Term
| Migratory birds use multiple sources of compass information for orientation: |
|
Definition
1. Geomagnetic field
2. Sun
3. Skylight polarization patterns
4. Star patterns |
|
|
Term
|
Definition
refers to the sharp jump in night time activity that occurs at the onset of the migratory response.
Also, birds orient strongly in the direction in which they are to migrate. (Put bird in funnel with ink pad, and you can see patterns of where they jump) |
|
|
Term
|
Definition
| The sun rises at specific times during the day, and provided that an animal has a sense of time, the relative position of the sun could be used to determine direction. What remains intact on even the cloudiest of days is polarized light. The sky in the direction of the sun is less strongly polarized than the sun in the other half of the sky, even on a cloudy day. |
|
|
Term
|
Definition
| If your eyes are sensitive to polarized light, the sun looks dark, and as you turn your head away from the sun, 90 degrees away the polarized light is the brightest. |
|
|
Term
| Polarized light as a possible recalibration cue |
|
Definition
| Savannah sparrows are migratory birds and use a magnetic compass. Birds exposed to a 90-degree shifted polarized light pattern recalibrated their magnetic compass, but birds exposed to a 90 degree shifted magnetic field did not recalibrate their magnetic compass. |
|
|
Term
|
Definition
The earth's magnetic field provides guidance for animal orientation and even true navigation because it can also be used to define the geographic position on the basis of field intensity gradients
3 Possible Mechanism:
1. Electromagnetic induction
2. Chemical magnetoreception
3. Magnetite-based magnetoreception (lots in fish) |
|
|
Term
| Lateralized functions of birds' visual system |
|
Definition
| Right eye/left hemisphere predominantly processes object vision. The birds were able to orient in appropriate direction when using the right eye, but not when using the left eye. This suggests that left hemisphere of brain deals with magnetic orientation. |
|
|
Term
|
Definition
Sun compass is based on a TIME compensation mechanism, enabling the animal to recalibrate as the sun moves across the sky. Tis is a momentary thing: you can mess the bird up today, but tomorrow morning when he wakes up he will correct himself and go the right direction unless you keep shifting the light--advantage of having a correction mechanism.
One hypothesis is that birds take a bearing on the sun at sunset, use it to fix on a correct direction until sunrise, at which point they recalibrate and a new bearing is used. |
|
|
Term
|
Definition
| If the skies are overcast, the birds have a random movement pattern. This works inside because you're taking out other cues. |
|
|
Term
|
Definition
Stars provide compass info at night, when the sun and related polarization pattern are no longer available. However, stars are not used with a time compensation mechanism; rather, the rotation center of the night sky encodes the geographical north direction.
Corrects for DIRECTION rather than time (as opposed to sun compass). |
|
|
Term
| Salience of cues depends on the time |
|
Definition
During the pre-migratory season, celestial info is given the greatest salience and used to recalibrate the magnetic compass.
During the migration, the majority of experiments suggest that birds rely on the magnetic field as the primary source of compass info and use it to calibrate celestial compass cues, i.e. the relative salience of magnetic and celestial cues is reversed depending on the stage of migration. |
|
|
Term
|
Definition
| the process by which animals ACTIVELY choose habitats in which they will conduct particular activities |
|
|
Term
| Habitat selection can occur on various spatial and temporal scales: |
|
Definition
Relatively small: microhabitats, foraging, nesting mating
Intermediate: territories, general neighborhood
Large: communities used by the members of species over evolutionary periods of time |
|
|
Term
|
Definition
the area or volume over which an individual animal roams during the course of its usual daily wandering and in which it spends most of its time
Often home ranges of several individuals overlap; typically home range is not used exclusively and is not defended, whereas territory is used exclusively and is defended.
Many species have territories within their home ranges. |
|
|
Term
| Roosting home ranges of Spix's disc-winged bat |
|
Definition
| No home range overlap while sleeping, but it does occur while awake. |
|
|
Term
|
Definition
Space use in animals is strongly correlated to body size. Energy requirements alone can explain how population density decreases as mass increases, but not the steep rate which home range increases as mass increases.
Also must look at spatial constraints on defense and frequency of interactions. Resources can be lost to neighbors.
Exclusivity of home range use decreases with an increase in body size. |
|
|
Term
| How large should a territory be? |
|
Definition
Historically, the choice was viewed in terms of two competing hypotheses:
1. Adjustment of territory size in response to resource density
2. Adjustment of territory size in response to costs of defense
Optimal territory size equals area on graph with bigger difference between benefit and cost.
Optimal territory size increases with a decrease in food density. |
|
|
Term
| Adjustment of territory size in response to resource density |
|
Definition
Animals adjust territory size to the density of the critical resource (usually food) so territory contains enough to satisfy requirements.
Territory size is positively correlated with body weight in many animals. Body size and home range are also positively correlated.
Resource analyses often reveal that territory sizes are smaller where food is more abundant or higher quality. |
|
|
Term
| Adjustment of territory size in response to resource density: example in iguanid lizard |
|
Definition
A food value theory states that territorial individuals may be more successful because they are spaced in such a way that each animal has adequate food (resource). Size of territory is not constant--it must vary as a result of food density.
Predictions: inverse correlation between territory size and food abundance and territory size will change in a short-term response
Researchers manipulated the food supply: territory compressed as food was added, and territory expanded as food was removed. |
|
|
Term
| Adjustment of size in response to costs of defense |
|
Definition
Variation in territory sizes occurs because more competitors are attracted to areas rich in resources, and such areas are therefore more costly to defend per unit area.
Increased resource density --> increased intruder density ---> increased costs (time and energy) ---> decreased territory size |
|
|
Term
| Effect of Intruder on Optimal Territory Size |
|
Definition
Increased food density causes increased intruder pressure, and thus optimal territory size decreases significantly.
Animals are better off fighting for very good habitat than getting very poor habitats because the net benefits are much higher for very good habitats even with increased costs. |
|
|
Term
| Territory Size in Great Tits |
|
Definition
Territory size in great tits is apparently determined by competition and not by resources. With removal of territory-holding male, neighbors expanded territories into vacated area.
Males with more neighbors had increased time interacting, increased costs, and reduced territory size.
The more neighbors you have, the more you have to keep intruders out, and thus the smaller the territory that you have. |
|
|
Term
| Unpredictability and Territorial Behavior, i.e. what to defend? |
|
Definition
Males should defend the resources that are directly linked to reproductive success; however, it should be done in a dynamic way.
Quality as a proxy of what to defend (cost) strongly depends on the social interactions--might want to spend more time defending that which has a higher quality. |
|
|
Term
| Spacing Patterns in Social Non-territorial Species |
|
Definition
If females cannot be easily monopolized (e.g. females' ranges are too large to be defended or females range too widely, or have unpredictable movements), then male might adopt several types of non-territorial tactics:
1. Follow and defend access to a group of females
2. Establish dominance relationships within that social group
3. Follow females and mates opportunistically when they are in estrus, e.g. cats.
Maintaining spatial behaviors, in non-territorial males, can be explained if the spacing pattern of males is a form of reproductive competition. Patrolling large home ranges allows male cats to encounter more females and have higher reproductive success (i.e. more kittens) = higher fitness
Higher ranking males have higher reproductive success (beat up other guys), but if females are not in estrus, males will not fight. |
|
|
