring

Finally, Lindy plans to visit Hawk Mountain’s Acopian Center for Conservation Learning for several months this spring, at which time the two of us will begin to analyze tracking and nesting data already collected. Plans for 2016 also call for me to make two additional trips to Africa or field work in South Africa and The Gambia.

No one has assembled a better team of vulture specialists and is working as hard as we are to protect this globally endangered species and I very much look forward to keeping you up-to-date with our field efforts in the coming months.

Do not hesitate to contact me by phone (610-781-7358) or email (Bildstein@hawkmountain.org) if you are interested in supporting our work.

Until then, all the very, very best,  Keith

By Keith L. Bildstein, Ph.D.
6 August 2015

Vulture survey route along the California coast.

Vulture survey route along the California coast.

I have dreamed about surveying turkey vultures in California for a long, long time. The opportunity finally arrived this July when spring 2015 Hawk Mountain trainee Katie Harrington returned to her home base in San Francisco late last month. Katie and her fiancée James Fahlbusch volunteered to help and the three of us mapped out seven, day-long road surveys that would follow the coast north and south of San Francisco as well as inland from just north of Redding to south of Bakersfield. The plan was to travel the roads at 35 mph and record all of the turkey vultures we saw. Then, repeat the same route in mid-winter 2015-2016 to investigate seasonal changes in vulture distribution and abundance. We also planned to record the flight heights and group sizes of all of the birds we saw, as well as to look for and record the locations of California condors along the way.

Having conducted road surveys in 22 other regions stretching from Canada at the species’ northern limits to Tierra del Fuego, at its southern limits, I was excited to say the least. The fact that California was exceptionally hot and tinder-box dry this summer only added to my excitement.

A California condor with wingtag soars overhead.

A California condor with wingtag soars overhead.

Our surveys, which covered 1,280 miles, produced 1,306 sightings of turkey vultures, or more than one vulture per mile, a relatively surprising find given that several of the routes passed through “agro-industrial” and suburban areas. We also saw seven California condors, most of which flew close enough for us to read their wingtags. Intriguingly, all but one of the condors sighted were flying in close proximity to turkey vultures.

Remarkably enough, the ecological relationship between these two species has been little studied. Except for the not-surprising fact that turkey vultures are known to be behaviorally subordinate at carcasses to the more massive condors we know little of the ecological relationships between these two avian scavengers. What we do know is that while larger and more-agile avian scavengers typically dominate smaller and less-agile ones at food sources, numerical abundance at a carcass sometimes allows smaller scavengers to dominate larger scavengers. And this is exactly what happens when large gangs of black vultures overwhelm and dominate far larger, but less numerous, Andean condors at carcasses in South America.

A turkey vulture feeding on a racoon.

A turkey vulture feeding on a raccoon.

Although turkey vultures are far less social than black vultures and rarely group in large numbers at carcasses, they may out-compete the large California condor in other ways. First, their keen sense of olfaction should allow them to locate rotting carcasses faster than condors, and thereafter consume at least smaller ones before the condors find them. Second, their larger numbers might allow them to finish off larger carcasses partially fed upon by condors–and then left for later–more rapidly, thereby reducing the amount of food available to the larger birds.

Intriguingly, our miniscule one-week field effort suggests that the two species sometimes share the same airspace and, presumably, the same carcasses. Given the current status of condors as a globally-endangered species and the amount of field work and funding now focused on speeding their recovery, careful studies of interactions–both behavioral and ecological–between condors and turkey vultures would seem to be in order.

Keith and Katie examine the racoon.

Keith and Katie examine the raccoon.

Our next road surveys in California are scheduled for winter 2015-2016. Katie, James, and I look forward to exploring the distribution and abundance of vultures then, as well as to observing the behavior of vultures and condors as they search for food across the California landscape.

At long last, my “California dreamin’ is becoming a reality.”

By Keith L. Bildstein, Ph.D.
21 June 2015

Yesterday, Hawk Mountain Sanctuary Summer Field Experience Interns Kaitlin Schafer and Emile Luttman, and I drove more than an hour through pouring rain to try to find a special Turkey Vulture.

