Exam 2 Flashcards
The goal of an annual cycle is to….
Spread out energetically costly life stages (reproduction, molting, migrating, and overwintering)
What happens when an American Redstart fledges lots of young?
Its molt it delayed, so it must molt while migrating. This causes birds to have duller feathers, causing them to be less successful in the next breeding season.
What are the consequences of an early laying date?
- young are not born at the same time as food is available
- vulnerability of offspring to unpredictable spring weather (cold snaps wipe out the nest)*
*best answer
How does climate change interact with migration distance?
- birds do not reach the right point at the right time
- breeding cues do not match between nest site and overwintering site
How does light pollution influence annual rhythms?
- night time window strikes
- sleep deprivation
ex) exposure to constant dim light causes decreased testicular width in european blackbirds
Migration
A seasonal cycle of departure and return - may be local (across elevations) or long distance (latitude)
How is a migration route determined? (4)
- type and frequency of barriers (bodies of water etc)
- historical distribution of species
- migratory stopover points
- predictability of resources
What types of birds migrate at night? (5)
- passerines
- rails
- owls
- cuckoos
- shorebirds
What are the benefits of migration occurring at night?
-avoid predation
- refuel at stopovers during the day
- night air is cooler, moister, and thermoregulatory costs are minimized
What types of birds migrate during the day?
hawks, soarers, swifts, swallows
What are the benefits of migration occurring during the day?
it is most advantageous for birds that utilize thermals or feed on the wing
What types of birds migrate flexibly? (during day or night)
Birds like waterfowl, gulls, and some passerines migrate to maximize favorable conditions
How do birds prepare for migration?
building up fat reserves
What are the costs and benefits of stopping at a refueling site?
Benefits
- arrive at breeding site in good condition
- predictability of resources influence priority of stopover sites
- continue migration
Costs
- in some places, for example with unpredictable resources, the costs of cold weather and foraging is greater than the cost of continued flight
What are the costs and benefits of not migrating for a tropical resident?
Benefits
- year round stability
- favorable conditions
Costs
- cannot take advantage of seasonal resources
- competition due to high density
high concentration of nest raiding predators
What are the costs and benefits of not migrating for a temparate resident?
Benefits
- does not incur costs of migrating
- take advantage of seasonal food availability
- decreased competition when migrants leave
- bread earlier than migrants
Costs
- endure periods of scarcity
- overwinter survival costs
What are the costs and benefits of migrating?
Benefits
- move to where food is available
Costs
- must breed later than residents
- susceptible to climate
- energetic costs
Resident
a bird that stays in one area year round
Obligate migrant
birds that always migrate
Obligate annual migrant
all individuals migrate
Obligate partial migrant
only some individuals migrate - but the individuals that migrate stay consistent
Facultative partial migrants
a variable number of individuals within a population will migrate and the degree to which any migrate will vary
Irruptive migrant
High seasonal variability and low predictability
ex) crossbill
What is the difference between a facultative partial migrate and an obligate partial migrant?
obligate partial
- due to genetic polymorphism
- a variation in physiology, morphology, behavior
- the individuals that migrate will always migrate
Facultative partial
- individuals migrate or not due to complex reasons, one individual may migrate one year and be a resident the next
Differential migration in dark eyed juncos
males migrate a shorter distance than females, and young birds will always migrate a shorter distance than older birds (young males < adult males < young females < adult females)
due to differing selection pressures
- young birds have higher mortality over larger distances (young birds migrate shorter distances than adults)
- male birds benefit more from increased proximity to breeding grounds than females (males migrate shorter distances than females)
How do birds navigate?
- experience (having migrated the same route before)
- the sun
- the stars
- earth’s magnetic field
- visual landmarks
there are magnetoreceptor cells in the bird’s ______ and _______
retina, hippocampus
Spacing of birds varies among… (3)
- among species
- among individuals
- between seasons
Territory
a fixed area or resource that is continually defended
How is a territory defended?
displays and chases, by males or pairs
What types of displays are used to defend a territory?
-vocal and nonvocal sounds
- plumage
- behavior
What are the costs and benefits of territoriality?
Benefits
- easy access to resources
- exclusive access to resources
Costs
- investing in territory defense
- risk of injury in confrontation
What types of resources create territorial birds?
When resources are predictable and defendable
ex) a swift is not going to defend a territory because insects are not a defendable resource
When are territories favored?
When resources are at intermediate levels
When is dispersal favored?
When resources are low
When is flocking favored?
When resources are high
_____ and ______ displays indicate status
threat, appeasement
Can a badge of status, like in the harris’ sparrow be cheated?
No, dominant birds will beat the shit out of you
Signals can be static or _______ like the crest of a stellar’s jay
dynamic
What are the costs and benefits of flocking?
