Peregrines As A Fitness Program

Peregrine falcon at Lake Erie, Presque Isle, PA (photo by Steve Gosser)
Peregrine falcon at Lake Erie, Presque Isle, PA (photo by Steve Gosser)

10 October 2013

Here’s my favorite bird patrolling Lake Erie’s shore at Presque Isle State Park, looking for a meal.

And here’s a potential food source — a flock of dunlin.

Dunlin at Lake Erie, Presque Isle, PA (photo by Steve Gosser)
Dunlin at Lake Erie, Presque Isle, PA (photo by Steve Gosser)

The peregrine is looking for a bird that’s easy to catch, one that’s flying alone. The dunlin are sitting ducks (er… dunlin) if they stay on the ground so they fly and flock tightly as soon as they see a peregrine.  This interaction has made dunlin more fit in the years since the peregrine population has recovered from the DDT crash.

A 2009 study at the Fraser River delta on the Pacific coast backs this up.  Peregrines never went extinct on the West Coast but they were very scarce in the 1970’s.  During this period wintering flocks of dunlin safely roosted on the sand at high tide and became fat — and a bit slower — in early winter.

The peregrine population began to recover in the 1990’s and soon found tasty dunlin meals as they migrated past the Fraser River delta in fall and spring. The dunlin quickly learned it was unsafe to roost at high tide during the day because peregrines were on patrol.  Instead they began to spend high tide flocking over the open ocean, flying continuously for three to five hours.  With this exertion they became much more fit and are now are measurably thinner in early winter, the time when peregrines are passing by.

Peregrine falcons have provided dunlin with a fitness program.  Be fit or be eaten.

Click here to read more about the Fraser River dunlin study.

(photos by Steve Gosser)

One thought on “Peregrines As A Fitness Program

  1. This type of balance always makes me wonder what bird made the peregrine as fast as it is…
    my personal opinion is it was the passenger pigeon…which to me, explains why peregrine’s seem to nest near areas that have concentrations of the feral rock dove…What is now known as the pigeon…
    What I find interesting and can find no data to back up my theory, is the passenger pigeon went extinct near the downfall of the midwest and eastern peregrine, to what was soley claimed to be DDT…
    theory here…Did the peregrine loose it’s main food source at the same time ddt was working on it from the reproduction standpoint? Feral rock doves were not yet widespread at that time…and the western population of peregrines did not have passenger pigeons because the passenger’s did not live west of the rockies…. Most people today don’t even know there was such a bird as the passenger pigeon…(At one time the most numerous creature on the planet…)
    Just a thought!!
    Interesting how your post correlates with the elk becoming “normal” in Yellowstone, after the wolves were re-introduced…Instead of acting like cattle…they (elk) became wary and did not stand in one spot eating the plants to nothing…but began moving from place to place and the plants had time to recover, which ended up helping out all the other native fauna!!
    Thanks for your thought provoking blog subjects, Kate!!

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