Assertive camp robber earns its name

By Jeff Mitton

On a camping and photography trip to western Colorado, I rose before dawn to have coffee and set up for a shot of aspen at dawn. It was a glorious morning, so I kept going until noon, when I returned to camp for lunch.

Lunch was cheese and crackers, but as I started I remembered the beer in the cooler. I walked the 20 feet to my vehicle, chose one and glanced back at the table to see that a grey jay had sunk the claws of its right foot in my cheese while it hammered away with its beak, taking healthy portions of cheese. I had been away from the table less than 10 seconds.

I walked the 20 feet to my vehicle, chose one and glanced back at the table to see that a grey jay had sunk the claws of its right foot in my cheese while it hammered away with its beak, taking healthy portions of cheese. I had been away from the table less than 10 seconds.I magnanimously surrendered the cheese to the jay, or maybe the thought of a bird's feet and beak in my cheese made that morsel unappealing. I grabbed a different hunk of cheese and moved to the other end of the table to record avian theft with my camera while I enjoyed my lunch.

The jay would take several gulps of cheese and then fly away, but return within a minute.

After six or eight feeding visits, it had reduce the hunk of cheese to less than half of its original size and now was able to lift the cheese with its beak and fly about 30 feet before dropping the cheese on the ground. It then took a few gulps and flew away.

Within a minute a jay was back at my table, obviously surprised and annoyed that its cheese was gone. That is when I realized that two jays were eating my cheese. The jay on my table saw the other jay return to the cheese on the ground and immediately flew to protect its fair share. I watched the confrontation and imagined that displeasure was expressed about the movement and hiding of shared food.

The grey jay, Perisoreus canadensis, also goes by the common name "camp robber" and from this recent experience I can say that the name, while not flattering, is fully deserved.

Two other species, Clark's nutcracker, Nucifraga columbiana, and Steller's jay, Cyanocitta stelleri, are also called camp robbers. All three species are in the family Corvidae (with crows, ravens and magpies), are found throughout the Rocky Mountains, cache food for consumption during winter and are year-round residents.

We have an abundance of robbers living in our forests.

Grey jays are omnivores and eat a wide diversity of foods, including cheese. They have been seen landing on moose to eat engorged winter ticks, which are much larger than wood ticks and live all of their lives on the same animal. Years ago I wrote a column describing magpies foraging on elk and eating winter ticks. Scrub jays have been reported to eat winter ticks from mule deer. So a minimum of three corvids have established feeding mutualisms to harvest winter ticks from large mammals.

Grey jays feed on chorus frogs, Pseudacristriseriata, in numerous populations around Chambers Lake in the Medicine Bow Mountains, and it appears that jay predation helps to establish and maintain variation among frog populations. Eight distinct patterns of dorsal color and pattern are found in populations and laboratory crosses have established the genetic basis for the color variation. The important part of this story is that the colors and patterns vary among populations and they are stable over time.

Because grey jays prey on chorus frogs, laboratory studies were undertaken to determine if jay predation focuses on the most conspicuous patterns, missing the most cryptic frogs. Experimental studies showed that grey jays selectively chose frogs most conspicuous against their backgrounds. So it seems that grey jay predation makes chorus frogs blend in their local environments and maintains differences among frogs living in different environments.

Jeff Mitton, mitton@colorado.edu, is a professor in the Department of Ecology and Evolutionary Biology at the University of Colorado. This column originally appeared in the Boulder Camera.

Oct. 10, 2014