Ohio observers look for common nighthawks 20 Aug-10 Oct. This is the
period when nighthawks gather in flocks along the journey south.
Excellent fliers, they cross the Gulf of Mexico and go as far as
Argentina for the winter. These flocks move and feed together, tending
to follow river valleys or other chains of water where insects too
gather at this time of year. At this time, a few birds may be seen
moving during the day, but the great fall aggregations come at dusk,
when numbers in the four figures can be seen.
        Where are migrating nighthawks the rest of the time?  Apparently
nighthawks travel by day, though some assert they move at night as well.
They don't fly south 24 hours a day, as far as we know. Although flocks
are known at times to rest during the daylight hours on the ground or in
trees, they mostly rest at night.
        My experience of their fall migration, other than the phenomenal flocks
of dusk, is that nighthawks may be seen singly or in small numbers
during broad daylight. They often fly low at this time, but can
sometimes be seen quite high (sometimes apparently using thermals), all
moving purposefully. Silent at this time of year, they would be hard to
detect in total darkness, but I can't recall having seen one in the
middle of the night during fall migration, even in streetlights or
against the moon. I have never seen large flocks in the half-light of
early morning, only one or two at a time darting low and fast over the
treetops not long after dawn.
        In spring, in my experience, nighthawks travel north singly or in small
numbers. They do not flock. Rust in The Condor 49:117 (on-line at the
SORA site) studied common nighthawks in Idaho for 36 years, and only
once did he see more than three nighthawks at once in spring. I see a
lot fewer nighthawks overall, in groups or not, in spring; on these
comparatively rare occasions I have seen a few flying fast quite high,
at any hour of daylight. The impression I get is that they are in a
hurry, and do not benefit from traveling in flocks at that time.
        The questions follow. During fall, have you seen large flocks of
nighthawks in the middle of the day or at first light? Have you ever
found a night roost, or a day roost, with large numbers of nighthawks?
Have you ever detected large numbers moving by night? How about in
spring?  Has anyone observed a large northbound flock?  Many readers
have seen the odd roosting solitary nighthawk at places like the Magee
bird trail in spring; some seem to hang around all day, as if they were
sleeping by daylight...are they moving by night, or just taking a day
off? What evidence does anyone know of that nighthawks migrate by night,
  or are they spending the dark hours suckling at the teats of goats, as
our forefathers thought?
Bill Whan
Columbus

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