Unit 6 Avian Behavior

Annual Cycles Birds face seasons of stress and seasons of opportunity Caused by month to month changes in day length, climate and resources in their habitats

Permanent Residents Birds that do not migrate face three main, sequential tasks they must perform Breed Molt Survive until the next breeding season

Migrants Migrants have special tasks to worry about Breed Molt Flock and fuel Migrate

Biological Clocks Devices found in the cells of birds that control the release of hormones and other chemicals that regulate metabolism, reproduction and behavior

Circadian Rhythms Every individual has an intrinsic rhythm approximately 24 hours in length in which the rate of metabolism, body temperature, and level of alertness fluctuate in predictable ways

Circannual Cycles Internal rhythms approximately one year in length that determine activities throughout the year Due to photoperiod (the # of hours of light and dark in day) Birds monitor day length using special receptors in the hypothalamus of the brain

Breeding Seasons Over many generations, individual species have found the best time for the group to breed Timing of breeding deals with food supply for parents and young, availability of nest sites, location of favorable climates, and times of low predatory risk However, this does not account for unpredictable things like drought or parasites

Energetic Cost of Reproducing Breeding must be timed so that food availability exceeds that of normal activities Birds must molt (breeding plumage) set up territories, mate and find food for young, then molt again Usually in winter months, there is only enough food for self-maintenance