Swainson's Hawk
Common
Name: Swainson's Hawk (SWHA)
Scientific
Name:
Buteo
swainsoni
Global/Continental
Conservation Status: Not
on IUCN 2004 Red List
National-level
Conservation Status:
U.S.
– Bird of Conservation Concern
Key
Reference(s):
BNA No. 265 (England et al. 1997);
USGS
Northern
Prairie
Wildlife
Research
Center
document (Dechant et al. 2003)
Distribution:
Breeds locally in e-c
Alaska
(formerly?), Yukon, and MacKenzie, and from British Columbia, c Alberta, c
Saskatchewan, s Manitoba, w and s Minnesota, and w Illinois south to s
California (rarely), Baja California (formerly), Sonora, Durango,
Chihuahua, c and s Texas, nw Arkansas (casually), and w-c Missouri.
Winters primarily on the pampas of s South America (south to
Uruguay and Argentina), irregularly north to El Salvador and s Florida;
small population winters in the Central Valley of California; casually
elsewhere (AOU 1998).
Habitat
Associations:
Savanna, grassland, and cultivated lands with scattered trees (AOU
1998).
Source(s)
of Research/monitoring Needs (Number in ( ) is Physiographic Area number):
Arizona Bird Conservation Plan; Nevada Bird Conservation Plan;
Montana Bird Conservation Plan; Osage Plains Conservation Plan (33);
California Bird Conservation Plan; BNA No. 265 (England et al. 1997);
Canadian Action Plan (Dunn 2002); PIF Monitoring Needs document (Partners
in Flight Science Committee 2004)
PIF
Continental Plan Monitoring Needs Category: ** (Long-term population
trend monitoring considered adequate, but some issues (e.g., bias) may not
be accounted for)
RESEARCH/MONITORING NEEDS (source(s) of needs)
Monitoring
- Priority
monitoring action – NOTE: Breeding
Bird Survey (BBS) provides acceptable data for the continental level (PIF
Monitoring Needs doc)
- Supplemental
SWHA Surveys
- Monitor birds & habitats in hardwood draws (including SWHA) -
undersampled (
Montana
); Improve monitoring of SWHA on prairie breeding grounds; regularly
update hawk watch analyses (Canadian Action Plan)
- Causes
of Population Declines
- Determine causes of population and productivity declines, esp where
apparently suitable habitat remains unused (BNA); Determine causes of
population decline if it persists (Canadian Action Plan)
- Need
for more Information on Breeding Distribution & Habitat in
Specific Regions
- Determine breeding distribution & nest occupancy of SWHA in
Arizona (Arizona); Determine population size, density per unit of
suitable habitat, survival rates, & meta-population structure for
SWHA in riparian-associated regions in California (California);
Describe historic conditions & distribution of hardwood draw
habitats, esp. areas converted to non-native vegetation (focus on SWHA)
(
Montana
)
- Analysis
of SWHA habitat distribution, existing land use practices, and likely
long- and short-term land use changes (tied to habitat use studies)
(BNA)
- see
needs under "Landscape" and “Wintering”
Habitat
Needs/Ecology/Life History
- Determine
specific habitat requirements of Arizona SWHA (
Arizona
)
- Information
on the ecology of fledglings just prior to migration (BNA)
- See
needs under “Wintering” and “Migration”
Effects
of Management Practices
- Effects
of different grazing strategies & prescribe burning on hardwood
draw vegetation & breeding birds (including SWHA) (
Montana
)
Landscape
- How
do landuse and landscape patterns relate to distribution and abundance
of SWHA? How do they affect prey base? (Osage Plains)
Species
Interactions
- Investigate
causes of declines in Richardson's ground squirrel and its association
with SWHA declines (Canadian Action Plan)
Migration
- Foraging
habits & metabolism prior to and during migration, esp reliance on
outbreaks of insects (BNA)
- The
most critical questions focus on ecology during migration (and winter)
(BNA)
- see
needs under "Habitat Needs/Ecology"
Wintering
- Most
critical questions focus on ecology during winter in
S America
(and migration); determine habitat requirements and use patterns (BNA
and Canadian Action Plan)
- Document
distribution on non-breeding grounds, esp detailed studies of spatial
& temporal consistency of segregation (age, color morph, breeding
location) on non-breeding grounds (BNA)
- Threats
on Wintering Grounds
- Has conversion of tropical rain forests & s grasslands to
pasture & farmland affected distribution? (BNA); Assess Mexican
wintering grounds of Central Valley SWHA population to determine
population threats (
California
)
- See
needs in "Effects of Management Practices”, “Monitoring”,
“Habitat Needs/Ecology" and “Invasives…”
Invasives/Exotics/Disease/Parasites/Contaminants
- Effects
of Contaminants
- Test SWHA regularly for contaminants/ pesticides & possible
effects on reproduction (
Arizona
); Continue periodic sampling of contaminant levels on breeding &
non-breeding grounds (BNA)
Demographics
- Study
demography of SWHA in all parts of the year (Canadian Action Plan);
determine sources of mortality; continue & expand long-term
demographic studies (BNA)
- Monitor
SWHA nesting activity to test assumption that 150 breeding pairs is a
reasonable & achievable objective (derive new estimate), and test
assumption that nesting pairs in montane scrub contribute to healthy,
self-sustaining populations (
Nevada
)
- Determine
productivity & survivorship of SWHA in relation to habitat used in
high elevation grassland (in
Arizona
) and hardwood draws/grassland (in
Montana
) (
Arizona
and
Montana
)
[Link
to References]
[Link
to PIF Bird Conservation Plans]
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