-
Are feet homologous between birds and theropods?
No, three main tows in theropods are 1, 2, 3, while birds are 2, 3, 4
-
Evidence against Archaeopteryx flight
- Skeleton overall like small theropod
- No supracoracoideus
- lacked openings in bones for air sacs
-
Evidence for Archaeopteryx flight
- Presence of large furcula (other theropods, dromaisaurs, also have fused clavicles but much smaller)
- Asymmetrical feather vane
- Remiges arched as in flying birds
- Placement of longest feathers (wings and tail)
- enlarged cerebellum
- enlarged optic and auditory lobes (compared to theropods)
-
Evidence supporting cursorial origin of flight
general skeleton like small terrestrial theropods
-
Evidence against cursorial origin of flight
- No supracoracoideus
- gravity
- pelvic girdle not really cursorial
-
Evidence in favor of arboreal origin of flight
- Claw shape on forelimbs
- claw shape on toes
- reversed hind toe
-
Paleozoic Era
230 to 600 mya (oldest we have to know)
-
Mesozoic Era
- 65 to 230 mya
- Includes Triassic, Jurassic, and Cretaceous
-
-
-
-
Archaeopteryx dating
160 mya
-
-
Enantiornithines
- Reptilian characteristics: skull, teeth, pelvic girdle
- Avian characteristics: Ribcage/sternum, forelimb, prominent pygostyle
- No uncinated process
-
Differences between enantiornithines and modern birds
- Direction of fusion of metatarsal bones
- Scapula contains socket
- supracoracoideus along scapula
- ectothermic growth rings
-
Ornithurnes
waterbirds, eventually went extinct
-
Skeletal adaptation for flight in birds
- Bone structure
- no teeth
- no bony external tail (in modern birds)
- fortified body cavity
- fusion of bones for strength
- keel on sturnum
-
Nervous system adaptations for flight in birds
- Large cerebellum
- enlarged optic lobes
-
Sensory adaptations for flight in birds
- large size
- forward orientation
- receptor cell density (retine 1.5-2x thicker than in other vertebrates)
- no external ears
- reduced olfactory apparatus
-
Muscle adaptations for flight in birds
- no heavy jaw or face muscles
- no heavy back muscles
- huge pectoralis (10-40% of weight)
- Supracoracoideus
- High concentration of red muscle fibers
-
Respiratory system adaptations for flight in birds
- air-sac system (typically 9 air sacs, 6-12)
- 1 way flow in lungs
-
Digestive system
- Rapid digestion
- Crop, proventriculus, gizzard
-
Reproductive adaptations for flight in birds
- seasonal regression
- no live births
- single ovary (except hawks)
-
Problems with biological species concept
- classifying allopatric populations
- non-monophyletic species
-
phylogenetic species concept
- modern version of morphological species concept
- minimum diagnosable units (super subjective)
- avoids non-monophyletic species
- solves problem on classifying allopatric population
-
Disadvantages of phylogenetic species concept
- species limit at mercy of N
- arbitrary definition of diagnosable
- depends on resolution of data
- unequal rates of character evolution
- human perception of "species"
-
Pre-mating reproductive isolating mechanisms
- behavioral
- temporal
- mechanical (not known in birds)
-
Oceanic vs continental islands
an oceanic island arises independently, continental islands were at one point attached to a larger land mass (ex. Britain, Trinidad, etc)
-
Limiting factors to colonization
- psychological barriers (crossing water)
- physical barriers
- depauperate flora
- depauperate fauna
- physiology of long distance migrants (zugunruhe)
- successful reproduction
- small population
-
Empirical trends in oceanic island birds
- density compensation (high densities, but only a couple of species) due to ecological release
- greater sexual dimorphism (ER)
- Longer bills (ER, big bills better because can take larger prey)
- more generalized habitat
- flightlessness
- loss of anti-predator behaviors
- differentiation (new selective pressures, genetic drift, founder effect)
- (adaptive radiation)
-
Breakdown of mating systems (%)
- Monogamy- 90%
- Polygamy- 3% (including polygyandry)
- Promiscuity- 6% (leks)
-
Polygyny Threshold
- territory on x axis, benefit on y
- point at which it is advantageous for females to mate with an already mated male rather than an unmated male with a very poor territory
- steeper curves for polygynous (increased differences between territories)
-
Secondary cavity nesting
- cannot make own cavity
- cavities have lower predation rates
-
Classical polyandry
- Simultaneous- lay eggs into multiple nests more or less at the same time
- Sequential- most effort is focused on one male; temporal difference between nests
-
Cooperative polyandry
- within the female's territory, there are multiple, often related males.
- Only one nest
- typically at least two males copulating, alpha and beta males
- harris hawk, galapagos hawk
-
Dispersion pattern
- often due to food availability
- the patchier food is, the more likely it is to be leking species
-
Type A territory
- "All purpose"
- usually nearly the same size as home range
- occupied by a single pair, a harem, or communal group (polygynandrous)
-
Type B territory
- "Bum sitting"
- matings and nest area only
- MODO
-
Type C territory
Colonial (rookeries)
-
Determinants of territory type
- Defensibility of food supply
- availability of nest sites
- If something is defended, a limited resource is involved.
-
Type D territory
- Display
- mating only, females have type B territories
-
Mixed-species flocks
- component species solitary or pairs
- nuclear species determine foraging route and emit rallying call
-
proximate vs ultimate causes
ultimate causes have to do with genetic advantage, proximate causes are usually "how" (physiology)
-
Advantages to being gregarious
- Predator avoidance (many-eyes hypothesis, confusion factor/dilution)
- Food finding efficiency
- Theoretically, predator component should be more important
-
Burskirk model
- Food searching behavior determines --> predator vulnerability, which in determines --> feeding sociality
- highly vulnerable = gregarious
-
Cost of flocking
- Competition
- Predator attractionn
- Foraging rhythm
-
Ultimate controls of timing of breeding
Food
-
Proximate controls of timing of breeding
- Endogenous rhythm
- Annual zeitgeber
- Modifying factors (direct food availability)
-
Zeitgeber
Photoperiod --> hypothalamus --> anterios pituitary --> LH, FSH, Prolactin
-
Endogenous rhythm
- biological processes which vary seasonally
- drifts in absence of stimuli; WTSP did not reach reproductive status
-
Early human impact on birds/ecosystems
- hunting
- introduction of mammals (and reptiles) on oceanic islands
- deforestation
- agriculture
-
Human impact on birds last 200 years
- 72 species extinct (at least)
- oceanic islands- 63
- continents- 9
-
Causes of extinction
- Introduced mammals- 2
- Introduced disease- 20
- Introduced snake- 2
- Human exploitation- 10
- Habitat destruction- 10
-
North American extinctions
- Labrador Duck (1875)
- Great Auk (1884)
- Passenger Pigeon (1899)
- Carolina Parakeet (1938)
- Ivory-billed Woodpecker (1941)
- Eskimo Curlew (1963)Bachman's Warbler (1965)
- California Condor
-
Burkirk's findings- Solitary birds
- Terrestrial foragers
- Hummingbirds
- Sentinel foragers
-
Burkirk's findings- Single-species Flocks
canopy frugivores
-
Burkirk's findings- Mixed-species flocks
- Omnivores in canopy
- Canopy insectivores
-
Type A territory food/nest
both even
-
Type B territory food/nest
- Food far from nest
- Nest scattered- not clumped
-
Type C territory food/nest
- Food far from nest
- Nest limited and clumped
-
Type D territory food/nest
- Food far from territory, patchy
- Nest [even]
|
|