Double brooding in house wrens is repeatable but constrained by time-of-season

Area of Science:

• Behavioral Ecology
• Avian Reproduction

Background:

• Some bird species produce multiple broods per season to enhance reproductive success.
• However, not all individuals in species like the northern house wren (Troglodytes aedon) initiate a second brood, even with sufficient time.

Purpose of the Study:

• To determine if individual quality, beyond seasonal timing, affects the likelihood of northern house wrens producing a second brood.
• To investigate the influence of age, body condition, and territory quality on second brood production.

Main Methods:

• Analysis of long-term breeding records to estimate the repeatability of second brood production.
• Cross-fostering experiments involving eggs from early- and late-nesting females to assess the impact of nesting date manipulation on second brood initiation.

Main Results:

• Individual traits like age, body condition, and territory quality showed little effect on second brood production.
• Cross-fostered females whose nesting was advanced were more likely to produce a second brood than controls.
• Second brood production was highly repeatable, with repeatability increasing significantly after accounting for first brood timing.

Conclusions:

• Individual characteristics play a substantial role in the likelihood of producing a second brood, independent of seasonal timing.
• While repeatability suggests inherent individual effects, the specific traits responsible remain unidentified and warrant further investigation.