Long-term insights into who benefits from brood reduction

Area of Science:

• Behavioral Ecology
• Evolutionary Biology
• Ornithology

Background:

• The resource-tracking/facultative brood reduction hypothesis posits that young birds are sacrificed under food stress to aid sibling survival.
• While studies support this, the direct beneficiaries, especially parents and post-fledging outcomes, remain under-researched.
• A life history perspective is rarely applied to brood reduction strategies.

Purpose of the Study:

• To investigate the beneficiaries of siblicidal brood reduction in blue-footed boobies (Sula nebouxii) under food stress.
• To examine benefits for mothers, fathers, and surviving offspring using a long-term dataset.
• To apply a life history perspective to understanding facultative brood reduction.

Main Methods:

• Utilized a 34-year individual-based dataset on blue-footed booby reproduction.
• Analyzed data to compare outcomes for mothers, fathers, and offspring from reduced versus intact broods.
• Focused on factors like survival, fledging condition, breeding probability, longevity, and lifetime reproductive success.

Main Results:

• Mothers of reduced broods showed a ~16% higher survival rate to the next breeding season.
• Surviving chicks from reduced broods achieved comparable fledging body condition, breeding probability, longevity, and lifetime reproductive success.
• No survival benefit was observed for fathers of reduced broods.

Conclusions:

• Facultative brood reduction in blue-footed boobies enhances maternal survival and ensures adequate growth for surviving offspring.
• Sacrificing a subordinate chick benefits mothers and surviving offspring, but not fathers.
• Experimental validation is recommended to confirm findings and explore underlying mechanisms.