tracking

Irruptions and Innovation

By Zoey Greenberg, Science Outreach Coordinator
Hawk Mountain Sanctuary

Stella, a snowy owl tagged by Project SNOWstorm earlier this year.

Stella, a snowy owl tagged by Project SNOWstorm earlier this year.

In 2007, Dr. JF Therrien deployed 12 transmitters on snowy owls on Bylot island in the Canadian Arctic. Snowy owls, like other raptors, can be difficult to monitor due to their territoriality and low densities. Arctic-breeding raptors typically establish nesting sites in remote locations, adding to the logistical dilemma of gaining insight into their life history traits, and the role they play within the Arctic ecosystem.

Satellite transmitters, citizen science, and long-term life history studies are extremely valuable tools that allow researchers to examine the movement ecology of birds, including snowy owls. Mixing and matching these tools can open doors to compelling scientific questions, and in the case of Therrien’s snowy owls, has resulted in papers covering a range of topics. New information on survival, reproduction rate, dispersal of adults, irruptions and winter movements are among recent Hawk Mountain publications that were made possible through this type of innovation. 

Two such papers were led by former conservation science trainees, in collaboration with others, including Dr. JF Therrien. These papers delved into the mystery of snowy owl irruptions, defined as the “massive movement of individuals over large distances, associated with large fluctuations in food supply.” Some of us have been lucky enough to see a snowy owl in Pennsylvania, on those rare winters when the birds venture further south than usual. I myself drove two hours to catch a glimpse, and I will never forget the sight of that owl hunkered down in the middle of a field, glittering in evening light. As I drove away, I couldn’t help but wonder; what brings them here?

Two primary hypotheses have been proposed to explain irruptions; the “lack-of-food” hypothesis suggests that snowy owls leave their normal wintering grounds because of food shortage in certain years. This implies that the snowy owls we see in Pennsylvania should be in poor shape, and likely close to starving. The alternative “breeding success” hypothesis instead links irruptive movements to a surplus of food on the breeding grounds.

A snowy owl that was spotted in a local PA field last year.

A snowy owl that was spotted in a local PA field last year.

Snowy owls specialize in lemmings, a prey resource that occurs in pulses, due to their population dynamics. One year there may be a plethora of lemmings scurrying around the tundra, the next year very few, due to high predation and other factors. Lots of lemmings means lots of chicks, which means lots more owls. The breeding success hypothesis implies that the reason we see snowies in Pennsylvania is because following a high lemming year, there are so many owls dispersing at the end of the summer that some young birds push south.

To add depth to our knowledge of irruptions, Teja Curk, a conservation trainee from 2016, assessed the body condition (mass relative to size) of snowy owls during both irruptive and “regular” years. Teja assessed body condition of snowies on both regular (Great Plains) and irregular (Northeaster North America) wintering grounds, to see whether the birds we see during irruptive years are, in fact, starving. She found that most owls (male, female, juvenile and adult) were in good shape during irruptive years and even discovered that body condition was better on the bird’s irregular wintering grounds. “Good shape” in this context varies depending on sex and age of the bird, however less than 2% of the owls approached the weight threshold that would deem them a starving bird. Her results provide support for the breeding success hypothesis.

Pablo Santonja and Irene Mestre, trainees from 2015, looked specifically at the age of the birds found south during irruptive years. Their results supported the same hypothesis, showing that the majority of owls (up to 90%) seen in eastern North America are juvenile birds, meaning they are less than 1 year of age. As with some other migratory species, the more dominant birds within a population don’t move as far. Adult snowy owls often out-compete young birds, so it makes sense that in a year where adults are laying up to 11 eggs, some of those young owls will need to leave to avoid competition from more successful, experienced adults.

Bylot Island, where the Hawk Mountain team tagged and tracked several snowy owls.

Bylot Island, where the Hawk Mountain team tagged and tracked several snowy owls.

This leads to an interesting point: perhaps these two competing hypotheses are not, as Teja notes in her paper, mutually exclusive. After a highly productive lemming year, many lemmings will be eaten due to a surge in predator numbers, and therefore the next year could produce low lemming numbers. If this happens, snowy owls could be forced to look elsewhere for food. So, it turns out, that both a surplus of food and a lack of food seem to play a role in the patterns of movement among snowy owl populations.

