Birds’ eggs are famously colourful and display varied and striking patterns, capturing the attention of many scientists and artists since time immemorial. But how diverse are avian eggshell colours after all?
Daniel Hanley, assistant professor at Long Island University – Post and his team of biologists at Palacký University, Hunter College, and the University of Adelaide looked into the colour palettes of birds’ eggs to see what the root of the diversity of egg colours is. Specifically, they wanted to investigate if the variety of patterns and colours could be created by the blue-green and brown pigments that are known to exist in birds’ eggshells.
Our optimization procedure required 1,293,600 unique combinations of model parameters, and upon each we ran a complex model on MetaCentrum’s computers and compared these to real measurements.
They started by deploying a reflectance spectrometer to measure the colour of eggs from more than 600 different types of birds found all over the world. The team then used a model to generate the colours that would be produced by mixing variable amounts of blue-green and brown pigments. They used the high-performance cluster provided by Metacentrum (the Czech representative of EGI) to generate predictions of all possible combinations of pigments.
“MetaCentrum’s resources were vital in our calculations”, says Hanley. “We varied other parameters in the colour mixing model, which meant that there were very many combinations – a difficult task for a standard computer”.
“The resources provided by MetaCentrum allowed us to optimise the model parameters and then generate all possible combinations of mixtures of these two pigments both very quickly and in much more detail than we could have otherwise”, Hanley adds.
Finally, Hanley and his colleagues compared the actual measured colours of birds’ eggs to these theoretical, pigment-based colours.
They found that the birds’ eggshells can look very different, but in fact they are actually not that diverse. For starters they represent less than 1% of the colours birds can see. Moreover, the team established that this limited colour diversity matches their predictions from the mixing model. This conclusion, published in Biology Letters, confirms that the egg diversity we see is due to combinations of blue-green and brown pigments.
Photographs of eggs: Daniel Hanley
Layout: Libor Vaicenbacher
Hanley et al. 2015 Not so colourful after all: eggshell pigments constrain avian eggshell colour space. Biology Letters, doi: 10.1098/rsbl.2015.0087