But there are many ways to make adjustments. All of these have costs and benefits. I think the beloved hairy armadillo brings the above into question. It is small but preys on eggs of large rhea. It builds a labyrinth of tunnels neath nest.
Nest collapses under weight of rhea which then abandons nest.
I maintain it is that long stationary period which is the major liability to egg layers, i.e., it allows predators more time to find them. Also, precociality in mammals is a very different thing than in birds. I mean, inasmuch as organogenesis is extended regardless in mammals. He says that their entire breeding system has evolved under the primary influence of nest and hatchling predation.