[CT Birds] Threat recognition - Part 2

[Clay Taylor]

All -

Dave's points are excellent - there are definitely different "threat levels"
that birds assign to things they encounter.     I have always felt that
unless you are wearing camouflage clothing and sitting very still in the
woods, the average bird foraging in the area absolutely knows you are there,
it just tolerates your presence because you present no threat.    Can you
surprise a bird with a sudden motion?   Of course - I think that it always
knew you were there, but did not feel threatened until you acted out.

As for passerines and raptors, Bud Anderson of the Falcon Research Group (
www.frg.org ) gave a fascinating lecture about his studies of sitting
raptors, and how their immediate behavior can predict the type and intensity
of their subsequent actions.   How often they look side-to-side (he had
definite frequency levels - twice a minute, 10 times a minute, etc.), fidget
on their perch, preen, ruffle the feathers, etc., makes it more or less
likely they would either stay, leave the perch to hunt, etc.    It was
really interesting.

If you are a shorebird or passerine, it behooves you to learn when Mr.
Harrier or Mr. Red-tail's actions, whether sitting or in flight, are benign,
or if he is looking for lunch.   I have seen shorebirds virtually ignore a
passing Harrier on some occasions, and other times take flight well before
it arrives.   Heck, there are times when a Cooper's Hawk is sitting in a
tree and passerines are nearby, going about their business like the hawk
wasn't even there.

Frank Gallo first told me about a "dread" - the tendency for terns and gulls
to suddenly take off en masse from a mudflat, sandbar, or nesting colony,
even if there is no visible threat.   Evidently, all it take is one member
of the flock to cry "wolf" (Hawk? Merlin? Birder? USAir?) and they all go up
as one, circle around, and alight back where they started.    The Early
Warning System is never ignored.

Back to the Jays and the Shrike - certainly the Shrike acts like an
aggressive predator, regardless of its size.   Since Blue Jays are the
Sentinel of the Woods (one squawk and the bird feeder clears out, right?),
they would pick up on that pretty quickly.    Actually, come to think of it,
the Blue Jays at our feeders right now are more than likely Northern birds -
anybody have a banded Blue Jay at their feeder right now that was definitely
banded there during breeding season?    I think not - remember those Blue
Jay flocks passing through Lighthouse Point in the fall?     Our present
Blue Jays might very well have seen Shrikes on their breeding grounds.

Clay Taylor
Moodus, CT
ctaylor at att.net

----- Original Message ----- 
From: <David.F.Provencher at dom.com>
To: <ctbirds at lists.ctbirding.org>
Sent: Thursday, January 17, 2008 6:32 PM
Subject: Re: [CT Birds] Threat recognition


>
> Threat recognition in an organism is a fascinating topic to me. Birds
> appear to be able to distinguish between different species of raptor, or
at
> least different genera. If the raptor is an actual predator of the bird in
> question, an evasion strategy occurs. If the raptor is not a predator of
> the bird in question, then there will be some level of surveillance the
> bird will apply to the raptor's presence but there seems to be an
> understanding that there is no imminent threat. Is this innate or learned?
> Another interesting threat recognition behavior I've witnessed is how
> shorebirds react to approaching humans. If you walk along a beach towards
> shorebirds they will allow you to approach to within a certain distance
and
> then move away or flush. However if you approach them from the water, say
> wading out into a couple of feet of water depth, they will allow a much
> closer approach before reacting. So do they perceive the level of threat
> differently because they perceive you differently, or do they perceive a
> different level of threat because of what you are doing differently?
>
> Mobbing, such as John mentioned, is another form of threat
> recognition/reaction. Mobbing seems to be an innate behavior. Certainly
the
> behavior spreads across the species barrier. But  why would Blue Jays mob
a
> Shrike? Certainly the Blue Jays are unlikely to have each been the target
> of Shrike attacks. Perhaps they have witness attacks on other birds and
the
> aggressive behavior exhibited by the Shrike triggers the mobbing reaction
> to the now imprinted Shrike/predator image the Jays have acquired. To
muddy
> the already murky water let me ask this, why are Blue Jays rarely if ever
> mobbed by other birds? Certainly they are aggressive and predatory at
> times.
>
> Threat recognition/reaction in birds can be immensely helpful to birders
> watching for predators as well. The first Gyrfalcon I saw in CT was being
> mobbed by three Northern Harriers (Hammonasset). The Gyr was perched
> mid-level in a tree and I might have never looked there if not for the
> spectacle of three Harriers swooping and wheeling.
>
> Dave
>
>
>
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