| Abstract: | The Klamath Basin National Wildlife Refuge (NWR)
complex, located in northeastern California and southern
Oregon, is situated on a major Pacific Flyway migration
corridor connecting waterfowl breeding grounds in the north
with major wintering grounds in California and Mexico. The
complex comprises five waterfowl refuges including Lower
Klamath NWR, Tule Lake NWR, Upper Klamath NWR,
Klamath Marsh NWR, and Clear Lake NWR, and one bald
eagle refuge, Bear Valley NWR. Lower Klamath and Tule
Lake NWRs are the largest refuges in the complex; historically,
they supported some of the greatest autumn and spring
concentrations of migrating waterfowl in North America.
Starting in 1953, standardized waterfowl surveys from small
aircraft have been conducted in autumn through spring. This
report summarizes waterfowl migration activity (i.e., abundance,
species composition, distribution on refuges, and chronology)
over four time periods?the long-term (1953-2001),
early (1953-76), recent (1977-2001), and the most recent
(1998-2001)?to describe changing patterns of migration on
Klamath Basin refuges from autumn 1953 to spring 2001.
Over the long term, waterfowl abundance (birds per
day) on the refuge complex averaged about 1.0 million in
autumn and about 360,000 in spring. A record peak count
of 5.8 million waterfowl was recorded September 24-25,
1958. Average abundance of autumn staging waterfowl for
the refuge complex, after reaching record levels in the 1950s
and early 1960s, began a decline that lasted until the 1980s.
A gradual recovery occurred during the 1990s, but autumn
abundance has not recovered to pre-1970 levels. In contrast to
autumn, average spring abundance was generally lower in the
early decades but has gradually increased through the 1990s,
particularly on Lower Klamath NWR.
Dabbling ducks represented an average of 68% of all
waterfowl in autumn and 55% in spring for the long term.
Northern pintail (Anas acuta) was dominant, representing 62%
of all dabblers in autumn and 51% in spring. A significant
decline in pintail abundance starting in the late 1950s altered
waterfowl composition on Klamath Basin refuges. As pintail
declined, other species such as mallard (Anas platyrhynchos)
and green-winged teal (Anas crecca) increased in abundance.
Although Arctic nesting geese, including white-fronted (Anser
albifrons), cackling Canada (Branta canadensis minima),
white geese (lesser snow [Chen caerulescens caerulescens],
and Ross?s [Chen rossii]) have become less prominent in
recent decades, they reached an historically high abundance
during autumn in the 1960s and 1970s, particularly on Tule
Lake NWR.
Tule Lake NWR supported the highest average autumn
waterfowl populations until surpassed by Lower Klamath
NWR around 1980. During the recent period (1977-2001),
Lower Klamath NWR accounted for 60% of all waterfowl
using the refuge complex in autumn and 61% in spring. Habitat
diversity and wetland productivity contributed to its greater
waterfowl abundance. Tule Lake NWR supported the most
geese over the long term, 79% in autumn and 66% in spring;
however, total waterfowl abundance on this refuge in autumn
has been in decline, likely because of reduced diversity and
productivity of sumps in the refuge. Upper Klamath, Klamath
Marsh, and Clear Lake NWRs accounted for less than 8% of
total waterfowl use in autumn and spring but provided diverse
habitats for migrants.
Waterfowl use-days on Klamath Basin refuges typically
peaked in mid-autumn, decreased as migrants passed
through the basin, and then reached a lesser peak during spring
passage. Waterfowl abundance reached a pronounced peak
in autumn during the early period (1953-76), but spring peak
buildup was much less pronounced. For the recent period the
autumn peak was more subdued.
Waterfowl abundance, species composition, and distribution
on Klamath Basin refuges have fluctuated over the
decades and have been influenc |
| Genre: | Federal Government Series |
| ProdID: | 53860 |
| Citation Author: | Gilmer, David S.; Yee, Julie L.; Mauser, David M.; Hainline, James M. |
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| Citation Language: | ENGLISH |
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| Citation Phsyical Description: | 66 p. |
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| Citation Public Comments: | |
| Citation Publisher: | U.S. Fish and Wildlife Service |
| Citation Series: | Biological Science Report |
| Citation Series Code: | BSR |
| Citation Series Number: | 2003-0004 |
| Citation Search Results Text: | Waterfowl Migration on Klamath Basin National Wildlife Refuges 1953-2001; 2003; Federal Government Series; BSR; 2003-0004; Gilmer, David S.; Yee, Julie L.; Mauser, David M.; Hainline, James M. |
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| Citation Year: | 2003 |
| Type: | citation/reference |
| Text: | Waterfowl Migration on Klamath Basin National Wildlife Refuges 1953-2001; 2003; Federal Government Series; BSR; 2003-0004; Gilmer, David S.; Yee, Julie L.; Mauser, David M.; Hainline, James M. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DOCUMENT): | http://www.werc.usgs.gov/dixon/pdfs/Klamath_Basin.pdf |
| Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
| Publisher: | U.S. Fish and Wildlife Service |