Named in honor of Irma Broun, the wife of the Sanctuary’s first ornithologist Maurice Broun, Irma the Turkey Vulture had been caught by then Hawk Mountain Graduate Student Jamie Mandel at a garbage dump in Penn Argyl, Pennsylvania, in August 2004. Shortly thereafter she was tagged with a solar-powered satellite tracking device. We also placed a data logger in her body cavity to record her core body temperate and heart rate. Placing the latter in Irma meant that we would need to recapture her the following year to extract the logger and download the data.

Former Hawk Mountain Graduate Student Jamie Mandell

Former Hawk Mountain Graduate Student Jamie Mandel at work in the field.

The bad news is we were never able to re-catch Irma in 2005 despite numerous attempts to do so. The good news is that both she and her tracking device are both still ticking more than a decade later. The tracking devices have a life expediency of three to five years, so Irma’s unit by far is our best overachiever.

This summer Kaitlin and Emilie have been spending time mapping Irma’s movements. Although she migrated to South Jersey during the winters of 2004-2005 and 2005-2006, since then she has been a year-round resident of an area near Easton, Pennsylvania, and Phillipsburg, New Jersey, shuttling between feeding and roosting sites on both sides of the Delaware River. Last week we decided to try and reconnect with her.

Using the movebank.org website that we use to store our tracking data, we located Irma’s roost site on the evening of Friday 19 June. She appeared to be resting for the night in the middle of a hilly old-growth forest outside of Riegelsville, New Jersey. Our plan, outrageous as it seemed, was to go to the forest, spot Irma, and photograph her.

We arrived at the forest a little after 8 a.m. on June 20. The rain had kept the vultures in their roosts later than normal so we thought that we might get lucky. As we approached Irma’s last location GPS location, we slowed the car to a crawl and began to search for basketball-sized black objects perched in trees.

Almost immediately Emile screamed from the back of our Subaru Forester, “Stop, stop!! Backup … I saw her.” Backup we did, and there she was, soaking wet, 30 feet up in a large sycamore, 30 yards from the side of the road. As soon as we put  binoculars on her we could see the antenna of the tracking device.

Irma then accommodated us by turning completely around to show us both the antenna and the device. Although feathers normally cover the device on perched birds, the rain had soaked her feathers permitting us to see the unit itself. After 15 minutes of snapping photos (and yes, we took dozens) and looking for other vultures in the forest (we saw none), we got back in the car just as the rain picked up and drove off… all three of our heads spinning. Fifteen minutes later we were having a hot breakfast in Riegelsville.

Irma and her tracking device, spotted more than a decade after this vulture was first tracked and tagged.

Irma and her tracking device, spotted more than a decade after this vulture was first tracked and tagged.

To successfully catch and satellite tag a wild bird is one thing. I still get chills when I do so. But to be able to track a wild bird and its movements for more than a decade is something else again.To be able to spot the same bird perched in a thick forest on a rainy morning more than 10 years after first releasing it is truly is an ornithological epiphany.

Emilie, Kaitlin, and I plan to finish our analysis of Irma’s movements this summer, and I plan to spend September writing up the results. All of the publications I have been involved with over the years have been unique, but this one not only will be unique, but remarkably unexpected as well.

And yes, pending funding, I plan to mount an effort to re-catch Irma later this summer, so that we can replace her current tracking device with a new one and keep the information rolling in.

More later.

Another view of Irma on the morning of June 20 in a wet forest outside Riegelsville, New Jersey.

Another view of Irma on the morning of June 20 in a wet forest outside Riegelsville, New Jersey.

By Keith L. Bildstein, Ph.D.
Santiago, Chile
31 May 2015

I have been studying Striated Caracaras, a.k.a. Johnny Rooks, on the Falkland Islands since December 2010. Until my most recent trip I have timed my visits to study the birds either in mid-summer or mid-winter. The plan had been to contrast rook ecology in those two seasons and to draw conclusions regarding seasonal differences in their behavior.

The trip I am now returning from has been a “temporal anomaly.” I spent two weeks on the islands in late May, which is “austral autumn’’ (think late November north of the Equator), to learn how the birds make the transition from the summer food largess to the cold and snowy winter lean times.

