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Unveiling Clutch Investment Strategies in Birds: A Case Study on Great Tits Using Generalized Additive Models
Lluís Socias-Martínez1, Elena Álvarez2, Louise R Peckre3
1Department of Sciences and Technology, Institut National Universitaire Jean-François Champollion The University of Toulouse Albi France.
Ecology and Evolution
|July 3, 2025
Summary
Great tits generally use a brood survival strategy, investing resources evenly across eggs, with slight favoritism towards middle eggs. This reproductive strategy shows limited plasticity and avoids negative environmental impacts.
Area of Science:
- Avian reproductive biology
- Behavioral ecology
- Evolutionary biology
Background:
- Parental investment in birds involves trade-offs in resource allocation among offspring.
- Hypotheses on egg investment include brood reduction versus brood survival strategies.
- Previous studies often overlooked non-linearity and temporal autocorrelation in egg investment.
Purpose of the Study:
- To analyze within-clutch variation in egg investment in great tits (Parus major).
- To test hypotheses of brood reduction versus brood survival strategies.
- To evaluate the influence of laying order, clutch size, and environmental factors on egg volume.
Main Methods:
- Analysis of 145 broods (1084 eggs) from a great tit population.
- Application of generalized additive mixed-effects models (GAMMs) to account for non-linearity and temporal autocorrelation.
- Examination of egg volume variation in relation to laying order and environmental variables.
Main Results:
- Egg volume varied with laying order, increasing from first to middle eggs, then slightly decreasing.
- Females adopted a brood survival strategy with small volume variations (approx. 5%).
- No significant negative effects of clutch size or temperature on egg volume were detected.
Conclusions:
- Great tits employ a brood survival strategy, with slight favoritism towards middle eggs.
- Egg volume plasticity is limited, with most variation occurring between clutches.
- Generalized additive mixed-effects models (GAMMs) offer a robust method for analyzing reproductive investment, cautioning against over-reliance on mean egg volume (D).
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