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3 Published Studies and a 3D Leap Ahead: Professor Mark Hauber’s Triple Slam

3 Published Studies and a 3D Leap Ahead: Professor Mark Hauber’s Triple Slam

Professor Mark Hauber

The spring semester ended on a trill of high notes for Mark Hauber, an expert on the evolution and behavior of birds.

“It’s been a good week,” Hauber said as he received widespread attention for his three new studies, published in quick succession in separate scientific journals.

Biology Open published Hauber’s study of how avian eggshells absorb and reflect ultraviolet light. On the heels of that article came the other two – one in Biology Letters and one in PeerJ, each covering markedly different research.

In Biology Open, Hauber’s international team documented their quest to understand how white, unpigmented eggshells protect bird embryos from harmful UV rays. They found that the structure and chemical composition of the eggshell’s outer layer can selectively absorb UV light. 

True Colors

In Biology Letters, Hauber and his three co-researchers revealed that the entire spectrum of eggshell colors, so diverse and striking to the human eye, represents only part of the spectrum birds are capable of seeing. They made this surprising discovery by studying the eggs of more than 600 bird species, viewing color as the birds’ own eyes would.

“Birds and humans both see the same pattern of light reflected by the eggs, but for birds, the resulting colors are very limited compared to what they could see,” Hauber said of his findings. “They have four color receptors in their eyes, while we have only three. So a bird’s color world is much more fine-tuned than ours.”

He noted that to birds, eggs appear 200-400 times less colorful than feathers, and continued, “We always thought bird eggs were as colorful as feathers and flowers, largely because eggs are so diverse in their appearance. But that diversity is due to patterns rather than colors. Egg color is an ancient trait, based on just two unchanging underlying pigments, and preserved throughout the evolutionary history of birds.”

Hauber now plans to test numerous hypotheses of why evolution has resulted in the specific colors and patterns we see on eggshells today.

One Word: Plastic

The study published in PeerJ was pioneering in its use of new technology.

Like previous studies of the same phenomenon, this one by Hauber, Professor Mandë Holford of Hunter, and other members of an international team looked at how often a particular bird species rejected “alien” eggs – those commonly dropped into the nest by another species, whose parasitic goal is to fool the nest’s occupant into protecting the eggs and raising the offspring. Breaking with tradition, Hauber and his team used 3D plastic printing to create the artificial eggs central to this research.

Up to now, similar studies have used fake eggs made of wood or plaster. But as Hauber pointed out, that longstanding egg-construction process is laborious, imprecise, and prone to human error. His 3D-printed plastic eggs have the benefit of uniformity, and a hollow center that can be filled with gel for a more convincing feel.

Hauber focused on American robins and the alien eggs of brown-headed cowbirds, because despite differences in appearance – robin eggs are blue, cowbird eggs are beige – robins are often fooled into accepting cowbird eggs as their own. When the plastic eggs were made to resemble cowbird eggs, 79 percent were rejected by the robins – the same rate achieved by real cowbird eggs. When the plastic eggs looked just like robin eggs, the rejection rate was a remarkable 0 percent.

In addition to being recognized by his peers for this new methodology, Hauber is receiving attention from the national media, including The Washington Post, The Christian Science Monitor and NPR. An article in Forbes reiterated the PeerJ article’s point that beyond its demonstrated uses for bird-egg research, 3D printing has the potential for widespread applicability across disciplines.

“For scientists, there is lots of brainstorming potential,” Forbes observed, “to study what Hauber and his team did and extend it into completely new and unrelated research areas.”

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