LIU Biology Professor's Research on Colored Eggs Provide Novel Insights Into How Nesting Birds Behave

BROOKVILLE, N.Y., May 17, 2019 /PRNewswire/ -- A team of scientists led by LIU Post Biology Professor Dr. Daniel Hanley have used a new experimental approach to study how birds evaluate whether an egg in their nest belongs to them or whether it was left by a freeloader—apparently an all too common practice in the bird world. Their groundbreaking work has just been published in The American Naturalist.

Birds' eggs can range in color from blue-green to brown, and can often be speckled. Traditional theory assumes that if the egg appears quite similar to their own, then a bird will likely accept it, but if it differs dramatically, the bird will reject it.

A recent study led by Dr. Hanley, which was published in the prestigious Proceedings of the Royal Society B, discovered that host birds in Europe and North America actually respond to some colors more fiercely than to others. It seems that hosts—what the foster parents are called—really "dislike" brown eggs and remove them at a much higher rate than blue-green eggs, despite how different they appear from their own eggs. Interestingly, in another new paper by Dr. Hanley and his colleagues, Hanley's team discovered that these same behaviors are also exhibited by an unrelated host that lives in South America. These findings illustrate that we have a lot to learn about how wild birds use color information in their decision making.

In their recent paper published in The American Naturalist, Dr. Hanley and his colleagues, Dr. Mark Hauber (University of Illinois Urbana-Champaign), Tomáš Grim and Karel Gern, used an experimental approach to study how the common blackbird responds to an unprecedented range of colors. Since birds can see a far greater range of colors than humans can, Dr. Hanley and co-author Karel Gern made a bird-specific color wheel to make paints for coloring artificial eggs. They manipulated the three main components of color: hue, saturation (i.e., intensity) and brightness. Dr. Hanley found that birds responded strongly to a far greater array of colors than had been previously tested. Also, the researchers found that the components of color interacted in the birds' perceptual space. For example, birds may respond to some hues only when they are intensely colored.

Armed with this new information, Dr. Hanley and his colleagues will probe the subtle differences in color perception among birds around the world. The nearly 10,000 species of birds have a wide range of evolutionary histories and ecologies, which have led to unique perspectives that this research group plans to explore. In a way, these birds are showing the authors their true colors.

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