On April 24 th, we’ll be going outside for lab so no lecture on Friday CHAPTER 17 – LIFETIME REPRODUCTIVE SUCCESS IN BIRDS There is a female cardinal incubating in there, you gotta look for her

 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 offspring number produced and how do you maximize offspring 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

 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  Songbirds – up to 20 years  Seabirds and raptors – over 30 years  Parrots – over 80 years! REPRODUCTIVE SUCCESS Tweety- bird is over 60 years old now!

 Survival rates vary with location and age  Northern and Southern Hemispheres differ  Overwintering and migration  Adult predator concentrations  Age is very important to survival  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

 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 difference!  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 REPRODUCTIVE SUCCESS Above a Goldcrest (Regulus regulus) who is regularly double brooded

REPRODUCTIVE SUCCESS Reproductive performance with age in European Sparrowhawks (Accipiter nisus)

 Annual reproductive effort 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

 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

 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 REPRODUCTIVE SUCCESS 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

 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