Ornithology Exam #1

Exam #1:

27 January 2025

INTRODUCTION

• Why Study Birds

  • Scientific Inquiry

    • There are 10,700 species of birds

    • Very diverse forms (huge ostrich to tiny hummingbird) 

    • Very diverse ecosystems (penguins swim underwater in cold, desert birds)

    • Fascinating behaviors (brood parasitism, migrations, breeding habits)

  • Economic Importance

    • Food (chickens, eggs/meat)

    • Hawk mountain

  • Models for research 

    • Physiology - krebs cycle discovered studying pigeons

    • Easily observed and counted

  • Conservation

    • Used to be billions, now none of great awk

  • Health

    • Highly pathogenic avian influenza = bird flu

      • Snow geeses, canada geese

• Lecture

  • Bird biology

    • Characters, evolutionary history, foraging

    • Flight, life history and reproduction, conservation

  • Evaluation

    • 3 exams

    • 3 assignments

      • Research article summary

      • Research paper

      • eBird training

• Reading Assignment

  • pp 1-7, 11-18 of textbook

Lecture #1

• What is a bird?

  • Feathers, Beak (no teeth), Claws, hollow bones, Keeled sternum, Wings, fly, 4 chambered heart, double circulation, Gizzard (Processes their food), Air sacs (in addition to lungs)

  • Flight

  • Feathers

    • Unique to (living) birds

    • Flight (gives them a stiff surface to allow them to fly)

    • Insulation

    • Mate attraction (males usually more colorful)

  • Bill or Beak

    • Turtles and platypus’ also have

    • Rhamphotheca - keratin based covering over bone

      • Stringing out food, stabbing fish, cracking seeds, tearing flesh

    • Why do they lack teeth?

      • They are heavy (gizzard is prolly heavier than teeth, turtles dont need to save weight and also dont have teeth)

      • Beak is proficient and adaptable for capturing prey

      • Teeth take too long to develop

        • chicks need to develop really fast in nest to avoid predators 

  • Fused or Reduced Bones

    • Benefit

      • Increases strength, reduces the mass

    • “Hand” bones

      • Only 3 digits

      • Carpometacarpus = fused metacarpals (palm)

      • Hand supports primary feathers of the wing

    • Reduced fibula (tiny wishbone when eating drumstick)

    • Digitigrade - walk on their toes

    • “Foot” bones

      • Only 4 digits

      • Tarsometatarsus = fused metatarsals 

      • All you see on bird is foot and toes

    • Synsacrum (pelvic bone)

      • Fusion of pelvic bones and vertebrae

      • Strong pelvis for bipedal stance and flight

    • Pygostyle

      • Fusion of caudal vertebrae

      • Support tail feathers and muscles operating it (short tails)

    • Pectoral Girdle

      • Keeled sternum

        • Very deep (deep/low projection, helps boats stay upright)

      • Furcula

        • Two clavicle fused together (our collarbone)

        • Wishbone

      • Flight muscle attachment

      • ⅓ of body weight

27 January 2025

OUTLINE

• Bird Characters and Importance

  • Skeletal

  • Perching foot

  • Internal anatomy

  • Physiology

• Origin and Evolution of Birds

  • Darwin

  • Fossil Intermediate

  • Which Group of Reptiles

• Reading

  • pp. 4-7, 24-28

• Assignment

  • pick article for slide, email underwoo with pdf

  • Review notes with flashacrds

Lecture #2

• Features of Birds

  • Uncinate Processes*

    • Rearward projections on ribs

      • Strengthens thorax (keeps body rigid for flight, sleek line to be efficient when moving through the air)

  • Pneumatic Bones*

    • Hollow bones

      • Air sacs penetrate some

    • Internal struts called trabeculae (for support, m maintain strength)

      • Like internal anatomy of airplane structure

  • Perching Foot

    • 3 toes forward, 1 toe back

    • Rear opposable toe called hallux, digit #1 (grips like thumb, allows them to perch)

    • Tendons posterior to ankle

    • Body mass drops down to stretch tendons

    • Maintains grip

  • Digestive Modifications

    • Gizzard

      • Muscular stomach

      • Grinding (they lack teeth, this processes their food)