Benefits
- safety in numbers
- mating availability
- sharing of information
- thermoregulation
Costs
- competition for food and for mates
- increased chances of disease and parasites
Flocking behaviors are encouraged when resources are… (3)
ephemeral, limited or abundant (the OPPOSITE of a territory)
- birds do not need to be as vigilant and can devote more time to foraging because many eyes watch for predators
Dilution effect
‘if there are 10 birds in a flock, then there is a 1 in 10 chance I will be targeted by a predator’
individual risk of predation is lower
flocking increases _______ fitness
individual
Hamilton’s rule
if benefits x relatedness - costs > 0 then a behavior will be favored
Communal roosting
a nighttime congregation during the nonbreeding season, same costs and benefits as flocking
important thermoregulatory functions
Colonial nesting
- common in seabirds
- favored when food is unpredictable and distant
- increased exposure to parasites and predators
Sexual selection
caused by differential access to mates based on individual characteristics
Bateman’s principle
describes behavior of males vs females and sexual selection
- sperm are ‘cheaper’ than eggs
- females are limited by the number of offspring that are produced
- males are limited by the number of eggs that they can fertilize (# of mates)
- sexual selection operates more strongly on males, the unlimited sex
- females, who are the limited sex, desire high quality offspring, so they are more choosy with their mates
What is the most common bird mating system and how can we describe it?
Social monogamy is characterized by pairs of birds that raise offspring together, but extra pair copulations occur for both males and females
When is the force of sexual selection the strongest?
When there is a greater variance in reproductive success (ex - some males produce as many as 40 offspring, but many produce zero)
this is represented on a graph by a steeper slope
in general ______ fitness increases more with number of mates than ________ fitness
male, female
intrasexual selection
sexual selection that occurs among members of the same sex
- size, aggression, alternate mating strategies, or sperm competition
intersexual selection
sexual selection that occurs between members of different sexes (females choose males)
- showy males with displays, dances, and fancy feathers
Why do male turkeys often display in dominant/subordinate pairs where the subordinate male does not mate?
pairs of males are often brothers, so the subordinate male gains fitness indirectly by being a wingman
Hamilton’s rule
benefits*relatedness - costs > 0
Describe the alternate mating strategies of ruffs
3 genetic polymorphisms caused by autosomal differences
- territorial males - darkly colored, defend and maintain territories/display in leks
- satellite males - lightly colored, do not defend and maintain territories/display in leks
- faeder - female mimics, who mate sneakily
- females prefer for there to be multiple males present
Name some adaptations that make sperm more competitive
- larger testes
- larger sperm stores
- larger copulatory organs (duck corkscrew penis)
- more frequent copulations
- mate guarding
How do females choose mates (3 reasons)
- direct benefits
- good genes
- arbitrary choice or runaway selection
Widowbirds
long tail is an honest signal of mate quality, because the tail encumbers the male and only high quality males can support the male
What are direct benefits that females use to choose mates?
- food
- high quality territory
- parental care indicated by feeding and territory
By selecting for large comb size, red junglefowl females ensure that their offspring get….
good genes
- red junglefowl comb size is directly correlated with offspring condition/quality
- males were vasectomized and females were artificially inseminated to prove that there is no female bias
This type of protein is responsible for presenting antigens to white blood cells. Individuals with the greatest diversity of this protein have better immune function. What type of bird mates to produce offspring with the most diversity of the protein?
MHC proteins, house sparrows
Blue tits want to choose mates with the greatest amount of….
heterozygosity
When females choose mates arbitrarily, their choice is often due to….
sensory bias
What type of sensory bias to zebra finches and grass finches have towards males?
females zebra and grass finches love males with white crests
What is the result of arbitrary choice on selection?
runaway selection may occur
Runaway selection
preference and expression of trait become linked due to assortative mating
this leads to runaway selection (like the ever increasing length of widowbird tails)
What is the traditional explanation for ornamented females?
ornamentation does not serve a purpose, it is simply a side effect of selection for ornamented males
What is the contemporary view of ornamented females?
males prefer ornamented females
highly ornamented female bluethroats are larger than their dull counterparts, which is a trait preferred by males
When does mutual mate choice occur?
monomorphic, monogamous species where both adults care for offspring
ex) inca terns choose mates based on length of moustache
How does ‘bird monogamy’ differ from ‘human monogamy’
-sexual exclusivity does not occur in bird monogamy ONLY social exclusivity
- extra pair copulations are common for birds
- human monogamy is sexually AND socially exclusive
Monogamy
a social pair bond with a single member of the opposite sex
the pair bond may last 1 breeding attempt or 30 years
What is the most common mating system for birds?
monogamy - up to 90% are socially monogamous
What percentage of birds are actually genetically monogamous?
