Review 2 Flashcards
Illustrate the gradient of migratory connectivity
Is one strategy preffered
highly connected = all the same birds in breeding and wintering areas
not connected = no relation between individuals in a breeding area and the individuals in the wintering area
- may restrict gene flow if population is small
- no strategy is preffered over others - very species dependent / guild dependent
- bet hedge that other wintering area is less competitive than would be if you stayed with your group
morphological
physiological
behavioural adaptations to hot in birds
List and briefly describe three advantages of group foraging with regard to resource aquisition
- more eyes - find food faster
- find food more efficiently
- reduce variation in daily food intake
compare the value of studies looking at DNA hybridization and DNA sequencing at two taxonomic levels species and order
sequencing for species - finer scale but more expensive
hybridization for order - coarser scale but cheaper
Describe a factor that might limit the size of a single species foraging flock - in contrast, describe a factor that might limit the size of a mixed species flock of tropical birds in the understort
diversity of specific resource vs diversity of insects available
Describe one major possible advantage and one major disadvantage to defending a territory that is bigger than needed during an average year
- ensure you have resources if there is a resource limiting event - more space to court females
- takes alot of energy to defend the large territory - lots of fighting with other birds
Compare and contrast digestive and reproductive changes during the annual cycle
Digestive - prior to migration birds are eating more - hyperphagy - and putting on more fat, some birds may also dissolve and absorb their digestive tracts prior to migration to reduce weight for flight and to stop digesting food so it can be used for energy
Reproductive - change occurs during and before breeding. Prior to reproductive event follicle growth will be stimulated as birds prepare in advance for mating, follicle growth will be extremely high just before ovulation. In males testes will be reduced for most of the yyear but can get up to 300x larger right before breeding
What is the sun arc hypothesis and how does it compare to other hypothesis for migration
Sun arc hypothesis - birds use the sun to navigate / during migration. Because the suns position is variable daily/ seasonally / based on llat/long must sync suns position with a precise internal clock in order to know where they are relative to the suns current position.
The other methods of navigation, the stellar compass, does not require as precise of an internal clock as stars do not move as quickly, they orient based on their relative position compared with a star or constellation. Or magnetic compass which can involve both special photorecptors and magnetite around the trigeminal nerve which allows birds to both sense magnetic fields - ie, sense where north it, and see magnetic fields and observe the slight changes based on topography, acting as both a compass and a map.