      • Largest in seed eaters

  • Reproduction Modifications

    • Oviparous - they lay eggs, never give birth to live young

      • Don't have to carry around heavy developing fetus

    • Only left gonad fully developed (more dramatic in females than males)

    • Gonads regress after breeding

      • All save mass for flight

    • Hickman et al. 2007

  • Heart

    • Four chambers

    • > 40% larger than mammals of equal mass

    • Pumps oxygen and nutrients (glucose) efficiently

      • Maintains their high metabolism and activity levels

  • Body Temp and Metabolism

    • Endothermic - can regulate their body temperature through the production of metabolic heat (produce their own heat, don't need it from the sun)

    • Higher body temp for higher activity

      • Birds run much hotter than mammals, higher body temp >40*C (ours is ~36*C) 

      • Increases their metabolism (when you add heat to a reaction it goes quicker), proteins break down at higher temps

    • Figure 6.1, p 142

  • Respiratory System (highly efficient)

    • Air sacs - most species have 9

      • Expand volume of system

      • Allow 1-way air flow through lung (unidirectional air flow)

        • Maximizes contact with fresh air in lungs

        • Replace almost all air in lung with each breath

        • Hickman t al 2015

        • Fig. 6.2, p 143

    • Lungs = faveolar

      • Bronchi branch into fine network of air spaces called air capillaries

      • Air capillaries surrounded by blood capillaries

        • Cross current flow for gas exchange

          • Blood flows in opposite direction to air in lungs

          • Fish have this too

      • Fig 6-4, p 144

    • Respiratory cycle

      • 2 cycles of inspiration/expiration to move air through

        • Gas exchange happening on both inspiration and expiration

      • Most efficient of all terrestrial vertebrates

• Why fly at high altitudes?

  • Bar headed goose has to fly over the himalayas at 30,000 feet (not enough oxygen for a human to survive up there), but they good

  • American birds fly at 5,000-10,000 feet

• Origin and evolution of birds

  • 1859 - darwins/s publication “On the Origin of Species”, highly controversial, lots of debate, critics really focused on birds and how they look nothing like other verebrates

    • Fossilized feather in germany 1 year later

  • 1861 - Archaeopteryx lithographica (archaeo = ancient, pteryx = wing, type of slate they were extracting from that quarry), to date 12 species found, originated 150 billion years ago

    • Archaeopteryx traits

      • Bird Traits

        • Beak

        • Feathers (asymmetrical primaries, main feathers on hand of bird, like birds capable of flight)

        • 3 digits on their hand

        • Furcula

        • Digitigrade (walk on their toes) and bipedal

        • 3 toes forwards, one back

        • Some fused foot bones

      • Reptile Traits

        • Teeth 

        • Lack a keeled sternum

        • Lack synsacrum

        • No uncinate processes

        • Long tail

        • Claws on the wing

        • No fused bones in the hand

      • Intermediate between birds and reptiles, what darwins skeptics were lacking

4 February 2025

OUTLINE

• Origin and Evolution of Birds

  • Which Group of Reptiles

  • Theropods vs Thecodonts

  • Evidence for each

• Evolution of Feathers

  • Hypotheses

  • Evidence

• Reading

  • pp. 24-45

• Assignment

  • Quiz at beginning of lab (all areas of lab)

  • summarize article for slide

  • identify ducks

  • review notes with flashcards

Lecture #3

• Archeopteryx Traits

  • Which group of reptiles did birds evolve from

    • Theropod dinosaurs (velociraptors) 

      • Small, bipedal, predators

      • ~180 million years ago

    • Thecodonts 

      • Very small (lizard sized), arboreal (lived in trees), quadrupeds

      • Elongated scales on back (gliding?)