VERY FEW - only 14%
Extra pair paternity rates vary by species and are an important source of ________
sexual selection
Barn swallows that have rustier plumage sire _______ offspring via extra pair copulation
more
polygamy
any system where an individual has multiple pair bonds with members of the opposite sex
is polygamy common among birds?
NO - only 3% of species
polygyny
multiple females mate with a single male
polyandry
multiple males mate with one female
polygynandry
multiple males and females form a breeding group
when is polygyny favored?
occurs when resources are clumped and defendable
- common in fruit eaters or reed breeders
- females join a harem becasue they do as well or better than solitary females on shitty territory
What are the costs and benefits of polygyny for females?
costs: must share male and resources the male defends, loss of parental care from male
benefits: dilution effect, information sharing, good genes (males that can maintain a large territory have better genes)
Why is polyandry rare?
- biparental care is a better system for birds
- based on the current system, it is more advantageous for males to mate multiply than females (the circumstances that cause the opposite are rare)
This hormone drops more rapidly in biparental and polyandrous systems due to the antagonistic relationship between levels of this hormone and parental care.
testosterone
What is one example of polygynandry?
male and female smith’s longspurs mate with multiple partners
- clutches have mixed paternity
- nests are cared for and defended by multiple males
What are the costs and benefits of extra pair paternity for males?
costs: predation risk on nest (males must leave nest undefended to seek out other females), female is left unguarded (and may seek her own extra pair copulations), energetic costs associated with sleeping around
benefits: increase reproductive success
What are the costs and benefits of extra pair copulations for females?
costs: increased risk of diseases, injury risk from other females, males reduce their parental investment
benefits: more diversity of genes in the nest, care from extra pair males, fertility insurance, extra pair males may be higher value, extra pair males may have higher heterozygosity
in polyandry, what sex does sexual selection act most strongly on?
females
What is brood parasitism?
laying your eggs in another female’s nest
What is the difference between interspecific and intraspecific brood parasitism?
interspecific: parasites lay eggs in the nests of birds of another species (brown headed cowbird)
intraspecific: parasites lay eggs in the nests of birds of the same species (american coots)
What is the difference between obligate and facultative brood parasites?
obligate brood parasites ONLY reproduce via parasitism and are always interspecific parasites. facultative parasites opportunistically lay eggs in the nests of others, but have a nest and raise some of their own chicks.
European starling brood parasitism
european starlings lay eggs in the nests of other european starlings
- female EUSTs do not count their eggs
- before starting to lay, females remove all eggs in the nest, if present
American coot brood parasitism
coots opportunistically lay eggs in the nests of other coots
- brood parasitism is so common that female coots learned to count their eggs
- variable egg coloration helps females keep track of which eggs belong to them
- females reject eggs by ejecting them, burying them in nest material, or pushing them to suboptimal incubation spots (causing a smaller chick size at hatching)
Obligate specialist brood parasite
only lay eggs in the nests of specific species
- old world cuckoos target warblers and crows
- african whydas target waxbills and pytillias
- honeyguides target bee eaters and woodpeckers
cuckoo adaptations to brood parasitism
-cuckoos mimic host egg coloration (females will only parasitize a single species whose eggs are matched most closely - forming a ‘race’ of birds that only parasitize one species)
- eggs are thicker shelled and larger
- eggs may be incubated before laying
- young push out eggs of competitors (NOT true for BHCBs)
Why do BHCB chicks not evict other nestmates?
presence of host offspring actually increases food availability for the parasite
indigobird example
indigobirds learn the host species song, and the closest imitation is the most attractive
imitation ability is correlated with gape similarity, essential for parasite acceptance
Obligate generalist brood parasite
- parasitize a large number of species
- one female can parasitize many different species in a single season
- some species will accept the eggs and some will reject them
ex) brown headed cowbird (BHCB)
Why do some bird species not reject eggs from a parasite?
