Thanks very much, David, for your note about the Caspian Terns -- and for those details from the foreman of the building. I photograph these terns frequently on Elliott Bay, but owing to the distance David described -- from the rooftop to the bridge -- I don't [yet] have super-clear shots of the terns roosting/resting area. I could use some digiscoping to get a better view ? alas, no spotting scope in this household.

These images are admittedly fuzzy, but perhaps they can help establish visually, the scenario described. The first two images show the roof in the past two days, with round objects that look like eggs, but it's difficult to discern without the clarity of sharper glass. I'm still not sure what quality of fun those terns are having on that rooftop. :)

-- Caspian Tern Rooftop from May 21 and 22, 2012:

http://www.thefreequark.com/wp-content/uploads/2012/05/caspianternroof1.jpg

http://www.thefreequark.com/wp-content/uploads/2012/05/caspianternroof2.jpg

-- Caspian Terns on Elliott Bay:

loafing on beach at low tide: http://www.flickr.com/photos/taylar/7194696060/in/photostream/
bringing fish to other terns/mates: http://www.flickr.com/photos/taylar/7193881486/in/photostream

Best,
Ingrid Taylar
Seattle, WA