      • ~230 million years ago

• Huxley - 1867

  • Believed birds evolved from theropod dinosaurs

  • Shared similar characteristics in pelvis and hind limb

  • 35 characters in common

  • Critics said due to convergent evolution (both bipedal)

    • unrelated species evolve the same structures because they do the same thing with it, common function (wings in birds, bats, butterflies, doesn't mean they are closely related)

• Heilman - 1926

  • Believed birds evolved from theropod dinosaurs, share many features

  • But thought therapods lacked a furcula therefore must have evolved from thecodonts

    • Shortly after this, theropods with a clear furcula were found

• Ostrom - 1970

  • Discovered deinonychus, a theropod

  • Found they share a lot of features with birds that no other reptile groups had

  • If Archaeopteryx wasn’t found with feathers, people would have thought it were a reptile

• Gauthier - 1980s to present

  • Used cladistics (systematic technique)

    • More objective and robust than traditional systematics

  • Confirmed theropod orogin

    • ~70 characteristics unite with birds

    • 9 important we will learn

• Bird Evolved From Theropod Dinosaurs

  • Shared traits as evidence

    • Hind foot

      • Loss of 5th toe

      • 1st digit reversed (one points to the back), hallux

    • Pubic bones

      • Pubic boot (pubis expands)

        • Eventually disappears in modern birds

      • Faces backwards

    • Furcula

    • Pneumatic bones

    • Air sacs

    • Feathers 

    • All major bird traits ^^^^^^^^^^^

    • Caudipteryx - covered in feathers (veined and DOWNY)

• Trait Also from Theropod

  • Semi-lunate carpal bones (our wrists)

    • Allows wing to flex properly and move to allow folding of the wing

    • Flexion and side to side movement

    • Wing folding 

    • Flight stroke

  • Hand bones

    • Loss of digits

      • 5 and 4

      • Only 3 digits like modern living birds

  • Fused bones 

    • Foot 

      • Tarsus

    • Hand

      • Carpometacarpus

    • Tail

  • Birds evolved from theropods!!!!!!!!!!!

• Thecodont Evidence

  • Feduccia - 1980s to 1990s

  • Birds and crocodilian ancestors share a few characters

  • Longisquama had feathers not scales

  • Argued flight evolved from arboreal ancestor

  • Issues

    • No definitive fossil link to thecodonts

    • 80 million year gap between thecodonts and birds

    • No hard evidence really to support 

• Conclusion: birds evolved from therapods

• Dinosaurs are not extinct, they evolved feathers and are birds

• Who do we consider a bird

  • Aves - modern, living birds (when teeth go)

  • Avialae - theropod dinosaurs, tings not fully evolved with all traits, not really adopted yet, but suggested by Gill and Prum 2019

• Evolution of Feathers

  • Functions

    • Flight

    • Insulation

    • Carry water (pretty unusual)

    • Waterproofing

    • Sensory 

    • Stability / Support (woodpeckers use it to prop themselves up)

    • Capture sound (owls)

    • Aid in prey capture

    • Mate attraction

  • Hypotheses

    • Epidermal scales

      • Both made of beta keratin 

      • Elongation, split, 

      • Evidence

        • Some lizards (in hot desert environments) have elongated scales

        • Feathers = B keratin

        • Feathers likely first evolved for thermoregulation (either for reflecting or conserving heat)

6 February 2025

ONLINE LECTURE

11 February 2025

OUTLINE

• Origin of Flight

  • Incline Running

  • Conclusions

• Vision

  • Resolution

  • Binocular vision

  • Eye structure

  • Color vision

• Reading

  • pp. 172-181

• Assignment

  • Quiz at beginning of lab (all areas of lab)

  • identify beaks / feet

  • review notes with flashcards

Lecture #4

• Newer Hypothesis (origin of flight)

  • Incline Running

    • Flapping protowings assisted climbing inclines

    • Flapping motion similar to flight stroke (early function of wings must be useful for something before fully developing)

    • Proto wings still functional

      • Experiment, trimmed 50% of wing feathers and they could still climb incline, if they could do that, they could climb trees and climb down (could lead to arboreal or cursorial flight)

    • Problem with idea

      • Therapods did not yet have some flapping ability (shoulder structure needed to flap wings like this)

  • Conclusion

    • Origin of flight not yet resolved

• Avian Senses

  • Vision

    • Live in a world of color

    • Can see a rabbit from a mile away

    • Largest eyes for their body size

    • Visual acuity / resolution (separate out fine details)

