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Nature Observations Tumblr Repost

Eaters of the Dead

Bald Eagle photographed in Pinery Provincial Park, September 2021.

Here’s another repost from my old tumblr blog norfolknaturalist.tumblr.com. I’ve added some newer photos of the species involved but otherwise unchanged. Much of this article was inspired by my reading of the book Life Everlasting: The Animal Way of Death, by Bernd Heinrich. I thought the subject and title were appropriate for Halloween season.

Just as we were about to turn into my parents’ driveway last weekend (in April 2018), we saw probably the most iconic bird in North America less than 100 metres away from us down the road. A Bald Eagle (Haliaeetus leucocephalus) was dining on a Raccoon roadkill in clear sight. 

Perhaps it’s surprising that a bird of such noble renown was seen stooping to consuming carrion, something that we often see as repulsive. The truth is that the line between ‘predator’ and ‘scavenger’ is often a very blurred one. Most animals that eat other animals are willing to eat one that has already died or been killed. To the predator, it contains the same nutrients that it would obtain from its own kill but with much less effort (valuable time and energy) on their part. This isn’t to say that eating pre-killed remains is without risk for a predator or a scavenger. Besides the conflicts with other hunters over the resource, there is an omnipresent and invisible threat to all dead flesh.

Bacteria: organisms that are so tiny they are dwarfed by individual cells of our bodies. Despite being so small, and unseen without a powerful microscope, bacteria operate everywhere in the natural world and one of the most profound activities they perform is nutrient recycling and breakdown. While they disassemble cells and consume dead flesh, bacteria proliferate. Bacteria are the reason that predators can’t eat an animal body that’s been dead for too long. They are the reason dead things go “rotten” and become unpalatable by almost any animals. They are the unseen “competitor” with the visible and charismatic predators.

After at least an hour of feeding, and the frequent interruptions of cars passing, the eagle flew off and left the dead Raccoon. That is when the Turkey Vultures (Cathartes aura) moved in, creatures much more commonly associated with scavenging. And for good reason. Turkey Vultures have the most powerful sense of smell of any bird, and can detect a dead animal from over a mile away. What’s more, they can eat flesh that other creatures would turn down as too far gone. Their digestive system is able to break down the toxins of the ever-present bacteria, making them capable of consuming rotten flesh, where others cannot. 

It may be a grisly business, the consumption of the dead, but it is an essential (and amazing) part of ecosystems around the world.

Turkey Vulture photographed in Long Point, October 2021.

Categories
Nature Observations

Return of the Ravens

Ravens are awesome, beautiful birds.

My parents’ farm property in Norfolk County has been blessed by the construction of a very exciting nest. One day when I arrived at their house and opened my car door I was greeted by the distinctive “croak” of a Common Raven (Corvus corax). The sound startled me, placing me in the woodlands of Algonquin Park, but there was no mistaking that call, and the size of the bird making it. I could see the calling raven, perched atop an unused silo. As exciting as this brief sighting was, the true significance of this bird’s presence was not yet revealed.

Later that same week, my Mom asked about the large crows and mentioned that they were building a nest on top of the silo. She said they went back and forth with sticks in their beaks. Maybe this news wouldn’t be so exciting to some people but for myself the thought of a raven nest that I could regularly observe was exhilarating.

And observe it I have!

On a recent visit, I went back to check out the nest and take some pictures. After only a few moments of watching the silo, I heard the sounds of one of these amazing birds returning and saw it carrying a  large stick in its beak. The raven dropped the stick onto the nest pile without even landing, continuing to soar through the sky on its powerful wings. Apparently, if a dropped stick doesn’t stay in the nest, the ravens won’t pick them up again off the ground (Stokes and Stokes 1989). The sticks are taken from tree branches, broken off by the ravens, not collected from the ground (Stokes and Stokes 1989). In addition to large sticks, the nest could contain dirt and grass clumps as well as an interior lining of gathered hair or bark (Stokes and Stokes 1989).

The raven didn’t even land, just dropped the stick from the air onto its nest.

A few minutes later, a turkey vulture (Cathartes aura) came drifting towards the silo. The large bird seemed to be planning to perch atop the silo, something I have seen vultures do previously. Swooping onto the scene with deep throaty “croaks” the raven pair chased the vulture off into the distance, something that was reminiscent of the classic behaviour of corvids mobbing raptors or owls.

One of the ravens pursuing a turkey vulture.

As I said at the beginning of this post, the call and sight of ravens makes me think of Algonquin Park, and that’s for good reason. Until now, it was the only location I had seen these birds. Ravens used to be common across all of Ontario but mainly due to habitat destruction and human persecution, they have been mostly absent from far southern Ontario for about a century (Cadman et. al. 1987). Ravens were even rare in Algonquin Park until the 1960s because of the poisoned baits left out for wolves (Tozer 2012). The most recent field guide I have (Bezener 2016) still has the raven range map cut off before reaching most of Southern Ontario.

I’ve tried unsuccessfully to find a good source for the current breeding range of ravens in Ontario, but I suppose I’ll have to wait for the next edition of the Breeding Bird Atlas, which is collecting data right now (2021-2025) for its creation. It’s an amazing project, and if you have the time to contribute go for it! Suffice to say, this nest of ravens is a fairly new thing in my area and is very exciting. I hope that they have a successful nesting season, and I have a feeling I will have more posts about this nest in the future! At the time these observations were made (March 29, 2022) the ravens have possibly already laid eggs in the nest, as Tozer (2012) gives a range for Alqonquin raven egg-laying as March 20 – April 19. Stay tuned!

Raven and turkey vulture, showing nicely the relative wingspans of these two large birds.

References:

Bezener, Andy. 2016. Birds of Ontario. 376 pp. Partners and Lone Pine Publishing.

Cadman, M. D., Eagles, P. F. J., and Helleiner, F. M. 1987. Atlas of the Breeding Birds of Ontario. 617 pp. University of Waterloo Press.

Tozer, Ron. 2012. Birds of Algonquin Park. 474 pp. The Friends of Algonquin Park.

Stokes, Donald and Stokes, Lillian. 1989. A Guide to Bird Behavior. Volume III. 397 pp. Little, Brown, and Company.

For Previous articles that have some relevance to this one, see:

Canada Jay (Perisoreus canadensis)

Algonquin Observations, Part 3 – Peck Lake Trail

Fuzzy Flies and Song Sparrows