Posts Tagged ‘black vulture’

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

18 Jan 2018

Monitoring the distributions and abundances of birds of prey is “key” to tracking changes in their conservation status.  And this, in turn, is key to protecting them.

Indeed, lack of monitoring once-abundant Old World vultures in southern Asia during the height of their diclofenac-induced population declines in the 1980s and 1990s allowed populations of three species of widespread and common vultures to plummet catastrophically by more than 95%, unnoticed by the conservation community. Conservationists were caught by surprise at this greatest global loss of raptor populations in recorded history, necessitating expensive captive-breeding programs, which, unfortunately, some believe may offer “too little, too late” to restore these once-common species to their former status.

It was with this self-inflicted catastrophe in mind that Hawk Mountain Sanctuary embarked an ambitious intercontinental population monitoring scheme stretching from southern Canada to southernmost South America, aimed at tracking both short and long-term shifts in the distributions and abundances of populations of the world’s two most common New World scavenging birds of prey, the black and turkey vulture, along with other less common avian scavengers including caracaras and condors.

The Sanctuary’s effort began in 2004 with eight winter roadside-survey routes in Costa Rica, totaling more than 1200 kilometers.  Since then, a series of more than 150 seasonal (both winter and summer) roadside counts have been undertaken across Canada, the United States, Costa Rica, Panama, Venezuela, Uruguay, Chile, Argentina, and the Falkland Islands.  In 2017 we began resurveying these routes to assess the extents, if any, to which populations of scavenging birds of have changed over the years.  Seven roadside-counts in central Argentina were the first to be redone this July.  In late December 2017 I re-ran two of the southernmost surveys in southern Patagonian Chile.  The latter two surveys are the focus of this entry.

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Road sign indicating the highway goes to the end of the world (Ruta del fin del Mundo).

Although the two survey routes are just beyond the traditional southern distributions of both black and turkey vultures, both are within the distributions of Andean condors, southern crested caracaras, and chimango caracaras.  (The routes, themselves, are part of the “Ruta del Fin del Mundo,” or the “Highway at the End of the World,” as the Chileans call it on their road signs.)  The goal was to learn if black and turkey vultures, both of which are extending the northern limits of their ranges in North America were doing the same southward in South America.  I was on my way to field work in The Falklands, and had scheduled four days to survey scavengers along the two routes I had earlier surveyed in the austral summer of 2010-2011.  One route followed the northern shoreline of the Strait of Magellan for 205-kilometers from 40 kilometers south of Punta Arenas, Chile, to Punta Delgada, Chile, close to the border with Argentina.  The other stretched 193-kilometers from 40 kilometers north of Punta Arenas to Puerto Natales, Chile, near the southern terminus of the Andes.  Although the forecast called for rain on three of the four days, I planned to complete my surveys. Thankfully the wet weather held off, and I was able to conduct all four surveys without interruption.

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An old store in a ghost town on the shoreline on the Strait of Magellan in Patagonian Chile.

Both routes took me through spectacular treeless Patagonian Steppe, desert-like regions with little vegetation that superficially resemble parts of the arid American West–open areas ideally suited for spotting both perched and flying birds of prey.  Although the surveys are just “indexes” of populations of scavenging birds of prey inhabiting approximately half-a-kilometer strips along either side of the roads, they do provide relatively consistent counts of scavenging birds of prey in an area.  Indeed the two counts along the first route yielded survey totals of 13 southern crested and 1 chimango caracara, and 13 crested caracaras and 3 chimango caracaras on the 19 and 21 of December 2017, respectively, supporting the validity of the survey technique’s ability to assess regional populations.  The second route was more variable with no Andean condors seen on the first count day and 10 seen on the second, but all-in-all, these results and our earlier surveys suggest that populations of the three species seen had changed little across the eight years of the austral-summertime surveys.  Whether this will hold for scavenger surveys in other regions remains to be seen.