- cognitive differences
- similarity of eggs: rejection depends how closely cowbird eggs naturally resemble the eggs of the host
- ability to reject: small birds may not be able to reject large eggs, or risk destroying their own eggs to reject a parasite egg
- mafia behavior from BHCBs: cowbirds destroy nests that reject eggs
Why do BHCBs not match their eggs to their hosts?
cowbirds put all their energy into egg production, and can produce 40 offspring in a season
being able to parasitize many nests of many different species is more advantageous than specializing
Great spotted cuckoo example
- great spotted cuckoos are a nonevicting parasite of carrion crows
- they produce noxious secretions when grabbed by predators
- carrion crowns will not reject cuckoo chicks or eggs because these noxious defenses help them fledge more offspring than they may have been able to before
- this is mutualism, both species benefit
Obligate specialist brood parasites can be described as being in an _______ _______ ______ with their host species
evolutionary arms race
Name at least 3 adaptations for brood parasitism
- noxious cuckoo secretions (great spotted cuckoo)
- chicks mimic gape of host chicks (indigobird)
- eviction behaviors of parasitic chicks
- eggs mimic host eggs
- incubation is headstarted before laying
Cooperative breeding
a breeding pair is assisted by helpers, occurs in ~250 spp
why would individuals give up an opportunity to reproduce to assist others
- relatedness to breeding pair
- limitation of habitat
- learning opportunity (be better parents)
- helpers inherit territory of adults
Scrub jays
- previous year offspring help parents and defend/feed offspring
- half of all pairs have up to six helpers
- increases number of offspring fledged by pair
- helpers gain indirect fitness benefits by helping
superb fairy wrens
- with helpers, females produce smaller eggs
- chick size remains consistent between groups though
- offspring can catch up due to helpers, female gets to lessen the burden of reproduction on herself
Why do helpers stick around?
ecological constraints
- harsh environment
- limited breeding opportunity
- limited habitat
Is helping behavior flexible? (number of helpers can vary depending on environmental conditions)
yes
ex) bee eaters have more helpers in years with decreased rainfall
ex) acorn woodpeckers have more helpers when territories are all full
ex) seychelles warblers had less helpers when lots of territories were vacant, and had more helpers as they filled up
Why do females prefer to help when the primary territory belongs to the mother?
extra pair copulations mean that paternity is dubious but maternity is always absolute - the female can guarantee her relatedness to her mother but not her father
white fronted bee eaters
form colonies of family members, mating occurs between groups
- birds know who is related and how closely, preferring to help kin
long tailed bushtits
if a nest is depredated, the individuals will seek out the nests of kin to become a helper
- recognition of kin occurs via vocalizations learned in the nest
Why do helpers assist breeders? (4)
- indirect fitness benefits are greater than possible direct fitness benefits
- limited territories or resources
- inheritance of high quality territory
- higher lifetime reproductive success is gained by being a helper
Which avian sex chromosomes designate a female? a male?
Female: ZW
Male: ZZ
How can we describe a bird that has the sex chromosomes ZW?
heterogametic female
what is a gynandromorph? How does it occur?
a gynandromorph is a bird that is 1/2 male and 1/2 female. These birds demonstrate sex determination differences between birds and mammals. The sex determination of birds is “locally” controlled or gene mediated while mammal sex determination is “globally” controlled or hormone mediated
Bilateral gynandromorph zebra finch
the gynandromorphic zebra finch we discussed in class developed a song control system on the male side (underdeveloped on the female side)
it sang and tried to mate with female zebra finches
How is sex typical morphology/behavior regulated?
by hormones (HPG axis)
- Gonadotropin releasing hormone (GnRH) is released by the hypothalamus to communicate to the anterior pituitary
- The anterior pituitary releases luteinizing hormone (LH) and follicle stimulating hormone (FSH)
- LH and FSH act on the target tissue, stimulating production of primary hormones
What does luteinizing hormone do in the male?
stimulates production of testosterone from Leydig cells
What does luteinizing hormone do in the female?
stimulates ovulation of mature follicles, production of testosterone and progesterone
What does follicle stimulating hormone do in the male?
triggers sperm production from sertoli cells
What does follicle stimulating hormone do in the female?
triggers follicular development
What unique adaptation do birds use to reduce weight during the nonbreeding season?
they reduce the size of their reproductive systems cyclically
While males develop both testes, females only develop one ovary. Which one is it?
the left ovary
List the anatomy a developing egg moves through in order, what occurs in each place and how long the egg stays there (7)
- ovary - yolking and ovulation (4-16 days)
- infundibulum - fertilization (20-30 minutes)
- magnum - albumin (1-3 hours)
- isthmus - membrane (1-2 hours)
- shell gland - shell (19-20 hours)
- vagina - laying
- cloaca - laying
What are the three membranes that surround the egg?
- amnion
- chorion
- allantoic sac
What does the amnion do?
surrounds the embryo in water and salts
What does the chorion do?
protects the embryo
what does the allantoic sac do?
has blood supply, functions in respiration and excretion of uric acid
What are some characteristics of the shell of the egg?
- has pores
- provides support
- protective function from microbes, inverts, etc
- gas exchange occurs
- prevents water loss
What selection pressures act on egg shape?
- egg length is correlated with body size (increased size = longer egg)
- egg shape is correlated with flight strength (elliptical = better flier)
It is theorized that strong fliers want to provision eggs better while minimizing girth of the egg
what factors influence clutch size?
