A project undertaken at The University of Melbourne, and supervised by Dr Iliana Medina
Nests are some of the most beautiful structures in nature, and they are also vital for the survival of their builders. Despite this, there is limited information on how they evolve and their importance in the life of birds. Some species build complex nests and such structures with a roof and well insulated, could allow species to colonise novel and extreme environments. In this project we explored the idea that nest architecture could have an effect on the evolution of lineages. Specifically, we tested whether changing nest morphology could be a key evolutionary innovation and lead to evolutionary success.
Willie Wagtail.
Our work revealed that this was the case, but not in the way we expected. Species that build nests with a roof (domed nests) take more time to build their nests (often weeks instead of days). Crucially, we detected effects at a broad scale and our findings suggest that species with domed nests have smaller geographic ranges, higher extinction rates (at an evolutionary scale) and are also less likely to live in urban environments. All this suggests that building a nest that is costly could affect the ecological success of a species. Hence, the transition from building domed complex nests to building simple open cups could have been key in the dispersal and further success of birds. This is important, because it means that evolution does not always favour increasing complexity of structures, and in this case the key was building more simple nests. We need to do more research to understand what it meant for species to build nests that are much more simple and potentially less protective, but our findings highlighted that species with certain nest architectures might be more vulnerable.
Our data collected in the field and in museum collections in Australia and across the world make the story even more interesting. Building domed nests takes longer on average, but we also found there is incredible variation in the designs of species that build these types of nests. It is not known why there is such variation in architecture and whether it is important for the birds, or whether it is just the result of different personalities and individual building styles.
Domed nests.
Overall, our project allowed us to gain a deeper understanding on how nest architecture varies within and across species, and the effects that such variation can have at broad evolutionary scales. It demonstrates that building these constructions is a fundamental part of their lives, and building behaviours can have consequences that we had not imagined before.