Transcript Conservation - USD Biology

Birds & Conservation
A Global & Local
Perspective
Major Conservation Issues
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Humans
Habitat
Toxic compounds
Exotic species
Island Effect
Nest Parasites
General Effects of Humans:
we take up space & demand resources
• Human population & associated effects
– Huge size (~ 6 billion)
– Future increases in population - some
models suggest peaks @ between 12-20
billion
• Development (all ↓ available habitat)
– Housing
– Industry
– Agricultural
Human Presence
Other Associated Human
Effects
• Excessive Hunting
– when going beyond sustainable levels
– turn of century feather collectors
– poaching of endangered species
• Examples:
– Passenger Pigeon
– Great Auk
– Eskimo Curlew & other shorebirds
Once the most abundant
bird in North America, the
Passenger Pigeon is now
extinct. Overhunting for
markets is though to be
one contributing factor.
Formerly a common spring migrant in
in eastern SD; now probably extinct
Eskimo Curlew
Texas 1962
Upcoming Schedule
• Final Field Trip – Sat., May 1
– Newton Hills State Park
– 0730-1400
• Final Exam
– Thursday, May 6
– 1230 to 1430
– Will cover material since second exam
(Social Systems through Conservation)
Other Associated Human
Effects……
• Road Kills
• Cats
• Collisions
– buildings, windows, communications
towers
• Human activities directly kill an
estimated 1 billion birds each
year in the U.S.
Avian Collision Study (Erickson et
al.2005)
Annual estimates of U.S. Mortality
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Vehicles (80 million)
Buildings/Windows (100 million-1 billion)
Powerlines (130 million)
Communication Towers (4-5 million)
Wind Turbines (20-40 thousand)
For comparison: house cats = about 100 million
annually in N. America
• Total anthropogenic mortality = > 1 billion
Habitat Destruction
• Loss
– destroyed altogether
– removal and replacement with humanaltered habitat
• Fragmentation
– partial destruction as well as separation
of once-connected areas into isolated
fragments
– leads to lower total area & possible
separation of populations in fragments
Habitat Destruction……
• Degradation
– lower quality due to a variety of factors
such as exotic species, increased edge,
toxins, etc.
• cheatgrass or other weeds
• agricultural runoff in a stream
Many habitats are threatened
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Tropical Rainforests
Temperate Forests
Wetlands/Riparian Areas
Grasslands
• With loss of habitat, there is less
area to sustain populations
New World Rainforest
p. 642
Gray: extant forest
Black: destroyed
p. 642
Gray: extant forest
Black: destroyed
SE Asian
Rainforest
Examples
• Golden-cheeked Warbler
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breeds central Texas
winters S Mexico
housing developments, recreation, etc.
cowbirds
• Riparian birds in South Dakota
– many woodland habitats now gone due to
dams and conversion to agriculture
– limited habitat area for populations
Note dramatic decreases in forest and grassland habitats
Migratory Birds
• Need suitable habitat for all phases
of life cycle:
– breeding, wintering, migration
• Habitats migrants use often differs
among seasons
• Conservation plans must be complex
to safeguard all important habitats
Habitat Conservation
Efforts
• Preserves:
– National Parks, National Wildlife
Refuges, National Forests & Grasslands,
state & local parks, private
• Conservation easements:
– private land set aside, CRP
• Endangered Species Act:
– mandates protection for species
threatened by human activities
• Need ecosystem-based approaches
Environmental toxins
• Pesticides
– DDT
– PCB’s
• Fertilizers
• Fossil Fuels
• Household Chemicals
Pesticides
• Widespread use:
– household & lawns
– agricultural
– pest control
• Many effects
– reduce prey populations
– non-target mortalities
• For example, Birds of Prey
– bio-accumulation and bio-magnification
Example of Pesticide
Effects: DDT
• DDT: 1,1,1-trichloro-2,2-bis-(pchlorophenyl) ethane
– widespread use mid-1900s
– population declines noticed in many
birds, especially predators
– Osprey, Bald Eagle, Peregrine Falcon
– Peregrine almost extinct in eastern US
• DDT banned in US in 1972
• subsequent rebound of all raptor
species affected
Bald Eagles before & after DDT ban:
Reproduction & amounts of DDE
p. 565
Local Toxin Example: Selenium
& colonial waterbirds
• Selenium (Se):
– trace mineral
– important in small amounts
– key component of enzymes
Selenium & colonial
waterbirds
• The problem:
– high concentrations of Se found in some
soil types: (e.g., marine shale)
– Se leaches from soil in high amounts
– agricultural run-off leads to high [ ] in
bodies of water
– Se will bioaccumulate (increasing levels
as you move up food chain)
Selenium & colonial
waterbirds
• Effects on birds:
– deformities
– reduced reproductive success
• Rookery @ Stratford Slough (Brown
Co., SD)
– ~ 1000 birds ‘destroyed’ due to selenium
Exotic Species
Exotic Species
• Exotic
Introduced
Non-native
– any species living outside of its natural
range
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human colonists (“acclimatization societies”)
agriculture
accidental transport
biological control
‘just for fun’
Examples of Exotic Species
• southern US: Fire Ants
• Guam: Brown Tree Snake
• US: European Starling
– House Sparrow
– Rock Pigeon
– Ring-necked Pheasants
• Hawaii: > 50 introduced bird species
Why are exotics a problem?
