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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 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 • • • • • • 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 • • • • 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 – – – – 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 • 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: 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: – – – – 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