B&B Adaptation and optimality perspectives Flashcards
What are the benefits and costs of storing fat reserves for a bird?
Avoid starvation Fuel for breeding, migration However, you have to spend more time foraging Flying takes more energy Slower and less agile Increased risk from predators
How do you remotely weigh wild robins?
Free living robins at Tredegar house, Sussex uni
Robins are remotely weighed using mealworms
Hop and off balance
Describe the daily foraging routines of birds
Diurnal songbirds must build up fat reserves during the day to avoid starving at night
Robins very precisely reach target dusk reserves ie if they wake up fat, eat less and if they wake up skinny, eat more
There is a hypothesis that there is low foraging efficacy at dawn to suggest why birds sing at dawn. Is this true?
When its dark, foraging success is low. When it is bright, foraging success in high so finding food does depend of light levels.
Maybe sing instead because foraging success is low at dawn
There is a hypothesis that there are less predators at dawn to suggest why birds sing at dawn. Is this true?
Dawn is a dangerous time so maybe not
Nocturnal predators often still active and diurnal predators get up early to start hunting
Owls, cats..
Maybe a higher predation risk at dawn and dusk
SDP models are used to explain strategic regulation of energy reserves. What does it do?
Links short term decision making to long term fitness
Identify an optimal state at the end of a series of days
Works backwards from the end of the final day, compute the sequence of behaviours which allow the bird to reach the end state
The “state” is the aspect of an animal’s biology that affects its long term fitness. Give examples of what a state can be
Energy reserves
Assessment of foraging success
Prediction of future weather conditions eg temp
True or false
SDP models relate energy balance (state) to the costs and benefits of different behaviours. eg singing, resting at different time of day and night
True
What would the SDP model say to explain why there is a dawn chorus
Birds build up fat reserves to survive overnight
Birds lose more reserves on colder nights
Night time conditions are unpredictable so birds budget for a worse case scenario
Most nights are not as cold as the bird has budgeted for
At dawn on most days, birds are left with more fat reserves than they currently need
Favours singing (lose some fat and no need to forage) over foraging at dawn
What are the ways to test SDP model of behavioural routines?
1) Test key assumptions
2) Test predictions about
- how the environment affects state
- how state affects behaviour
3) Test predictions about average daily routines
Use SDP model to test if singing is costly
1) Is it costly
- energetic costs
- forfeit foraging time
- attract predators
2) Environment - state - behaviour
- birds lose more fat reserves on colder nights
(it was found an extra 0.5g is lost for every 10c drop in temp)
- birds sing more at dawn when they are fat (found true)
- Singing IS costly
- Robins lose more fat on cold nights
- Robins sang less when their body mass at dawn was low
- But robins put on more mass before cold night (forecasters?)
What are the consequences of anisogamy?
= unequal gametes
Typically, females invest a large amount in reproduction
- through producing a relatively small number of large eggs( vice versa?)
- parental investment - nutrition, nourishing inside body, after birth provide lots of resources
Males may only provide sperm
Influence the pattern of mating arrangements
- Females reproductive success is limited by resources and so they are distributed accordingly
- Males reproductive success is limited by access to females so they are distributed accordingly
What did Ims 1987,1988 find when studying anisogamy?
eg dispersed food patches
Aggregated food
Dispersed food - experimentally aggregated females
Dispersed food - experimentally aggregated males
Dispersed food - dispersed females and thus dispersed males. Monogamy because only 1 male could defend 1 female
Aggregated food - aggregated females and thus aggregated males. Polygyny. Denser patches. 1 male could have several females
Dispersed food - experimentally aggregated females - aggregated males. Polygyny. Males followed females
Dispersed food - experimentally aggregated males - dispersed females. Found according to food not males.
Dispersal of resources affects female dispersal which affects the mating system
Aggregated females gives high monogamy/polygamy potential?
Polygamy
In some circumstances, neither females nor their resources can be defended. What is this known as?
Lekking
Female choose which male to mate with
Groups of males display on tiny resource-free territories. Females are not defended
This is usually for species with huge female home ranges and high population densities
eg Topi, black grouse
