The Carrion Birds

Typically, owls do not leap to mind when one thinks of carrion-feeding birds.  Mostly, we think of vultures, or crows, or ravens.

Because of this, I was relatively surprised to see these pictures...taken by one of my North Carolina camera traps about a year ago.

A colleague at the university had brought me a freshly dead road-killed squirrel.  He gave it to me thinking I'd turn it into a specimen (it was in good shape).  Although the thought crossed my mind, I didn't really have a good facility set up for dealing with skinning mammals and making specimens from them.  I decided the best use for this carcass was as an attractant in front of one of my cameras.

There is a tendency to just throw bait like this down in front of the camera and hope for the best.  However, raccoons were rampant at this site....and although this particular camera set was "high and dry"....and not along a stream corridor....I knew raccoons would find it all the same.

So, I wired the carcass to a wood stake, which I drove into the ground in front of the camera.

I also put a spray of coyote urine on the stump and a small dab of gland lure (including some good old essence of skunk) near the stake with the carcass.

I was hoping for Coyotes.

But...that's not what I got. 

There was the standard cast of characters (white-tailed deer, oppossum, raccoon, gray fox, etc.).

But I was not expecting the Barred Owl (Strix varia) that showed up and tore into the carcass.

The individual (or individuals) pictured above came to the carcass roughly 5.5 days after we estimated the squirrel had died. Between the morning and the subsequent evening of October 19th, we recorded pictures of Barred Owls (or a Barred Owl) over a 250 minute time period!  An Owl also showed up on the evening of October 20th, which would have been roughly 7 days after we estimated the squirrel had died!

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Later, I drug the ribs and spine of a roadkilled white-tailed deer to the site and got STILL MORE Barred Owl pictures!

The carcass was deployed on December 17th, and the first Barred Owl showed up on the 18th.    On December 30th, another picture of a Barred Owl on the carcass was obtained.

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Substantiated reports of Owls (especially Barred Owls) eating carrion are uncommon in scientific literature.  Owls are known for to store food...so they aren't adverse to eating dead things.  However, finding a dead thing that YOU killed and hid yourself seems different than actively searching for something that's already dead.  Dead things don't exhibit the visual and auditory cues that I'd assume owls use when hunting.  So, perhaps carrion-feeding is purely opportunistic. 

Many reports of owls injured along roadsides occur annually.  It is usually assumed these individuals are hunting along roadsides.  But....several anecdotal reports exist that mention Barred Owls on roadside carcasses (apparently) feeding.  I wonder how many owls injured on roadsides are actually scared when feeding on carrion and get whacked by a car when they try and flee.

Further Readings on Owls and Carrion Feeding, or Studies on Scavenging Rates:

DeVault, T.L., and O.E. Rhodes Jr. 2002. Identification of vertebrate scavengers of small mammal carcasses in a forested landscape. Acta Theriologica 47:185-192.

DeVault, T.L. et al. 2003. Scavenging by vertebrates: behavioral, ecological and evolutionary perspectives on an important energy transfer pathway in terrestrial ecosystems. Oikos 102:225-234.

Diaz-Ruiz, F. et al. 2009. First record of rabbit carrion consumption by Eurasian Eagle-Owl (Bubo bubo) on the Iberian Peninsula. Journal of Raptor Research. 44:78-79.

Eckert, A.W., and K.E. Karalus. 1987. the owls of North America. Weatervane Books, New York, USA.

Hiraldo, F. et al. 1991. Unspecialized exploitation of small carcasses by birds. Bird Study 38:200-207.

Kapfer, J.M., D.E. Gammon, and J.D. Groves. 2011. Carrion feeding by Barred Owls (Strix varia). The Wilson Journal of Ornithology 123: 646-649.

Kostecke, R.M. et al. 2001. Survival of avian carcasses and photographic evidence of predators and scavengers. Journal of Field Ornithology 72:439-447.

Prosser, P. C. Nattrass, and C. Prosser. 2008. Rate of removal of bird carcasses in arable farmland by predators and scavengers. Ecotoxicology and Environmental Safety 71:601-608.

The Right-of-Way Wanderers.