I have known for some time that the bulk of the 150 or so rooks that inhabit Saunders Island in the northwestern part of the archipelago spend most of their summers at and around Gentoo and Rockhopper penguin colonies at the wind-swept “Neck” in the northwestern part of the island (see first photo below) and then move from there to a farm settlement (second photo) at the eastern edge of the island in winter. Penguins and their young provide the rooks with food in summer and the island’s farmer-owner and his family provide most of the food in winter. Ten miles separate the Neck from the Settlement sites and I have seen individually-marked rooks at both locations on the same day, meaning they are able to make the journey between the two sites in a single flight or rapid series of flights.

A penguin colony at "The Neck," a summer hotspot for Johnny Rooks.

A penguin colony at “The Neck,” a summer hotspot for Johnny Rooks.

Rooks waiting to feed at the Settlement. The rook on the rail at the far right is a juvenile.

Rooks waiting to feed at the Settlement. The rook on the rail at the far right is a juvenile.

When I arrived on Saunders on the 18th of May the overwhelming majority of birds, and almost all of the young birds-of-the-year, still were at the Neck and consuming an unusually large number of dead Gentoo Penguins that had washed up along drift lines surrounding the Gentoo breeding colony. It wasn’t clear what had killed the penguins, but more than 100 rooks were taking advantage of the carcasses nevertheless. And so were several dozen Turkey Vultures. Indeed, there was so much food laying around that the rooks and vultures were feeding relatively amicably without the normal food-fighting that characterizes most of their feeding events. And most of the rooks had clearly bulging crops suggesting that they were “filled to the rim” with penguins.

Within a week, however, things began to change. Cold, southerly winds blowing in from Antarctica chilled the island with the first dose of winter weather, the penguin food largess shrank, and the birds began their mini-migration toward the Settlement.

They did so in a way that surprised me. Groups of four to 10 rooks–overwhelming young-of the year—took several days to make the 10-mile journey, moving about two to six miles each day and sampling habitats along the way. Relatively little in the way of food exists in the treeless Patagonian steppe between the Neck and the Settlement, and after several days of meandering, the birds arrived. In a manner of speaking, the birds seemingly “settled in” for the winter. By the time I left Saunders Island on May 28, more than 60 of the rooks had made the autumn transition during a period in which temperatures dropped below freezing for the first time since the last austral winter.

I had not given it much thought but the onset of cold weather and the lack of available food immediately shifted the birds’ behavior. Until the first freeze, rooks and vultures were feeding together at carcasses. The day after the freeze, gangs of rooks dominated Turkey Vultures at food resources as they normally do in mid-winter. The change literally happened overnight. Unfortunately I was not there to see if the situation reversed itself when warmer temperatures returned the day I left, but the switch was obvious.

Boise State University graduate student Anna Autilio and I were conducting observations of feeding behavior at experimental goose carcasses we had arranged for the birds. The observations will form a main part of Anna’s master’s thesis.The afternoon after autumn’s first frost, rooks feeding on the goose were noticeably ravenous, much more so than they had been in the days leading up to the arrival of cold front. It was as if a physiological trigger had gone off and the birds clearly were in “feeding frenzy” mode. For many of the individuals involved it would have been the first frost of their life… and something of a “difficult learn.”

Anna and I had conducted a survey of rook distribution and abundance in the area immediately surrounding the settlement earlier in the day. As we began the survey on our all-terrain vehicles at the edge of the settlement, a first-year rook flew up and perched several meter away. The bird then proceeded to walk up to a puddle of ice-covered water along the track in front of us and tried to skim a drink from it. As its beak skidded across the ice that glazed the puddle I couldn’t but help imagine what was going through its head.

Without parental guidance, the first-year hadn’t a clue how to drink from the ice-covered puddle. The bird flew off several seconds later and I spent the next hour and half on the survey aiming my ATV at the frozen-over puddles that dotted our route. I couldn’t help but break the ice, making the water below potentially available to the young rooks, thinking all the while about what was in store for these youngsters as their first winter approached… a time of the year when as many as a third or more of them would perish.

Everyone faces a number of challenges in life, but the longer I study Johnny Rooks the more I appreciate just how lucky we humans are compared with our raucous avian friends.