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L4 Why is "adaptive radiation a major theme in the biodiversity of birds?
Adaptive radiation = rapid speciation. Birds began speciated 65 million years ago, and now are 10,000 sp. (greatest of terrestrial vertebrates). The observed biodiversity of birds is due to adaptive radiation.
L4 How are "biodiversity hotspots" defined and which definition(s) can best conserve birds?
Avian biodiversity studies:
- Diversity in life history
- Diversity over time: adaptive radiation
- Diversity over space: hotspots
How many sp. of birds i comparison to mammal and reptiles?
- 10,000 sp. birds
- 5,700 sp. mammals
- 8,200 sp. reptiles
What measures of birds do we measure life history diversity?
- Body size and flight (e.g. Hummingbird, peregrine falcon, penguin, and ostrich)
- Diversity in diet and beak shape
- Diversity in reproductive rate and lifespan (e.g. albatross, ducks, and songbirds)
Biodiversity and evolutionary history
- Species are organized into taxonomic groups based on their evolutionary history
- The phylogeny shows which birds are descended from a recent common ancestor
Diversity over time: Evolutionary history overall
- Most extant Orders of birds evolved in the past 65 million years, after the extinction of the dinosaurs
- The oldest extant orders of birds include the Pheasants/grouse, ducks/geese, and Ostriches and rheas
Diversity over time: evolutionary history Passeriforms
evolved relatively recently. Most closely related to parrots than to woodpeckers or owls
Diversity over time: evolutionary history
- Hummingbirds and swifts are closely related (tiny feet, narrow wings, very flexible shoulder joint)
- 450 sp. (2nd most diverse order)
- evolved recently
- We don't know the closest relatives of hoatzins or flamingos
Specialized and unique taxa
- Only 1 sp. of Hoatzin; SA birds that eats leaves and ferments them for digestion
- Nestlings have claws on writst for tree climbing
- In its own order (evolutionary history still debated)
Specialized and unique taxa
- 6 sp. of flamingo in world
- Unique beak for filter feeding upside-down to eat tiny brine shrimp
- Some DNA evidence suggests herons are closest relatives
- But recent genetic study found thatgrebes were more closely related
Diversity & Adaptive Radiation
- Passeriformes = ~ 5,000sp
- Adaptive radiation = rapid high rate of speciation
- Hummingbirds/swifts = ~450 sp.
Adaptive radiation: passerines (perching birds)
- Order Passeriformes contains half of the world's birds = 5,000 sp.
- Includes flycatchers, crows, vireos, thrushes, tanagers, warblers, sparrows, blackbirds, etc.
- Order evolved most recently and underwent a MASSIVE adaptive radiation (rapid and high rate of speciation)
Adaaptive radiation on Islands
- Diet and hawaiian Honeycreepers: Nectar, fruit, seed, insect, generalists
- Diet and Darwin's Finches: insects, seeds, cactus flowers
Adaptive radiation on continents:
Habitat and Parulidae (New World Warbler)
- Mature deciduous forest: black-throated blue, cerulean
- Forest Edge/successional: yellow and blue-winged
- Mature Coniferous Forest: ape May, Blackburnian
- Regenerating coniferous forest: Magnolia
Where is the diversification rate (sp. per MY) of passerines highest?
- Oceanic islands, tropical regions, NA, and southern SA
- Isolation, along with a wide variety of ecological niches, promotes a high speciation rate
Biodiversity over space: hotspots
- Hotspots: are locations where there is an unusually high diversity of a given taxon.
- These are sites that should be targeted for conservation and habitat protection
- But there is much debate on how best to measure and define hotspots.
- Save the greatest number of sp? Save the most at-risk sp.? Save the rarest and most unique sp.?