If you ask me, these papers are a beautiful example of the scientific method at work; formulating ideas, testing those ideas, and polishing the conclusions in pursuit of certainty. Hats off to our trainees and their collaborators for hard work and intriguing findings. Teja is currently at the Max Planck Institute for Ornithology in Germany pursuing a PhD. Pablo is living in Spain, and Irene is now returning from three years in Australia.

Both of these papers utilized a data set resulting from a 25 year-long study in which live snowy owls were weighed, sexed, and aged. Christmas Bird Count (CBC) was also a valuable asset in both studies. For those of you unfamiliar with CBC, every winter thousands of volunteers gather together on the same day, collecting bird records within a territory and submitting them to a database that provides an impressive summary of which birds were seen, where, and how many. These papers demonstrate the utility of both citizen science and long-term studies, and in a rapidly changing world, this cross-pollination of resources is critical. We are very proud of our trainees for their hard work, and grateful to citizen scientists around the globe who give their time to participate in the expansion of our raptor knowledge.

Gaining a holistic understanding of an ecosystem requires acknowledgment of moving parts within, not separate from, the whole. Hawk Mountain’s research is part of several collaborative efforts to better understand the role of snowy owls within the big picture, including Project SNOWstorm and the Bylot Island Ecological Studies and Environmental Monitoring.  

Future projects will include building a model that combines reproductive and mortality rates to assess population trends of snowy owls. This past August, three transmitters were deployed on chicks before they left their breeding grounds. Investigating the movement patterns of these birds will hopefully allow for a comparative look at owls throughout the Eastern tundra, Western tundra, and those in between.

Check out Project SNOWstorm’s website (including a blog written by J.F Therrien on the most recently tagged snowy owls in Barrow, Alaska, as well as interactive maps): projectsnowstorm.org/posts/tracking-young-snowies-in-the-arctic/

Cape Coral Kestrels

By Kirsten Fuller, Spring 2018 Conservation Science Trainee
Hawk Mountain Sanctuary

Kirsten with a recently banded male American kestrel.

Kirsten with a recently banded male American kestrel.

Over the last year I transitioned from my familiar world of science education and immersed myself in the exciting field of raptor research!  In January, I was lucky to have the opportunity to travel to Cape Coral, Florida to learn about American kestrels with Hawk Mountain research biologist Laurie Goodrich, and long-term kestrel researcher Sue Robertson. 

Sue and her husband Bob first noticed the abundance of American kestrels wintering in Cape Coral in the late 1980’s.  They began trapping and banding the birds, and nearly 30 years later the data is still being collected.

These small falcons prefer open fields with low grass, which makes it easier for them to spot their prey.  In the winter, these birds have plenty of insects to eat in Florida, but they also find small rodents appealing.  This was our bait of choice. We searched for kestrels as we drove around the northern part of the peninsula, which is less developed than the southern part.  When a bird was spotted, we would toss the trap out the door of the car, taking care to do this quickly and stealthily.  It was then a waiting game for the bird to abandon its perch and land on the trap.

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Once we had a bird trapped, we moved quickly to release it and begin the banding process, during which Sue taught me how to measure the length of the tail feathers and the wing chord.  The majority of birds we trapped were male, which was interesting because 30 years ago Sue found that the majority of the small falcons in the same area of Cape Coral were female.  In the past, this may have been attributed to females migrating earlier than males and therefore staking a claim on the available optimal habitat.  A more equal distribution of male and female kestrels in the optimal habitat in Cape Coral, as we observed, may be a reflection of the declining trend in American kestrels that scientists are seeing nationwide.

Over the past 30 years, the available kestrel habitat of Cape Coral has changed quite a bit.  What was once a habitat perfectly maintained for kestrels, with mowed plots of land and plenty of telephone wires for perching (foreshadowing the impending land development), there are now rows of homes and less undisturbed open habitat. 

Sue teaches Kirsten how to measure and band a recently trapped kestrel.

Sue teaches Kirsten how to measure and band a recently trapped kestrel.