      • Ability to distinguish between two points from a distance

      • Some birds 2-3x better than humans

        • Especially raptors

    • Binocular vision

      • 3 dimensional with depth perception 

      • Requires 

        • Eyes must be able to focus on same object (have overlapping field of vision)

        • Examples

          • Evans and heiser 2004

            • Woodcocks have 360 field of mostly monocular vision, they have better vision behind them (to see predators approaching because they are always in the dirt

          • Pigeons bobble their head so they can look at the same object from many different dimensions

          • American bittern throw their head up when they get startled, their binocular vision is downward cuz they catch fish, so they do that to aim binocular vision at predator, they also do it to add to their camouflage (improves vertical camouflage)

    • Eye structures - external

      • Most transparent covering = nictitating membrane 

        • Moistens their eyes without losing their vision

        • Underwater mask, important for diving birds who are underwater

    • Eye anatomy - internal

      • Light passes through cornea and lens to retina

      • Retina contains photoreceptor cells (rods and cones)

      • Both cornea and lens change shape to focus image on retina (in mammals only the lens changes shape)

      • Sclerotic rung - ring of bones around their eyes to support all the internal eye muscles (lacking in mammals)

      • Pecten

        • Unique to birds

        • Highly vascularized (lots of blood vessels)

        • Supplies oxygen and nutrients to retina (retina lacks a direct blood supply)

      • Iris

        • Function - act like a diaphragm on microscope to adjust the opening of how much light comes in to adjust the size of the pupil

          • Pupil contracts in bright light and dilates in dim lights

        • Color function - mate attraction and species recognition

      • Retina cross section

        • Photoreceptors

          • Rods detect black and white

            • Found in nocturnal birds

          • Cones detect color 

            • Diurnal birds

              • Most diurnal birds have tremendous amounts of cones (up to 1 million/mm2), the more cones the better the resolution

          • Fovea - depression in retina with high densities of cones, high resolution, usually 1 per eye = central fovea, allows birds to detect really fast movements (flying through environment, capturing prey, need to be able to really pick up on these movements)

          • 2nd Fovea in diurnal raptors

            • Temporal fovea, gives them really good forward binocular vision

      • Pecten benefit

        • Allows for a high density of cones (not possible in mammals)

        • No need for blood vessels in retina that would interfere with vision 

      • Tapetim lucidum

        • Reflective layer at the back of eye

        • In low light conditions it bounces some of that light back through the eye to help capture more light (light back → retina), found in nocturnal birds (owls)

        • Eyes light up when you shine light on them

13 February 2025

OUTLINE

• Origin of Flight

Lecture #5

• MISSED - get notes from jake

• SIght

  • Humans - trichromatic vision

  • Birds - tetrachromatic vision

    • Birds are capable of seeing some of the UV light (another dimension that we camt)

    • Birds see 300-400nm (near UV)

  • Functions of UV vision

    • Orientation (perceive environment, navigate themselves)

    • Foraging (some berries reflect UV light differently than foliage around them, makes them stand out, voles pee reflects UV light, kestrel can pick up on where they are most active)

    • Mate selection

      • Mate selection in Zebra finch

      • Measured UV reflectance in males

      • Compared female choice between males with and without UV, used glass filters between males and females to prevent them from seeing

      • Results - strong evidence that females significantly preferred the males with UV cues

• Monomorphic Species

  • European starling (got here because people love shakespeare)

  • Monomorphic plumage = one plumage type, males and female look the same

    • Many of these birds are actually dimorphic when UV is measured

• Avian Hearing

  • Some birds have great ability (owls, under 2 feet of snow) but most birds hear worse than us

  • External ear

    • Just a hole in the head

    • Feathers cover ear = auriculars

      • Keep wind / bugs out of the ear

      • Lets sound through

    • Owls - have an operculum

      • Allows them to adjust the opening 

  • Middle and inner ear

    • Middle

      • Tympanic membrane

      • Columella (1 bone) - transmits the vibrations

        • Humans have 3 bones

    • Inner

      • Cochlea - large fluid filled chamber, lined with hair cells, hair cells convert vibrations to nerve impulses

