Thanks for clueing me in to these resources, Ernest.
Quoting Ernest Buford <[log in to unmask]>:
> On Sun, 4 Apr 2004, Gregory R. Askew wrote:
> > Two marsh hawks were at the pond road side of Shelburne pond. Does anyone
> > the earliest I might scope the area for bitterns and rails?
> > Greg
> I expect eBird would answer this question. The Vermont Daily Field
> Card is another helpful reference. You can find it online here:
> or from the VTBIRD page (now that I've realized that I didn't have
> this link there until now).
> American Bitterns can be expected the second week of April,
> according to the field card.... rails soon thereafter.
> Ernest W. Buford
> Rubenstein School of Environment
> and Natural Resources
> University of Vermont
> Burlington, VT 05405
> (802) 656-3324