Ornithology (post-midterm)

What are the two methods of visualizing birds’ vocal communication?

oscillograms (time vs. loudness) and sonograms/spectograms (time vs. pitch)

syntax of birdsong

note → syllable → motif

sounds birds can make

pure tones, modulation, harmonics

dominant vs. fundamental frequency

dominant is the loudest, fundamental is the lowest pitch

larynx

stop swallowed food from going to lungs

syrinx

the structure through which birds create sound, have both trachial elements and bronchial elements, which can vary between species

tracheophone suboscienes

only sing from trachea

how can birds be so loud?

the syrinx is surrounded by the clavicular air sac, making it nearly 100% efficient at converting moving air to sound

how can birds be so articulate with their sounds?

the labia, which push and condense air into the airway to create sound, operate independently

differences between the suboscine syrinx and the oscine syrinx

2 extrinsic muscles / 2 extrinsic muscles + 3-6 intrinsic muscles

what are the 4 things sound quality depends on?

1. tension of the membranes due to syringeal muscles (tighter = higher pitch)

2. Pressure of the interclavicular air sac (higher = louder)

3. Diameter of the airway (wider = louder)

4. Actions of the vocal tract

what are song learning birds?

oscines, bellbirds, parrots, hummingbirds

closed-open continuum

spectrum of types of song learners: closed learners can only learn songs when young, open learners can learn new songs throughout life

stages of song learning

1. Sensory acquisition (listen and memorize)

2. Sensorimotor produce and listen and compare practiced song to memorized song)

2 main vocal pathways and their components

posterior: motor control, higher vocal center (HVC), robust nucleus of Archipallium (RA)
anterior: song learning
- both HVC and RA are involved in song learning, as they’re larger in males, those with larger repertoires, and in early breeding szn

bird song

• long and complex

• influenced by sex hormones

• used in territoriality and mate attraction

bird calls

• short and simple

• used to coordinate behavior of pairs, families, and flock

  • short notes = easy to locate, mobbing call

  • alarm call = hard to locate

what do females prefer (vocally) (5)?

• More frequent singing

• Fast delivery

• Accurate songs

• Long songs

• Large repertoires (~50% of species studied in field)

chromosomes of birds

males are homogametic (ZZ), and females are heterogametic (WZ)

what adaptations do male birds have to store their sperm?

• sperm produced at night when lower body temp.

• sperm stored in seminal vesicles near skin surface where temp is lower

3 components of sperm

head: genetic material
midpiece: metabolism, power
tail: propels

something interesting about bird ovaries…

females only have one left ovary to save weight for flight

preovulation

when the yolk and its surrounding vitelline membrane forms, takes 4-16 days, many developing ovums at once

parts of the egg

yolk: lipids, proteins, food!
albumen: water, insulation, shock absorption
vitelline membrane: surrounds the yolk, early analogue of a
stomach and intestines

5 functions of eggshell

• provide structural support

• protect egg from microbes

• conserve water

• facilitate gas exchange

• calcium carbonate

why is there so much variation in eggs?

• coloring for camouflage OR visibility

• spots (from melanin) help reduce water loss

• spheres maximize volume and surface area, while pyriforms reduce rolling

briefly describe how an egg forms

In the ovary, the yolk and the vitelline membrane form. Then, fertilization occurs and a layer of albumen is added. Finally, another layer and the shell membrane are added.

amnion

surrounds the embryo which floats in a contained environment of water and salts.

chorion

a protective membrane that surrounds all the embryonic structures including the dwindling yolk sac

allantoic sac

Functions in respiration and excretion. A network of blood capillaries within it connects the chorion to the shell membranes and function to remove CO2 from the egg and import oxygen from the outside to the growing embryo.

how can sex ration can be manipulated?

• differential survival of M/F offspring

  • different resource allocation, M require more food

• females producing more M/F eggs

  • ex. more F on good territory and more M, who will disperse on bad territory

anisogamy

the concept that since females invest more in reproduction, they are the limiting factor and can be pickier

direct benefit theory

trait is sexually-selected for if it provides female with direct benefits: better territory, protection, parental care, infection avoidance

good genes theory

trait is sexually-selected for if it is an honest single of the male’s genetic/physiological superiority

Hamilton-Zuk hypothesis

part of the good genes theory that says ornaments and colors convey good health and lack of disease in males

sexy sons theory

trait is sexually-selected for if it will provide a son with a higher chance of reproductive success. ex. a female will choose a male with a long tail so her son will have a long tail so another female will choose her son and thus pass down her genes

lekking

mating system where males congregate to attract females, then females leave and raise the offspring alone; occurs when food is easily obtainable and/or females have large home ranges

hot spot model for lekking

leks occurs where females are

hot shot model

leks occur where dominant male is

female preference model

leks occur where largest cluster of males are

when does monogamy happen

90% of birds are socially monogamous because coparental care = more offspring survival