However, that is only part of the story.  Although I did not have time to record other species seen along the routes, I did see a number of other fascinating birds and animals, including handfuls of cinereous harriers and variable hawks, together with rheas, flamingos, black-faced ibises, southern lapwings, and guanacos.  One of the most fascinating behavioral aspects of the surveys was that road–killed rabbits and other small mammals that had been hit by traffic the evening before each survey were quickly fed upon by southern crested caracaras early the following morning, with the caracaras unquestionably out-competing kelp and dolphin gulls that tried unsuccessfully to “horn-in” on the action.

The situation reminded me of what I saw several years ago while studying Old World vultures in the Masai Mara of south-western Kenya, where in early-morning, first-in-the-air, ruppells, white-backed, and lappet-faced vultures congregated at and fed upon lion- and hyena-killed prey from the previous evening’s predation events.  Although my Patagonian observations occurred only across several days, there was little doubt that a daily feeding pattern existed.  The fresh-killed rabbits I spotted from early to mid-morning each day—and that each attracted as many as a dozen or more caracaras—had all but disappeared by late morning, with nothing but bright-red splotches on the concrete roadway offering evidence of what had happened the previous evening, an obvious example the unintended effects of human commuters.  Another intriguing behavior was that of Andean condors, several of which were seen in low-flying (<5 meters) flight along the roadsides, something I often associate with carrion-seeking turkey vultures in both North and South America.

These recent surveys convince me that even without black and turkey vultures, road surveys can be both fun and scientifically profitable, and I look forward to conducting them again in another 5 or 10 years.

More roadside scavenger counts are planned for central Argentina in January and in Arizona in February.  I will keep you posted on the results.


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By Adehl Schwaderer, Hawk Mountain Conservation Science Trainee

03 Jan 2018


As a Hawk Mountain Conservation Science Trainee, you have the opportunity to be a part of many influential experiences, including counting migrants as they pass North Lookout and educating visitors about the importance of raptor conservation. But the experience that I have learned the most from this autumn was working with my fellow trainee Zoey Greenberg on our black vulture movement ecology project. This blog is part two of our vulture series so be sure to check out part one to gain a complete understanding of our project.


The plan was to locate three black vultures, Versace, Gifford, and Hillary, based on their recent GPS locations and observe what the birds were doing at these locations. To be honest, I wasn’t sure what to expect. I was excited to get started and gain new field experience, but no one had ever attempted groundtruthing with this species before, and it is still a new concept. We accepted this challenge with enthusiasm but were anxious about getting results. In the end we knew that no data would still be valuable information, however who doesn’t want groundbreaking results from their first ever field study?



Versace perched on a barn in the Kempton Valley, notice her wing tag and antennae of the telemetry unit.

Thankfully, our first day in the field was a success! Zoey and I followed Versace’s movements from the previous month, which led us to a large roost of black and turkey vultures in the Kempton Valley. We were ecstatic, and from that point on, we were on a roll! Throughout the next three months we kept up our tracking efforts and found many more roosts (some permanent and some temporary), observed interesting behaviors, and made an effort to trap and tag these birds. By doing all of this, we were able to confirm some of our suspicions. However, we also discovered things we did not expect.


One of the suspicions we were able to confirm was that black and turkey vultures more often than not share the same roost sites. These two species have very different tendencies when searching for food, feeding, and perching, but that did not stop them from co-existing at the same roosting sites and air space. We also suspected that the vultures would use some roosts more consistently than others depending air temperature, trees available, and proximity to their next meal. We determined what each roost site was being used for, as well as observed a shift in preferred roost locations and species composition as winter set in and turkey vultures began migrating south.



Turkey vulture trapped and tagged in Kempton Valley by Adehl, Zoey, and David Barber. 

We found the most unexpected results attempting to trap “our” black vultures. We enlisted the help of Hawk Mountain biologists, David Barber and Jean-François Therrien, who both have extensive trapping and tagging experience with vultures and other raptors. The goal was to capture and wing tag a substantial number of the black vultures we followed around in the Kempton Valley.



To do so, we staked down road kill (a vulture delicacy) at several roost sights we had determined were used mainly for feeding. Once the bait was staked, we placed noose traps made of fishing line and parachute cord in a diamond around the carcass. Once everything was in place, we would wait for the vultures to descend on the meal and consequently get their feet stuck in our traps—a process that does not harm the birds).


That is exactly what we did. We waited… and waited… and waited to no avail. The first site we chose to bait was seemingly perfect. There was already an area on the property where the landowners frequently discarded rotting vegetables and meat scraps. In addition, dead trees and conifers, which provided many roosting options for the birds, surrounded the dump.


However, shortly after we began baiting, two unwelcome visitors decided to join the flock: an adult and immature bald eagle. Now you may be thinking, “Wow! How amazing you get to observe vultures and the majestic bald eagle in one place!” Well, you would be wrong. We learned immediately that vultures and eagles do not enjoy sharing the same air space, or the same dining room table for that matter.


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Adehl holds the trapped and newly tagged turkey vulture.

We are confident that this interaction caused us to be unsuccessful in trapping vultures at this trap site, and the second area we chose to bait and trap. As soon as the eagles were seen at the roosting areas, black and turkey vultures were not seen roosting in those locations again during our observations. We did not expect this to occur because in other locations, like the Conowingo Dam in Maryland, eagles and vultures co-exist in the same feeding sites with no apparent issue. We believe the higher tolerance in these areas could be due to a larger food source with enough to go around for everyone, meaning that there is no need to initiate a food fight. The availability of only one carcass at our bait sites and providing large carcasses that were more easily discovered could have been the reason that the vultures and eagles in our study did not get along at our sites. However, all was not lost! In the end we did manage to trap and tag one turkey vulture, which was a very valuable learning experience for Zoey and myself.



Ultimately, I was able to witness unique behavioral patterns through this opportunity that will stick with me the most. I will never forget the breezy autumn morning when over twenty turkey vultures performed aerial acrobatics on a freshly plowed hill between bouts of picking through the soil with their bills and talons. Nor will I forget standing in the pouring rain, watching more than forty black vultures run across the bars of an information tower with their bills clapping and wings spread wide.


Zoey and I learned so much by only taking the time to stop and observe, and we are excited to see what else others that take the time to do the same will discover.

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By Zoey Greenberg, Hawk Mountain Conservation Science Trainee

21 Dec 2017

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Female black vulture named Donald over a quarry during September of 2016 near Palmyra, PA.

The tires crunched on gravel, and I shut the engine off. We had entered vulture country. With scope, data sheets, and binoculars in hand my project partner, trainee Adehl Shwaderer and I walked carefully up the gravel road as we scanned the tree tops for hunched silhouettes or soaring shadows. This was our first foray into the Kempton Valley, east of Hawk Mountain, in search of black vultures (Coragyps atratus). Our expectations were not high. However, we had innovation on our side: we were testing a method called “groundtruthing” to better understand the movement ecology of several vultures that had been tagged with satellite transmitters by Hawk Mountain scientists. After investigating their movements in Google Earth, we had discovered interesting patterns including an individual who spent time near quarries, and another that seemed to prefer cities. The problem was, we didn’t know why.


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Some tools used for groundtruthing method: laptop, smartphone with hotspot, and a vehicle.

Groundtruthing works like this: we, the field researchers, embark into the field with an internet hotspot and laptop in tow. We look up the locations of tagged vultures on an online database called MoveBank.org and then drive to meet individual birds and watch their behavior. By combining technology with old-school methods, we are able to gain visual access to black vultures and unveil mysteries about their movements that remain when we rely exclusively on satellite tracking data to explore patterns. As I became more comfortable with groundtruthing, I realized that the beauty of the method exists in its simplicity, utility, and the truism that even in this day-and-age there is no substitute for in-person observation.


A wonderful realm of study exists when we move beyond discovering where birds are, and incorporate studies that investigate why. Black vultures provide irreplaceable ecosystem services for us through their removal of carcasses that can carry harmful diseases. However, due to their curious nature and adaptability, they are often involved in conflict with humans that can result in noise-hazing, shooting, and other forms of human persecution. Therefore, investigating their movement patterns is necessary.


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Versace’s movements within the Kempton Valley, November, 2017.

