Lars makes several good points regarding the role of vegetation and the
hardiness of Anna's Hummingbirds. In some cases they do seem to get
along fine without human assistance, even though they certainly make use
of it when it's available.
I suspect that the most extreme stories of ANHU survival -- such as the
bird in Bend that Mark Gonzalez mentioned -- are probably correlated to
someone who had a very high heating bill that year, due to poor
insulation, or else kept a brooder lamp going in their backyard hen
house. In the Corvallis/Albany area, occasionally someone who finds
droppings, and traces them to an Anna's Hummingbird that found a
roosting spot under their eaves close to an attic vent or porch light.
Anna's Hummingbirds seems to be good at exploiting the niches that human
habitations offer. If insects get drawn into spider webs around our
windows or around our porch lights, hey, they'll take advantage of those
for winter protein! But they also seem capable of finding "natural"
niches that allow them to survive moderate cold spells.
Yesterday morning one was singing at the Luckiamute State Natural Area
North trailhead (the trail that goes out to Luckiamute Landing), with
the thermometer just beginning to creep above 25 F after colder
temperatures overnight. The nearest residence is 1/2 mile away. However,
this spot has Red-breasted Sapsuckers year-round, so there are an
abundance of sap wells to feed and glean from.
Anna's just turned up in LSNA's north unit last year, but they've been
present consistently ever since. In winter, they tend to hang around
patches with S/SE exposures where a wild variety of ostensibly "native"
conifers (native to some part of the Willamette Valley, though likely
not this spot) were planted under a CREP grant 16 years ago, and were
recently enhanced by an even more bewildering variety of "native" shrubs
including evergreen shrubs such as Oregon grape.
Similarly, on a snowy day during the Airlie CBC a couple of winters ago,
my daughter Martha and I watched a male Anna's displaying on the south
edge of an overgrown Xmas tree farm about 1/3 mile from the nearest
residence, which is a farm on the outskirts of Palestine (now a
variable-density semi-rural residential area on the outskirts of North
Albany).
Like the LSNA site, this site likewise has a wild variety of conifers
plus a few evergreen broadleafs (invasive English holly and madrone).
The hummingbird was making use of a south-facing embayment in the
conifers, where the snow was melting off of the trees much faster than
elsewhere. Between displays, it would glean from the needles of the
conifers.
Conversely, the town of Banks is one of any number of valley-floor
residential areas where ANHUs are either still absent, or only recently
established. I suspect that Lars has put his finger on a key factor,
with his description of this as "a rather sterile bedroom community." It
could be interesting to compare Anna's Hummingbirds abundance, say, in
the older neighborhoods of Woodburn vs. the barren-looking, newer
bedroom developments out by I-5.
Happy birding,
Joel
--
Joel Geier
Camp Adair area north of Corvallis
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