- energy and resource availability: for every 1 kJ of yolk, 5kJ must be eaten (20% of energy makes it to the egg)
what is the most demanding part of egg production?
yolking
Where does the energy for egg production come from in capital based breeders? What type of birds use this system?
- the fat stores
- larger birds
Where does the energy for egg production come from in income based breeders? What type of birds use this system?
- daily intake of energy
- smaller birds
what are some costs associated with egg production?
- energy investment
- increased flight costs (heavier)
- decreased immune function
- decreased aerobic capacity
What are some functions of nests?
- protection from predators
- protection from parasites
- insulation
What are some nest materials that birds use?
- vegetation
- feathers
- hair
- gravel
- bark
- mud
- spiderwebs
- saliva
What are some costs and benefits of cavity nesting?
benefits:
- stable thermal environment (better insulated)
- more protection from predators
costs:
- o2 may be restricted
- higher levels of ectoparasites
- hard to find a suitable location to build nest
What are some costs and benefits of open cup nesting?
benefits:
- less ectoparasites
- more o2
- more available locations to build nests
costs:
- thermal environment may fluctuate
- more exposed to predators
How do rosy faced and yellow collared lovebirds demonstrate that nest building may have a genetic component?
rosy faced lovebirds transport nesting material by tucking it into the tail
yellow collared lovebirds carry it in the bill
hybrid lovebirds try to tuck it into the tail and fail
How do village weaver birds show that nest building has a genetic component?
hand raised male village weaver birds can build nests, but nest quality will improve with age
what is the difference between a primary and a secondary cavity nester?
primary cavity nesters must excavate a cavity (woodpecker), secondary cavity nesters find and use old cavities (bluebirds)
what is the ideal temperature for incubation?
37-38C or 99-100F
True or false? Eggs must be incubated as soon as they are laid or the embryo will die
False. eggs do not need to be incubated immediately, but once they start incubation, it cannot stop
What are some costs of incubation?
- energetic costs of generating heat
- predation risk
- lost time investment (foraging, mating defending etc.)
Eider duck example
eiders with larger clutch sizes incur greater costs such that in the following year costs persisted
(more eggs = reduced immune function, smaller clutches laid, laid later)
What is the most common method of incubation (who incubates?)
biparental incubation is the MOST common, then female only, then males only, then no incubation (least common)
In which species is there female only incubation?
North american passerines
hummingbirds
galliformes
ducks
in female only incubation, the male often feeds the female on the nest
in which species is there male only incubation?
ratites
in which species is there biparental incubation?
seabirds, hawks, etc.
What is a brood patch?
an area with no feathers, that has increased blood flow to heat eggs. the skin on the brood patch is softer and firmer. Either sex can develop a brood patch.
Name 3 methods of incubation
- belly flap (penguins)
- feet (boobies)
- mounds
- brood patch
What species can never develop a brood patch?
brown headed cowbirds
When temperatures are too hot, how do birds cool eggs?
- shading them
- wetting them
how is heat generated for mound builders?
rotting vegetation, tended by the male, provides the heat to incubate the eggs
What hormone regulates incubation/brood patch formation
prolactin
this hormone opposes prolactin
testosterone
synchronous brood
all eggs are laid before incubation begins, all babies hatch at once
all babies are the same size
asynchronous brood
eggs hatch at different times, incubation begins immediately
sets up a sibling hierarchy based on size and encourages competition
blue tits
prefer synchronous broods to recruit male help
what causes nest attentiveness to increase?
increased mate feeding (by extension, lower predation), decreased ambient temperature, increasing body condition
what causes nest attentiveness to decrease?
increased ambient temp, decreasing body condition, decreased mate feeding (and by extension, increased predation)
Does incubation have a genetic component?
Yes, crested mynahs cannot increase their incubation time when introduced to cold climates, common starlings can
Chicks communicate to parents via _______ while still in the egg
vocalizations (occurs late in development)
Why do birds rotate their eggs?
prevent the chorioallantois from adhering prematurely to the shell
How long is incubation?
