Mono Lake in eastern California is an unusual lacustrine environment.  It is hypersaline and quite alkaline (pH is about 10).  The size and chemistry of modern Mono Lake has been strongly influenced by human activity, principally by the diversion of water from the inflowing Owens River to the Los Angeles urban area.  About three dozen species of birds use the lake as a resting site during migration, as a source of food (brine shrimp), and as a nesting site.


Bird nests along the shores of Mono Lake can be subject to inorganically- & biogenically-induced encrustation by calcite and aragonite (CaCO3) (calcium carbonate) when lake levels rise after storm/flood/runoff/snowmelt events.  The specimen below shows a bird nest having two eggs encrusted by calcium carbonate (“calcareous tufa”, a friable precursor to travertine).  The hollow tubes surrounding the eggs represent molds of the stems of shore plants.


I’m calling this a fossil bird nest, but I doubt it is Pleistocene or older.  It’s more likely to be Holocene in age, and it is probably a California gull nest.


Bird nest (likely a California gull nest) encrusted by calcareous tufa from the shores of Mono Lake, eastern California, USA.

(Cranbrook Institute of Science collection, Bloomfield Hills, Michigan, USA)



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