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Johnny Rooks digging for kelp maggots on the Falkland Islands.

By Keith L. Bildstein, Ph.D., Sarkis Acopian Director of Conservation Science
and  Katie Harrington, Hawk Mountain Research Associate
Hawk Mountain Sanctuary

29 August 2016

Bear with me on this; it is really quite exciting…

Kelp maggots are the larvae of coastal dipterid flies that feed on rotting seaweeds, including kelp that drifts up along sandy shorelines.  In the northern hemisphere, these larvae (aka maggots) are themselves fed upon by shorebirds and passerines, including crows, which excavate them from kelp wracks that accumulate along the shorelines of sandy beaches.  Although studied little south of the equator, kelp maggots also inhabit the rotting kelp that drifts up along the shorelines of the Falkland Islands, including those on Saunders Island, a 49-square mile landmass in the northwestern part of the archipelago.

Neck Maggot Feeding Summer

Johnny Rooks digging for kelp maggots

For more than four years, we and our colleagues have watched the Striated Caracaras (aka Johnny Rooks) that we have been studying on Saunders Island, digging and probing beached kelp adjacent to penguin colonies there, and have wondered if these largely scavenging birds were receiving ecologically significant amounts of nutrition from the buried invertebrates.  In February of this year, we began to study this feeding behavior in detail using a protocol that allows us to quantify the rate at which individual caracaras secure maggots.  Our observations involve counting the numbers of maggots individual birds catch and consume during 30-sec feeding bouts.  We continued to collect data using this protocol on our most recent trip this August to assess the extent of seasonal differences in feeding rates.  We also collected maggots and weighed them to determine their individual mass, allowing us to determine their nutritional value. Our results, albeit preliminary, suggest that although birds capture maggots at higher rates in austral summer than in austral winter, in both seasons they manage to do so at rates of capture that are high enough to provide substantial nutrition for the birds engaging in this behavior for several hours or more daily.

The dogged determination and methodic nature with which the rooks dig is impressive, with many birds digging alternately with their left and right feet five inches or more into the rotting kelp while securing dozens of maggots over brief periods.  Clearly, more study is needed, but our initial observations suggest that this nutritional resource plays a significant role in the life of Striated Caracaras year round.

Summer maggots

Exposed kelp maggots

Intriguingly, on the most recent trip we also saw groups of rooks digging in upland pastures where they were feeding on what appeared to be small earthworms and grass grubs, with about the same rate of capture as when they were catching kelp maggots.  On our next trip in February 2017, we plan to expand our observations considerably.  In the interim, we will be presenting preliminary results of our work at the annual meeting of the Raptor Research Foundation in Cape May, New Jersey, in October.

Of course, insect eating is not unknown in raptors.  Kites, American Kestrels, and many other falcons routinely do so, as do larger birds including Steppe Eagles overwintering in Africa.  However, digging in the ground for insects is relatively uncommon among birds of prey.  Honey buzzards reportedly do so, and kites and Common Buzzards dig for earthworms in recently plowed fields in Europe.  That said, at least some rooks appear to do it routinely as well, and not only on Saunders Island.  In August 2013, during a short trip to Steeple Jason, a tiny island in the Falklands more than 50 kms from Saunders Island, one of us saw large numbers of caracaras digging for earthworms in peaty soil at the base of the island’s steep escarpment.

Our work with caracaras indicates that they are severely food stressed in winter on the Falklands.  Digging in the ground for invertebrates at first may not seem “raptorly,” but beggars cannot be choosers, and the taste of a live invertebrate may beat that of a rotting vertebrate anyway.

Red-backed rescue - cropped

Keith rescuing the female Red-backed Hawk from a pack of Striated Caracaras.

