Key Points from Bird Behavior and Physiology

Territoriality in Birds:

• Primarily males defend territory; females may also defend, particularly during winter.
• Both sexes usually participate in defense of space.

Colony Study:

• Study involved swapping young birds from large colonies with those from small colonies.
• Objective: To determine if preference for colony size is innate or environmental.
• Result: Birds showed preference for their hatch colony size, indicating genetic basis for colony nesting.

Flocking Behavior:

• Flocking occurs when resources are unstable or abundant, making individual territorial defense unworthy.
• Benefits of flocking include:
• Antipredation: Flocking is an anti-predator adaptation.
• Increased competition for food and disease risk in large flocks.

Predation and Flock Size:

• Study by Tarako explored time spent feeding vs. flock size.
• Flock size increases fighting time and decreases individual predator scanning time; optimal flock size estimated at four birds, shifting to seven with predator presence.

Mixed Species Flocks:

• In tropical areas, birds join mixed flocks, recognizing warning calls and maximizing feeding while minimizing predation.

Hormonal Influences on Behavior:

• Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH) from the anterior pituitary trigger gonads (testes) for testosterone production.
• Testosterone influences behavior (mating, singing, territoriality) with feedback mechanisms balancing levels based on external factors.

Reproductive Structures:

• Males may exhibit colliculoprotuberance, a sperm storage structure enhancing competition.
• In species with cloacophalli (waterfowl), males engage in forced copulation.

Sperm Competition and Fertilization:

• Variation in sperm counts among bird species (1.7 to 8 billion sperm per ejaculate).
• Fertilization occurs when sperm swim up the oviduct post-follicle rupture, utilizing the acrosome for penetrating the egg membrane.