migration and navigation Flashcards
24 hour cycle
controlled by the pineal gland
circadian rythem
cycle influenced by zietgebers which are natural cues that aid in regulation of body cycles such as light cues
circannual cycle
tracks roughly one year without external cues
hypothalmus
region of the brain that can sense low light which penetrates the brain which induces signal to the pituitary gland
pituitary gland
releases neurohormone leading to luteinizing hormones and follicle based hormone production to control daily cycles and breeding onset
dispersal
having multiple nests in a single year and sending grown offspring out of the nest dispersing the population
ex: robins
nomadic
wander throughout their lives following food and nesting resources
ex: snowy owl
irruptive
large groups of a species show up in atypical locations all at once
ex: waxwings
migration
movement of long distances over a map in a regular cycle often following seasonal availability of food resources
routes of migration
north to south: north temperate zones
south to north: south temperate zones
inland to coast: waterbirds and Eurasia
high to low: tropics, white crowned
to and from wet spots: tropics
costs of migration
energetic costs, navigational errors and unknown territories, weather, predators, time away from breeding; most migrants have an increased mortality rate their first year
benefits of leaving the tropics for breeding
migration allows for use of seasonal high protein food sources; tropics are high in predators
benefits of leaving temperate zones for winter
many temperate regions have harsh winters with low temperatures and food availability
lifetime reproductive success
roughly equal in migrants and nonmigrants because residents live short lives and have large clutches while migrants live long lives and have more clutches
leap frog migration
some members of the species stay in place or make a small movement wile other populations move from north of them to south of them or vice versa
disjunct migration
not all members of a species follow the same migratory pattern; can lead to different evolutionary pressures and eventually speciation
migratory patterns
can be determined by sex, season, time or age; many species travel faster in the spring to compete for breeding grounds but take their time in the fall
loop migrations
making northern movement overland and returning over the coast
nocturnal migration
a common pattern because at night it is cooler, more humid, and the air is more stable
fat stores
4% of the body in resident birds, 19% in short distant migrants, and up to 50% in long distance migrants
staging grounds
locations where large numbers of birds congregate to prepare for a migratory bout typically over a body of water
homing
most birds are good at finding their way back home even if they are in an unknown area, utilizing a built in map and compass
directional heading
a genetic compass
navigation
the mental map, must be learned from experience
star compass
birds can learn the movement of the night sky while sitting in their nests for incubation, learn the central star (polaris or betelgeuse) which the rest of the stars move around and can apply what they know when moved from one hemisphere to another
sun compass
the sun moves at a steady rate and has a consistent location based on season and time of day allowing birds to use it to determine direction
magnetic compass
magnet in the forefront of their brain that pulls to magnetic north
other forms of navigation
olfactory cues and learned landmarks are both used in local and known areas
Emlen funnel
an inkpad surrounded by a funnel covered by a screen allowing vision up but not out of the funnel; used to track the direction of migration via migratory restlessness
zugunhru
migratory restlessness; trapped birds try to walk in the direction in which they would take off, longer distance migrants are more restless
learning orientation
indigo buntings must see the sky within their first month to be able to orient properly
