Increased Reproductive Output and Telomere Shortening Following Calcium Supplementation in a Wild Songbird

Area of Science:

• Animal Ecology
• Evolutionary Biology
• Physiological Ecology

Background:

• Life history theory posits that increased parental investment incurs fitness costs, impacting survival and future reproduction.
• Calcium is vital for avian reproduction, essential for egg production, embryo development, and nestling growth.

Purpose of the Study:

• To investigate the costs of reproduction and life history trade-offs in tree swallows (Tachycineta bicolor).
• To experimentally assess the effects of calcium supplementation on reproductive investment and fitness proxies.

Main Methods:

• Nesting female tree swallows at a high-elevation Colorado site were supplemented with calcium during the breeding season.
• Telomere length, a proxy for fitness and longevity, was measured at the beginning and end of the breeding season.
• Reproductive output and offspring telomere length were analyzed in relation to maternal calcium supplementation.

Main Results:

• Calcium-supplemented mothers exhibited higher reproductive output.
• Offspring of supplemented mothers had longer telomeres.
• Mothers who received calcium supplementation experienced relatively shorter telomeres by the end of the reproductive season.

Conclusions:

• The study supports the existence of reproductive trade-offs, where increased reproductive effort leads to costs for the parent.
• Findings challenge previous research suggesting that excess calcium may reduce the costs of reproduction.
• Experimental manipulation of calcium availability provides insights into the biological responses and costs associated with reproduction.