birds & conservation

Birds & Conservation

A Global & Local Perspective

Major Conservation Issues• 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 abundantbird in North America, thePassenger Pigeon is nowextinct. Overhunting for markets is though to beone contributing factor.

Eskimo Curlew

Texas 1962

Formerly a common spring migrant inin eastern SD; now probably extinct

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• 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 human-

altered 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

• Tropical Rainforests• Temperate Forests• Wetlands/Riparian Areas• Grasslands

• With loss of habitat, there is less area to sustain populations

New World Rainforest

Gray: extant forestBlack: destroyed

p. 642

Gray: extant forestBlack: destroyed

SE Asian Rainforest

p. 642

Examples• Golden-cheeked Warbler

– 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-(p-chlorophenyl) 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

• Sources:– 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:predationcompetition

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:– 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, Black-

capped 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