When I've listened to night migrants over Etna, NY, or for the purpose
of counting calls from a entire night of recording, I generally consider
night to end around civil twilight. More specifically, my audio cue is
when the apparent night sounds cease and the Blue Jays and American
Crows begin calling. There's usually a gap of a minute or so of
separation between these groups in the morning (night and day). As for
the start of a night migration...I'm usually late in setting up, so
don't typically hear when the first birds start calling, relative to
civil twilight.
Sincerely,
Chris T-H
Harry Lehto wrote:
Hi,
in discussing night flight calls I am a bit confused about the concept of "night". Astronomically, I have no problem with the true night, and the various twilights. If the limit of "night" is taken at sunset/sunrise, then various day birds fall into the category of night flight calling birds even if they are not proper night migrants. Tits (chikadees), crows and finches start to vocalise before well sunrise, during the civil twilight, and gererally they do not crowd the sky in the deep hours of the night.
There appears also to be an assymetry between dusk and dawn. During the same
light conditions the duirnal birds at dusk tend to be much quiter than at dawn,
so this is not that miuch of a problem in the evening.
My question is when do you guys consider the night over?
Regards
Harry
[email protected]
Finland
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