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rmax, generation time and body size
Exponential population growth
Demographic and environmental stochasticity
Optimal reproductive tactics
Semelparity versus iteroparity
Reproductive effort (parental investment)
Expenditure per progeny
Parent-offspring conflict
Patterns in Avian Clutch Sizes
Altrical versus Precocial
Nidicolous vs. Nidifugous
Determinant vs. Indeterminant Layers
Open Ground Nesters
Open Bush Nesters
Open Tree Nesters
Hole Nesters
Nest attentiveness and male feeding
Flicker egg removal experiment
Lecture # 15
8 March 2016
N = 5290 Species
Trade-offs between present progeny
and expectation of future offspring
Iteroparous organism
Semelparous organism
Patterns in Avian Clutch Sizes
Altrical versus Precocial
Patterns in Avian Clutch Sizes
Altrical versus Precocial
Nidicolous vs. Nidifugous
Determinant vs. Indeterminant Layers
N = 5290 Species
Patterns in Avian Clutch Sizes
Open Ground Nesters
Open Bush Nesters
Open Tree Nesters
Hole Nesters
MALE
(From: Martin and Ghalambor 1999)
Patterns in Avian Clutch Sizes
Classic Experiment: Flickers usually lay 7-8 eggs,
but in an egg removal experiment, a female flicker
laid 61 eggs in 63 days
Great Tit
Parus major
David Lack
Parus major
European Starling, Sturnus vulgaris
Chimney Swift, Apus apus
Seabirds (N. Philip Ashmole)
Boobies, Gannets, Gulls, Petrels, Skuas, Terns, Albatrosses
Delayed sexual maturity, Small clutch size, Parental care
Boobies, Gannets, Gulls, Petrels, Skuas, Terns, Albatrosses
Delayed sexual maturity, Small clutch size, Parental care
Albatross Egg Addition Experiment
An extra chick added to each
of 18 nests a few days after
hatching. These nests with two
chicks were compared to 18 other
natural “control” nests with only
one chick. Three months later,
only 5 of the 36 experimental
chicks survived from the nests
with 2 chicks, whereas 12 of the
18 chicks from single chick nests
were still alive. Parents could not
find food enough to feed two
chicks and most starved to death.
Diomedea immutabilis
Latitudinal Gradients in Avian Clutch Size
Latitudinal Gradients in Avian Clutch Size
Daylength Hypothesis
Prey Diversity Hypothesis
Spring Bloom or Competition Hypothesis
Latitudinal Gradients in Avian Clutch Size
Nest Predation Hypothesis
Alexander Skutch ––––––>
Latitudinal Gradients in Avian Clutch Size
Hazards of Migration Hypothesis
Falco eleonora
Varanus giganteus
Evolution of Death Rates
Senescence, old age, genetic dustbin
Medawar’s Test Tube Model
p(surviving one month) = 0.9
p(surviving two months) = 0.92
p(surviving x months) = 0.9x
Peter Medawar
recession of time of expression of overt effects of a detrimental allele
precession of time of expression of the effects of a beneficial allele
Age Distribution of
Medawar’s test tubes
recession of time of expression of overt effects of a detrimental allele
precession of time of expression of the effects of a beneficial allele