111 Birds after midterm 1

Feeding

Key activity to fuel metabolism

• High metabolic needs

Foraging itself is costly

maximize foraging efficiency (energy vs time)

Foraging itself is costly

Higher metabolic rate

Exposure to predation

Exposure to competition

Exposure to extreme environmental conditions

Foraging efficiency is determined by

Natural selection

morphology:

• Body size

• Wing size and shape

• Bill

• Feet

• Gut morphology

Behavior

Key feature of birds: lack of teeth; bills

grinding function replaced by internal gut morphology

• some re-evolution of other tooth functions: grasping, killing

Structure of the avian bill

Cere (only some birds)

Rhamphotheca

Cere

fleshy cuticle surrounding the base of the bill or nares, present in some birds

Rhampotheca

vascularized keratinous covering

Bill movement

Cranial Kinesis

Prokinesis

Rhynchokinesis

Cranial Kinesis

The ability to move part of the skull relative to the braincase

Prokinesis

The whole upper bill rotates around a hinge (nasofrontal hinge)

• Increased control of gape

• Shock absorbance

• Greater speed of opening and closing bills

Rhynchokinesis

allows movement of the tip of the upper mandible

• Less substrate displacement when probing

Bills are living, sensitive structures

Herbst corpuscles

Herbst corpuscles

• Mechanoreceptors in “sensory pits” in the bills of probing birds for tactile sensing while foraging

• Allows for remote touch of prey via pressure differentials and vibrations

Bill types and functions

• Raptorial: killing (tomial tooth), cutting, tearing

• Parrot bills: also cutting…but mostly fruit

• “Spear-like”: stabby, and in combination with

S-shaped neck

Bill types and functions Nectar

• Nectavores – strategy 1:

• Long bills (tubular; terete) for accessing nectar deep in flowers

• Often co-evolved, mutualistic pollination

• Nectavores – strategy 2:

• Peck and steal

Bill types and functions

Filter feeders: sift seeds and animal matter from water and sediment

• Lamellae: fine teeth- or comb-like structures along the edge of the bill

• Generally use the tongue as a pump to move water into and out of the bill

“Probing” shorebird bills

Usually fairly rounded, long-ish, and thin

• sometimes males and females of the same species having slightly different bill lengths so pairs don’t compete

Seed-eaters

short, conical bills good for crushing

Leaf-gleaners

small, delicate, precise bills

Aerial insectivores

Wide bills with wide gape, often with rictal bristles

Woodpeckers!

• Laterally-compressed, chisel-like bill

• Unique tongue wraps around skull and inserts in the right nostril; helps cushion hammering and capture prey

Lingual papillae - Avian tounge

• projections on the tongue that assist with capturing, gripping, and manipulating food items

• Structure similar to teeth and can be used to capture, hold and direct food.

Digestion

Digestion is faster in birds

• High metabolic rate, need energy quickly and need to get rid of excess weight from food

Variation in avian digestive systems

Esophagus

Where the food enters from the mouth and is propelled via muscle contraction (esophageal peristalsis) to the stomach

Crop

Modified section of the esophagus for food storage, moistening, and development of probiotic microbiota

Variation in crops

An avian ruminant

In the Hoatzin

For fermentation

Very enlarged crop

Proventriculus

chemical breakdown of foods (hydrochloric acids)

Gizzard

mechanical breakdown of foods; serves the function of grinding molars; often contains grit or pebbles to help with grinding

Proventriculus Seed-eater

Seeds & grain: developed proventriculus & well-developed gizzard

Proventriculus Fish eater

Less-developed proventriculus & well-developed gizzard

Proventriculus Fruit eater

well-developed proventriculus & less-developed gizzard

Proventriculus Hoatzin eater

Very specialized crop, reduced proventriculus & gizzard

Small intestine

Where nutrients are absorbed

Caeca

A mysterious, multipurpose organ which aids in residual breakdown of food using bacteria and fermentation, and the reabsorption of water and salts

Variation in intestinal caeca

Gut morphology, like many things in birds, can change seasonally (as food resources change)

Large intestine

A short tract where water and electrolytes are reabsorbed (aided by antiperistalsis, or reverse muscular contractions which send waste backwards into the ceca, and undigested material is consolidated into feces and transported to the cloaca

Cloaca

Convergence of the digestive, reproductive, and urinary systems. A holding area before exiting through the vent.

