The picture above is a shot of a Victorian-era museum collection of wild bird eggs. These kinds of fantastic collections began around the time of Darwin, with egg collection an outgrowth of egg collections gathered for scientific purposes and a spontaneous outgrowth of curiosity about the diversity of the natural world coupled with the kind of relative (and conspicuous) wealth that allows people to travel to collect, buy and display curiosities that otherwise have no useful and practical purpose.
Bird egg collecting proved to be such a fad that collection of rare bird eggs threatened to tip certain rare birds over the abyss into extinction. In 1954, the Wild Birds Protection Act in the U.K. made it illegal to posses or own any wild birds' eggs taken since that time, and today it is illegal to sell any wild bird's egg, irrespective of their age -- a fact that is now true in the U.S. as well.
Ironically, old bird egg collections are an important resource for scientists studying bird biology, enabling them to track the rise of pesticides and other contaminants in the food chain.
The eggs, above, are a couple of odd ones I had around the house.
The dark one is an emu, the largest eggs is an ostrich, and the other two are chicken eggs that I had for breakfast.
I include the chickens eggs to show the scale of the other two, but also to show the diversity of what eggs can look like. Egg identification, without benefit of a nest or provenance, can be pretty hard, as bird eggs can change shape to some extent. Coloration and markings may also shift from bird to bird as well. Egg identification is an in-egg-zact science, especially where speciation is not complete (a surprisingly large number of birds) and the number of look-alike eggs are quite numbing.
Another small thought: We have pushed a lot of birds over the edge to extinction and near-extinction, but I am always struck by the fact that we never give credit to the fact that a lot of species (or what we would call species if they were wild) are now being created by man.
Chickens alone present a startling array of expressed diversity, to say nothing of cattle, roses, corn, broccoli, etc. We are already creating new species of birds (falcon and parrot hybrids are examples) and fish (hybrid trout, salmon, pan fish, etc.). to say nothing of the many odd things being done with recombinant DNA to make animals and plants grow larger, be more resistant to disease, and ship better.
We stand in the door of one of the largest booms in species creation ever, and yet when was the last time anyone gave that idea a nod? And yet, take a look at the two chicken eggs, pictured above. Would any birder claim these eggs were from the same species?