10-14 days (songbird)
80-90 days (long lived seabirds)
What factors cause incubation length to increase?
increased lifespan
Describe how a chick hatches
the embryo punctures the membrane that encloses the air chamber, then punctures the shell around the fat side of the egg and pushes the top off
How do parents care for their young? (7)
- brood young
- thermoregulatory help
- NOT incubating (incubating is for eggs, brooding is for chicks) - feed chicks
- teach young
- tool building
- where to find food
- how to fly - remove wastes
- transfer of antibodies
- allopreening
- protection
How can we describe precocial young?
nearly self sufficient upon hatching
(this is the ancestral condition)
precocial young still have parental care though - they follow parents that provide protection and lead them to food sources
What is the difference between precocial young and superprecocial young
superprecocial young do not recieve any parental care and are completely independent from the moment they hatch
- this is common for mound builders
How can we describe altricial young?
blind, naked, and helpless young that require lots of parental care/feeding/protection before becoming independent
Who grows faster? Altricial or precocial young?
altricial young
Ricklefs theory on offspring growth
Ricklef’s suggests that altricial young grow faster due to a tradeoff between growth of tissue mass vs maturation of tissue function
- precocial chicks must follow parents, so all tissues must be fully functional, inhibiting growth ability
- all altricial chicks do is grow, they do not need to mature their tissues for a significant amount of time
What type of curve can we use to describe the growth of chicks? (sigmoidal, hyperbolic, or linear?)
sigmoidal curve (growth is the slowest early and late in development)
Why do aerial insectivores like swifts and aquatic predators like penguins overshoot their adult weight as fledglings?
they require an energy reserve or buffer while they learn to fly and hunt on the wing all at the same time
What can we say about the relationship between adult size and growth of a chick?
large birds grow slower
What can we say about the relationship between predation pressure and offspring growth?
As predation pressure increases, growth rate increases
- therefore, a cavity nester like a flicker would have offspring that grow slower than an open cup nester of similar size
Who develops thermoregulation faster- precocial or altricial chicks? Why?
Precocial chicks - they are already well insulated by down/have more muscle mass for shivering compared to altricial chicks
thermoregulatory ability also improves as surface area:volume ratio decreases
large broods retain heat better
What types of investment by parents do we expect in a precocial chick?
investment in the egg, investment in feeding, and/or investment in brooding
investment in the egg
peak energy investment occurs when young are in the egg
What types of investment by parents do we exprect in an altricial chick?
investment in the egg, investment in feeding, and/or investment in brooding
- investment in feeding
- investment in brooding
peak energy investment occurs when young are nestlings
Would we expect for precocial or altricial birds to have more monogamy?
altricial birds
- growth patterns encourage biparental care, encouraging monogamy
When does parent-offspring conflict occur?
- parents want to balance costs and benefits of parental care ie) to fledge the largest amount of offspring for the least cost
- parents need to consider their personal fitness and their future reproductive efforts
- offspring are the most successful when parents invest the maximum amount
- offspring want parents to invest the maximum amount regardless of personal cost
“conflict that occurs over the amount of parental care that is optimal for parental fitness vs offspring fitness”
Name some costs of parental care (3)
- energetic costs (expenditure increases by 50%)
- time costs (less foraging, less mate attraction)
- predation risk (must take care of several screaming, immobile mouths for several weaks)
How do offspring beg for food? (4)
- change posture
- open beak (brightly colored gape)
- peck at parent’s beak (gulls)
- vocalize
is begging an honest signal of offspring hunger?
when offspring beg more, parents bring more food. however, begging more often increases the costs incurred by begging, keeping the signal ‘honest’
What are some costs of begging? (3)
- increase predation risk
- energetic cost of increased activity
- increased cortisone levels
How might parents reduce the number of their brood in lean times?
- create a size hierarchy, encouraging competition
How is a size hierarchy created in birds?
- asynchronous incubation
- differences in egg size
- differences in egg composition
- differences in incubation quality
Why is a sibling size hierarchy advantageous?
- get more young when resources are abundant
- bet-hedging strategy
- reduce brood size when resources are scarce
American coot sibling conflict example
- adults vary egg investment by changing composition
- incubate asynchronously
- initially, the youngest offspring is fed first, then parents switch and feed the oldest first
- coot chicks have ornamental plumage, so parents will favor the most ornamented chicks
- the disparity between more highly ornamented chicks and less ornamented chicks (experimentally altered) increases over time, so it is advantageous to hatch first, especially if you are not very ornamented
In which species is siblicide common?
boobies
eagles
egrets
Why is siblicide common in egrets, but not in herons, a closely related group?
egret prey is more easily monopolized than heron prey, so it is easy for heron chicks to get all the food and kill their siblings
- herons in egret nests become siblicidal
- the behavior does not disappear when egrets are placed in heron nests
Why would a female want to bias the sex ratio of her offspring?
