Notes on the charismatic falcons visiting an Alberta grain terminal

I've recently become acquainted with a remarkable drama that plays out, perhaps daily, at the Alberta Grain Terminal (Alberta Terminals Ltd.) in Edmonton, against the backdrop of the harsh prairie winter.

Feb. 8, 2013, Courtesy of Charles McDonald

The life-and-death stakes for the actors couldn't be higher but on a given day the outcome for individuals - prey, predator, and observer - is uncertain. Many, many hours may pass while several thousand Rock Pigeons peacefully pursue their interests. Over a span of several days there are some more inevitable results: Rock Pigeons will be killed, falcons will eat and the attending humans will witness multiple spectacular encounters, the kind most of us would consider ourselves fortunate to behold just once, ever.

Often in attendance are some excellent photographers, but I'm not one of them. My skills and gear are better suited to setting the scene. If it's eye-popping photos you're after, you may want to skip down to the end of this post where you'll find samples and links to photo collections of Edmonton's finest falcon photographers.

The Scene: The Alberta Grain Terminal (53.584336, -113.547914) towers 43 m. over a low-lying industrial area beside the Yellowhead Highway and the C.N. Rail line. Grain and canola seed are spilled during the transfer between the rail cars and storage facility and this attracts a lot of Rock Pigeons which in turn draw in a variety of predators. The best vantage point lies to the south in a parking area outside the chain link fence securing the Edmonton Police impound lot.

Renowned Alberta naturalist Jim Lange, then an employee of the Canadian Nation Railroad, was the first to note the presence of hunting falcons at the terminal a decade ago. He has generously provided some historical perspective.


Jim notes:

The falcons have appeared every winter since 1993. I do not believe that the falcons were in Edmonton prior to that time as the job I had with CN in the Walker Yard was in the flight path of the falcons traveling towards the 97th St. area and I would certainly have noticed them. We saw Merlin and Snowy Owls frequently but no large falcons.

Jim coauthored, with Dick Dekker, a paper characterizing the hunting behaviour of Prairie Falcons and Gyrfalcons at the AGT:

Dekker, D. and J. Lange. 2001. Hunting habits and success rates of Gyrfalcons (Falco rusticolus) and Prairie Falcons (Falco mexicanus) preying on feral pigeons (Rock Doves, Columba livia) in Edmonton, Alberta. Canadian Field-Naturalist 115:395-401.

The Players: (a) Rock Pigeon: These get top billing. They're impossible to count but at a given moment several thousand birds may be present at the terminal taking advantage of the abundant food and relative warmth of the building's south face. Thousands more may use the site: loose flocks of birds continuously arrive and depart. The arrival of a falcon typically results in the sudden flight of multiple, characteristically compact flocks of pigeons from the roost. The sky overhead seems filled with birds.

During my time at the terminal I've been reminded that Rock Pigeons are exceptionally good fliers. They're not just strong and fast. Most often a pigeon will respond precisely to an attacking falcon with a life-saving change in speed and direction.

Rock Pigeons and falcons have been evolutionary dance partners for a very, very long time.

The Players: (b) Gyrfalcon: With an average weight of 1,450 g., a Gyrfalcon has no trouble carrying and possessing a Rock Pigeon (up to 380 g.). At least three different gray-phased birds, two adults and an immature, have been seen at the terminal this winter. Their appearance can be very fleeting: a Gyrfalcon will sometimes pick off an unwary pigeon and fly off into the distance before the flock and the photographers can react. Other attacks may last several minutes. I recently watched a large (female?) Gyrfalcon capture a pigeon and carry it to a perch on east face, out of sight. Twenty-or-so minutes later, she flew into view, this time with an obviously full crop, and coursed back and forth through the frantic blizzard of Rock Pigeons, before disappearing to the south.

The Players: (c) Prairie Falcon: On average, they weigh 550 g, not much more than their intended prey, and this has very significant consequences. I was lucky enough to view multiple attacks at mid-day last Friday. My friends Don and Charles stayed longer and saw four kills by the Prairie Falcon, each preceded by multiple ascents, pivots and stoops countered by wheeling evasions by tight flocks of pigeons.

Why would Prairie Falcon have to kill three or four times its weight in prey in a single afternoon? Meet the rest of the cast.

The Players: (d) Common Raven:  Several Common Ravens are always present, often roosting on the building only metres from a row of pigeons. Usually even a close fly-by doesn't cause panic but occasionally a raven will try to snatch a healthy pigeon.

Jim Lange:

On two occasions I had fellow workers there describe Ravens actively hunting down and killing pigeons while in flight. I watched them finish off one on the ground that they had already wounded and were searching for.

Courtesy of Don Delaney.

At the top of the food chain a successful predator or scavenger must also defend its meal from rival guild members. Alas, the Prairie Falcon we observed, perhaps a smaller male,  could at best descend to the ground or a low rooftop with its kill where it was soon forced to surrender its meal to the ravens. Sometimes a pitched falcon-on-raven chase would follow but inevitably the Prairie Falcon would have to rest and hunt again.

