I spent a few hours this morning at Prospect Hill Park in Waltham hoping for a Summer Tanager reported to be heard but not seen yesterday. I hung out along Bond Trail for about an hour, and near the intersection with Sunset Trail, just up the hill from the "wet spot", heard what I thought was the Summer Tanager. I'm pretty good at picking out the Scarlet Tanager song (sounds to me like a hoarse Robin) and chip-burr call, but this song sounded more Vireo-like. It took a while to locate the bird, but it turned out to be, no doubt about it, a Scarlet Tanager with a slightly aberrant song. Could this be the same bird heard yesterday? I did hear the Raven calling in the distance as reported yesterday and, of note, saw:Turkey VultureYellow-bellied SapsuckerEaster Wood PeweeGreat Crested Flycatcher (several)Pine Warbler (many)Blackpoll Warbler (at parking lot near "Little Prospect")Indigo Bunting (three males, near water tanks at "Big Prospect")Scarlet TanagerChimney SwiftHouse WrenRed-eyed Vireos (many) plus there usual suspects.There were a few other birders there who, also, had not seen the subject bird.