It was an invaluable experience to learn from knowledgeable and passionate conservation researchers, Laurie and Sue.  Plus, it wasn’t so bad to hang out in Florida for a few days in January, and I got to catch a glimpse at a Burrowing Owl! I am back at Hawk Mountain now, and I am so thrilled to see American kestrels buzzing around farmlands near the Mountain, preparing for nesting season.  Check out the Hawk Mountain kestrel nestbox cam at www.hawkmountain.org/kestrelcam, and learn more about our farmland raptor conservation efforts at www.hawkmountain.org/farmlandraptors.

A beautiful male American Kestrel, trapped and tagged in Northern Florida. 

A beautiful male American Kestrel, trapped and tagged in Northern Florida. 

Springtime in Montana

By Dr. Jean-Francois Therrien, Senior Research Biologist
Hawk Mountain Sanctuary

Spring sunrise in Montana, over the Mission Mountains.

Spring sunrise in Montana, over the Mission Mountains.

It’s spring time in Montana. Well, at least according to the birds. Not that the weather has been any better than in the East lately, but birds are showing definite signs of a change in seasons. Following Hawk Mountain's global and inclusive mission geared toward collaborating with like-minded colleagues and organizations to lead lasting raptor conservation programs, I was recently invited by long-time researcher, collaborator, and friend, Denver Holt, from the Owl Research Institute, to get a feel of the pre-breeding season in his study area in scenic Mission Valley, Montana.

Holt, founder and leader of the Owl Research Institute, has been conducting field-based owl surveys for over 30 years now, including long-term monitoring of snowy owls in Alaska. Thus, there is an amazing opportunity to combine and compare results from our ongoing long-term research project in snowy owl breeding grounds in the Canadian Arctic, and to learn about the population status of this charismatic species across North America.

In addition, spending a few days in the field in Montana allowed us to identify potential projects for future collaborative work. Among them, assessing the pre-breeding condition of individual owls and how it is affected by the previous winter conditions, and then how it relates to upcoming nesting success, is on top of the list. The fact that we know very little of the basic ecology for most of those species is not a surprise for any owl biologist. However, according to any source of available information, several North American owl species are facing an uncertain future. Indeed, population trends of long-eared and short-eared owls are both showing alarming decline on a continental scale. In light of the threats impending on these species, such collaborative research projects have to happen now.

Numerous accounts have recently suggested that to understand the reproductive ecology of any species in order to better protect them, we need to have a holistic view and turn our attention to the non-breeding season. With that in mind, there is an amazing opportunity for collaboration with the Owl Research Institute and their extensive field-based experience.

Dr. JF Therrien (senior research biologist at Hawk Mountain) and Denver Holt (founder and president of the Owl Research Institute) just before releasing a long-eared owl.

Dr. JF Therrien (senior research biologist at Hawk Mountain) and Denver Holt (founder and president of the Owl Research Institute) just before releasing a long-eared owl.

Those few days in Montana confirmed for me that they sure know the ropes of studying owls in the field: before lunch on the very first day, we had already captured and released 5 long-eared owls to assess their pre-breeding condition. We then proceeded to observe a phenomenal amount of great-horned owls (most of them sitting tightly on their nest), as well as short-eared owls flying and displaying territorial behaviors over the grasslands at dusk, among other things.

Research collaborations are an essential part of conservation science. Individuals alone can go a certain way, but with colleagues, we make real change. That is why at Hawk Mountain, we put much value in cooperation, team work, and network building. To learn more about our work with North American owls or any other species of raptors, or if you wish to financially support our research efforts, contact me at therrien@hawkmountain.org.

A Back-to-Back Snowy Owl Adventure

By Rebecca McCabe,  PhD Student, McGill University
Hawk Mountain Research Assistant

The view on Amherst Island

The view on Amherst Island

It was 6:15 a.m., and the sun had not yet come up as we stepped from our cars onto the ferry deck on the ice-covered waters of Lake Ontario. We were on our way to Amherst Island, a 70 square-kilometer island off the coast of Kingston, Ontario, which is a known hotspot for wintering snowy owls and the reason why we were there.

