Social Behavior

Front 1

Flocking is favored when.

Back 1

• Incurred costs of defending a specific space outweigh resulting benefits
• Space does not have adequate resources
• Space is not economically defensible

1. Density of resource to low
2. Density of resource to high

Front 2

Flocking

Back 2

-an aggregation of individuals

• Loose temporary groups
• organized temporary foraging associations
• long-term foraging associations with exclusive membership

Front 3

Dominance in Flocks

Back 3

• Stable flock membership facilitates Individual recognition and development of dominance hierarchy
• Mostly linear hierarchies
• Social Rank increase with

1. Size
2. Age
3. Tenure in flock

• Dominance relationships lower frequency & intensity of overt hostility

Front 4

Feeding in Flocks

Back 4

• Cooperative feeding

1. Capture ability improves when part of a group
   

• The "beater effect"

1. Prey that is flushed & missed by one bird can be grabbed by another

• Learned food locations(improved search)

Front 5

Safety in Flocks

Back 5

• Predator detection

1. Flock members warn each other of danger & flee at the same time

• Contact calls used to maintain cohesive flock structure
• Alarm call used to warn about danger

2. Each member of flock can thus spend less time looking for predators & more time eating than if alone

• time for eating also lost to aggressive interactions with increases with group size
• So intermediate group size is likely ideal

3. Mobbing behavior

• Drives off predator.. reducing risk
• Teaches predator recognition to inexperienced members

Front 6

Mixed-Species Flocks

Back 6

• Tropical flocks may include 60 birds of 30 different species
• Temperate flocks average 10 to 15 birds of 6 or 7 species
• Migratory flocks can be 100's or even 1000's of birds of many different species

Front 7

Mixed-Species Flocks

Back 7

• Flock sizes increases primarily as a result of
• The addition of new species
• less within niche competition
• not more individuals of a few species
• Nuclear species provide main element of flock structure
• "Followers" join opportunistically & are subordinate to the nuclear species

Front 8

Advantages Pertain to Multi-species Nesting Colonies

Back 8

• Combined numbers maximize anti predator behavior

1. Social Interactions
2. Information transfer

• Ecological differences minimize competition

1. for next locations
2. for food