Posts Tagged 'nests'

How many eggs were laid?

Here is a nice pile of eggs on display at the IVPP. As is quite common in dinosaur nests, there are several layers here and while it is subtle, there is a curve to the arrangement of the eggs to give an indication that these eggs were originally laid in a broad circle.

Clearly this nest is rather incomplete and would have originally contained many more eggs. Taking an estimate of that total from this little is probably a bad idea but there are more complete nests out there and some are apparently absolutely complete and every egg can be identified and counted. Great news in general of course, but does this mean we know how many eggs were laid by the mother?

You might think ‘well, obviously’ but sadly the situation is far less clear than this. Looking to the birds a great many small passerines lay two or sometimes even more clutches a year. Just finding a nest of half a dozen eggs doesn’t mean that this was the some total of the eggs laid by a mother that summer. Other birds are communal nesters with lots of females all dumping their eggs together into a single nest. Or males can solicit females to lay in their nest and so accumulate eggs from multiple females, though perhaps only one or two from each.

In short, even finding a nest of a couple of dozen eggs being brooded by an animal is no great guarantee that those eggs were laid by one female, or that was all she laid. It’s not, I hasten to add, a poor assumption but equally it’s far from certain. Which is rather a shame as obviously and understanding of the reproductive output of an individual (and thus a conceptual one for a species) can really help our understanding on dinosaur biology and ecology. I wouldn’t argue against using this kind of data, but I’d be quite cautious about how it could be used.

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