Myself, Jean-François Therrien (Hawk Mountain), Tom McDonald (Rochester, NY), and Dave Okines (Prince Edward Point Bird Observatory) arrived on the island with the hopes of deploying transmitters on snowy owls as part of the collaborative research of Project SNOWstorm (www.projectsnowstorm.org).

The sun rises over the frozen Lake Ontario.

The sun rises over the frozen Lake Ontario.

As the sun finally rose, we were already driving the main roads searching for white silhouettes in the distance. Luckily for us, Amherst had plenty of snowy owls! We estimated over 25 owls on the island, and now all we had to do was trap a few. We came up short in the morning and afternoon, but as soon as the sun started to set, our luck changed. Within 20 minutes both Dave and Tom had trapped an owl.

Snowy owl Stella, a female trapped and tagged by Project SNOWstorm in Amherst

Snowy owl Stella, a female trapped and tagged by Project SNOWstorm in Amherst

We were fortunate to have a wonderful host, Janet, who allowed us to bring the owls back to her place so we could process them out of the cold. The two immature females, later named Emerald and Stella, were in good condition and each weighed over 2 kg making them eligible to receive a transmitter before being released back into the night.

In just a short amount of time we have learned that the neighboring birds  established territories approximately 3 km from one another on the island, and Emerald has spent more time inland whereas Stella has been going offshore onto the ice during the day. I look forward to following these two individuals as they make their way north in the upcoming months.

One week and 2,370+ km later, I am scanning for snowy owls from the passenger seat again, but this time I am looking out on the prairies of Saskatoon, Saskatchewan. My co-supervisor Karen Wiebe (University of Saskatchewan) and I follow behind raptor bander Marten Stoffel in our pickup truck as we search the tops of telephone poles and fence posts. We spent six hours that day driving the survey route and had easily seen over 30 snowy owls. We were also very fortunate to trap and band six, a record day of trapping snowy owls on the prairies for Marten!

Male snowy owl trapped and tagged in Saskatchewan. 

Male snowy owl trapped and tagged in Saskatchewan. 

The next day we decided to go out again to see if luck was still on our side, this time driving about 150 km northeast of where we were the day before. I was shocked at the stark difference between locations and by the lack of owls we encountered on our second day. The habitat appeared similar but we only saw one adult male that afternoon. Marten decided to try trapping it, even though it was a more difficult catch with blustery winds and the male sitting high atop a transmission tower. Moments before calling it quits, I watched intently (and completely mesmerized) as the owl leapt from its perch and with a few strong flaps, came streaming in towards the bal-chatri before getting trapped.

Spending just a few days on Amherst Island and in Saskatoon and getting to see where these owls spend their winter was not only exciting but informative. I was able to observe them on their territories, take note of their favorite perches, and see first-hand the conditions they were in. As I move forward with my PhD at McGill University and analyze the movements of our GPS tagged snowy owls, my time spent in the field has allowed me to gain a better understanding of how these magnificent birds move throughout the landscape, the habitats they occupy, and the threats they face.

Becca with a recently trapped and tagged snowy owl right before release.

Becca with a recently trapped and tagged snowy owl right before release.

To learn more about these efforts or to support the project, visit hawkmountain.org/snowyowls.

Percy the Victorious Vulture: A Hit in Zimbabwe

By Merlyn Nomusa Nkomo, Former Conservation Science Trainee
Hawk Mountain Sanctuary

Black vulture perched on a boulder. Photo buy Nina Duggan.

Black vulture perched on a boulder. Photo buy Nina Duggan.

Vultures are generally not people’s favorite animal, especially with kids. They see them only in movies and story books that do no justice to the story of vultures, but only portray them as loathsome beasts. It cannot continue like this in our time; we cannot afford to let children go on being ignorant about issues of the state of their planet or the important role every organism plays in the ecosystem around them. If we let it happen, the world is going to be handed over to a more disastrous people than we have been, people that will not appreciate the life in it.

