Hi Tweets,

Re Max Gotz' Black Swift (BLSW) observation.

Good going, Max!

The behavior of the two swifts up to their separation is equivocal, either
aggression or courtship/mating. Their close corkscrewing flight after
separation plus Common Nighthawk (CONI)-like wing flare argues for actual
mating: that sounds like post-coital display. Mallard males, for example,
will swim in a tight circle about the female with whom he has mated seconds
before. I'd think that if this were conflict, one bird would be doing its
best to escape the encounter rather than joining its tormentor in display.
My vote's for mating and post-copulation display rather than aggression.
Coincidentally, there's been a fair number of BLSW's cruising low over my
part of Vancouver (west Kitsilano/east Point Grey) in the last few
evenings, and I've watched a fair number of what I'd take to be displays of
irritability and chasing, usually straight-down right-on-your-tail flight
for a couple of hundred feet, sometimes vertically up, but unlike Max's
birds, with no physical contact and invariably with one or both levelling
out and flying off horizontally in different directions, with no hint of
display he saw. I heard them for the first time ever the other evening, a
soft, rapid 'chuk-chuk-chuk-chuk-chuk', given during these chases.

Another characteristic that seems to distinguish BLSW from Vaux's Swifts
(VASW) is a habitual way of rising languidly to take an insect to the
stalling point and gracefully falling off on a wing, unlike VASW which just
seems to frenetically barrel around everywhere (which reminds me--do you
know why we're not supposed to split infinitives? because in Latin,
infinitives are usually only one word, and whoever decided centuries ago
that the rules of English grammar had to follow those of ecclesiatical
Latin decided arbitrarily that English infinitives had to follow the same
rule and be indivisible. To split an infinitive, therefore, is to boldly
go....;-)

And Jack's right: there's a ton of stuff we don't know about BLSW.


Michael Price The only alien planet is Earth.
Vancouver BC Canada
mprice at mindlink.net - J. G. Ballard