At the beginning of our project, we relied on the signals of three birds, Gifford, Hillary, and Versace. (Donald, who turned out to be an adult female, flew to Washington DC after being tagged. We have not heard from her since.) By following these individuals, we discovered three night-time roosts within the first week and I feel confident that any bystander watching our first roost discovery would have been convinced we’d won the lottery. A silent performance of spastic jumping, “air-fives”, and the spontaneous creation of a vulture dance quickly occurred before we got back to business and counted the birds.


In the weeks that followed, we experimented with various observation techniques and read multiple papers on roosting ecology, black vulture foraging strategies, and behavioral study methods. We talked vultures at breakfast, lunch and dinner. We bored our housemates at the trainee residence with discussions on the most pungent types of road kill and the antics of our favorite birds. We filled our brains with vultures, and above all, became true detectives through a process of trial and error that taught us the value of being innovative in the field. Those first weeks were memorable, solidifying in me a hunger for scientific questioning.


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Zoey with a tagged turkey vulture.

There was an additional aspect to this project that I found consistently rewarding: the opportunity to speak with landowners in the Kempton Valley. Many of the roost trees preferred by “our” vultures were on private property, and in addition to observing the birds, we were looking for optimal trapping sites near already-established roosts in hopes of catching wing-tagged birds. This would provide us with information on associations among individuals. However, our trapping method entailed staking road kill to the ground and waiting for vultures to arrive while we waited nearby. In general, people aren’t thrilled about the prospect of hosting dead possums in their backyard. Nonetheless, we were rarely told no. Even landowners who professed a hatred of vultures were open and willing to hear our reasons for loving the birds, and eventually developed a tolerance of their own.


Vultures are hard to sell, and they do have some less-than appreciated habits, such as defecating on cars and toying with the rubber on windshield wipers. However, every “bad” habit has an explanation. For example, vultures are scavengers, meaning they rely heavily on maintaining strong neck muscles for tearing and pulling apart carcasses. To a vulture, rubber is an irresistible training opportunity to both strengthen their neck and satisfy their characteristically curious nature. It became clear that explaining to people why the birds were choosing their property provided them with a new dimension of understanding. This makes groundtruthing not only important for answering scientific questions, but also for enhancing a culture of appreciation around birds that struggle to gain respect. After all, our home ranges overlap with other species, and as such, perhaps we have a duty to critically evaluate our collective perception towards all of our neighbors, including vultures. After spending this season in the field, I am convinced that the Kempton Valley is a perfect place to start.


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Conservation science trainees Adehl (left) and Zoey (right) embark on an early morning search.

So what’s next for the vulture detectives you ask? Our field tested method of groundtruthing will be used to fill in more gaps in places with tagged vultures, contributing to our knowledge of why the birds go where they go. Ideally, this information can then be directly applied to informing locals, politicians, conservationists, biologists, and other groups affected by or connected with vultures in their region. As for Adehl and me, early morning roost searches and tactfully placed road kill may remain in both of our futures. There are few sights that compare to a group of dew-covered vultures eyeballing you from above as they slowly swivel their body to absorb the sun’s first rays. With a sight like that there’s only one outcome: once a vulture detective, always a vulture detective.


To learn more about our interesting findings, stay tuned for Vulture Detectives: Part 2 written by Adehl Shwaderer.


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By JF Therrien, Hawk Mountain Senior Research Biologist

07 Aug 2017


JF reviews American kestrel nest box data with summer intern Jenna Schlener.

Hawk Mountain has a rich research and monitoring history. For several decades now, on-staff researchers have been carrying the torch, keeping numerous inestimable monitoring projects going. The migration counts conducted at Hawk Mountain indeed represents the longest running raptor monitoring project in the world.

Starting some 80+ years ago, the counts were first designed to assess the usefulness of the protection offered by the newly created Sanctuary. Not long after, Hawk Mountain’s curator Maurice Broun and others realized the invaluable long-term dataset that those counts represent and they could be used to study population trends of 16 North American raptor species. Then in the mid 1950s, Alex Nagy, then Hawk Mountain’s assistant curator, installed a few bird boxes on his farm to see if he could get American kestrels to use them. What most likely started as a humble backyard experiment resulted in what is now the American Kestrel Nest Box Program, which will proudly celebrate its 65th anniversary next spring.