The Cuddeback is one of my "rover" cameras.  I move it around every few months at this site trying to find interesting stuff.  My Bushnells are the workhorse "fixed" cameras that remain in one place at my sites (hopefully for a year per location).

On September 23th, 2010 I moved my Cuddeback to a location along a transmission line Right-of-Way (ROW).  This ROW runs through the study site, and cuts a large tract of relatively undisturbed deciduous hardwood forest in two.  In the process, it crosses a stream and runs into an open pasture nearby.  The ROW therefore creates an easy travel corridor through the woodland, while also crossing a water source, before emptying into an open field.  I had high hopes for carnivores, particularly Bobcat (Lynx rufus). 

So, I decided to check out the ROW for a camera location in late September, 2010. Although ROWs have upsides, they have downsides: namely, its hard to conceal a camera when mounting it along a ROW through public property that may be frequented by hikers and powerline employees.  As such I couldn't put it right on the edge of the woods facing into the ROW, which is what I wanted to do.  I had to put it slightly back into the woods.  Because I was going to use some scent lures and bait, I also made sure I focused on hilltops when scoping out camera set locations....I wanted the wind to get that scent out from up on that hill.

I came across a wildlife trail running perpindicular to the ROW from the woods.  It was up on a hill in between the open pasture to the southeast and the stream crossing to the northwest.  It seemed like it had what I envisioned. 

Above: an aerial photo of the region with an outline of the study area.  Note the ROW transmission line bisecting the property that is clearly visible.

So, I drug an old stump (probably from some ROW clearing) in front of the camera.  I dug a small hole at the base of the stump for bait.  It was my plan to use the stump for the scent lures and coyote urine spray, while putting potential bait in the hole (trying to simulate the classic "dirt hole" set that traditional trappers use).

Basically, though, for two months this spot yielded deer.



....nothing but deer.

Oh, and a few squirrels......

Even the occassional construction vehicle, moving along the Right-of-Way to perform maintenance.

I was beginning to think this was a dud camera set. 

Then...after two months...things started to get interesting.  I had been placing scent lures in front of the camera for weeks.  A dab of commercial coyote gland lure one week, the next week gray fox gland lure...every time finishing it off with a spray or two of coyote urine.  A squirrel carcass once.  The unused turkey neck from our Thanksgiving dinner another time.  One week, I finally went through the trouble to drag a few nuggets of excrement from my faithful pooch out to the camera and set it there.

That seemed to finally do the trick.

At last, a carnivore....the Gray Fox (Urocyon cinereoargenteus)....who takes a minute to mark on top of my dog's excrement.

...a few days later, another fox investigates the handiwork.....

....a pair of Gray Fox investigate on December 13th....

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Around December 15, 2010 I upped the ante.  I picked up the ribs/spine of a roadkilled deer off of a side-road that I'd been watching.  The county hadn't come to pick it up for weeks.  It was mostly picked clean, but still juicy and with plenty of meat on the bone.  I hauled this out to the spot and wired it to a stake in front of the camera.

The first visitors were a pair of 'possums (Dildelphis virginiana), a common scavenger 'round these parts.....

A Barred Owl (Strix varia) also stopped by (more on this later).......

...as did another Gray......

A 'possum AND a white-tailed deer....



A hawk...based on its relative commoness in the area, I'm going to guess Red-Shouldered Hawk (Buteo lineatus), but that's just a guess.



In December I caught something that is amazingly rare in the southeast: SNOW!

The one and only Racoon (Procyon lotor) captured on this camera.  Had I put this deer rib cage out in a setting closer to water....'coons would have raided it on the first night.  As it was, I only got this big old ridge runnin' raccoon to stop off for a gnaw.

A very nice Gray Fox shot in the early parts of the new year (sniffing about where I had sprayed the 'yote urine on the log)........

A deer in mid-leap....

More 'possums.....

Finally, a Gray Fox slinks past the set, but must not stick around long for this is the only picture of him on this night.

And even though I was reluctant to move the camera (I don't know why), a picture in the last batch that I looked through changed my mind.

Look close.  It's exactly what one never wants to see on their camera trap: a picture of some dude possibly checking it out from the seat of his vehicle.

So, the camera had to get moved.