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

24 August 2016

With an extensive open-country distribution throughout much of southern South America, Red-backed Hawks are the functional equivalent of North America’s widespread Red-tailed Hawk. The mid-sized Buteo—red-backs weigh in at just over one kilogram, or roughly the same body mass of a Red-tailed Hawk—feeds mainly on small birds and small mammals across much of its continental range.  But on the Falkland Islands, where the species also is common, red-backs focus on Upland Geese, a large terrestrial goose that weighs 3.5 to 4.0 kilograms, or more twice the body mass of a Red-backed Hawk.  Given this rather unusual predator-prey size relationship, red-backs, which are non-migratory on the Falklands and remain paired-bonded throughout the year, hunt geese together in male-female duos with one hawk distracting the goose while other surprises and “takes down” the un-suspecting waterfowl.  In many instances, both members of the pair kill the goose before feeding on it simultaneously, with both gorging themselves and often returning to the carcass for a day or more as they strip every last piece of edible tissue from it.

This cooperative feeding routine works well for the red-backs on the main islands of East and West Falkland, where there are few if any Striated Caracaras to worry about, but such is not the case where the two species co-occur on the smaller, peripheral islands.  Our principal Striated Caracara (aka Johnny Rook) study site, Saunders Island, which is inhabited by several dozen Red-backed Hawks, as well as over 80 Striated Caracaras, is a case in point.  On Saunders Island as elsewhere, caracaras may be incapable of subduing and killing Upland Geese on their own, but they are not above competing for a dead goose once a pair of red-backs have killed it.

Such was the case on Saunders last week when my colleague Katie Harrington and I came upon a pair of Red-backed Hawks feeding upon a recently killed Upland Goose in a sheep meadow at the eastern end of the island one morning earlier this month.  Both hawks, but especially the female, had already gorged themselves on the carcass while cooperatively fending off several dozen, mostly juvenile caracaras that were attempting to partake in the feast. As we approached the group to read the bands on the caracaras—we have fitted more than 1,100 of Johnny Rooks with individually numbered rings as part of our long-term studies of the species—the male red-back took off. The female tried to do the same but was unable to do so given an enormously over-filled crop, which made it impossible while she was being attacked by more than a dozen caracaras that had pinned her down on her back and were feverishly “footing” and pecking at her.  Sensing that she was not long for this world, I jumped off my ATV and ran her down after she broke free from the swarming caracaras.

Keith with red-backed

A close-up of Keith holding the female hawk, with it’s bulging crop.

My decision was instantaneous, our initial approach, which had spawned the male’s successful departure, had left the female vulnerable, and although interfering in nature is not something I typically do, in this case our approach had tipped the competitive balance in this ongoing interaction, and my rescue attempt was aimed at minimizing the consequences.  The carcass was a little more than a kilometer from our cottage at our farm-settlement headquarters, and I remounted my ATV, cradling the hawk in my left hand while steering and thumb-throttling the ATV with my right.  We reached the settlement several minutes later where I placed the female in a dog kennel to give here time to digest her crop peacefully.

Four hours later I released the hawk, who by then had digested about half of food in her crop, but to no avail, as a group for more than a dozen caracaras appeared as out of nowhere and proceeded once again to pin her down in what appeared to be a death grip.  Once more I sped toward the hawk, ran her down, and re-rescued her, placing her back in the kennel with a plan to release her the following morning.

By the time I had grabbed her from the kennel the next day morning, the distended crop was no longer visible, and although half-a-dozen caracaras again initially pursued her, this time they kept their distance, as the lack of a crop most likely signaled them as to the danger in approaching too closely.  After flying off and perching on a fence post for about 5 minutes, the hawk flew off un-pursued in the direction of the goose carcass and her mate.  She was re-sighted at the settlement several days later holding her own against a group of caracaras fighting over a goose carcass that had been fed to the farmer’s pigs.

The sharper talons of the predatory Red-back Hawk make them formidable opponents to the less predatory and less well-armed caracaras—at least when not encumbered by an over-filled crop.  However, when they do have a large crop, the interspecies-competitive relationship changes, and in mid-winter (austral-winter August is the equivalent of boreal-winter February) when both species are hard-pressed for food, it becomes something of a raptor-eat-raptor world on the Falklands Islands where things can change rapidly for individual birds.

Stay tuned… next week I will blog about yet another potential dietary item for food-stressed Johnny Rooks: kelp maggots.

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.

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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.

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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.

collages

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.

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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.”