Subject: Re: Varied Thrush favorite food?
Date: Oct 28 20:28:31 1996
From: Don Baccus - donb at rational.com


Dennis is back in force:

>Cooper's I could imagine, but SSHA, wow! I
>always thought they were junco-size feeders.

I think you're right. However, individual raptors will do really weird
things, as I've learned via the mechanism of trapping them using live
lures.

We used different sized lures (pigeons, starlings, house sparrows,
Republ...oops, I don't really mean that!) for different sized
raptors, but occasionally our hatch-year trappers and hatch-year
raptors hvae a little communication problem. Female sharpies will
get caught on a pigeon weighing much more than them (like a factor of
4 or 8 or more) a few times a year, by rookie banders who misidentify
them frequently as female Coops, or gos, or even golden eagles...

By "caught", I mean (in falconry terms) "bind to the lure", followed
by being dragged to the trap, not being able, of course, to hurt the
pigeon due to the great disparity in size. But, yet, not letting go.

Topping it all off, in this regard, as far as I'm concerned, was the
female kestrel caught on a pigeon in '94. Each lure-bird setup is
equipped with a shelter, so the bander can hide the "wrong-sized"
bird while luring with the right-sized bird for the specific individual
stooping the station (sorta like Goldilocks and the three lure birds).

This mamma kestrel CRAWLED into the "house" into which the pigeon had
been hidden, bound to it, and was dragged at least 15 feet to the trap.
I'm sure it was convinced it had found the kestrel equivalent of
Sutter's mill.

The point of all this is that yes, a varied thrush is bigger prey
than a "normal" sharpie will go after. But, some individuals are
going to go after them, just as we often see redtails intimidated
by our pigeon lures that slaver all over themselves lusting over
the starling that gets flapped moments later.

There's a lot of variation in, ummm, chutzpah?, among individual
raptors. Makes me wonder about insectivores and the like, if
there's a similar variation among individuals regarding the size,
difficulty, etc of predation.

>Every day that I'm home--i.e., weekends--I see one or more SSHAs hanging
>around the house. If they eat only one small bird/day or /2 days, it seems
>to me one could easily wipe out my yardful of birds in a winter, yet that
>doesn't happen. Wonder how many birds they do consume over a winter, and
>what the range of one is during that time.

I'd guess the range is fairly large, and they distribute their hunting
efforts. If they constantly hunt your feeder, I'd expect the birds
using it to get extremely on-edge and aware, bad for the sharpie's
success ratio. They thrive on slackness.

> I kid you not, though, over the
> past 3-4 weeks, there is *always* a SSHA around.

Accipiters seem fascinated by locales with abundant prey, and somewhat
confused as well, as far as I can tell. At the Goshutes, each season
we always get the random gos, or Coops, or sharpie (usually a few per
season) which will spend a week or so hanging out in the lure-bird
aviary. They'll watch us enter the pigeon cage to feed or water
the bird, staring at us as we undo the latch and open the door. They
watch quizzically: "how do they do that?". They are very approachable
and unafraid or more likely considering the wildlands where most breed)
unknowing of humans. Indeed, this year, one of our rooks accidently
let a house sparrow go while a sharpie was perched about 10 feet away,
watching her hold this bird. The sharpie had been there a couple of
days, watching the human-bird interactions with fascinations. When
this house sparrow was accidently let go (believe me, they are a bitch
to hold onto), the sharpie nailed it about three feet from her hand!
And flew off...finally, success at the larder, previous frustration
beside!

Occasional birds will attempt to get in the cages, but we've never
run across any Einstein-like advances in latch-flipping skills with
these birds. Yet. I came close to grabbing a Coop barehanded, once,
though, which had crawled (yep!) under a tarp protecting starlings
from rain, trying to get in the cage after several failures at getting
in via the door on the top. It heard me, popped it's head out, and split
before I could get it.

>I've never seen a contact yet, but the chases are great.

I see. It's an immature, right?

Interestingly, in the Goshutes most birds seem to pay little attention
to the migrating (or even perching) raptors - except other raptors.
Some instinctually-implemented adaptation to the fact that few of
them feed, but rather mostly move south? Or, a lack of recognition
because the accips aren't perching in their normal hunting/ambush
style, but rather flowing down the ridtge? Clarke's nutcrackers
("crackers", for short) and Townsend's solitaires are frequently
flying around on flight days, annoying counters and trappers a
lot. They just ignore the several hundred raptors flying by.

Likewise, the migrating raptors rarely chase resident passerines,
though our site might be skewed by the aviary mentioned above (usually
with 100+ pigeons, 50-60 turtle-doves, 20 or so starlings, 30 or so
house sparrows in residence). Though occasionally one can see accips
hunt late evening or early morning, i.e. pre- or post-roosting. Not
often, though.

- Don Baccus, Portland OR <donb at rational.com>
Nature photos, on-line guides, at http://www.xxxpdx.com/~dhogaza