I personally did not think anything of vultures before my year-long internship at VulPro in South Africa. I did not love or hate them, but I knew they were not my preferred choice for birds to work with. I certainly thought I was going to be bored to death with them. My childhood had only just exposed me to the cute and grand side of wildlife: the lion prides filmed on television and the fluffy, little animals I would see at the wildlife orphanage from time to time. However, I always felt drawn to the weird animals, the strange ones that were not as easy to love, like painted wild dogs instead of cheetahs and lions. After seeing a lot of species of vultures, all affected by human actions, helplessly ceasing from poisonings, paralyzed from lead, and sometimes reduced to being flightless and confused from power line collisions, my passion for championing their cause was ignited. All birds should fly free, and it is up to us, the humans of today to make the right decisions to make it possible.

Percy the victorious vulture Cover.jpg

The children’s book Percy the Victorious Vulture was published in April 2017 while I was a trainee at Hawk Mountain. This book features the message of the importance of education birds and birds that are survivors of the hazards they face in the world today. The text in the book is very simple and precise, and it teaches kids about the importance of vultures, scientific techniques of tracking and trapping, monitoring, migration, and interactions of wildlife with humans in human-dominated landscapes.

With just this one small book, I am certain that Hawk Mountain Sanctuary has changed people’s perceptions on black vultures and vultures as a whole, and has opened a window through which readers can look into the everyday lives of the species.

I was very excited when I got my own copy of the book, as it gave me the idea of writing similar books on African raptors, since such education material is much needed in my region, and encouraged me to spread this story in my community. After talking to librarians in my city, they agreed to let me use their library space for education programs. This was wonderful, as the space is central for most people and is a hub for students and adults in the city. All the education and awareness work I had been doing before at the Natural History Museum had been a little exclusive because of time and location. A book reading was a perfect program to begin with, being at the library, and it justified my conservation education effort.

Merlyn prepares to begin the reading of  Percy the Victorious Vulture .

Merlyn prepares to begin the reading of Percy the Victorious Vulture.

The turnout was amazing, kids with their parents and friends, and even some young adults who came to just ‘check it out’, all had never been to a book reading before, nevermind one about vultures. I myself had never been to a book reading and had no idea what happens at one other than reading it aloud to the audience. I was nervous, but eventually the day arrived, and kids filled the hall. Anybody that has presented in an educative capacity knows that kids are not the easiest crowd, and that they are sharp and can spring questions on you that take you back to the roots of a concept. It can be very intimidating. You also need to be entertaining and engaging, or else you’ll lose their attention, and they’ll be bored.

I talked to my friends at the museum, and they helped me put together my makeshift raptor education trunk. Unfortunately they had lost their vulture mount to an infection and only had a martial eagle and another raptor’s head that I could use. I put it in the box together with a cattle ear tag labelled 43 (Percy’s wing tag number) and made my way to the library. At the library, I set it up on a table and used the specimen mounts to define what raptors are and to compare adaptations of raptors to their different lifestyles, especially focusing on eagles and vultures which I had pictures of on a slideshow. Almost all of the kids in the room had never seen an eagle or vulture, and it was clearly exciting to be that close and able to touch them. The time came to read the book, and everyone was eagerly waiting to hear the story of Percy. To prevent stuttering and calm the nerves, I started off with introducing African vultures and their distribution using beautiful posters loaned to me by a friend, I know this information so well it is like telling a story I have told a thousand times but still get excited over; this made it easier to move on to the ‘book reading’ that I had no idea how to do.

Attendees' hands shoot up to answer Merlyn's raptor questions. 

Attendees' hands shoot up to answer Merlyn's raptor questions. 

I only had one copy of the book, and this presented the challenge of how to read and showcase the lovely illustrations while maintaining that excitement and enthusiasm readers must have with kids. Fortunately the kids were attentive and patient with me, and the contents of my raptor box kept them awake. At the end of the reading, I invited questions expecting a dozen questions to be fired my way but nothing came. I decided to then fire questions their way, and the response was amazing. These kids remembered all of the complex scientific terms I had read and explained plus some I had defined in passing. They seemed to have been absorbing everything I was reading. To be honest, just one question was asked, “Where can we buy or get copies of this book?” Unfortunately, I did not have the answer to this question.