      • Semicircular canals - balance and equilibrium (important for animals with high activity levels), fluid with calcium carbonate crystals, hair cells at base, stimulated by movement

        • On roller coasters you get wobbly after

  • Hearing ability

    • Frequency and sensitivity, vast majority of birds can't hear faint noises (except for strigiformes / owls who can hear better than us)

  • Directional hearing in horizontal plane

    • Sound hits right or left ear first, we turn head to hear where its coming from, birds do too

    • Birds also hear vertically too

    • In barn owls

      • Localize sound in vertical plane too

      • Ears and facial disk asymmetrical (one set is higher than the other)

        • Facial disk oriented to detect

          • Sounds above - right

          • Sounds below - left

  • Ear tufts in owls

    • Communication and camouflage, but not for hearing

• Echolocation

  • 2 families of cave nesting birds

    • Oilbirds and swiftlets

      • Feed on the nuts of oil palm trees, natives use them as a source of oil

    • 15-20 millisecond clicks (not ultrasound, not the same as bats)

    • 1-5khz, ~10% as effective as bat echolocation, allows them to move around in the dark, but not find tiny insects

• Mechanoreception

  • Herbst corpuscle - tactile / touch receptors, layers of cells that surround a nerve or sensory cell, detect physical pressure changes put on that cell

  • Numerous in certain areas (bills of ducks and shorebirds, probe around in mud and water to find food, base of sensory feathers)

14 February 2025

LAB Lecture - Feathers

• Quill = calamus

• Modifications to Shapes

  • Club-winged Manakin - creates sound with wings (vibrates wings really fast, twice as fast as hummingbirds), thick rachis allows them to vibrate

  • Birds-of-paradise - have biofluorescent feathers (reflects light back at a higher wavelength)

  • Narrow modification = makes sounds

• No such thig as sea gulls, shorebirds tho

• Shorebirds

  • Sandpipers

    • Scolopacidae

    • Stand on one leg

    • Long, thin beaks

    • More modeled with browns/reds, variations

    • Quite hard to differentiate

      • Between

        • Semipalmated sandpiper - semipalmated webbed feet (hard to see), look at leg color, yellow blackish greenish, go off shape and thickness of beak, stouter

        • Least sandpiper - little tony curve, more of a point, narrows to the point

      • Between

        • Lesser Yellowlegs - smaller, fairly proportionate beak, beak points up

        • Greater Yellowlegs - bigger, very long beak compared to the width of its head, more barring on side of body

      • Between

        • Wilson’s Snipe - vertical stripes on top of head, more streak colored breast

        • American Woodcock - horizontal bars of dark color on top of head, buffy colored more solid colored breast

  • Plovers

    • Charadriidae

    • More uniform color patterns

18 February 2025

OUTLINE

• Baroreceptor

• Smell and Taste

  • Structures and examples

• Bird Brains

  • Basic structure and variation

  • Spatial memory

  • Sleep

• Assignment

  • Page 183-203

Lecture #6

• Baroreception

  • Detect changes in atmospheric pressure

    • Paratympanic organ, middle ear

  • 10m difference in altitude

  • Important for

    • Detect approaching storms

    • Find right altitude for migratory flights

• Sense of Smell

  • Olfactory bulb - process scent in brain

  • Birds have poor sense of smell (great horned owls eat skunks)

  • Relative size of olfactory lobe - highest is 33% of cerebrum to 5% of cerebrum

    • Nocturnal predators have best sense of smell

  • Nasal cavities - olfactory receptors on mucosal membranes covering their nasal turbinal bones

• Smell and Foraging

  • Black vultures detect carrion (rotting flesh) releasing ethyl mercaptan

  • Kiwi are nocturnal bird preying on soil invertebrates, has a great sense of smell to find food, rely entirely on scent to find their food in the dark in the soil

    • ONLY BIRD to have nostrils at the tip of their bill

  • Mallard courtship, scent required for mating, odors from uropygial gland, secretes oil for conditioning feathers and waterproofing, some species also produce pheromones (like in mallard)