Research and monitoring projects sometimes begin after a carefully designed approach. However, in reality, many such projects simply start serendipitously, as in the previous examples. Traveling around Hawk Mountain to visit the 125 man-made nest boxes of the American Kestrel Nest Box Program during summer 2017, we noticed odd and conspicuous behaviors of bigger, darker birds. Indeed on distinct occasions, black vultures would suddenly appear flying low overhead or even flying out a window from the very barns our kestrel nest boxes are attached to. At that point, we had little doubt; those vultures are likely using the building to nest.

Black vulture chick named Versace wearing wing tag and transmitter photo credits R.Smith

JF holds a newly tagged black vulture named Versace.

From a research point of view, having access to nest sites is highly valuable. In addition to being able to handle adults and chicks to assess their life history traits (body condition, growth rate, disease prevalence, etc.), monitoring nesting activities allows us to assess breeding success and breeding rate, age at first breeding, and nest site fidelity on the population level over time. Those aspects are all immensely important to understand the complete cycle of individuals that compose populations.

Finding this access to several nests for any raptor species is challenging, because individuals are often territorial. Their nests occur at low density and are usually concealed. Therefore, monitoring nesting raptors often becomes an unrealistic task, given the time required and the area that would need to be covered to locate a fair number of them. A good breeding monitoring project requires a relatively easy way to access several nests across a relatively small area to allow researchers to visit them periodically.

Black vulture chick photo credits J.Dallas

Black vulture chick found in a local barn. Photo by J. Dallas. 

During summer 2017, our team found just this. We were able to successfully monitor 3 black vulture nests that we found without even searching while checking our kestrel nest boxes. Those birds were using Pennsylvanian barns just like giant man-made nest boxes, and thankfully they were all in a relatively small radius around Hawk Mountain.

This project has just begun, and we are now looking to double or triple the number of monitored nests in the coming years. So if you notice black or Turkey vultures flying out of abandoned buildings or barns, please let us know. We would be thrilled to add new nest locations to our newly-born monitoring program.

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Tagged black vulture. Photo by Holly Merker.

By using individual markers (such as wing-tags and telemetry transmitters), we will be following the where and wherefore of those individual birds through their lifetime. Anytime you see a vulture, keep an eye out for wing-tags (a brightly colored tag showing a distinct number). Any sighting of a tagged individual represents important information for locating roost sites, feeding hot spots, survival rates, and dispersal behavior. Help and support these studies by reporting any sightings at this link.

Monitoring programs such as these are an essential part of conservation science: they form the backbone of long-term population assessments. They allow researchers to keep track of historical population size and productivity in order to identify declines in a timely fashion and become aware of problems that otherwise could have gone undetected.

To learn more about our work with North American vultures or any other species of raptors, or if you wish to support our monitoring efforts financially, contact me at therrien@hawkmountain.org.


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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.


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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.


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The team pauses to take a self: From left, Jean-Fancois Therrien, Marc Bechard, Jennie Duberstein and Keith Bildstein.

The team, from left, Jean-Fancois Therrien, Marc Bechard, Jennie Duberstein & Keith Bildstein.

By Keith Bildstein, Ph.D.
Sarkis Acopian Director of Conservation Science, Hawk Mountain Sanctuary
May 26, 2014

I have just returned from field work on the northernmost population of North America’s southernmost race of turkey vultures, Cathartes aura aura, a diminutive and largely tropical sub-species that weighs only two-thirds as much as other North American turkey vultures.  Our field team was made up of Hawk Mountain Research Associate Dr. Marc Bechard of Boise State University, former Sanctuary trainee Dr. Jennie Duberstein of the U.S. Fish and wildlife Service, me, and Hawk Mountain’s Senior Research Biologist Dr. Jean-Francois Therrien.

Our work in the approximately 100,00-square-mile Sonoran Desert in southern Arizona which included placing satellite tags on both turkey vultures and black vultures, turned out to be—as  often is true of field work–full of surprises.  Our new trapping site at a pair of dairy farms on the outskirts of Buckeye, Arizona, southwest of Phoenix, was far better managed than many of the farms we had visited before, and its owners were gracious beyond belief. One of the potential trap sites offered little in the way of clear views of any traps we might put out, but a second site near a massive ossuary, or boneyard, proved to be perfect.