Measuring global bird "hotspots"
- Divide the planet into grid cells and define a 'hotspot' as the top 2.5% of cells in each category
- Overall sp. richness: total number of bird species recorded as breeding in each grid cell
- Risk of extinction: Number of breeding bird species in each grid cell that are listed as threatened with extinction
- Endemism: Number of endemic sp., defined as the species with the smallest geographical breeding ranges
Location of "hotspots" depends on defintion
- Sp. richness: in continental mountainous areas
- Most endemism and threatened: large islands and/or island archipelagos
- Rapid speciation on islands, combined with small ranges,means high endemism but also higher risk of extinction
Bird biodiversity and Conservation
- Few locations (2.5%) are hotspots according to all three definitions
- One 'hotspot' does not fit all - ie one region typically does not protect both a high number of sp. and the most rare/threatened sp.
- Which to choose given limited conservation resources --- saving more species overall or saving the most unique species
The latest word... target hotspots that have?
- Many threatened species who have small ranges (threat/endemism approach)
- Pimm et al. 2014
L6 What are some examples of shared adaptations within or between Orders of birds?
L6 Which orders contain the most species?
- Passeriformes 5,000 sp.
- Apodiformes ~450sp.
- Piciformes ~400sp.
L7 Most mortality occurs when during the ?
- 85% of annual mortality during migration
- The only year-round estimate
- Sillett and Holmes 2002
Tracking of small (less than 50g) birds now possible
Light loggers (geolocators) tellus the timing of sunrise and sunset at the bird's location
Case study 1: Migration tracking of Purple martin
Where are the critical stopover sites on migration?
- During fall mig. >3 week fall stopover in Yucatan
- Many range-wide research site in breeding grounds
- Fall mig. route varies with breeding longitude
- Along U.S. coast there is no single key stopover region
- But the Yucatan Peninsula appears to be used by most birds (a migratory bottleneck?). Long duration in Nicaragua and Yucatan.
Case study 2: Migration tracking, Wood thrush
- Extensive deforestation along US Gulf Coast - is there enough forest left for Wood Thrushes to refuel properly?
- 73% funnel Northward through a narrow span along the central US Gulf Coast
- Global population bottleneck
L7 Migratory bottleneck
- Is a location where a large % of a species stops on migration fro a prolonged period. These locations make the species highly vulnerable to disturbances at those sites
- i.e. Yellow Sea for Godwits, Yucatan & Nicaragua for Purple Martins
- These sites should be targeted conservation (hunting,habitat, pollution etc.)
Is any location where a migratory bird stops en route
Assessing stopover habitat quality
- Are parks in urban landscapes adequate stopover sites for migrants?
- Mist netting in urban and rural sites found higher numbers of migrants in urban site... but are these sites actually good for birds?
- How to choose which sites to conserve? Measure habitat quality and bird body condition
Seewagen et al. 2011 found what when comparing NY and rural?
- Capture rate: Urban woodlot > Rural
- Food supply fromearly, middle,late: both similar (arthropod dry mass)
- Refueling rate: Both similar for wide variety of sp. Measured triglyceride in blood. Inc. TRIG = inc. nutrient intake
- High trig means bird has high refueling rate
L7 Using examples, explain what a migratory bottleneck is and why they are important to consider in bird conservation
L7 What is a migratory stopover and how might they vary in quality? How could this be tested?
L8 Hager et al. (2013) found what?
- Mortality rate increases with window area of the building
- Mortality rate decreases as vegetation within 50m of building decreases
- By surveying 20+ buildings on Illinois campus every day, each afternoon, during migration
What ways that collisons occur?
- Reflection of suitable habitat
- Habitat seen on other side
- Habitat seen inside
Estimating total mortality
Hager et al. 2013
- Variability in searching ability between observed. Not all birds are seen (obscured or hidden)
- Predators may also remove carcasses before people arrive
- Estimated that for every bird found there were actually 2-5 more that were killed
How many birds killed in Canada each year from window collisions?