3 things extra-pair mating leads to

• reduced parental effort by male

• STIs

• sperm competition (when females store sperm of multiple males they mated with during single breeding cycle)

male adaptations to sperm competition

• relatively large testes

• large sperm stores and long spermatozoa

• mate guarding

• frequent pair copulations

pros and cons of extra-pair copulation

direct pros:
- more help raising young
- fertilization insurance
indirect pros:
- good genes
- increases odds of finding genetically compatible sperm
- inbreeding avoidance (in cooperative breeding)
cons:
- time and energy
- risk of predation
- risk of disease

polygyny

1M:many F
arises through males defending clumped, limited resources (resource-defense polygyny)
OR arises from abundant resources (lek polygyny)

polyandry

1F:many M
arises when seasonal, clumped resources allow females to lay more clutches than they can brood
- leads to sex role reversal, males build nests and provides all parental care, females are colorful

promiscuity

there are no pair bonds, individuals mate and move on

polygynandry

when several females and several males form a social breeding unit.
- males defend territory and provide care to young in proportion to their confidence in paternity

cooperative breeding

mating systems in which breeding pairs are assisted by helpers
- helpers usually offspring from previous year
- can encompoass other systems, ex. cooperative polygamy or cooperative polygynandry
- arises when there is intense competition for food territories (benefits males to get at least something)

theories for how cooperative breeding evolved

• kin selection / inclusive fitness

• direct benefits (increased survival, easier EPC)

• ecological constraints (resource limitation)

• life history (ex. nest site limitation)

What threats are there to nesting?

PREDATION (primary selective pressure), starvation, desertion, hatching failure, adverse weather

What is ancestral in passerines?

enclosed nest

What are 3 things that can be done to improve nest safety?

• camouflage

• safe placement (high up, in cavities, with thorns, near predators)

• behavioral mechanisms (mobbing, distractions)

incubation

• 10-90 days

• in most families, both parents incubate in shifts

• if starts when clutch is complete, synchronous hatching. if not, asynchronous hatching

What is the relationship between nest predation and parental activity?

The more nest predation (ex. open-nesting birds in the tropics vs. hole-nesting in temperates), the less parental activity

How is egg temperature regulated?

Kept at 35-40.5 C by…

• brood patch

• shading or wetting

• egg turning

• in mound builders: decomposing plants, geothermal springs, sun

Types of brood parasitism

• intraspecific, facultative, done opportunistically

• interspecific, obligate, everyone does, don’t build nests or provide parental care, spectrum of host generalists to host specialists, parasitic chicks use supernormal stimulus

What are the two modes of development and their features?

1. Altricial - parental care is essential, no down, small eggs & yolk, fast growth rate after hatching & tissue growth favored

2. Precocial - minimal parental care, down, large eggs & yolk, slow growth rate after hatching & tissue maturate favored

Tissue allocation hypothesis

In altricial birds, tissue growth is favored after hatching. In precocial birds, tissue maturation is favored.

bright gapes

Patterns and colors in chicks’ beaks and mouths that provide parents with visual stimuli to provide food

Relationships related to brood size

As brood size increases, fitness of individual chicks decreases. In species where food can be monopolized, there is more bullying and siblicide.

brooding

keeping chicks warm by sitting on them, AFTER incubation and hatching

parent-offspring conflict

long-lived species parents are less likely to take risks than short-lived, favoritism can occur by parents to maximize individual quality OR maximize fledgling success - parents should value their own survival over their offspring

nestling period

hatching → leaving the nest

fledging period

hatching → flying

imprinting

learning during critical learning period that is irreversible, determines mate & habitat preferences, includes imprint on “parent” which is important in colonial species where parents learn recognition too

6 functions of visual communication

• species recognition

• sexual selection, courtship displays

• territorial defense

• aggression

• submission

• predation avoidance

Benefits of multiple mating by females

• more help raising young

• fertilization experience

• genetic compatibility (odds increased)

• genetic diversity

• inbreeding avoidance

types of nests/nesting

cup nests, cavity nests, enclosed nests, pensile/hanging nests, communal nesting, mud nestsa

ecosystem functions

what birds do for the ecosystem - predation, scavenging, seed dispersal, pollination

ecosystem services

what birds do for humans - pest control, disease regulation, forest maintenance, fruit production

birds that have gone extinct and why

dodos (human introduced predators), passenger pigeons (hunting, habitat loss), great auk (overhunting), carolina parakeet (hunting, habitat loss), ivory-billed woodpecker (habitat loss)

what traits make a bird more vulnerable to extinction?

specialization, restricted ranges, slow reproduction, colonial/social species

6 threats to birds

1. Habitat change

2. Overexploitation

3. Introduced species (including cats)

4. Collisions

5. Disease

6. Pollution

other things about the syrinx

syrinx is located at the junction of the trachea and bronchi. is formed by an expansion of the cartilaginous rings of those two structures.

Tympaniform membranes allow the shape of the syrinx to change which alters the sounds produced