Avian Reproductive System

• Lay hard-shelled eggs (amniotic egg)

• No viviparity (live birth)

• Extensive parental care (incubation of eggs and care of young)

• Large seasonal changes in reproductive tissue

• Most species, females have only one functional ovary (possible adaptation for flight)

Seasonal Regression

Reproductive organs are heavy!

In all birds, reproductive organs regress to a small, non-functional state during the non-breeding season

Male reproductive system

Photoperiod stimulates release of gonadotropins, which stimulate growth of testes

Testes increase up to 300-500 times in size from fall minimum to spring maximum

Male Reproductive Tract

Sperm formation is temperature sensitive; maturation of sperm is assisted by a nocturnal drop in temp and external swellings of the seminal vesicles holding sperm

Cloacal protuberance

Copulation - bird sex

Most species lack an intromittent organ (except waterfowl, ratites)

Copulate by brief cloacal contact = “cloacal kiss”

Generally, females are in control of paternity (who is the father) of her eggs; must allow access, sperm selection

Male reproductive system

Intromittent organs are extremely rare

Phallus in waterfowl is corkscrewed counterclockwise

grooved with backward-facing spines; rapidly everts via lymph

Why do ducks do this freak ass shit

Probably evolved in response to breeding habitat (water) and mating system (extra-pair copulations)

Female reproductive system

In most species, only a single ovary (left)

• except kiwis and a few exceptions

Immature birds have all primary oocytes

• born with all the eggs you will have her entire life

Most species have sperm storage tubules; can store sperm for 10-24 days

• they choose who the father of their offspring is

Female reproductive system - breeding seasons

Ovary enlarges enormously during the breeding season

• Only the left ovary; right ovary is vestigial in most birds

Female reproduction - Rapid follicle development

each ovum matures (embryo“yolked up”) in 6-8 days

• takes like a week to add the yolk

Energy expensive

Female Reproductive Tract - Anatomy (LABEL FOR EXAM)

Folliles: Get the yolk

Ostium: female birds are fertile for about an hour

Magnum: receives egg white, Albumin
Isthmus: shell membrane
Uterus: Receives shell, egg is spinning

Colaca/vagina: egg comes out

Sperm storage

2 storages of sperm in female tract

up high in Ostium

down low in Vagina

Waterfowl female reproductive system

Female vagina is also corkscrew but goes the other way (clockwise)

Don’t fit together naturally

Female has to relax and allow male to copulate for fertilization to be successful

Forced copulations end up fertilizing blind pouches

The ecology behind reproductive morphology; extra-pair copulations

Male wants to fertilize as many females as possible

Females will accept fertilization from of variety of males if he is better than her pair, or to increase diversity

• females seek copulation outside of their pair

Lots of mate guarding

Importance of copulation method

• generally the socially bonded male receives the most fertilization

Male reproduction for bonded males still only have less than a 5% copulation rate

Avian Egg (LABEL EGG DIAGRAM)

Nice hard shell

• protection

• nourishments, water

• Ventilation and gas exchange

Know:

Chalazae - shock absorber of egg
Air space
Blastodisc
Vitelline membrane
Yolk
Egg white

Avian Egg - nutrition

Most fats come from the Yolk

Albumen: mostly water, with a bit of protein

Shell: gas exchange
Allantoic sac, uric acid: there’s space for non-soluble nitrogenous wastes

Gas exchange in eggs

egg must breathe, take in oxygen and release carbon dioxide

Egg can drown

Cover them in oil and the egg dies

Avian clutch size

Clutch size – the number of eggs laid in a single attempt

• Ranges from 1 (albatross, hummingbirds) to 20+ (waterfowl)

Lack’s rule – clutch size is larger at higher latitudes (resource pulse)

Clutch size

The number of eggs laid in a single attempt

clutch size declines with laying date: fewer eggs later in the season, earlier is better

Lack’s rule

clutch size is larger at higher latitudes (resource pulse)

Determinants of clutch size

• Food, birds predict how many young they can feed

• Parental care, time laying with resources

• Nest predation risk, if it’s a risky area birds lay less eggs

• Egg shelf life, maladaptive development in the tropics

• Body size and life history: bigger birds tend to have smaller clutches

Clutch size exceptionalists

Species that can raise more than one brood in a season face tradeoffs

Brood parasites don’t have a clutch size

Costs of egg production

Altricial – smaller absolute egg size, less yolk, faster incubation time

Precocial – much larger eggs, more yolk, longer incubation time

Altricial

• smaller absolute egg size, less yolk, faster incubation time (they are pink globs of goo)

• Offspring are nidicolous and helpless – invest more in raising them

• Almost all are income breeders – obtain nutrients to produce eggs on the breeding grounds

