<Reading and hearing the dove clip led me back to the smaller and more
together guys.
What I find just hard to understand on this take off is the reaction time o=
f
all of these little guys.
On this wing take off clip as well as others at the same site I could not
hear the difference between the first bird and the last in take off.
By eye I could not see the difference either. They seemed perfectly
together.=20
Anyone find a way to use audio to clock the reaction time of birds?>
I would like to see that answer too Rich.
There is a little bit of data regarding Flocks out there....
This data answers a little to how quick birds react in a flock.
One of the advantages that animals may obtain by grouping is a better chanc=
e
of avoiding predators. Assuming a predator generally will attack the closes=
t
individual, a bird can reduce its "domain of danger," the area in which it
can be the closest prey to a predator, by joining a flock. Where there is
cover, of course, hiding rather than flocking may be a more effective
predator defense strategy.
Simply reducing the domain of danger may not be enough to cause the
evolution of flocking behavior, even in open country. Flocking may, in fact=
,
backfire. The flock may be so conspicuous or represent so much potential
food that it attracts predators that might otherwise miss or ignore a lone
bird. However, there are other possible advantages of flocking. For
instance, in some situations being in a flock may reduce the amount of time
each bird must spend watching for predators, and thus increase the amount o=
f
time it has for feeding or other activities. Suppose a certain bird must
spend half of its time feeding in order to survive, and can watch for
predators the other half. A cat might sneak up on the bird by moving only
when the bird was busy feeding. If two birds forage together, and they feed
and look out at random, one bird or the other will be looking out
three-fourths of the time. A little arithmetic shows that ten birds feeding
together will have at least one individual watching for predators 99.9
percent of the time.
This bit of theory is supported by results from an interesting experiment
with Laughing Doves (also called Senegal Turtledoves, a species from Africa
and south-central Asia that is invading Europe and has been introduced into
western Australia). Experimenters used bait to attract natural flocks of th=
e
doves and then "flew" a model hawk down a slanting wire toward them. The
entire procedure was filmed, and the reactions of the birds analyzed in slo=
w
motion. When flock sizes were between 4 and 15 birds, the size of the flock
and the speed with which they became aware of the hawk and fled were
directly related: the more birds, the quicker the reaction. Flocks of less
than 4, however, reacted even faster than flocks of 4 to 15; but because
they were always skittish and had many "false alarms," they did not feed
well. In contrast, flocks of more than 15 birds had slower reaction times;
often because they became engrossed in battles over the food. Similar
results have been obtained from observations of falcons attacking wintering
shorebirds on a California estuary. Hunting success was high when solitary
shorebirds were the prey and when large flocks were attacked. Success was
low when flocks of intermediate size were the targets.
So, at least over an intermediate range of flock sizes, the notion that mor=
e
eyes are better than fewer seems to hold. In that range, larger flocks may
detect predators more easily. Furthermore, flock members may reduce their
chances of being eaten once the predator is detected. The sudden flight of
large numbers of birds, or their simultaneous calls, may temporarily
bewilder a predator and allow the flock to escape. It may also be more
difficult for a predator to pick a victim from a wheeling flock than to
catch a lone individual. This phenomenon is well known to the duck hunter
who blasts away at an entire flock and does not hit a single bird.
Finally, flocks of birds may turn the tables on predators. Both European
Starling and Red-winged Blackbird flocks have been observed to attack their
attackers and force them into water or onto the ground.
Martyn
Martyn Stewart
Bird and Animal Sounds Digitally Recorded at:
http://www.naturesound.org
N47.65543 W121.98428
Redmond. Washington. USA
Make every Garden a wildlife Habitat!
425-898-0462
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