Tuesday, April 28, 2009

Peregrines at the Port of Olympia

This morning I got a phone call from Ann, who works in a building near the cranes at the Port of Olympia. Ann is a devoted birdwatcher, and for years from her office window has watched a pair of Peregrine Falcons, who have a nest box on the orange southern-most crane at the Port. This year they are back, defending their nest and likely they have eggs they are incubating, soon to hatch.

Ann had several questions about what she's been seeing. Over the years she has gotten accustomed to seeing the same pair of birds: Peregrines mate for life and the adults stay year around to defend and re-use a successful nest-site. Individuals also have distinctive unique markings, so Ann has gotten to know the birds at the Port. This year, however, she called and told me that one of the birds was different: she had noticed it was much bigger than the other. She was wondering what that was about.

Among Peregrines ( and many other birds of prey) there is a factor operating called sexual dimorphism. What this means is that there are strong differences between male and female birds. You can easily see this in mallard ducks: the male has a bright green iridescent head and other bright feathers, while the female is a dull, dun brown, better for camouflage.

In Peregrines, females are often much larger than males. Their feather markings are the same, but there are distinct size differences. As Ann and I talked about this, it became clear that the female of last year had probably died. Ann remembers hearing that a peregrine falcon had been found dead this winter near the Port. The remaining "widowed" male must have courted and formed a pair bond with a new female, who happens to be gi-normous.

Ann has a great window out on the lives of these birds. She was watching the other day and reported a typical Peregrine hunt. The big female was hunting, zooming at high speed just outside Ann's window. Ann did not see the target prey bird, only a burst of feathers when the female falcon dove at high speed right into it (It was probably a city pigeon. Remember when Randy Johnson aka the Big Unit pitched a 95 mph fastball into a hapless pigeon at Safeco Field? Bird explosion.)

The female then deftly retrieved the stunned pigeon (all of this happening in flight, at speed) and took it off to a nearby light standard, where she perched and began to pluck the breast feathers. Ann reported that feathers were flying in great abandon. The Peregrine then ate voraciously, pulling out choice breast meat, then diving in further for the rich organ meats of heart, liver, spleen, etc. This whole process took about 20 minutes.

Finally this female left her plucking post, carrying a choice chunk of meat back to the nest box. Ann did not see what she did with that token: it may have been for her mate, who was perched, guarding the box & eggs. Other falcons such as kestrels are known to cache their extra food, storing it away for times of hunger. So it's possible this bit of pigeon ended up in a falcon cache nearby.

I remember hearing another story some years ago, from a crane operator at the Port. He has a good view from his perch, both of the Peregrines, and of Budd Inlet. It was during nesting season, when the Peregrine pair are especially, ferociously territorial. It was near dusk; the operator was looking out over the inlet and saw a Great Horned Owl, flying low over the water, heading east and making a fatal mistake of moving near the peregrine nest box. He watched as one of the falcon pair saw the owl and took off after it with deadly intent; he saw the falcon hit the owl at high speed, driving it into the waters of the bay. The owl was unable to get out, and drowned.

From the perspective of a nesting falcon, this was a smart move. Great Horned Owls are known to take falcons at night, when the owls' sense of hearing and night vision tips the predatory balance to them. From the perspective of the owl, it would have done better to wait until it got darker to start its night work.

A good place to watch these birds is from the waterfront near the observation tower. Look north for the huge orange crane: it is supported by a large concrete brace. Look at that brace and follow it up to the highest, southernmost edge. There is a gray nest box up on that cement ledge; often you can see the peregrines perched nearby, or flying nearby.

Another great resource is the Falcon Research group: www.frg.org. Based near Bellingham, this group was founded by Bud Anderson, who is a raptor biologist with a special expertise in falcons. Click into the page on Urban Peregrines; it gives a lot of insight into the lives of our local falcons. Also, FRG has a live falcon camera at the WAMU building in Seattle: look at FRG's website to find the link.

Resources: photos from the Internet

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