Machtans et al (2013)
- Houses: ~2/year (10.1 houses) = 22.4M
- Mid-rise: ~5/year = 2.4M
- High-rise: ~10/year = 64,000
- Used published studies to estimate observed kill rate at different building types
- Scaled up kill rate to account for birds not found
- Mortality rates also depend on window area and local vegetation
Death rate for birdfeeder houses and urban and rural places
Machtans et al 2013
- Highest:Rural with feeders
- 3. Rural no feeders
- 2. Urban with feeders
- Lowest: Urban no feeders
- Birds need safe motels during journey
- We can provide shelter, cover, fruiting trees,and a natural source of seeds in our own yards (far from windows)
- City parks/woodlots are important stopover sites
- bird feeders shouldbe very close to windows (<1m) or far away (>15m) to reduce collisions
How many migrating birds are killed by wind turbines?
Zimmerling et al. 2013
- 24,000 birds are killed annually with a 10-fold increase in number of turbines over the next decade, total numbers killed will climb to ~250,000/yr
- Across all sites, avg. 8 killed/yr at single turbine
- Search efficientcy ranges widely from 0.3 to 0.85, due to differences in vegetation below turbines and experience/skill of searcher
- Predator removal prob. also varies widely (0.1 to 0.9) due to local habitat and predator type/number
- Used site-specific search/predator data to estimate number birds killed per turbine
- Multiple by # of turbines per province
- Some have killed many breeding hawks and migrating bats
- Ideal sites are often on key migration routes (steady strong winds)
- Many ENGOs oppose turbine development based partly on the threat they pose to wildlife
Purple martins are included as one of the top 10 birds killed by wind turbines
estimated annual collision mortality 0.089%
- Gas flare: Flying into gas flare. In Saint John, gas plant killed 7,500 songbirds
- Industrial tailings: 1,600 migratory waterfowl deaths
- Solar panels: Have heard stories of cooking birds alive when landed on them
L8 In what way(s) are human structures a threat to birds on migration? Discuss using evidence and case studies
Which poses a greater threat to migratory songbirds, mortality from window collisions? or from wind turbines?
Discuss using evidence and case studies
In a recent study, how might migratory refueling in the tropics contribute to long-distance migration?
By providing them with enough energy to fly a good proportion (36.8% 2010; 44.0% 2011 for max flight range)of their migration.
Wintering ground threats
- Tropical deforestation and songbirds
- oil and shipping threat to Arctic Seabirds
Tropical deforestation: Costa Rica
(Also in Brazil, increasing northward)
- Most CA have cut down over 50% of their rainforest since the 1960s
- Massive deforestation coincides with strong pop. declines of mig. forest birds on breeding grounds
Migratory songbirds and habitat loss
- Insectivores typically defend territories (not as pairs)
- Ind. aggressively defend from conspecifics
- Birds that eat seed, fruit, and nectar typically live insingle or mixed species flocks - but still lose their home (and food sources) after large scale deforestation
Most in-depth studies of winter territory competition in a mig. songbird have been done with American Redstart
- Older males claim the best habitat - coastal mangrove forest - and aggressively exclude young males and females who end up in dry scrub forest
- Living in mangrove means more insect food, better body condition, and earlier departure on spring migration
Marra & Holmes 2001
- Higher bird density in mangrove than scrub
- Higher percentage of male in mangrove (61%) than scrub (24%)
- Return rate after migration in mangrove (65%) and scrub (40%)
Removal experiments in Jamaica
Marra et al. 1993
When removed older males from mangrove habitat, became filled in with birds from scrub habitat (more females in area after removal)
Predictions, reasoning, andmethods
Studs & Marra 2005
- If mangrove habitat is higher quality, predict that birds that move from scrub into mangrove will
- 1. enjoy improved body condition
- 2. will depart earlier on migration
- Study site had mangrove beside scrub; they removed older males from mangrove to allow scrub birds to "upgrade" to a supposedly better territory (where they should do better)
- Scrub birds that remained on their territories were the control (who should be worse off than the upgrade birds)
Results from upgrade experiment
- Decreased in condition of control, and slight increase of upgrade
- Upgraded birds did left earlier than control birds
Carry-over effects to breeding ground
- Carbon isotopes in the food chain differ between C3 plants (moist forest) and C4 plants (dry scrub)
- Birds that live in mangrove have more depleted δ13c values than scrub birds (the upgrade experiment showed this)
- δ13C can be used as a habitat signature tool, even for birds arriving at the breeding grounds
- Allowed researchers to determine former winter territory quality of breeding birds
δ13C and Carry-over effects
and its implications (not results)
- seasonal Carry-over effect: winter territory quality affects birds even after they begin migration
- Poor body condition in winter is hypothesized to reduce the bird's reproductive success
- If low quality tropical habitat lowers breeding productivity, in addition to winter survival, they could drive strong pop. declines.
Winter habitat and timing of breeding
Norris et al. 2004
- Females from scrub have later nests
- Males from scrub are late arriving
- Males want to be early to set up territories
Winter habitat and reproductive success
- Scrub males suffered a 11% drop in breeding success
- Scrub females suffered a 26% drop in reproduction
Poor quality winter habitat likely causes population declines on breeding grounds because:
- It prevents many young birds and females from getting territories
- Non-territorial birds have higher mortality rate than territory owners (Wood Thrush radio tracked. 6% mortality for territory owners, 26% for wanderers)
- Dry habitat leads to poor body weight and late departure on spring migration (removal and upgrade AMRE)
- Poor habitat imposes negative carry-over effects: later arrival for males and much lower breeding success for females
Bird biodiversity and shade coffee
Agro-ecosystems can be highly diverse environments (birds, bats, insects, etc.)
- Heavy shade coffee (~33) has high bird biodiversity than sun coffee (~3) in comparison to rainforest with ~38 bird sp.
- Coffee is one of the biggest and most valuable export crops in Latin America
- Globally, some 10 million ha of land (over 50 countries) is devoted to coffee growing
- In many places, coffee is grown on small farms under the canopy of native trees
Birds are good for coffee too
Karp et al 2013
- Coffee borer is a tiny beetle that kills the coffee bean and reduces yield.
- Recent study pot netting over coffee plants to test if birds are important predators of the borer.
- After the netting was installed,coffee plants without birds had twice the number of borers
Coffee and conservation
- Huge potential to save birds - if we can protect these family farms and pay farmers for their high quality product
- Farmers get a much higher price for selling bird friendly coffee
- In Canada, 60% of adults drink coffee. 30 million cups of coffees per day
How is competition for territories in tropical forests linked to migratory songbird declines on the breeding grounds?
Migratory seabirds and ocean threat
- Arctic seabirds migrate south in the winter too
- Tracked Little Auks from breeding colonies to determine core wintering areas
- Lives at sea for months at a time during non-breedin season
- Live on the surface in large groups (concentrate in relatively small core region)
- Makes entire colony vulnerable to threat in that wintering hotspot
What explains the hotspot off the E. Newfoundland for Little Auks?
Cool air temperature, and high concentration of copepods (Calanus)
Winter hotspots for two colonies off the east coast of Newfoundland coincide with
- Major oil and gas site (and potential areas of development) and major shipping lanes
- Future threats with expected new shipping lanes through the arctic as a result of climate change
Explain why Little Auk colonies in the arctic are threatened by events on their wintering grounds
Early 1900s - Cowbirds invaded the eastern US (due to changing forest landscape) and began to impact naive forest birds
Cowbird impacts on naive forest birds
- Cowbirds now parasitize dozens of species of forest birds that have no evolved defenses
- Cowbird find host nests in forest, but feed in adjacent agricultural fields
- In small forest fragments it is common for >50% of songbird nests to contain cowbird eggs
- Many nests contain 2-3 cowbird eggs and only 1-2 host eggs
Evidence that cowbirds are linked to songbird pop. declines
- 1. Nest-level: parasitized nests have far lower reproductive succes than non-parasitized nests
- 2. Population-level (correlation): when cowbird populations decline, reproductive success of host populations increases
- 3. Population-level (experiment): when cowbirds are removed, host population reproductive success and population size increases
For all 3 species, cowbird, cowbird parasitism causes a drop of what in bunting, flycatcher, and cardinal
Cox et al. 2012
50% in reproductive success
Population level - correlation
effects on songbird productivity methods and predictions.
- Cowbirds have declinded in N. Missouri since the 1970s because forest cover has increased
- Predicted that parasitism rate should decline, andsongbird nest success should increase
- Southern Missouri is a 'control' - forest cover is high and cowbird abundance is low. Predict little change over time in songbird productivity
- Studied nests of 3 spcies (Indigo Bunting, Northern Cardinal, Acadian Flycatcher)
Cowbird effects on songbird productivity results
- In N. Missouri, cowbird parasitism rate (% nests with cowbird eggs) decreased by 50%
- Number of cowbird eggs per nest (intensity) also decreased sharply over time
- Heavily forested S. Missouri: No significant increase in productivity over time (note these populations have double the productivity compared with N. missouri)
- In N. Missouri where forest cover is low (23% cover) and cowbirds have decreased, the # fledglings per nest increased by 30%
Cowbird removal experiment
Griffith and Griffith 2000
- % vireo nests parasitized decreased with increased female cowbirds killed per year
- Least Bell's vireo population increased with removal of cowbirds
- (vireo from west coast in california and mexico)
Fragmentation and nest predator
- Nest predator are also more abundant in fragmented landscapes
- Agricultural matrix provides artificical source of food, and increases population sizes of mice, chipmunks, raccoons, skunks, crows, blue jays, etc.
- In small forest fragments it is common for over 60% of nests to be eaten by predators
Edge effect and nest predation
Cox et al. 2012
- Edge nests have about 60% nest predation while "only" 40% of forest interior nests are eaten by predators
- Small fragments have a higher proportion of edge habitat than large fragments
- Overall predation rate decreases strongly as distance of the nest to the edge of the forest increases
- Edge nests had more predation by snake and raptors
Source and sink
- Source: average female produces more young than necessary to replace herself when she dies
- Sink: average female produces fewer young than necessary to replace herself when she dies
Are small forest fragments sinks?
Because expect more parasitism and nest predation
- Measured productivity and fledgling survival
- Found dozens of nests, monitor each nest every 3-4 days to determine how many are preyed upon, parasitized, then radio-track the fledglings to see how may survive the 3-weeks after fledgling
- Number of eggs laid per female -> number of young fledged per female -> number of fledgling per female surviving the next 3 weeks -> Number of juveniles surviving migration to breed the next year (estimated survival to next year based on other studies)
- Hooded warbler: 0.31< 0.50 (female morality)
- Rose breasted Grosbeak: 0.24 < 0.50
Cat predation and adult bird mortality
- Domestic cats are non-native predator on birds and other small animals
- U.S. ~84 million pet cats; 30-80 feral cats
- Monitored impact by using kitty cam, and reported prey captures by owners
- Kill rate was 12 birds/hunting cat/year
- 50-80% of pet cats hunt wild animals (according to owners)
- feral cats 80-100% hunt wild animals
- Kill rate of birds varies greatly mong studies due to different prey base and methods
- 1-34 birds killed/pet cat/year
- 24-51 birds killed/un-owned cat/year
- Ran the model thousands of times by randomly selecting different values for all the variables,within the obsered range
- Most models predict 2-3 billion birds killed by cats each year in US!
Cat kill far more birds than ANY other human caused bird mortality
- Cats: 200-300 million birds/year
- Window Collisions: 25 million birds/year
- Wind turbines: 24,000 birds/year
Forest fragmentation does what?
What does Cat kills amount to?
- Decrease nesting productivity of song birds due to higher number of cowbirds and nest predators
- Forest fragments are usually population sinks, where breeding productivity is too low to replace adult mortality. Leads to population declines.
- Cats kills billions (2-3) of birds in NA each year, and are 10x more lethal than even window collisions.
What is the evidence that cowbirds are an important cause of population declines of songbirds?
- Nest level
- Population level correlation (Missouri) and experimental (removal)
How did researchers estimate the number of adult birds killed by cats?