  • Crested auklets sniff each others necks, smell good like oranges, pheromones smell like organs, in courtship they sniff each other

• Taste

  • May not be well developed (don't have as many taste buds s mammals), taste buds located on rear of tongue and walls of oral cavity

  • Chilli peppers have capsaicins that repel (most) mammals, but have no effect on birds

    • Why do plants deter mammals with capsacians and not birds = birds are much better at dispersing seeds over a large distance

• Brain and Intelligence

  • Display insight learning aka problem solving (crows and parrots are great at this)

    • Crows in japan crack walnuts by dropping them on roads to have cars crack them open, and that when the light is red cars wont drive by

  • Social learning aka learning by observing others

    • Chickadees (or tits in europe) learned how to break into milk bottle and drink cream on top, then they all did ot

  • Tool use

    • Cactus finch from galapagos, uses cactus spine to probe into trees and get bugs to come out

• Avian Brain

  • Forebrain

    • Olfactory bulb - processes scent

    • Cerebrum - center for learning, sensory processing, and integration of information, problem solving

    • Pallial neurons - nerve cells for advanced learning (ONLY in birds and mammals)

  • Midbrain

    • Optic and auditory lobes - vision processing and hearing

    • Cerebellum - balance and equilibrium (works with semicircular canals of inner ears), high activity level = big cerebellum

  • Hindbrain

    • Medulla oblongata - controls autonomic functions (heart rate/breathing)

• Variants in bird brains

  • Modified to reflect something about their lifestyle / foraging abilities

    • Flamingoes gave relatively small cerebellum and optic lobe - filter feeders, dont fly much, pump water through their beak

20 February 2025

OUTLINE

• Brain and Intelligence

  • Structural variation

  • Spatial memory

  • Sleep

• Foraging behavior

  • Optimal foraging theory

  • Where to forage

  • How long to stay

• Reading

  • pp. 190-202

• Assignment

  • Quiz at beginning of lab (all areas of lab)

  • identify taxonomic

  • Finish lab packet

  • review notes with flashcards

  • Spinal feather tract

  • Apterya feather tracts

Lecture #7

• Variations in Brains

  • Shearwater has hygge olfactory bulb = very good at scent, use it to find plankton that they feed on and their nest burrows in the dark

  • Crow has largest cerebral hemisphere = great at problem solving, intelligence well developed

• Avian Brain vs Primate Brain

  • Birds have higher number of pallial neurons (indicator of intelligence)

  • Birds have smaller brain in mass, but more of their brain devoted to intelligence

  • Birds have more forebrain and pallial neurons than similar sized primates

• Spatial Memory

  • Seed catchers

    • Store food caches for winter (in trees or ground), can remember for up to 8 months later, 2000-3000 seed caches

    • Titmice, chickadees, nuthatches, corvids, jays in pa do this

    • More common in places that get cold over winter

  • Test

    • Remember where things are in relation to things in the environment

    • Use spatial reference to large objects

    • Move objects around, birds would search in that direction of the big rock they moved

    • Controlled by hippocampus of cerebrum

      • Hippocampus is very large in seed caching birds (larger than those who do not rely on memory to find food)

      • Shows neurogenesis (production of new neurons)

        • Add new brain cells

        • Chickadees hippocampus expands ~30% in fall, shrinks back in spring

        • Same thing for male birds who sing more versions of songs, grows in summer and shrinks outside breeding season

• Sleep in Birds

  • Short bouts (minutes, seconds)

  • Same basic patterns of sleep as humans

    • Rapid Eye Movement (REM)

      • Dreaming and restore brain function

    • Slow Wave Sleep (SWS)

      • Deep sleep

      • Restores body and brain function (physical and mental health)

  • Birds can sleep while flying!!

