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Data from: Preston’s universal formula for avian egg shape

Cite this dataset

Biggins, John D; Montgomerie, Robert; Thompson, Jamie; Birkhead, Tim (2022). Data from: Preston’s universal formula for avian egg shape [Dataset]. Dryad.


The main data are 50 photographs of eggs, one from each of 50 species. 

25 of these species have pyriform eggs, based on the traditional usage of this descriptive term.

The photographs were taken to allow an investigation of egg shape, so they are lit from behind to provide a clear silhouete and were arranged to have the plane containing their longest axis parallel to the 'film' plane.

A csv file contains basic information about each egg.

A second csv file contains the results of processing these photographs (using the script GetErrors.R) to assess the error associated with various methods of summarising egg shape, including Preston's universal formula.

A third csv file conatins some summary information on many more eggs obtained from a different study.


The eggs are in Museum collections. They were photographed and measured on site.

The photographs are processed using GetErrors.R 

For each egg, this produces the errors arising from various methods of summarising the egg's shape.

The output from GetErrors.R provides the 'raw' data for various comparisons of the methods for sumamrsing shape.

Using this output, FigTables.R performs the analysis reported. 


Leverhulme Trust, Award: RPG-2015-221