- since females are heterogametic, they determine offspring sex
- male reproductive success is largely determined by condition
- in lean times, female offspring have higher reproductive success than males
- female parents desire more ‘grandchildren’ to increase her fitness
- when resources are scarce, like when the female is in poor condition or she has to take care of offspring by herself, the offspring are likely to be in poor condition (unlikely for males to have reproductive success)
Who provides parental care for fledgelings?
the male
Fledging
nest leaving behavior by altricial birds
Why is the sex ratio 1:1?
there is a strong advantage to being the limited sex (EVERYBODY wants you)
so like frequency dependent selection, where the ideal frequency is 50% males 50% females
What is a life history trait?
a trait that describes a ‘life event’ such as
- growth rate
- age at maturity
- clutch size
- lifespan
- offspring size at hatching
What is a tradeoff?
organisms only have a finite amount of resources across growth, reproduction, and self maintenance (survival)
tradeoffs occur when some traits are invested in while others are not
- long life span, less offspring per breeding attempt
- short life span, more offspring per breeding attempt
kestrel example of an evolutionary tradeoff
kestrels raising artificially larger broods are less likely to survive
- investing more in current reproductive attempts takes away investment in survival
senescence
a late life decline in survival and/or reproduction
Rate of living theory
aging is inevitable caused by accumulated damage to cells and tissues (via replication errors, accumulation of toxic byproducts, etc)
What predictions can we make with the rate of living theory?
- aging and metabolism are correlated (live fast, die young)
- species should not be able to evolve a longer life span
Is rate of living theory supported or unsupported? Why?
rate of living theory is unsupported because despite having very high metabolisms, birds live much longer than other animals of similar size
Evolutionary reasons for senescence
-wild animals often do not die of old age
- natural selection may favor traits that are deleterious in old age, but increase breeding success at younger and younger ages, especially when there is high offspring mortality
Collared flycatcher example
- females that breed at age 1 have smaller clutches compared to birds that breed at age 2
- females given artificially larger broods have smaller clutches than control females
Explain the relationship between mortality, age at maturity, and fecundity
as annual mortality increases, age of maturity decreases, and fecundity increases
OR
as annual mortality decreases, age of maturity increases, and fecundity decreases
Lack’s hypothesis
selection will favor the clutch size that produces the most surviving offspring
- the factor that limits clutch size the most is food availability
Why do great tits have less offspring than predicted by lack’s hypothesis?
- there is a greater benefit from saving energy for future reproductive attempt
- higher quality offspring have greater reproductive success than low quality offspring
What is the main shortcoming of lack’s hypothesis?
it assumes that there is no tradeoff between current reproduction and survival and future attempts
offspring number comes at a cost to long term offspring quality
Skutch’s hypothesis
tropical birds lay smaller clutches due to higher predation rates
- they feed less often to prevent predators from locating the nest
What predictions can we make using skutch’s hypothesis and what are the results of testing? (3)
- parents visit larger clutches more
- nests visited more often are more likely to be depredated
- parents feed offspring less than in temparate climates
- predation rates are not higher in the tropics
- tropical species do not visit nests less often
What factors influence clutch size and how? (3)
- Food availability (lack’s hypothesis) explains clutch sizes within a species
- predation rates (skutch’s hypothesis) explains clutch sizes within latitudes
- annual mortality explains clutch sizes between latitudes
Explain investment differences between tropical and temperate birds
tropical birds have higher nestling mortality, so investment is greatest later in life
temperate birds have higher annual adult mortality, so there is high investment early in life
How does natural selection generate negative correlations between reproduction and longevity?
there is a depletion of genetic diversity - selective events limit ‘intermediate’ combinations of longevity and reproductions
Name some roles that birds serve in ecosystems and human culture
- religious significance
- relationship between humans and honeyguides
- pollinator
- seed disperser
- scavenger
- pest control by insectivores
- ecotourism
Name some threats that birds face
- habitat destruction (deforestation, agriculture, human development)
- climate disturbances
- light pollution
- pollution (pesticides, etc.)
- disease
- invasives (feral cats, rats/mice, mustelids etc.)
Name some invasive species that have adverse effects on bird populations
- cats
- rats
- mice
- cattle
- goats
- mustelids (weasels, stoats, skunks etc.)
- malaria
- influenza
what is the number one anthropogenic threat that birds face?
agriculture
open cup nesters tend to have relatively _______ incubation periods than cavity nesters
shorter - due to predation pressure differences (higher for open cup nesters)
species with precocial young tend to have relatively ______ incubation periods than species with altricial young
longer (more invested in development while still in the egg)
longer lived species tend to have ____ clutches than shorter lived species
smaller - invest in lower reproductive output over a longer period of time
species in areas of low predation tend to have _____ clutches than species in areas of high predation
larger - skutch’s hypothesis - less young means feeding them less and drawing less predators to the nest with activity
species in areas of abundant food tend to have _____ clutches than species in areas with scarce food
larger - lack’s hypothesis
altricial hatchlings grow _____ than precocial hatchlings
faster - tissue maturation hypothesis
larger birds grow _____ than smaller birds
slower
cavity nesters grow ____ than open cup nesters
slower - due to predation pressures
species with low annual mortality grow _____ than species with high annual mortality
slower
what is the primary environmental cue that birds use to time transitions between stages of the annual cycle?