  • Unihemispheric short wave sleep

    • Sleep with one eye open

    • Half of brain is functioning at once

    • Predator vigilance hypothesis

      • Studied flocking birds (mallards), birds at edges of the flock use unihemispheric sleep more than birds at the center, strong support

      • At the edge of the flock 90% were looking away from the flock

• Foraging Behavior

  • When it gets colder birds are feeding much more intensely

  • Work outside in the winter make you more hungry than working inside

• Foraging Decisions

  • Where to forage

    • Patch of habitat to go to

  • How long to stay

  • What to eat

  • How to search

• Optimality Theory

  • Our profit from eating something, making a certain decision = (our energy gained - energy cost to obtain that) / foraging time

  • Costs and benefits to any behavior

  • Maximize benefits and minimize costs

  • Natural selection favors individuals (for reproduction) that “behave” optimally (make the smartest decision)

    • Bird with calculator counting calories\

• WHere to forage

  • Prediction - most profitable feeding areas

  • Evidence

    • Great tits in captivity, made 6 artificial patches of habitat that differed in prey density, looked at percent of time spent searching in each of those patches

      • Over time, the birds to forage in the most profitable areas, to start there isn't much difference but as they learn their surroundings, its obvious, but still visited low density patches

        • Prey abundance varies in time and space in the nature, not believing high density patches ALWAYS have food and low density NEEVER had food, making sure it didn't change

        • Do forage in most profitable areas, but keep their options open

• How long to stay

  • Capture rate declines over time because prey supply is depleted (eat them all) or prey take evasive action (try to hide)

    • Exponential like growth at start, then decreases

  • Leave when capture rate drops below average for other available patches

21 February 2025

LAB Lecture

• Field Trips

  • Look for movement, listen for sounds, scan for irregular shapes

  • Describe where birds are in reference to landmarks, clock to describe position

25 February 2025

• Outline

  • Foraging Behavior

    • How long to stay

    • What to eat

    • How to search

    • Learning

  • Foraging Niches

  • Bill Structure

    • Variation

    • Cranial kinesis

• Reading Assignment

  • 452-453, 538-540, 12-15

Lecture #9

• Diminishing Returns

  • Pied wagtails moved on when the capture rate really drops

• What to Eat (Prey Selection)

  • Prediction - max energy gain and minimum foraging time (optimal foraging)

    • Handling time - deal with prey, break into a seed, crack open the shell, subdue and swallow an animal

    • Most profitable is a fly 7mm long, black bars = flies available, white bars = flies captured

      • 8mm flies are most abundant, but ate the 7mm flies the most

  • Exception to the rule

    • Not always optimal

    • 8 finches and sparrows - seed preference

      • Did not eat optimal seeds

      • Chose those with less handling time

      • Trade off to mitigate predation risk

• How to Search for Prey

  • Much like we do, someone loses something, we ask what it looks like, blue color, try to pick out where it is in the environment

  • Set of prey characteristics that act as filter to remove unimportant stimuli and focus on the key item = search image 

    • Search image testing on blue jays

      • Prediction - if they're using a search image, then their foraging success will improve over time

        • With 1 species of moth, improve over time, supports prediction

        • 2 species moth photos mixed - no improvement, cant form a search image because prey keeps changing

• What influences foraging success

  • Weather

  • Stealth ability / camouflage of birds

  • Compietioton 

  • Bird size

  • Age / experience

  • Influence of time / age on learning

    • American oystercatcher

      • Specialize on worms or molluscs

        • Worm feeders - 7 weeks

          • Worms are easier to catch

        • Mollusc feeders - up to 1 year training

          • Sneak up on clam and jab beak in and snip muscles

• Foraging niches

  • Niche - sum total of an organism's resource use (abiotic and biotic factors) and general ecological requirements

    • Principle of competitive exclusion - if two species share the same ecological niche, one or both species will go extinct or one or both will develop a new niche

      • Boreal forest warblers suggested to be an exception to this principle (all seemed to forage in confierous tree)

        • They all forage in different PARTS of the tree, slight overlap but for the most part foraged in different parts of tree and had slightly different foraging styles

        • And nesting periods were slightly offset as well, peak food needs were not at the same time

        • Evolved niche segregation

• Feeding - Bill Structure

  • Natural selection doesnt just work to improve feeding, still has to be functional for other things as well

    • Other uses of bill other than capturing prey

      • Defense

      • Preen

      • Build nests

  •   White winged cross bills - use the cross to lever open pinecone seeds