Thanks to Keir's checking up on a report submitted by Pam Lloyd to Cornell's ebird from last Friday the 18th , a photo during Keir's searching was forwarded to me last night which showed a hen CANVASBACK on Prospect Lake.
This is a rare species for the park, the last sighting on Feb 27, 2007, observed by Scott Whittle
see the photos on the links below:
http://www.flickr.com/photos/8867349@N08/8409124019/in/photostream
http://www.flickr.com/photos/8867349@N08/8394004788/in/photostream/