Hi all,
By now most of you are probably aware that both of these Willamette
Valley endemic subspecies -- Streaked Horned Lark and Oregon Vesper
Sparrow -- are on the ropes.
The larks have been federally listed as "threatened" within the past
couple of years while the sparrows seem to be in a similar situation if
not worse. Range-wide, we're talking about something under 2000 birds.
In recent weeks, the Center for Biological Diversity has filed a lawsuit
against USFWS, basically arguing that the larks should have been listed
as Endangered, with the according higher level of protection.
But I've heard some other news through the grapevine suggesting that
things have gotten a little worse for Streaked Horned Larks since 2013.
The biggest point of concern recently is Corvallis Airport, which Randy
Moore at OSU has been monitoring assiduously for about a decade now.
This had been the single largest known concentration of nesting Streaked
Horned Larks, with upward of 100 pairs (about 1/10th of the estimated
rangewide population). In 2014 the number of nesting pairs dropped to
26. Ouch!
The reason for the decline is still under investigation. In 2014 there
were around 50 males territorial males on site so the main problem seems
to be a lack of females, but the reason for this imbalance is still a
puzzle.
Another emerging problem is that avian pox has recently surfaced in the
South Puget Sound population -- which is migratory, and could be mixing
with our resident population by now.
Last year we enlisted birders (as Portland Audubon did in 2013) in a
volunteer effort to search for color-banded Horned Larks, which might be
from either the South Puget Sound region or Corvallis Airport. This year
I'm thinking that we should extend that, to also check for symptoms of
avian pox.
One optimistic hypothesis for the drop in population at Corvallis
Airport might be that larks simply left the area, because they found
suitable habitat elsewhere.If they did, it certainly doesn't show up in
the geographic distribution of reports on eBird, even though the overall
number of eBird reports in the region has increased. And -- except for
one bird at nearby Herbert Farm -- the missing larks didn't show up in
surveys for banded birds, despite very substantial effort.
To feed my own curiosity, I've created some PDFs that show the
geographic distribution of breeding-season eBird reports over the past
three year. I'll be happy to send those to anyone who wants to look. The
trend is even more negative once you realize that a few of the points
are misplaced because they represent county-wide "big-day" lists by a
couple of groups that were focused on setting single-day birding records
for Polk & Yamhill counties.
For Oregon Vesper Sparrows the eBird patterns are just slightly more
encouraging than for Streaked Horned Larks. There are a few more reports
but mostly these are clustered around the same locations (such as Bald
Hill Park & Farm on the west side of Corvallis). The number of locations
with breeding-season reports in Polk and Yamhill counties has declined.
The main new bright spots seem to be in Clackamas County where Joe
Blowers documented up 7 Vesper Sparrows (three of those juveniles) in
repeated visits to a single farm, and the new Nature Conservancy
preserve in Yamhill County, Noble Oaks, where Chris Adlam found a couple
of pairs.
For Oregon Vesper Sparrows, the other good news is that the Umpqua
Valley is still a stronghold. Unfortunately that's not the case for
Streaked Horned Larks, which have disappeared from the Umpqua region.
Sorry this is not as much fun as seeing a new shearwater or dove species
for Oregon, or finding a few Mountain Chickadees out of range. But
dwindling and disappearing species are the other part of the picture,
for birders in Oregon ... kind of the unspoken elephant in the room.
If you're interested in helping to look for banded or avian
pox-afflicted Streaked Horned Larks this winter, of if you'd like to
help document ongoing habitat impacts for grassland birds around the
Willamette Valley, please contact me.
Happy birding,
Joel
--
Joel Geier
Camp Adair area north of Corvallis
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