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Posts Tagged ‘summer’

By JF Therrien, Hawk Mountain Senior Research Biologist

07 Aug 2017

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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.

tagged at nlo by holly mercker

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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