Any chance it might be a yellow rumped warbler?  The end isn't exactly  
chu chu chu, but it is three-parted and it makes sense for this time  
of year and the habitats you describe.
Pieter van Loon
Marlboro





On Apr 29, 2010, at 11:48 AM, Roy Pilcher <[log in to unmask]> wrote:

> I first heard the song at Aitken State Forest on 2010-04-22 and then  
> again
> today on 2010-04-29 also at Aitken State Forest but approximately  
> half a
> mile  separation.
> From the "heft" of the song, it would suggest a warbler size  bird.
> The song was intermittent.
> The song seemed "hurried"  almost "explosive".
>
> Bird was up slope when heard on 2010-04-22 in what appeared to be pure
> deciduous woods.  Today, 2010-04-29, the song came from a small   
> stand of tall
> spruce/fir, [my tree ID is lacking] and high up.
> Song is a trill fallowed by a chu chu chu.  Most times there are  
> three  chu
> chu chu's but occasionally two or four.
> Caution! I may not be hearing the full song as I have lost and am  
> losing
> the higher frequency sounds.
> If I get some  leads I can check with the Cornell site, but  
> hopefully there
> will be the  opportunity for a some additional ears!
> Thanks in  anticipation.
>
> Cheers,
> Roy Pilcher
> The Gables at East Mountain, Rutland,  Vermont
>
> Speaking the same language.
>