This book reading I had planned to teach kids about vultures ended up teaching me a lot more. It reaffirmed the value of conservation education and awareness, especially at grass root level where perceptions are being sewn and grown in the minds of our future. I will endeavor this year to continue seeking opportunities to educate more youth and most importantly developing raptor education material for children in my region, for there is truly so much diversity in species, ecosystems, and cultures regarding raptor conservation. I’m afraid this counts as a publicized new year’s resolution!

Merlyn (right) poses with some of the children who attended the education program.

Merlyn (right) poses with some of the children who attended the education program.

On the Vulture Chronicles: Vulture Detectives Pt 2

A black vulture tagged by Hawk Mountain named Versace, perched on a barn in the Kempton Valley. Notice her wing tag and antennae of the telemetry unit.

A black vulture tagged by Hawk Mountain named Versace, perched on a barn in the Kempton Valley. Notice her wing tag and antennae of the telemetry unit.

By Adehl Schwaderer, former Conservation Science Trainee
Hawk Mountain Sanctuary

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?

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Click here to continue reading this blog on The Vulture Chronicles

Click here to read Part 1!

On the Vulture Chronicles: Vulture Detectives Pt 1

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

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

By Zoey Greenberg, former Conservation Science Trainee
Hawk Mountain Sanctuary

he 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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A Day in the Field Searching for Goshawks

Photo by Rebekah Smith

Photo by Rebekah Smith

By Rebecca McCabe, Graduate Student,
& Zach Bordner, Broadwing Field Assistant
Hawk Mountain Sanctuary

With our backpacks on and GPS units in hand, we set out on an early Friday morning to begin our quest for the ‘Gray Ghost’ aka the Northern Goshawk. This is the first time Zach and I have searched this tract of forest along the Kittatinny Ridge.

Becca and Zach surveying and recording data in the field.  Photo by Rebekah Smith. 

Becca and Zach surveying and recording data in the field. Photo by Rebekah Smith. 

We begin by making our descent down to the valley floor where a stream flows through a thick corridor of rhododendrons and hemlocks. We cross over to the opposite bank and start our climb up the North facing slope, where the habitat changes dramatically with the elevation, from lush riparian vegetation to large hardwoods and an open forest floor. The sounds of the early morning songbirds pulsate all around us.

We spend the next four and a half hours hiking off-trail on varied terrain, zig-zagging up and down,  jumping from rock to rock. In between watching our footing, our eyes scan the trees looking for nest structures. We jot down observations in our field notebooks and GPS any stick nests we come across.

Photo by Zach Bordner

Photo by Zach Bordner

One in particular looks good so I walk around it looking for a good place to prop the scope up for a closer look. As I was setting up the scope Zach comes across a log under a tree where a pile of feathers lay. He calls me over and we investigate the scene. A plucking perch and a stick nest less than 50 meters from one another, a good sign indeed! Unfortunately, our excitement quickly dwindled as we scoped the nest with no signs of recent activity.

We continued to search the area surrounding the old nest structure and plucking perch but had no other signs of a Goshawk let alone another raptor. We started our journey back to the car, a little defeated, but intrigued by the habitat and the possibility that the Gray Ghost is somewhere in this forest. 

YOU can help support this important project by purchasing a Northern Goshawk t-shirt! A percentage of the proceeds will help fund our research and conservation efforts. 

For more information about our Pennsylvania Goshawk Project, visit hawkmountain.org/PAGoshawkProject

Out in the Field

By Katie Harrington, Research Associate and Former Conservation Science Trainee
Hawk Mountain Sanctuary

I have just returned to Hawk Mountain from a two-month field effort conducting behavioral and dietary studies of Striated Caracaras, or Johnny Rooks, as the locals call them, in the Falkland Islands. Set off from the coast of South America in the South Atlantic, in a back eddy of the circumpolar current, the Falklands embody the sense of expedition, expanse, and natural beauty that would make any graduate student –especially me– weak in the knees.

Being my third visit to Saunders Island, human population of 4, I had a sense of what to expect: gales and squalls, immense starry skies, long summer days, and thousands of birds. I stayed in a cottage at the Farm Settlement and shared the company of my hosts, the Pole-Evans family, at their farmhouse in the late evenings. During the days, I would figuratively saddle up on an ATV, part the sheep, brake for hens, and set off on the undulating dirt track toward the Neck 10 miles to the northwest, where I’d spend the day with roughly 100, mostly juvenile, Johnny Rooks.

