The Sunset View Cemetery Whip-poor-will is back again.  Probably arrived 
a week ago, but I didn't have the chance to check before last night.

First song began at 8:40pm, two minutes after the end of Civil 
Twilight.  Typical of behavior when first arriving the bird sang short 
bursts (10-20 seconds) of song, moving to a new location every 2-3 
minutes.  When first heard it was about 600-700 feet south of the of the 
cemetery, and then worked its way to various locations at and near the 
back end of the cemetery.

When within about 500 feet of me, I could easily hear the "tic" note 
that sometimes precedes each repetition within the song. This note adds 
an extra rhythmic "down-beat" to the extended song as a whole.  Always a 
delight to hear it accentuating the song.

The start time for vocalizing of 8:40pm was two minutes _after_ the 
posted end of Civil Twilight (which for humans is when our eyes switch 
from using cones to using rods, and colors are exchanged for grays).  On 
this date the posted end of Civil Twilight was 33 minutes after the 
posted sunset time for the location.

Slightly over a week ago at the Snake Mountain Road, Weybridge site, the 
start time for vocalizations was 8:24pm.  This was two minutes _before 
_the posted end of Civil Twilight at 8:26pm (31 minutes after the posted 
sunset time).

The Weybridge site is on the east face of Snake Mountain, and thus the 
real end of Civil Twilight there would be sooner than the listed time, 
due to the shadowing of the mountain.  The Waltham site looks across the 
Champlain Valley with a far distant horizon to the west.  On a very 
clear night, such as last night, the real end of Civil Twilight would be 
slightly later than the posted time, and in fact the Whip-poor-will 
began two minutes after the posted time.

Pretty neat, and a very useful tool when seeking to confirm the presence 
of Whip-poor-wills, especially late in summer and early fall when that 
is the only time they might vocalize (very close to the end of Civil 
Twilight), and then with but a single song often only 2-4 seconds in 
duration.

Ian