Precocial

much larger eggs, more yolk, longer incubation time

Offspring are nidifugous and self-sufficient

Some are capital breeders – take nutrient reserves with them from migratory staging grounds

Precocial - pros

+ Out of nest quickly (reduced nest predation risk)

+ Less parental care after hatch

Precocial - cons

– Requires chicks can find food (easy, abundant food)

– Much greater investment in eggs

– Slow growth after hatch

Altricial - pros

+ Eggs are “cheaper” (less cost losing them)

+ Faster growth after hatch

+ Continued neural development after hatch

Altricial - cons

– In nest longer (predation risk)

– Extensive parental care (feeding) after hatch

Calcium

Calcium is limiting!

Incubation physiology

Females loose feathers on chest and have warm watery area to keep chick warm

Egg turning

Birds turn eggs so eggs are equally being incubated

Bird vs Lizard brains (good exam slide)

1) Avian brains are LARGE compared to non-avian reptiles

2) Increase in optic lobes

3) Increase in cerebellum (balance, coordination)

4) Increase in cerebrum (higher cognition)

5) Decrease in olfactory bulb

Avian brains are WHAT compared to non-avian reptiles

Large

Avian brains have an Increase in (compared to reptile)

optic lobes, cerebellum, cerebrum

Avian brains have a decrease in (compared to reptile)

olfactory bulb

bird vs. mammal brains

Both groups have a well-developed 3-part brain:

Forebrain

Midbrain

Hindbrain

Forebrain

(basal ganglia & cerebrum) – complex behavior, instincts, learning

Midbrain

cerebellum & optic lobes) – vision, muscle coordination, physiological control

Hindbrain

(medulla oblongata) – links spinal cord and peripheral nervous system to control regions in the brain

Modern view of bird brains

Bird brains are smooth and we associate smooth brain = dumb, but in birds it’s actually differen’t tissue and they have large smooth cerebrums so they actually are still very intelligent

Important parts of bird brain

Pallial tissue

Hyperpallium

Hyperpallium

functional equivalent to cerebral cortex –higher learning

Forebrain: hyperpallium

• Center of learning/intelligence

• Best developed in crows, parrots, passerines

• Damage severely impairs behavior

• Wulst region especially important for visual perception

Forebrain: striatum

• Controls eating, eye movements, locomotion

• Controls reproductive behavior, parental care

• May play a role in vocal learning

Midbrain: optic lobes and cerebellum

• Cerebellum: balance and coordination (flight)

• Two huge optic lobes

• Both larger than mammals

Hindbrain

• Olfactory bulb – smaller than mammals

• Medulla oblongata – “housekeeping” tasks like breathing

• Hypothalamus – hunger, thirst, hormonal control

• Hypophysis – pituitary gland (“master gland” that regulates stress, growth, reproduction)

Olfactory bulb (hindbrain)

smaller than mammals

Medulla oblongata (hindbrain)

“housekeeping” tasks like breathing

Hypothalamus

hunger, thirst, hormonal control

Hypophysis

pituitary gland (“master gland” that regulates stress, growth, reproduction)

Orientation in skull

With huge eye sockets taking up space, the brain sits “vertically” inside the skull

Avian vision

The most important sense

Vision is essential for safe flight

Largest eye:body size ratio in the animal kingdom

Eyes – a review

Light travels through clear cornea and into pupil

Iris controls pupil size and how much light gets through

Lens focuses light to keep things sharp

Light hits receptors on the back of the eyeball (retina) which translates light into nerve impulses sent through the optic nerve

Eye itself is filled with aqueous humor and vitreous humor

Visual reception basics

Cones = color

Rods = light and dark

Avian eye – key differences

Larger – by a lot!

Scleral ring stabilizes eye, but reduces mobility

Nictitating membranes (third eyelid)

Two lens system of vision (cornea+lens)

Pecten provides glucose to eyeball

Multiple fovea

Size of avian eye

Lots of variation in eye size

• larger in nocturnal species and raptors

Human eyes are ~1% of head mass

European Starling: ~15% of head mass

Birds also have a relatively huge optic lobe

Avian variation in eye shape

There is variation and it relates to behavior and ecology

Reduced eye mobility – scleral ring

Large bird eyes require additional support

Scleral ring

• bony ossicles around the eye

• Reduces eye mobility - birds turn their heads a lot

Protects the eyeball, holds shape during fast movement

Nictitating membranes

Third, clear eyelid that acts as protective goggle

Good for high speed, underwater