day length or photoperiod
what hormone is responsible for triggering the production of testosterone
LH or luteinizing hormone
remember that follicle stimulating hormone triggers the development of follicles in the female, and sperm in the male - generally responsible for production of gametes in some way. LH is responsible for triggering primary hormone production (estrogen in females and testosterone in males) for both sexes.
what hormone shifts activity away from reproduction towards survival?
corticosterone or CORT
noise pollution and zebra finches
groups are exposed to either bird song or traffic noise prenatally/postnatally in varying combinations (song/noise, noise/noise, etc)
all groups have the same average clutch size
however, birds exposed to noise are less successful at hatching offspring (noise/noise = most severe, combinations with intermediate effects)
the relationship between hatching success and egg size goes away when birds are exposed to noise
birds that were exposed to noise also had lower hematocrit, tarsus length and telomere length, persisting even after exposure
Considering temperate residents, tropical residents and migrants, who has the highest species density, with more competition?
tropical residents
Considering temperate residents, tropical residents and migrants, who has the shortest breeding season?
migrants
Considering temperate residents, tropical residents and migrants, who has the fewest broods annually
migrants
Considering temperate residents, tropical residents and migrants, who has the highest annual mortality rates?
temperate residents - low food availability in winter and harsh conditions
which hypothesis predicts that female fitness is limited by the number of eggs produced, while female fitness is limited by the number of eggs that are fertilized?
bateman’s principle
according to this mechanism of sexual selection, evolution of elaborate male traits is favored because trait preference and trait expression become genetically linked through assortative mating
runaway selection
these birds have a testis on one side of the body and an ovary on the other
bilateral gynandromorphs
this egg membrane aids in embryonic respiration and excretion
chorion
levels of this hormone increase rapidly in response to stressors such as escaping a predator, lighting for a territory and enduring bad weather
corticosterone or CORT
in this mating system, several males and females form a communal breeding unit
polygynandry
proposed that clutch size is limited primarily by food availability
lack’s hypothesis
list two functions of nests
thermoregulation, protection from parasites, protection from predators
Who has higher variation in reproduction in monogamous birds, males or females?
neither, variance is equal
who has higher variation in reproduction in polyandrous birds, males or females?
females
who has higher variation in reproduction in polygamous birds, males or females?
males
females often choose males for showy displays or ornaments. what are two possible benefits of female mate choice?
good genes: superiorly ornamented males produce better offspring
heterozygosity
direct benefits: a male’s ability to provide parental care or territory, gift giving male behaviors
describe precocial vs altricial hatchlings
precocial
- grows slowly
- feathered, much better at thermoregulating early
- only need to be led to food
- larger at hatching
- mobile
altricial
- grow quickly
- featherless, not good at thermoregulating early
- helpless
- smaller at hatch
- blind
- require much parental care
- not mobile
Given that facultative brood parasites do not always engage in brood parasitism, under what conditions are they likely to parasitize another nest?
- low body condition
- have already laid many eggs
- the opportunity arises
- harsh environmental conditions
Give one reason (hypothesis) why a host of an obligate brood parasite would NOT evolve defenses against parasitism
- retaliation by the parasite (cowbird mafia)
- parasites provide benefits to the host via predator deterrence
Why would a female brood parasite remove one of the host’s eggs before laying her own in the nest?
- reduction of competition for her offspring
- egg counting behaviors by the host
List two specific adaptations of host species that decrease the impact of brood parasitism
- unique begging calls and gape patterns, egg recognition, egg counting, and moving suspicious eggs to subpar spots for incubation
How do helpers benefit female superb fairy wrens?
helpers allow the female to lessen costs to her without sacrificing reproduction
- there is less yolk, but feeding is increased after hatching by helpers
With respect to the pattern of differential migration that is seen in Dark Eyed Juncos, what are the three selective pressures acting on the sex/age classes and as a result of these selective pressures, how are the sex/age classes arranged on their wintering grounds?
- mortality caused by migration is higher for young birds than old birds, therefore young birds migrate a shorter distance than older birds
- reproductive success is influenced by time of arrival on the breeding grounds, specifically for males: it pays to be earlier, so males stay closer
- overwinter survival increases the further south a bird migrates (less competition) so there is selection on all individuals to go as far south as possible
young males - closest to breeding grounds (more north)
old males - 2nd closest
young females - 3rd closest
old females - farthest (furthest south)
