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Published on: August 22, 2018
Determinants of eggshell strength in endangered raptors
Aurora M Castilla1, Anthony Herrel, Stefan Van Dongen
1Estación Biológica de Sanaüja, Agencia Estatal Consejo Superior de Investigaciones Científicas (CSIC), Solsona, E-Lleida, Spain. castilla.aurora@gmail.com
Summary
Falcon eggshell strength varies significantly with falcon size, with smaller species having thinner, softer eggs. Female body mass, age, and laying order also impact eggshell thickness and hardness.
Area of Science:
- Avian biology
- Conservation science
- Reproductive ecology
Background:
- Eggshell strength is crucial for reproductive success and can be influenced by environmental factors.
- Previous research has primarily focused on contaminants like DDE affecting eggshell thinning in raptors.
Purpose of the Study:
- To investigate factors influencing eggshell thickness and hardness in various falcon species and hybrids.
- To provide quantitative data on eggshell characteristics beyond contaminant effects.
Main Methods:
- Comparative analysis of eggshell strength (hardness and thickness) across different falcon taxa (e.g., peregrine, gyr, saker falcons) and their hybrids.
- Statistical modeling (linear mixed models) to assess the influence of female body mass, age, and laying order on eggshell properties.
Main Results:
- Smaller falcons (<1,000 g) exhibited significantly softer and thinner eggshells compared to larger falcons (>1,000 g).
- A positive correlation was found between eggshell hardness and thickness.
- Heavier females produced larger, harder eggs with thicker shells and membranes; older females and later eggs were smaller and softer.
Conclusions:
- Falcon body size is a primary determinant of eggshell strength.
- Female characteristics (mass, age) and laying sequence significantly influence eggshell properties.
- Hybridization did not negatively impact eggshell hardness or thickness in the studied species.
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