Lecture 9 - Avian Life Histories

•Chapters 12 – 17•Read the book – many details

•Courtship and Mating•Breeding systems

•Sex•Nests and Incubation

•Parents and their Offspring

Overview

• Passion• Field trips and the natural world• Lab exam – Tuesday – March 9?• Feedback on results – with Field Notes

• Job information – emails?

Outline

1. Pair formation or other variations2. Breeding systems3. Nesting, Care of young4. Fledging5. Cooperative breeding

Mates• Sexual selection:

– female preference for particular males– Maintains male ornaments and displays

• Good-gene hypotheses– Elaborate plumage and displays signal genetic superiority

– Index of health (parasites, stamina)

Mates• Runaway selection hypotheses

– Taking ‘good-genes’ hypotheses to the extreme

– Elaborate displays and bizarre plumage

Types of Pair Formations• Monogamy

– One male and one female– Promiscuous– Extra-pair copulations are the rule and not the exception (see Gill (2007, p. 361))

• Polygamy– Many of one sex to one of the other– Polyandry– Polygyny

Pair Formations - see Table 13-1

Monogamy (social)– One male and one female– Breeding season or for life– Shared parental responsibilities

• Nest building• Incubating• Food

PromiscuityExtra-pair copulation • Copulation by females with additional males

• source of sexual selection for bright plumage

Advantages• Insurance against infertility• Increased genetic variability

– inc. fitness

Monogamous Relationships

• Lifelong– Geese, swans, eagles, albatrosses, petrels, gulls

• Different pairs each season– Most passerines

• Different pairs with each brood– House Wren, Bank Swallow

• Promiscuous – Ruffed Grouse

Pair Formations

• Getting a divorce– Failure of mate to show up after winter– Female may leave for better feeding ground

– BCCH female leave males after 1st brood for higher ranked male

Polygamous Relationships• Polygyny - several females for each male– Grouse, blackbirds– Increased reproductive burden on female

• Polyandry- several males for each female– Phalaropes, jacanas, tinamous– Increases reproductive burden on males

Evolution of Polygyny

• Food availability – where food is superabundant = polygyny

– Patchily distributed resources• More common in relatively simple habitats (e.g., marshes & grasslands)

• Regular imbalance of sex ratios

Gibbs et al.-Science 250:1394-1397, ‘90

“ a polygynous species”

* Reward

Leks• “Nature’s version of a singles bar”• Resources (e.g., food or nest sites) are superabundant

• Resources unpredictable in– Time– Space

• Resources costly to defend• Copulations performed by few males

– Always those that hold central positions in lek

Polyandry• Sex-role reversal

– Females defend territory– Males incubate eggs and feed young

• Phalaropes – females are brightly colored

Female sandpiper defending territory

Selection of Nest Site

• Usually completed by individual that is primary incubator

• Male may start several nests for female to choose between

• Perennial nests – no new site selection between years (raptors, penguins and procellariids)

Nest Types

• Constructed nest– Majority of nests– Extremely varied

• Cup• Dome• Pouch• Cavity

Nest Types• Ground nest or scrapes

– Little or no construction• Excavated nests

– Primary cavity nesters –excavate their own cavity

– Secondary cavity – use previously excavated cavities

– Burrows – Burrowing owls

Cavity Nesters

Construction material• Inorganic

– Mud/clay– Stones

• Organic– Woody material– Fine grasses– Hair - TEWA– Saliva– Feathers - TRSW– Spider silk– Snake skins - GCFL

Nest Building

Australian Native Hen – “Megapode” or “Mound Builders”

Australian Native Hen – Incubation Mound - see Gill (2007, p. 463)

Tanimbar Scrubfowl - Indonesia

Forest Kingfisher nest

Buff-breasted Paradise Kingfisher

Why Build a Nest?• Reduce predation risk

– 75-88% of nest losses due to predation

– Differential mammalian predation for ground nests

– Cavity nests are safest• Protect eggs from weather

• All birds form and lay shelled egg for external incubation– Oviparity– (Viviparity = retention of eggs & live birth)

• Embryos are intolerant of high temperatures

• Highly variable shape & coloration

Eggs

Clutch Size• Number of eggs laid in one set• Subject to:

– Energy constraints– Lifetime reproductive success

• Egg production is energetically costly– 40-50% of basal metabolic rate for altricial

nestlings– 125-180% of BMR for precocial nestlings

Number of Clutches• Most species will replace lost clutches once

• Some permanent residents always have > 1 clutch per year– Mourning Dove in SE US will have up to 6 clutches per year

• Evolutionary tradeoff between lifetime reproductive success and life span

Incubation• Maintain adequate temperature for development of embryo

• Most birds develop brood patch– Loose feathers– Existing apteria

• Some birds (e.g., lack apteria [penguins]) use feet for brooding

• Eggs are turned

Incubation Duties

• Varies among species and types of pair formation– For most passerines both sexes incubate

– For most polygamous species, female incubates (except polyandry)

• Often elaborate relief ceremonies

Care and Development of Young

Stage of Development at Hatching

• Altricial (nest dweller)– Young do not leave nest immediately– Typically few if any feathers– Relatively helpless– Most passerines

• Precocial (nest fugitive)– Can leave nest immediately– Capable of locomotion– Covered in natal down– Some thermoregulatory dependence on parent

Brooding• Continued thermoregulation of young by adult

• Especially important in altricial young– Protects against hyper- & hypothermia

• Precocial young are brooded at night

Feeding of Young

• Responsibilities of 2 sexes differ among species

• With overlapping broods, males tend to do most

• Polygyny – females do most• Polyandry – males do most

Nest Parasitism

• Do not incubate own eggs – dump egg(s) in another species’ nest

• 5 families with obligate parasites• 1 species of obligate nest parasite in North America– Brown-headed Cowbird– More than 100 species known to host cowbird eggs

Nest Parasitism• Depresses nesting success• Rates higher in fragmented habitats• Young may evict eggs of host or kill host’s young (European cuckoos)

Cooperative Breeding

• Defined by regular involvement of helpers in feeding and care of young

• Reported in about 300 species (3 % of species)

• Most species long-lived – minimal loss of reproductive success to helper

Cooperative Breeding

• Advantages:– Group Defense– Improved Survivorship– Acquisition of skills

• Parental nepotism – favoring relatives– Young exhibit delayed dispersal

Cooperative Breeding• NA Species:

– Florida Scrub Jay– Red-cockaded Woodpecker

– Acorn Woodpecker

– Groove-billed Ani

* Reward

Characteristics of Cooperative Breeding

• Habitat, territory or nest-site limitation• Tropical or sub-tropical distribution• Sedentary (relatively stable

environments)• Suitable habitat saturated – part of

population remain non-breeders• Low fecundity• Deferred maturity, high survival• Population has relatively old age

structure