A bone pile provided an ideal trapping site in the Sonoran Desert west of Buckeye, Arizona.

A bone pile provided an ideal trapping site in the Sonoran Desert west of Buckeye, Arizona.

Our plan was simply enough to trap and tag six turkey vultures and four black vultures, conduct a few day-long roadside counts, and spend a day looking for several of the individual vultures we had tagged in May 2013. We had nine days to accomplish all of this and, as there was no rain in the forecast, the plan seemed quite reasonable.  In the past, our experience with trapping turkey and black vultures has been that the latter species is easier to trap than the former, in part because black vultures dominate turkey vultures at carcasses, and in part because of the black vulture’s more social nature (i.e., if you catch one you are likely to catch many).

But not this time around.

The first six birds we caught were turkey vultures!  Blacks, although relatively common in the area, rarely showed up at our trap site, and were more skittish than the turkeys. We did catch one on the sixth day of trapping, but decided to turn to road surveys on the seventh day, as the likelihood of trapping more black vultures seemed rather low.  Presumably most black’s in the area were feeding somewhere else, and unfortunately, we never found that location.

A perched turkey vulture along one of our survey routes near the ghost town of Ruby, Arizona.

A perched turkey vulture along one of our survey routes near the ghost town of Ruby, Arizona.

We spent the next two days counting vultures along two road-survey routes that covered more than 300 miles of Arizona secondary roads south of Gila Bend and Tucson Arizona, mainly in the Tohono O’odham Indian Reservation and the Coronado National Forest.  Unlike the counts we conducted in January, the routes were filled with single and small groups of turkey vultures, many of which appeared to be searching the roadways for road-killed carrion, including snakes. Overall, we saw more than 10 times as many birds as we had seen along the same routes in winter, suggesting that the bulk of the population migrates south from the region in winter.

We spent the final day in the field searching for the five vultures we had tagged last May. The first one we searched for was “Jennie,” a vulture that, having migrated about 250 miles into Mexico last October, returned to Arizona less than a week later and overwintered in the area south and west of Gila Bend.   Unfortunately, Jennie was roosting in the Barry M. Goldwater Air Force Range, a bombing range south of Gila Bend that was off bounds for us, and was feeding at a dairy farm west of Gila Bend that the owners would not allow us to enter.  The next three birds were roosting and hunting closer to Maricopa Arizona and we set out in search of them just before noon.

The last known location of the next bird, “Desert Rat,” took us to a roosting site in a nut grove across the street from a large dairy farm.  Although we did not actually see the bird, we did find a number of molted feathers under a nut tree, confirming the presence of vultures at the site.

Keith and Linda Wallace-Gray with her vulture namesake in May 2013.

Keith and Linda Wallace-Gray with her vulture namesake in May 2013.

The next bird we looked for was “Julie,” who had last been sighted over a recently cut  north of Stanfield, Arizona.  Although we failed to see Julie, we did see another tagged vulture, “Linda” feeding together with six other birds on a road-killed jackrabbit at the edge of the hay field. Linda’s transmitter had been “misbehaving” and was sending signals episodically, with the last fix being recorded more than a month earlier in early April.  She was close to where she was then, and our sighting of her helped explain the episodic nature of her signals.  Although her tracking device was still in place on her back, the antenna for it was missing, a fact that almost certainly explained the spotty nature of her signals.  Given that we had seen close to 100 birds the day we were searching for the tagged individuals, and that as many as 500 birds almost certainly were using the area, our visual sighting of Linda, albeit without her antenna, was like winning the lottery … a “grand finale” of sorts for our field work.

Our plans are to revisit Arizona next January, not only to finish our tagging efforts there, but also to conduct additional road surveys. Although we are but one year into our studies of Arizona’s Sonoran Desert vultures, we already have learned much about their ecology.  Equally importantly, we also have learned to expect the unexpected in this population, which gives me reason to believe we need considerable additional monitoring to understand this most-southern race of North America’s most common and widespread avian scavenger. So please stay tuned.


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