Over the next few weeks, Science Borealis is excited to feature a series of stories developed for a story-telling event held at the joint conference of the Society of Canadian Ornithologists, Association of Field Ornithology, and Wilson Ornithological Society in July 2024. These stories were prepared with the help of Borealis Blog editors and polished for oral presentation by coaches from The Story Collider. We hope you enjoy these behind-the-scenes glimpses into the lives of ornithologists!
By Cara Herrington
It was a typical winter morning on the southern tip of Vancouver Island – cold and damp with high grey clouds and occasional fleeting rays of sunlight. Gillian Radcliffe, Research Director for The Pacific Northwest Raptors, and I sat in our camper van, eagerly waiting for our first turkey vulture sighting of the day.
Turkey vultures are magnificent birds
Turkey vultures are the most widespread of the New World vultures. With their distinctive features—a bald red head, ivory beak, and brown plumage—these vultures are a sight to behold. They weigh between 2000 and 2300 grams and have a wingspan of about 1.8 metres. Their most distinctive feature is the ‘V’ shape of their wings when they are in flight. This unique wing position improves flight efficiency by allowing them to ride thermals, a trait that has led to them being called a ‘solar-powered bird’.
Tracking turkey vultures
These migratory birds are expanding their breeding range into northwestern Canada. Since the spring of 2022, Gillian and I have been trapping turkey vultures on Vancouver Island to fit them with solar-powered GPS/GSM transmitters. Our goal is to use the data collected from the transmitters to understand turkey vulture movements in their new geographical range. We are also intensely interested in their migration across the Juan de Fuca Strait, specifically the weather conditions they rely on to cross successfully.
Our fieldwork has not been without its challenges. While turkey vultures are plentiful in the sky, their cautious nature on the ground makes them difficult to trap. Since the early spring, we had only managed to trap two individuals. But we were undeterred by the low numbers, driven by our passion for understanding these magnificent creatures.
Changing our strategy
Having had little success trapping turkey vultures during the spring and summer, we extended our trapping season into the winter months. This choice gave us a unique opportunity to study the turkey vultures that had begun overwintering on the island’s southern tip. If we could deploy even one transmitter successfully, it would provide valuable information about how a turkey vulture survived the winter season and if it migrated or remained in subsequent seasons.
Our persistence paid off when one bird, dubbed Irwin, was hungry enough to enter our trap. After carefully assessing his body weight, plumage condition, and overall health, we decided he was a good candidate for tracker placement. This tracker had a slight modification compared to the other two trackers we had previously deployed. A hydrophobic (water repelling) pad was glued to the bottom of the tracker during the manufacturing process, a new addition designed to offer some cushioning between the tracker and the bird’s back. Irwin was fitted with his tracker and set free.
We sat in the van and watched him perched on a nearby tree. He began to preen his feathers out of the harness and into more comfortable positions. Then, Irwin took off. We excitedly looked forward to the next morning when the first data points of Irwin’s movements would be uploaded from the tracking unit to the online interface.
Something is wrong
The 10 a.m. tracker check-in revealed that no data points had been collected. While this did create a level of concern, we also understood the limitations of this technology. These transmitters are solar-powered units, so deploying them on the West Coast during the rainy season is not without risk. Without enough battery power, the units struggle to connect to satellites. At this point, all we could do was wait and hope for clear weather. Over the next few days, there were some breaks in the clouds, and we got snippets of data, always at midday when the cloud breaks were the longest.
To our dismay, the data points all occurred in the same place, a small stand of trees not far from where Irwin was captured. Again, this raised concerns, but we also understood the behaviour of these birds. If a vulture finds a good carcass to feed on, it is not unusual for it to stay in the vicinity for a few days until the resource is used up. The scatter of points was enough to suggest small levels of movement either within the canopy or on the ground. However, after waiting a few more days, we finally conceded that we were not seeing any real change in the data.