It’s an amazing study population that Dr. Keith Bildstein began banding in 2006. Over 80 percent of the individuals I observed I could call by the name on their leg band, Z26, K27, G22, etc., which allowed me not only to observe population-level patterns, but also to learn more about different individuals’ behavior over space and time, that is, who hangs out where and with whom, for how long, and doing what.

Rooks raking shoulder to shoulder in the kelp wrack that has washed up on the beach.

Rooks raking shoulder to shoulder in the kelp wrack that has washed up on the beach.

For my graduate work at Moss Landing Marine Labs in Monterey Bay, California, I am investigating the role the Rooks play in energy flow in their marine environment. It’s well known that Johnny Rooks associate with seabird colonies, but it’s less understood the extent to which they depend on invertebrates, both terrestrial and marine, as a nutritional resource. You might not think a raptor, formerly persecuted for slaying sheep and frequently labeled a penguin-killer, would spend hours each day silently and determinedly raking for larvae in accumulated kelp wrack. I certainly didn’t, but they do! It’s this behavior I set out to learn more about.

Layered in merino wool, I’d sit for hours, recording three different layers of resolution, from macro to micro: (1) total time an individual Rook spent foraging within the kelp wrack, (2) proportion of time spent actively digging and ingesting invertebrates versus a catalogue of other behaviors within a 4-min period, and (3) ingestion rates within a 30-sec period. Combined, these layers will help me better understand kelp raking as a foraging strategy, and the implications of changing social or climatic conditions.

X36 Yellow hours after receiving a tail mounted accelerometer. If all goes according to plan, we'll find out exactly how he spent the next twenty-four hours after we download the data!

X36 Yellow hours after receiving a tail mounted accelerometer. If all goes according to plan, we'll find out exactly how he spent the next twenty-four hours after we download the data!

A second goal of mine was to deploy and retrieve accelerometers that I had built before leaving San Francisco.  Having learned to wire, solder, and program the archival Arduino microloggers, I had my fingers crossed that I wouldn’t lose them forever. Rooks are wily and persistent, especially when it comes to disarming and destroying miniature gadgets, so I wasn’t entirely sure my plan would work. Luckily, by using two layers of heat shrink and Tesa tape and then tail mounting the units, it did! Keith warned me going into this, saying that it’s easy to trap Rooks, but it’s harder to retrap the one that's wearing your unit. Although, with a single snare and cubed mutton, we fortunately “lassoed” all six of our “accelerometered”  birds! What a rodeo! I’ll now be able to plug these data into visualization software, and by syncing the movement records with behavioral observations I conducted while the birds wore the units, I’ll be able to extract activity signatures and quantify total time spent doing each activity for a twenty-four hour period. I’m deeply indebted to banded Rooks  X36, P25, V26, Z26, M26 and K27. Thank you young Rooks!

For many of my days, I’d sit still and observe, doing my best to blend in with the environment. Frequently, when I would put down my binoculars I’d find a Gentoo Penguin peering closely at me, within arm’s reach, or a pair of King Penguins slowly waddling past me toward the water. Or I’d be closely watching one Rook raking while another, often a recently fledged one or a juvenile, would sidle up beside me to stare at me, head turning upside down for a better look, or to play with my thermos. On many days there would be a Sea Lion hunting and preying upon Gentoos 100m offshore, grabbing and slapping the penguin’s body back and forth on the water. Southern Giant Petrels would get the first go at the remaining carcass, but once it washed ashore it became a hierarchical battle between them, the Rooks, and the local Turkey Vultures. Southern Crested Caracaras steered clear with Petrels around. Not to say they didn’t hold weight at the Neck though, as whenever they flew over, the gulls, oystercatchers and Rooks all would flush in alarm.

Recently fledged K28 after kickboxing a ball of dried basket kelp. 

Recently fledged K28 after kickboxing a ball of dried basket kelp. 