• Freedom from usual population
limitation
– no natural predators
– no usual diseases
• Competition with or predation of
native species:
– native species may have not evolved
defenses or necessary behaviors to ‘deal
with’ exotics
Effects
of Fire
Ants:
predation
competition
Brown Tree Snake in Guam
Bird
Exotic Birds
• European Starling:
– introduced to Central Park in NYC ~
1890
– now most common bird in US
– competes for food & nest cavities
• House Sparrow & Rock Pigeon
– more confined to human areas
– still compete w/ natives
– House Sparrow vs. Purple Martin
More Exotic Birds
• Ring-necked Pheasant & other game
birds (Chukar, Gray Partridge, etc.)
– favored for hunting
– may compete w/ native grouse (???)
Birds and Islands
Island Biogeography
• ‘The small island effect’
• Small islands support small
populations
• Island populations often not exposed
to full range of ecological factors
– predators
– pathogens
Island Biogeography……
• Evolve unique adaptations, which
often lead to speciation
– flightlessness
– ground-nesting
• More sensitive to changes in
environment
– Hawaii
– Guam
– fragmented habitats
Hawaii
• Isolated volcanic islands
• populated by founder species that
colonized
• adaptive radiation
• many unique, locally adapted species
– flightless Ibis & honeycreepers
• few predators
Hawaii…… Human effects
over last 2 millenia:
• introduced pigs & other ungulates
– over-grazing/browsing
• introduced rats (nocturnal)
– predators of many unsuspecting birds
• introduced mongoose (diurnal)
– preys on many birds (not rats!)
• introduced mosquitoes
• avian malaria w/ introduced birds
– spread by mosquitoes
Hawaii……
• ~ 1/2 of original species remain
• many remaining are threatened by
habitat loss, diseases, & vagaries of
small population size
Guam
• Brown Tree Snake
• elimination of all wild populations of
Guam’s endemic birds:
– rail, kingfisher, songbirds, etc.
Island Biogeography &
Mainland Ecosystems
• Naturally occurring ‘islands of
habitat’:
– Black Hills
– ‘Sky Islands’ of desert southwest
• Human-caused fragmentation:
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once extensive areas now only patches
forest
grassland
etc.
Cowbirds and Conservation
• Brood parasitism has negative impacts
on host reproductive success
• Cowbirds feed in open areas but
parasitize many forest-dwelling
songbirds
• Human activities have allowed cowbirds
to expand their range
– Forest fragmentation  more open areas
– Cattle ranching  associate with
bison/cattle
Cowbirds and Conservation
• Brown-headed Cowbirds have
parasitized over 220 species
• Of these < 25 eject cowbird eggs, 37
desert nest to renest, only a few build
a new floor over clutch. Most are
susceptible.
• Parasitism probably not responsible for
continent-wide population declines, but
do impact some endangered species.
– Least Bell’s Vireo, Kirtland’s Warbler, Blackcapped Vireo, SW Willow Flycatcher)
Cowbirds and Conservation
• Control Issues:
– Some view killing cowbirds as inhumane
– Cowbird removal is only a short-term
solution to the problem
– Cowbird removal is expensive
• Bell’s Vireo: over $665K/year (225 traps/yr,
each trap gets about 3,000 cowbirds/yr)
• Kirtland’s Warbler: $90K/yr
• Black-capped Vireo: $45K/yr
– Removal doesn’t increase population size
for all species
Cowbird Removal: Successes
• Golden-cheeked Warbler: rate of
parasitized nests down from 90% in
1987 to 22% in 1996.
• Black-capped Vireo: rate of
parasitized nests down from 90% in
1987 to <10% in 2000-2002; nest
success increased from 3% to >40%.
• SW Willow Flycatcher: rate of
parasitized nests down from 63% in
1989-1991 to 15% in 2003, nest
success increased from 20 to 61%.
Cowbird Removal: Mixed Results
• Least Bell’s Vireo: populations
increased following cowbird control
and efforts to improve habitat
• Kirtland’s Warbler: cowbird control
and habitat restoration increased
population from 200 breeding pairs in
1972 to 1800 breeding pairs in 2007.
• SW Willow Flycatcher: After 12
years of cowbird control CA pop. still
decreased. Suggests that habitat, not
cowbirds, is limiting factor.
Cowbirds and Conservation
• What to do about it?
• Habitat issues are primary concerns
– Increase nesting habitat for songbirds
– Decrease habitat fragmentation that
favors cowbirds
• Cowbird Control = not a long-term
solution
– May help very small populations increase
to reestablish a stable breeding
population, but don’t promote long-term
recovery