April 28, 2012: Interstate Bridge Peregrines and Osprey

April 28, 2012: Interstate Bridge Peregrines and Osprey

April 28, 2012: Interstate Bridge Peregrines and Osprey

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by Bob Sallinger

kgw.com

Posted on April 28, 2012 at 7:56 AM

Updated Tuesday, Oct 29 at 6:46 PM

Portland is full of amazing birds of prey. Yesterday I spent the morning perched atop the Interstate Bridge. Peregrines have nested on this bridge since 2001 and last year osprey also began nesting on the bridge. Peregrines like osprey have adapted so substitute man made structures for their natural nesting habitat. 

Peregrines typically nest on ledges on high cliffs. There are records dating back to the Middle Ages of peregrines substituting castles and cathedral ledges. Today many falcons nest on tall bridges and skyscrapers. Peregrines do not build stick nest. Rather they hollow out what we call a "scape" in the sand and gravel that accumulates on ledges and then lay their eggs right on the substrate. On the Interstate Bridge the falcons nest in a nest box on top of one of the bridge towers that Audubon and ODOT installed for them nearly a decade ago.

Further south on the bridge a pair of osprey have built a nest lower down on the bridge structure. Osprey are pretty low key when it comes to defending their territory but peregrines are not. According to bridge workers, the osprey have been subject to occasionally harassment by the peregrines but they have clearly persisted. The nest is built in a pretty amazing location sitting on the bridge superstructure right above the traffic.

The reason for yesterday's visit was to collect the peregrine's eggs. The falcons nested very early this year and laid three eggs. Unfortunately the eggs did not hatch. The falcons incubated their eggs for about 35 days...four days being the typical incubation period and then abandoned the nest. It has been a full week since incubation last occur ed---a time period that makes it absolutely certain that the eggs are no longer viable. We collect the eggs to that we can study what kind of contaminants the falcons have in their systems.

It is possible that the falcons will renest this season at this site and the osprey continue to incubate at their nest.

The following are some pictures of yesterdays adventure. Enjoy!

 

 

 

 

 

Peregrines-eye View from top of Interstate Bridge (Bob Sallinger)

Peregrine Falcon on Interstate Bridge (Bob Sallinger)

Egg Collection at Peregrine Nest Box on Interstate Bridge (Bob Sallinger)

Osprey Nesting on Interstate Bridge (Bob Sallinger)

Close-up of Both Osprey at Nest on Intersate Bridge (Bob Sallinger)

Osprey Nest from Distance on Interstate Bridge (Bob Sallinger)

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