The Furnarids are a bird family - a group of species that share a common ancestry. They are to be found only in South & Central America. There are over 200 different species of Furnarids, of which over 70 are listed for Argentina and found in every kind of habitat. Feather colors combine rufous, browns and greys. Many are habitat specialists and can be very secretive and hard to identify in the field - therefore knowing the calls is most helpful. Another common feature is that their nests are always enclosed. However, the nest construction technique and materials used to build such structures vary enormously between species, ranging from hollows in trees, mud banks or under rocks, globular nests built of twigs and placed inside bushes, on trees or on posts; others are made of reeds or grasses. And let us not forget the remarkable soccer-ball sized "clay oven" built by the Horneros.
The phylogeny ("family tree") of the Furnariidae followed here is based on recent DNA studies (listed below) that helped to resolve the relationships within this enigmatic group. They exposed several cases of convergence, i.e., where similar traits have evolved separately, often leading to confusion when trying to sort out the family tree by features such as morphology, habit use, etc. The new molecular studies use DNA comparisons to arrive at a more robust result, showing 5 branches within Furnariidae.

The studies propose the following evolutionary story of the family: originally these birds were all cavity nesters, living in dense rainforests. Tree-cavities imply an enclosed nest with a small opening. The rising of the Andes range some 40 million years ago, however, produced great changes to the the continent's climate and vegetation, creating areas such as Patagonia, a vast rainshadow zone of arid steppes and bushland. In other parts forests gave way to the pampas grasslands, open wetlands, scrub, deserts, puna, etc. Furnarids were able to adapt, conquer and survive in all of these new habitats. It is thought that this "radiation" of species owes its success to a remarkable ability: being able to construct an enclosed nest with whatever resources are available in their specialized niche, employing widely different construction techniques. Notably the Furnarids have all kept true to that ancestral design concept of nesting in enclosures, while the resources have determined where and how the nest is built.
These papers propose that this extraordinary plasticity shown by the Furnariidae was key to the success of the family, allowing it to radiate, evolve, and adapt to all of the habitats found in South America.
The "family tree" shows a clear tendency of how the earlier species are forest birds, while the more recently-evolved species are adapted to open, often treeless habitats, such as reedbeds. It is quite exciting to refer to this evolutionary story when seeing these birds in the field, and also to recognize some convergences, such as with the Reedhaunters, previoulsy thought to be closely related but now placed in different branches.
Sadly, habitat specialization also spells trouble for the conservation of these species. While few species are currently threatened, the development and land use changes that are occuring in South America (be it in wetlands, forests or arid areas) will undoubtedly be problematic.
Many thanks to the authors of these wonderful papers! AE