Download Chp17_ReproductiveSuccess

There is a
female
cardinal
incubating in
there, you
gotta look for
her
On April 24 th ,
we’ll be going
outside for lab
so no lecture
on Friday
CHAPTER 17 – LIFETIME
REPRODUCTIVE
SUCCESS IN BIRDS
REPRODUCTIVE SUCCESS
 An important aspect of evolutionary success is reproductive
success
 Significant trade-offs must occur here
 Breeding is expensive, how much energy do you spend?
 Future breeding opportunities are important, longer life means more
years as a breeder
 But, costs spent on breeding now means less energy for survival and
breeding later!
 How does this trade -off get navigated
 Welcome to the study of life history traits
REPRODUCTIVE SUCCESS
 Two very important life history traits will be considered
 Longevity – how long you can expect to live
 Fecundity – how many offspring you can expect to have
 These two traits impact each other
 Highly fecund individuals typically live shorter lives
 Older individuals typically are not as fecund
 Outside influences, e.g., environment, impact these two
 The trade-off becomes: How do you live a long time without
sacrificing of fspring number produced and how do you
maximize of fspring output without killing yourself
REPRODUCTIVE SUCCESS
Species that are short-lived tend to be more fecund and begin breeding much
earlier than long-lived species. Have to get the most reproduction in in a short
time, but does that contribute to early demise?
REPRODUCTIVE SUCCESS
Plasticity in your response to the environment, both as an adult and as a
juvenile/embryo, is of great interest in research
REPRODUCTIVE SUCCESS
A variety of
environmental
and physiological
constraints must
be considered in
understanding life
history of animals
REPRODUCTIVE SUCCESS
 Birds live longer than
mammals of comparable
size
 Surprising!
 Higher metabolisms
 Greater energy expenditure
 Higher expected oxidative by product levels
 See a variety of life-spans
Tweetybird is
over 60
years old
now!
 Songbirds – up to 20 years
 Seabirds and raptors – over
30 years
 Parrots – over 80 years!
REPRODUCTIVE SUCCESS
 Survival rates vary with location and age
 Northern and Southern Hemispheres differ
 Overwintering and migration
 Adult predator concentrations
 Age is very important to survival
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Eggs and nestlings/juveniles very vulnerable
Fledglings die off at high rate
After one year adult mortality lower
At old age senescence could be a factor
 Death rate increases with age
 Highly debated since most non-captive individuals never get truly old
REPRODUCTIVE SUCCESS
Here we see age-related
mortality in Florida Scrub-jays
(Aphelocoma coerulescens)
Studies are now addressing possible
issues with old age in scrub-jays
REPRODUCTIVE SUCCESS
 Fecundity is, obviously, important too
 Annual vs. lifetime fecundity
 One wants to maximize on both without impacting longevity!
 Should you have one or more broods/year?
 Depends on where you live, how you’re eating, and who you’re mated
to
 Should you have lots of eggs or few eggs/nest?
 Depends on your condition, what the babies eat, and predators
 However your age (longevity) and experience make a big
dif ference!
 Young birds often just not good at being parents (just cannot get their
jobs figured out), or lack a prime territory or mate
 Delay your first breeding attempt?
 However, old birds have fewer offspring
Above a Goldcrest (Regulus regulus) who is regularly double brooded
REPRODUCTIVE SUCCESS
Reproductive
performance with
age in European
Sparrowhawks
(Accipiter nisus)
REPRODUCTIVE SUCCESS
 Annual reproductive ef fort has strong impacts
 May decrease physical condition now
 This could decrease future reproduction
 May decrease survival
REPRODUCTIVE SUCCESS
 To sum up:
 Reproduction can shorten
your life span
 However, maximum
reproduction increases with
every year you reproduce
 You have to balance what
you do this year with the
future
 Decreases in fecundity
 Chances of predation
 The environment has
influenced evolution, which
may lock you in a certain
path
 Plasticity
REPRODUCTIVE SUCCESS
 What determines how many eggs to produce in a clutch? ( this
is an important part of fecundity )
 Food availability is obviously important
 Whether you’re a capital or income breeder, what you eat goes to the eggs
 The density of the population (which can strongly influence resource
availability) may be important
REPRODUCTIVE SUCCESS
REPRODUCTIVE SUCCESS
 Predation is impactful to
reproductive success
 Adults – you’re no longer in
the breeding population
 Nests – your eggs just got
eaten, ‘no success for you’
 Strong predation pressure
on nests may induce
smaller clutches of young
 Less noise from nestlings
 Less distance between
parents and fledglings
 Less visits to nest/young
Obviously this is a predator-prey
interaction that the cat just is not going to
win, but predatory mammals, reptiles,
and birds are an issue
REPRODUCTIVE SUCCESS
 Life history traits important to life tables
 Projecting reproductive success
 Projecting population trends
 Tracks several important attributes of a cohort
 Age at first reproduction
 Fecundity (number of independent offspring produced)
 Offspring survival
 Longevity of adults
 We won’t construct life tables, but I do want you to
know what they can be used for and the information
they contain
REPRODUCTIVE SUCCESS
 Information for life tables
from females is usually
more reliable
 They are the ones making
new bodies in population
 You can more reliably track
their reproductive success
 Information of this type is
used in management
decisions for population
control or promotion of
growth
Expected annual fecundity of two
species, area under the curves are
essentially the same