Ok - Burt Guttman raised the question of why vacant lots provide some of the
best winter birding, while beautiful-looking "habitat" is practically bird
free. This is something I've given quite a bit of thought to, due to the
extraordinary birds we've found at the "compost piles" at Marymoor Park in
Redmond.

Now, Marymoor is just about exactly a square mile, and while it has all been
heavily impacted by humans, about a third of it has reverted to a nice,
mostly native riparian forest along the north shore of Lake Sammamish. The
slough has about a half-mile of natural shoreline (the only such section on
the entire river pretty much). Additionally, the East Meadow is dominated
by forbs and bunch grasses. Other meadows at Marymoor are unfortunately
just Reed Canary Grass. And of course much of the park is grass soccer
fields and the arboretum-like mansion district.

Yet many great birds have shown up in the area they use to dump debris.
Some of the birds that have shown up there include Ash-throated Flycatcher,
Western Kingbird, Northern Shrike, Horned Lark, Sage Thrasher, American
Pipit, American Tree Sparrow, Clay-colored Sparrow, Vesper Sparrow, Sage
Sparrow, Swamp Sparrow, White-throated Sparrow, Lazuli Bunting, and Western
Meadowlark. Not a bad list for a 100-yard circle in King County.

Now, a bit of a description of the "compost piles" area. It's just east of
the Interpretive Parking Lot in the middle of the park. On the south edge
is a huge mass of blackberry bushes. There are a couple of large piles of
sand, a large mound of gravel covered in weeds, a large weedy patch in the
middle, another pile of blackberries to the northeast, a single small stand
of maybe 2 cherry trees. The parks people dump downed branches, trimmings,
grass cuttings, weeds, leaves, gravel, sand, ground rubber, old signs, an
old toilet, Christmas trees, Scott's Broom that's been pulled out of other
areas, etc. in heaps on the ground. These heaps are being constantly
dumped, moved, hauled away, etc.

So why do birds like the piles? Well, first off, let me note that basically
ZERO birds breed in that 100-yard circle. (okay - maybe some Song Sparrows,
towhees, and House Finches might nest in the blackberries, but that's
probably about it). It is strictly a migrant attractor, and a foraging site
for wintering birds. They come there to eat. Most of the best birds have
been seed eaters. We've had at least 15 species of sparrow!

So here's what I speculate occurs.

First, the ground is mostly hard-packed gravel, on which things are dumped.
Most of what's dumped there has been cut; it lays there and dries, and the
seeds fall to the ground. Picking seeds off hard gravel is easier than
finding them deep in the duff or around the roots of grasses. Also, since
big piles of stuff are dumped there, the seeds are concentrated.

Second, the hard gravel is not the easiest place for plants to grow. Those
that manage are weeds - the kind that make a lot of seed - thistles,
mustards, sunflowers, mullen, etc. These plants attack the world with a
huge number of seeds and are willing to grow anywhere they can get even the
barest crack in the soil. They need lots of sun, so the lack of shade in
the compost piles is an advantage for them. If the soil were better or if
the soil was disturbed less often, they might give way to other species.
But the active use of the piles and the hard soil favor these weeds, which
then produce a lot of seed, which falls back onto the hard gravel surface,
which is easy to glean from.

The blackberries around the edges form a thicket that allows the birds to
quickly escape predators. The thorns probably deter accipiters and shrikes
from continuing pursuit. So there's a lot of free food and a handy refuge.

The Parks System has been talking for years about getting rid of the
"compost piles". I expect they'll eventually move this operation to
somewhere less visible than smack in the center of the park. I'm struggling
to figure out how to make a bird magnet like the piles without making it
look like an eye-sore. I'm not coming up with any great ideas, and I fear
we'll lose some of our best birds to beautification.

== Michael Hobbs
== Friends of Marymoor Park webmaster
== http://www.marymoor.org
== fomp at marymoor.org