We return to the capture site
At this point, we decided to travel back to Metchosin, where Irwin was captured, and investigate. Satellite imagery showed the transmitter was located in a stand of trees on private property. We obtained permission to enter the property, and once we were on the ground, we got a better understanding of the terrain. In the middle of the trees was a pond with two small creeks feeding into it. There was marshy ground covered with skunk cabbage and other damp-loving plants near the creeks. On the berms surrounding the pond, there were large, well-spaced fir trees, and the forest floor cover was easy to negotiate. All in all, a relatively easy area to search. Unfortunately, we weren’t exactly sure what we were looking for. Would Irwin be alive and roosting in the trees, perhaps just a little weak due to the wet and cold winter weather, or would we find something worse?
We focused our search efforts in areas where data points had clustered and spread out from there. We looked up and down every tree, searched under the growth on the forest floor, and scoured the banks of the pond. We saw no vultures in the trees or the air above. We did find an old deer skeleton, long picked clean. Next to the skeleton, we found several turkey vulture tail feathers. Our minds raced. Perhaps Irwin, desperate for food, attempted to pick what he could off this skeleton; perhaps he was grabbed from behind and killed; or perhaps he was able to get away, but with the loss of his tail feathers, he was now grounded, walking along the forest floor searching for what little he could to eat. This made sense, given that the tracker did appear to be moving around the middle of this small, wooded area.
With evening approaching and no sign of an injured or dead vulture, we decided to head home and continue monitoring the incoming data from there. We continued to receive a handful of data points every afternoon, but we had expected more data to be collected due to improvements in the weather. This fueled our hypothesis that Irwin was moving among the trees on the ground where sunlight was not able to charge the unit fully. We traveled back to Metchosin, determined to find and rescue Irwin.
Our second trip to the search area
This second search-and-rescue operation went much the same as the first. We looked up and down every tree, walked around the edges of the pond, and looked in and under tangles of brush. Still, we found nothing. The day was coming to an end, and we were feeling defeated. I knew it was going to be a long, silent drive back up the island as we pondered our failure. Was Irwin alive and struggling to survive, or was he already dead? Was there something we did wrong that resulted in this beautiful vulture meeting this fate?
I was staring despondently over the pond when something caught my eye. I couldn’t quite make out what it was, but I knew it wasn’t natural. It was floating in the middle of the pond, small, pointed, and black. It was surrounded by pond debris that it had evidently picked up as it bobbed in the water. I lifted my binoculars to my eyes for a better look, but I still couldn’t quite make out what it was. It was a small, black, square-shaped, human-made object. “Hey guys, I think I found it!” I called out to Gill and her partner Allan who had been helping us look. (I am paraphrasing as I may have said some choice words in my excitement and disbelief.) Gill and Allan confirmed my suspicions. The tracker was just barely floating on the surface of the pond that we had circumnavigated many times over our two days of searching.
Mystery solved
The next thirty minutes were a whirlwind of activity. We drove to one of the homes on the property, borrowed a canoe, carried it back to the pond, launched it, paddled out, and retrieved Irwin’s tracker. The solar panel was sticking out of the water just enough to catch a few hours of sunlight at midday when the sun was high enough to shine directly over the pond. The movement we had seen in the tracker data was not due to a grounded bird struggling to survive but to the unit bobbing back and forth in the subtle eddy of the water.
As I plucked the tracker from the water, the reason for it being there became clear. The straps of the harness, designed to fit like a backpack on a turkey vulture and hold the tracker in place, were severed – not by an attacking predator but by the sharp and determined beak of Irwin himself. Shortly after his release, Irwin must have decided to roost in this stand of trees above this pond and set to work removing this less-than-fashionable device. It is possible that the added padding on the tracker allowed Irwin to get under the harness and cut it. While there is no way to prove if this hypothesis is true, we have since decided not to use this padding material.
Our research into the movement of turkey vultures on Vancouver Island continues. With perseverance and patience, we have fitted tracking units on 12 turkey vultures. Yet, none have proved to be as tenacious and industrious as Irwin. We often think of him as the turkey vulture that bested us and wonder about the secrets he was so determined to keep.
Feature image: Cara Herrington and Phoenix the turkey vulture, a bird ambassador from the Pacific Northwest Raptors. Image: The Raptors, used with permission.
