Editing Behavioral ecology (section)

===Resource defense===
The term economic defendability was first introduced by Jerram Brown in 1964. Economic defendability states that defense of a resource have costs, such as energy expenditure or risk of injury, as well as benefits of priority access to the resource. [[Territorial behavior]] arises when benefits are greater than the costs.<ref>{{cite journal|last=Brown|first=Jerram|title=The evolution of diversity in avian territorial systems|journal=[[The Wilson Bulletin]]|date=June 1964|volume=76|issue=2|pages=160–169|jstor=4159278}}</ref>

Studies of the [[golden-winged sunbird]] have validated the concept of economic defendability. Comparing the energetic costs a sunbird expends in a day to the extra nectar gained by defending a territory, researchers showed that birds only became territorial when they were making a net energetic profit.<ref>{{cite journal|last=Gill|first=Frank|author2=Larry Wolf|title=Economics of feeding territoriality in the golden-winged sunbird|journal=Ecology|year=1975|volume=56|issue=2|pages=333–345|jstor=1934964|doi=10.2307/1934964}}</ref> When resources are at low density, the gains from excluding others may not be sufficient to pay for the cost of territorial defense. In contrast, when resource availability is high, there may be so many intruders that the defender would have no time to make use of the resources made available by defense.

Sometimes the economics of resource competition favors shared defense. An example is the feeding territories of the [[white wagtail]]. The white wagtails feed on insects washed up by the river onto the bank, which acts as a renewing food supply. If any intruders harvested their territory then the prey would quickly become depleted, but sometimes territory owners tolerate a second bird, known as a satellite. The two sharers would then move out of phase with one another, resulting in decreased feeding rate but also increased defense, illustrating advantages of group living.<ref>{{cite journal|last=Davies|first=N. B.|author2=A. I. Houston|title=Owners and satellites: the economics of territory defence in the pied wagtail, ''Motacilla alba'' |journal=Journal of Animal Ecology|date=Feb 1981 |volume=50|issue=1|pages=157–180|doi=10.2307/4038|jstor=4038}}<!--|access-date=4 December 2012--></ref>