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Avian eggshell thickness in relation to egg morphometrics, embryonic development, and mercury contamination
Sarah H Peterson1, Joshua T Ackerman1, Mark P Herzog1
1U.S. Geological Survey, Western Ecological Research Center Dixon Field Station Dixon CA USA.
Ecology and Evolution
|September 5, 2020
Summary
Bird eggshell thickness varies by location on the egg and is strongly predicted by bird body mass. Eggshell thickness is not affected by mercury contamination or embryonic development.
Area of Science:
- Ornithology
- Ecotoxicology
- Bioacoustics
Background:
- Eggshell thickness is crucial for avian physiological, ecological, and ecotoxicological studies.
- Empirical data on eggshell thickness for many bird species and regions are limited.
- Understanding eggshell thickness variations is vital for accurate avian research.
Purpose of the Study:
- To measure and analyze eggshell thickness in 12 avian species.
- To investigate the relationship between eggshell thickness and egg morphometrics, embryonic development, egg status, and mercury contamination.
- To provide a comprehensive review of existing eggshell thickness data for the studied species.
Main Methods:
- Eggshell thickness was measured at the equator and poles of eggs from 12 avian species.
- Relationships between eggshell thickness and egg morphometrics (width, length, volume), body mass, embryonic development, egg status, and mercury levels were analyzed.
- Data from monitored nests of American avocet, black-necked stilt, and Forster's tern were used to assess eggshell thickness in relation to egg viability and embryonic age.
Main Results:
- Eggshells were thicker at the equator than at the sharp pole (average 5.1% difference, varying by species).
- Within species, eggshell thickness correlated with egg width and volume for some species, but not egg length.
- Among species, mean eggshell thickness strongly correlated with mean egg width, length, volume, and bird body mass, with body mass being the strongest predictor.
- Eggshell thickness did not differ among viable, abandoned, dead, or unhatched eggs.
- No relationship was found between eggshell thickness and mercury concentration or embryonic age.
Conclusions:
- Bird body mass is the most significant predictor of mean eggshell thickness across species.
- Eggshell thickness varies within an egg and across species, influenced by morphometrics and body size.
- Eggshell thickness is a robust indicator, unaffected by mercury contamination or embryonic development stage in the studied species.
