Declining immunity with age in the wild

Area of Science:

• Evolutionary biology
• Gerontology
• Ornithology

Background:

• Birds generally exhibit slower aging and longer lifespans compared to similar-sized mammals.
• Field studies using banding-and-recapture methods track age-related changes in wild bird populations.
• While advanced senescence is rare in wild birds, physiological deterioration is observed.

Purpose of the Study:

• To review recent findings on aging-related changes in the immune response of European songbirds.
• To investigate immunosenescence in wild barn swallows and collared flycatchers.
• To explore the link between immunosenescence, fitness, and the evolution of aging.

Main Methods:

• Challenging the humoral immune response of free-ranging adult birds during the breeding season.
• Administering antigens (Newcastle disease virus and sheep red blood cells) to assess antibody production.
• Monitoring antibody titers, offspring body mass, and survival rates in relation to age.

Main Results:

• Older barn swallows, especially breeding females, exhibited lower antibody responses to Newcastle disease virus.
• Older female collared flycatchers produced lower antibody titers to sheep red blood cells compared to younger breeders.
• Offspring of older female flycatchers had lower average body masses.

Conclusions:

• Age-related declines in immune function (immunosenescence) are evident in wild songbirds.
• These immune changes may have implications for reproductive success and offspring health.
• Studies in wild populations can bridge laboratory research with understanding the evolution of aging.