Are Metal Concentrations in Lesser Flamingo Eggs and Eggshells Good Indicators of Environmental Pollution?

Abstract

Metallic elements in excess may cause adverse biological effects. Flamingos, with a lifespan of up to 50 years, are therefore likely to accumulate metals from the highly saline waters where they feed and breed. The concentrations of accumulated metals would be reflected in organs, feathers, and eggs. There are no data available on metals in flamingo egg contents. Concentrations of 24 elements in egg content and eggshells from Lesser Flamingo Pheoniconaias minor breeding at Kamfers Dam South Africa suggest metal pollution, but with considerable variation between eggs, reflecting their nonbreeding, nomadic movements. Strontium in eggshells exceeded toxic reference values. Copper in egg contents suggests reproductive stress. Lower than-expected metal concentrations (especially mercury) in egg contents we attributed to several excretory pathways prior to oogenesis and embryogenesis, thereby protecting the embryo. Molar concentrations of selenium and mercury were not correlated. However, the mean molar ratio of 8.2 suggests a highly protective effect afforded by selenium. Relative compositional differences show that eggshells are not a proxy for egg contents. We highlight previously unrecognised routes of post-hatching pollutant uptake via consumption of eggshells and parental crop milk. The post-hatching development of flamingo chicks may therefore be more susceptible to pollutant disruption compared with embryonic development. We conclude that P. minor eggs are not good indicators of environmental metal pollution, nor does it reflect post-hatching risks. This first report on metal concentrations in egg contents of any flamingo species shows that a more nuanced approach is needed to protect Phoenicopteridae from pollution.