birds and life-history strategies Flashcards
what is life history
dictionary definition: a account of the series of events making up a person’s life
in biology there are different life stages:
- growth to sexual maturity
- reproduction
- inter-breeding season survival
why is life history important
constructing phylogenetic tree
allows us to compare species worldwide e.g. clutch size
how do measure life history in birds
size: adult female body mass, egg mass
development: incubation period, fledging period, age at first breeding
survival: adult survival rate
reproduction: clutch size, broods per year, annual fecundity (clutch size x no of broods)
egg mass variation
normally 2-5% body mas but in Southern Brown kiwi is 25% and common ostrich is 1%
egg mass variation across species
cuckoos weigh 100g: eggs 4.5g
European storm-petrel 100g: egg 21g
diversity in egg size is because of variation in clutch size
Altricial-precocial spectrum
altricial-> semi-altricial->precocial
altricial: helpless and dependent
precocial: independent can feed and move itself almost immediately
super-precoial: chicks are hatched completely independent of adults
phases of an avian breeding attempt
Prelaying: Territory establishment,
courtship and nest building
Laying: Egg-laying duration
Incubation: Eggs tended prior to hatch
Hatching: Duration between first and last egg hatching
Nestling: Time for which chicks tended
by one or both parents
Fledging: Interval between hatching and flight (parents feed less)
incubation
maintaining egg temp (37-38 degrees). good for embryonic development
loose breast feathers and use bare skin (brood patch) to maintain contact with eggs in open nest
chick growth
chick growth curve is usually sigmoidal (S shape)
king penguin chick mass far exceeds mass of adults-fat retains water to promote survival
variation in chick growth rate
growth rate is a trade-off between predation risk and food availability
higher growth rate in altricial than precocial
faster in costal vs pelagic(open ocean): more diverse food in coast
faster growth in temperate vs tropical birds
fledging
- obtaining new plumage and following down
- the process of leaving the nest
- becoming fully competent at flight (best definition)
many different definitions
2-selected and K-selected species (there is a graph for this)
r-selected (e.g. blue tit): heavy selection for short life cycle and high reproductive output. occur in temporally and spatially unstable environments. unstable colonisers.
k- selected (e.g. wandering albatross): heavy selection for longevity and spreading reproductive attempts over a long period of time. occur in persistent and stable environments.
all species somewhere in the middle
senescence and problems in detection
senescence: decline in survival and reproduction and/or survival with age
man species live briefly and may die before even breeding once.
birds appear to sense as soon as they first breed (breeding increases death risk)
hard to measure
migration
track birds
some move very far: sea bird migration
migrate for long day length for foraging
migration is population rather than species specific: depending on location may migrate to different areas
partial migration
different populations and induvial in a population may have different migration patterns e.g. robins.
further north causes more migration due to more extreme conditions
migratory behaviour is inherited.
applying life history: Florida scrub-jay
loss of habitat
birds nest and feed on native oak scrub.
every year they produce one brood and it is very rare that chicks starve in nests.
fire generated habitat: adapted
life history of suburban jay
birds in suburban areas decreasing
birds nest and feed in gardens
produce two broods per year and chicks often starve to death in nest.
loose cue for breeding phenology (timing) due to artificial diet so lay eggs to early
worse survival output for nestling
comparative laying dates
suburban birds always breed earlier than wildland birds
because suburban birds have access to ad libitum (as much as desired/needed) food all year-round and have lost chick-food availability as a cue to initiate breeding
egg versus chick survival
egg survival is better is suburban areas due to lack of snake predation
when eggs hatch, survival of nestlings is worst in suburban areas than wild areas