It was evident that the presence of Common Ravens at the grain terminal makes life much more difficult for Prairie Falcons, perhaps disproportionately so for males, which are significantly smaller. It doesn't appear that ravens and Gyrfalcons take much notice of each other although Jim Lange observed:

As for the Ravens stealing the prey, both the Prairie and Gyrfalcons were regularly carrying their pigeons all the way the centre of the City Centre Airport to avoid conflict.  

The Players: (e) the photographers: I've met a couple of the local photographers who have put in the time and practice to capture some remarkable images. I'm in awe of their work. The action unfolds so quickly - it's got to be one of the fastest pursuits in nature - usually hundreds of metres away. The falcon is but one of thousands of fast-moving dots overhead. It's not easy to put a streaking falcon in the view finder behind a hand-held 500 mm lens. I've tried.

Don Delaney, who introduced me to this spectacle, is also a very keen student of falcon behaviour.  Please visit his galleries on Flick'r to see his growing collection of extraordinary actions shots of Gyrfalcon, Prairie Falcon, evasive Rock Pigeons and other wildlife. Note that each of Don's photos posted to Flick'r is accompanied, in the comment stream, by additional (amazing) photos from the sequence. He has generously shared some of his shots and comments below.

I'll let Don take it from here:

The Gyrfalcons and Prairie Falcons deliver a killing bite to the head moments after the strike. It was exciting to catch that action.

Feb. 10, 2012, courtesy of Don Delaney.

Prairie Falcon delivering a killing bite.

Feb. 8, 2013. courtesy of Don Delaney.

I was very fortunate to capture two Gyrfalcons in one frame.

Feb. 9, 2013, courtesy of Don Delaney

I think these are two female Gyrfalcons. The males are considerably smaller, and males are rarely reported here.

Feb. 9, 2013, courtesy of Don Delaney

Feb 11, 2013, courtesy of Don Delaney.

Charles McDonald, another Edmonton resident, has also taken stellar photos of Gyrfalcon, Prairie Falcon and Northern Goshawk in recent weeks.

Like Don, Charles offers some samples and commentary. Thanks Charles:

To me photographing the Falcons hunting at the grain terminal is one of the most challenging aspects of bird photography I've encountered so far. These birds can be extremely fast as they make a kill which can be quite a challenge to track and follow them with the camera as it enters the flock. The tremendous action is a sight to behold and it's most rewarding to capture a beautiful image from the spectacle.

This was my first ever encounter with this Northern Goshawk. I was very glad just to a couple of shots of as it came out of nowhere and snatched a Rock Pigeon and quickly left the area. A very fast and skillful hunter!

Feb. 3, 2013, courtesy of Charles McDonald

Another favorite of mine from the grain terminal for the context of the image. After numerous attempts the Prairie Falcon makes off with it's kill while the rest of the Rock Pigeons continue to panic in the background.

Feb. 8, 2013, courtesy of Charles McDonald

This is one of my favorite images from the grain terminal. I was fortunate enough to have this one fly almost over head just after it caught a Rock Pigeon. This image clearly shows the death bite from the Gyrfalcon.

Feb. 10, 2013, courtesy of Charles McDonald

Raymond Lee of Edmonton has also captured some outstanding images at the Alberta Grain Terminal. You can view more of his fine work here.

Raymond writes:

What kept me from traveling hundreds of kilometers looking for owls during my free time was the hunting action of the falcons at the Alberta Grain Terminal. It is so addictive to watch and photograph. With a decent camera and a telephoto lens, one can bring home some nice falcon in flight photos if the raptor is flying at a reasonable distance. A capture of the falcon catching its prey or flying off with a prey in its talons is a huge bonus.

This photo is my favourite capture! The action happened directly above my head. The trail of feathers resembles an aircraft falling apart in an aerial combat. Every time I look at this photo, I can feel as if the collision had just happened a second or two ago.

Courtesy of Raymond Lee.

Prairie Falcon hunting.

Courtesy of Raymond Lee.

Prairie Falcon hunting.

Courtesy of Raymond Lee.

Adult Gyrfalcon.

Courtesy of Raymond Lee.

Juvenile Gyrfalcon.

Courtesy of Raymond Lee.

Acknowledgments:

• Many thanks to Jim Lange who discovered these on-goings and has shared his observations with the local naturalist community.
• Again I'd like to thank Don Delaney, Charles McDonald and Raymond Lee for sharing their experiences and photos.

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Citation:

• Dekker, D. and J. Lange. 2001. Hunting habits and success rates of Gyrfalcons (Falco rusticolus) and Prairie Falcons (Falco mexicanus) preying on feral pigeons (Rock Doves, Columba livia) in Edmonton, Alberta. Canadian Field-Naturalist 115:395-401. Accessible here.

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Spectacular photos by some strangers:

• Will James Sooter's Peregrines from California (thanks for the link, Don).
• Morten Hilmer's white Gyrfalcon from northeast Greenland (thanks for the link, Brandon).
• Mia McPherson's eye-level, in flight images of a Prairie Falcon in Utah.

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Some interesting pigeon and falcon video from the BBC: