onithology exam I

Brown Kreeper- song bird, phylogenicly distinct

·      Build little hammocks out of bark and spider webs

·      “300 billion birds that inhabit the planet fall into 30 orders, 193 families and are represented by ~10,000 species. Birds occupy…”

·      ~2 billion birds killed by feral cats annually

·      Ivory bill woodpecker and North Carolina Parakeet extinct in the US

·      Disadvantages in small populations

·      Inbreeding depression

·      Lower genetic variation

·      Finding a mate

·      Genetic drift- overcomes natural selection

Ecological function:

·      Mass consumer of resources (food web context)

o   Many shore birds harvest horseshoe crab eggs

o   Stopover sites- high quality resource sites that various groups of birds use when migrating

·      Nutrient deposition and transport

o   Waste is dispersed as they travel, high in nitrogen (a limiting nutrient)

o   May result in eutrophication

o   Feces/urine excreted at the same time

·      Pollination

o   Plants produce nectar, form mutualistic relationship with birds

·      Seed dispersal

Diffuse Coevolution of seed dispersal systems

·      Reciprocal evolutionary change among interacting species. Given that dispersal agent composition changes in space and time, most animal-dispersed plants w/ large ranges can expect different spp. to drive their dispersal systems.

·      Diffuse coevolution-

·      Seed dispersal distance importance

o   Intense competition and particularly, high seed predation and seedling death due to pathogens, makes dispersal important

o   Animal dispersed have longer seed shadow tails

Community organization and structure

·      Energy flow is a central organizing theme in community ecology, the amount of energy captured by a species determines its abundance

·      Amount of energy available is determined by its biotic and abiotic factors. Additionally, it strongly depends on its trophic position, which h is its location with regard to energy flow

·      Rule of 10

Trophic Position Affects Abundance

·      Given a trophic position, top predators are destined to be rare and species poor because at each higher trophic level, there is ~80-90% energy loss from respiration and maintenance

·      Low abundance makes these populations highly vulnerable to local extinctions via allele effects, demographic, genetic or environmental stochasticity, or inbreeding, thus top predator populations often change considerably in space and time

Ecological Function – community structure

·      Removed kangaroo rats

·      Increased population in five other species of mice

·      Resulted in marked changes in vegetation (i.e. increased grassiness, decrease in annual Forbes)

Birds as Keystone Species (BKS)

·      Keystone species- importance > abundance

·      How do we classify communities?

o   Species that make it up

o   Functional diversity

o   Phylogenic diversity

o   Interaction diversity

Examples) the Red-naped Sap Suckers whose sap from cambium wells is stolen from >40 species

BKS- Primary Cavity Nesters

·      Woodpeckers are primary cavity nesters

·      They are then used by secondary cavity nesters — they affect many other species

·      Secondary cavity nesters:

·      Black-capped chickadee

·      Tufted Timice

·      various Nuthatches (i.e. White-breasted Nuthatch)

·      Great-crested Flycatchers

o   member of songbird lineage

·      Prothonotary Warblers

BKS- Species & Snags

·      most woodpeckers use standing dead trees or snags

·      snags are a significant predictor of local avian species diversity

·      total bird abundance, abundance of resident species, species richness, etc. reduced by the removal of downed woody debris and snags

Ecological Function—Insectivores

·      Yellow-bellied Sapsuckers drill holes for sap, other species use the sap holes afterwards as a resource

·      Brown Creeper

·      Purple Martin

·      Ecosystem Functions (Summary):

o   Seed dispersal

o   Pollination

o   Nutrient deposition

o   Grazing

o   Insectivory

o   Top-down regulation

o   Scavenger

o   Ecosystem engineers

Community Diversity — Why Do We Care?

Biodiversity is important because:

1.     Contributes to ecosystem function, high-diversity communities tend to lose resources more slowly, may be more resistant to invasion by non-residents

2.     “Diversity begets diversity”- due to coevolution, an increase in spp. richness at low trophic levels tends to promote diversity at higher levels

3.     “Diversity begets stability”- high diversity communities tend to stabilize oscillations in community composition across trophic levels as well as productivity

4.     Not all species are driving productivity or having large impacts on other species, but they may become important in the future — “drivers” and “passengers”

·      “Today’s passengers may become tomorrow’s drivers”

5. Ecological Guilds

·      Ecologically similar species may be lumped into guilds when appropriate

·      The ecological function of all members is assumed to be ~ equal (biodiversity Qs)

Who Else Benefits from High Plant Diversity?

·      Migratory birds

·      Many migratory birds are predominantly insectivores

·      High plant diversity attracts insects

·      Examples) Indigo Bunting, Baltimore Oriole, Black/White Warbler, Rose-breasted Grosbeak

Bird Characteristics

Unique features among extant vertebrates:

1.     Feathers: modified reptilian scales or protein beta-keratin which function in thermoregulation and flight

·      Used in displays (e.g. attraction, aggression)

·      Feathered dinosaurs used feathers for thermoregulation

2.     Bills: always toothless and covered with a horny sheath

·      A toothed beak would increase their weight, makes flight more difficult

3.     Digestive tract: GI system modified since they don’t chew, includes gizzard

Gizzard- grinds masticated food

·      Lowest pH of a bird’s digestive tract is 0.2 to 1.2

4.     Lightweight bones: inside is strutted and mostly hollow, makes them lighter, benefits flight

·      Filled with air

5.     Keeled sternum with circular (wishbone): all flying birds have a keeled sternum which anchors numerous flight muscles

Furcular- two fused clavicles (or collarbones)

·      Furcular provides strength without bulk

6.     Hands and wrists: bone fusion has greatly simplified the hands (4 phalanges vs. 14 in humans)

·      Wrist is also greatly fused (fusion ~ strength)

7.     Respiratory system: to meet high oxygen demands of an active organism with high body temp, birds have a unique system for respiration

Other defining characteristics:

1.     Legs and tarsometatarsus bones ~ equal length

·      Walk on their toes

·      Not all birds exhibit this

2.     Eggs: most reptiles lay eggs, 5 mammals spp. lay eggs, but all birds hatch young from an externally laid egg

Eggs and Life History Strategies (LHSs):

·      17-fold difference in clutch size exists among birds

·      Maturation may take one year to more than 10 years