Date: 3/13/18 9:37 am From: Joel Geier <joel.geier...> Subject: [obol] Re: Least Bittern and Upland Sandpiper
To address the questions and speculation about observer effort and effect of wintering vs. breding habitat changes, let's take these one at a time:
1. Least Bittern (LEBI):
Klamath Bird Observatory (KBO) surveyed systematically for LEBI and five other secretive marsh species at numerous sites in south-central Oregon, starting in 2008: http://www.landscope.org/connect/conservation-projects/project/1742# I'm not sure if they managed to cover all of the sites listed, or if this study continued beyond 2008. In that year they had negative results at Sycan Marsh, Klamath Marsh NWR, and Wood River Wetlands, but seem to have detected LEBI at Malheur NWR ,near Frenchglen.
The Birds of Oregon: A General Reference (BOGR) species account for LEBI, written by Kevin Spencer, cites Willett (1919) as finding a nest at Malheur L., and reporting that LEBI was a common breeder there at that time. The account also notes that conditions have changed since then with the introduction of carp which "undoubtedly affected invertebrate and amphibian populations." The species is also sensitive to hydrologic conditions (water levels and contamination).
The BOGR species account mentions the lower Colorado River as a wintering area. The formerly vast marshes where the Colorado River flows (or used to flow) into the Gulf of California have been greatly diminished due to water outtake for irrigation and urban use, so it makes sense that populations in the western part of LEBI's nesting range could be affected by loss of winter habitat.
2. Upland Sandpiper (UPSA)
As I mentioned previously, the Grant County Bird Club has had a monitoring program for UPSA in the Bear & Logan Valleys and other known nesting sites. So there has been pretty consistent, focused effort for this species. The last time I asked Tom Winters about UPSA status in Grant County, he was skeptical whether any were still using those sites.
Wayne Hoffman's sighting from the Riley Pond area, mentioned by Dave Irons, sounds like a migrant situation. However the Grant Co. eBird report that Trent Bray mentioned (as yet unconfirmed and thus hard to find on eBird) gives a little more hope that a few might still be nesting there.
The BOGR species account by Mark Stern cites reduction of forbs in nesting meadows (cinquefoil is thought to be particularly important), along with encroachment by pines and overgrazing of meadows as factors that may have diminished nesting success. Habitat might also be lost when water tables in meadows drop due to downcutting of streams, after riparian vegetation is damaged by grazing. This is certainly evident in the meadows around Big Summit Prairie, which produced a few reports in the 1980s.
UPSAs winter in the pampas of central South America where no doubt they face additional threats. However, according to the BOGR account the North American population overall was stable or increasing (as of 2003). If Oregon's population has diminished while the continental population is stable or increasing, that seems to point the finger squarely at issues on the breeding grounds.