While the Rooks spent most of their days at the Neck foraging or digesting, the four recently fledged Rooks that arrived midsummer introduced me to another side of the species. I’d watch and try not to laugh as they ran toward inanimate, inedible objects and kickboxed them, grabbing on and stumbling over themselves while they held on their “toys.” They’d lie there on their side, partially flapping, partially kicking, and doing what I could only call playing with the objects. Energetic and clumsy, they seemed to be learning to navigate their world. I could certainly relate to their seeming enthusiasm.

Working with the Rooks has been an incredible opportunity to contribute information on a little-studied species, engage with the amazing South Atlantic ecosystem, and build relationships with local residents who have been so generous in supporting our work. Keith and I will return to the islands in July to present our findings at a “Farmer’s Week” get-together in Stanley, the capital of the islands, before continuing to Saunders Island to rejoin the Rooks. Until then, I’m sure they’ll be raking away, running under fences, and continuing to perplex and delight, and, perhaps, frustrate all who encounter them.  

Turkey Vulture Life Histories Revealed

By Wouter Vansteelant, Visiting Scientist
Hawk Mountain Sanctuary

I saw my first Turkey Vultures in March 2011 when driving from the Newark airport to Hawk Mountain. I had been invited by Keith Bildstein to work on a paper about raptor migration along the Black Sea coast of the Republic of Georgia. It was my first visit to the USA, and during the weekends of that spring I frequently marveled at the Turkey Vultures soaring through the Kempton valley. Little did I know that I would come back to Hawk Mountain to study Turkey Vulture migration six years later.

It's been about 7 weeks since I arrived, and one of the most exciting things I've been able to study here so far is undoubtedly the life-history of David. David was part of a family of four Turkey Vultures (2 chicks and their parents) to be tagged in an old farmhouse in Saskatchewan in 2013.  Out of four Turkey Vultures that have been tagged as fledglings in Saskatchewan, David was the only one ever to reach adulthood, allowing us to map the entire life-history of a Turkey Vulture from fledging until adulthood the first time. 

Movements by Turkey Vulture "David" in Saskatchewan (Canada) after fledging the nest in 2013 (red star) until establishing a small home range in summer 2016. Dotted tracks indicate movements after August 1 and full tracks indicate movements before August 1 each year. 

Movements by Turkey Vulture "David" in Saskatchewan (Canada) after fledging the nest in 2013 (red star) until establishing a small home range in summer 2016. Dotted tracks indicate movements after August 1 and full tracks indicate movements before August 1 each year. 

After leaving the nest (red star) David did not spend any time exploring the surrounding area. Instead, the first time he left the immediate surroundings of the farmhouse was when he departed on his first outbound migration (red track). Although he did not migrate with his parents, he left around the same time as other Turkey Vultures breeding in Saskatchewan and found his way to Central America. He then returned to Canada in spring 2014 and spent most of the summer making extensive exploratory movements without settling in a clearly defined area (brown track). In August that year, David passed within a few miles of the farmhouse where he hatched the year before. His mother had died during spring migration but his father was breeding again in 2014. David, however, did not visit his natal site and spent a few days along the river 20km SW of the farmhouse before initiating his 2nd outbound migration (dotted brown track). When David returned in 2015 he quickly settled in an area approx. 240km ESE of his natal site. He made some long exploratory movements in early summer but spent most of the summer in the same area (orange track). In 2016 David then returned directly to the same area and spent the entire summer there (yellow track).

David's movements suggest he was breeding for the first time in 2016. Unfortunately this could not be confirmed in the field, but David is still alive and transmitting today. We cross our fingers for his safe return to Saskatchewan this year, so that local birders can try to connect with this bird in the field and confirm his breeding status.

David is one of a few wild vultures in the world for which the entire life-history could be recorded by satellite-tracking. As such many open questions remain, not in the least regarding what factors drive the decision of individual birds to settle in one area rather than another. These questions can only be answered by satellite-tracking many more vultures throughout their entire lives, and connecting with these birds in the field across the entire flyway as frequently as possible.

I hope Hawk Mountain will be able to track many more juvenile vultures in the year to come, and wouldn't mind to come back another year to help with analysing the data.

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You can follow Wouter at @WMVGs on twitter to keep up with his latest finds.