Why Another Checklist?
This project started in 2006 as a way to try to explain to some friends some of the new ideas that might lead to rather drastic changes in bird checklists. The initial intent was to focus on the Metaves hypothesis and potential changes in the Emberizidae (sensu lato).
As I started to write it up, I noticed more and more changes both being made to bird checklists and in the literature. The project grew into a longish essay I put on the web in 2007. However, the more I worked on it, the more there was to do! I found that a family-level listing wasn't enough. The composition of the families was changing too. I needed to go down to the generic or even species level. I needed to make my own world checklist.
Unlike other checklists, this one is based on genetic studies to the highest degree possible. With one or two exceptions, it relies on published studies (including those available “ahead of print”). The strong focus on genetics means that previous morphological studies are often treated as second-class citizens. This is especially true when they aren't consistent with the genetic data, even if the genetic data is somewhat soft. Nonetheless, I rely on such analyses to fill in the gaps left by the genetic data.
My approach contrasts with most checklist committees. They usually put substantial weight on traditional classifications, and which try to avoid speculation, even when its clear that the traditional classification is wrong. In particular, they try to avoid making erronenous changes, and put a premium on stability.
The purpose of this checklist is speculation. I'm trying to map out potential changes in the taxonomy. The price of this is giving up stability. I try to avoid erroneously maintaining the status quo, and try to keep abreast of the latest findings, even if incomplete.
The truth is that much of the genetic analyis is incomplete. It is still the case that only part of the avian tree has reliable results. For the rest, some is still relatively uninvestigated, some has results that are not clear cut, and some studies are not well executed. In some cases I've taken my best guess based on available data, sometimes speculating well beyond the genetic data.
The instability of the TiF worldlist may make it unsuitable for everyday use, although it should serve the useful function of highlighting potential changes regardless of your preferred checklist. Unlike a print checklist, the TiF list can be easily updated as new information, corrections, and better interpretations come to my attention. The “What's New” button at the top will show you the latest changes.
Those who follow the checklist will notice that I've bumped the version number up to 2.5. This indicates the adoption of an explicit genus-level phylogenetic hypothesis for most bird families, embodied in tree diagrams. I expect this will substantially increase the stability of the TiF list.
Previously, only the combination of Sibley and Monroe (1990) and Sibley and Ahlquist (1990) had attempted anything of this sort (the famous “tapestry”). From the beginning, the TiF list has used an explicit family-level tree. That has now been extended to a genus-level tree for most families. In some cases it has been pushed to the species level, and in a very few cases, to subspecies.
The list was originally based on the 3rd edition Howard and Moore checklist, but the species list has been modified based on decisions by recognized authorities and publications in ornithological journals. The overall species list is now most similar to the IOC list. I have also made heavy use of the SACC and HBW projects. The SACC is to be particularly commended for their open revision process, which provides unparalleled information about why particular taxonomic changes were made. For those interested in lumps/splits and other changes in bird taxonomy, I recommend Richard Klim's Holarctic Checklist, Don Roberson's Bird Families of the World, and the Bird Taxonomy and Nomenclature Forum at BirdForum.
The Checklist
The TIF checklist currently groups the birds in 44 orders and 235 families. Both a order-level and family-level trees are now availalbe in pdf format. Due to its length, the family tree is split into 5 parts.
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| 44 Orders | 235 Families |
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The checklist can be viewed in two ways. You can either view the annotated checklist on these web pages or download a list. The downloadable lists are csv files that can be imported into spreadsheets such as Excel, or easily manipulated by programs such as perl. Four lists are available in csv format. The ABA and AOU lists above include only ABA or AOU species, but in TiF order, with TiF families. The S. American list has a slightly different species list than the AOU's SACC working list.
Further, Stephen Nawrocki has provided an excel version of the worldlist.
You can view an annotated version by clicking on the list of bird orders on the right, or by going to the family index, or by clicking on the family names in the various tree view pages. In the annotated list, recently extinct species and species whose taxonomic placement is particularly uncertain are color-coded. In some cases, superfamilies, subfamilies, tribes, and other groups have been added to help show how the birds are related.
Scientific Names of Species and Groups
Linnaeus established a hierarchy of ranked groups for use in taxonomy. The number of ranked groups has expanded considerably since his time. His naming system is based at the species level. A species name has two parts, a genus name and a specific epithet. The genus, which is capitalized, denotes a group of similar birds, the specific epithet indicates which one. Thus Piranga rubra denotes the Summer Tanager, one of 9 tanagers in the genus Piranga. The Summer Tanager has a particular status among all of the Piranga. It is the type species. It defines Piranga as the genus that includes the Summer Tanager.
We group similar genera into families, families in orders, and orders into classes. The class Aves includes all birds, and nothing but birds. The names of the various ranked groups are usually constructed from the generic names with their level distinguished by a suffix. The ranks commonly used in bird classification are, from highest to lowest, superorder (-imorphae), order (-iformes), suborder (-i), infraorder (-ides), parvorder (-ida), superfamily (-oidea), family (-idae), subfamily (-inae), and tribe (-ini).
As with genera, the scientific name of each group is usually based on a type species, on the oldest-named type species in the group. Thus Parulini is the tribe containing Parula americana (the type species of Parula), while Parulidae (the wood warblers) is a family containing Parula americana. The standard ranks are insufficient to organize the complexity of the tree of life, and various un-ranked groups will also be used, sometimes with informal names. Informal names that are unique to these pages or used in a non-standard way are indicated by single quotes.
A number of the existing avian families have long-established names that predate these conventions. In those cases the old name continues to be used. One such example is the Cathartidae, the American Vultures. The oldest genus name in the group is Vultur, not Cathartes. However, Vultur orginally contained both New World and Old World vultures and as orginally constituted did not have a clear type species. It was only later restricted to the Andean Condor. This may be why Cathartidae came into use. In any event, Cathartidae has been in use since at least 1840, and long use can trump temporal priority. In fact, Vulturidae has been very rarely applied to living birds. A google seach gives about 120,000 for Cathartidae, and only 3580 hits for Vulturidae, mostly concerning fossils. There are a number of other avian families where long use trumps priority.
The Avian Tree and the Linear Order
Why do we need these ranked groups? The relationships between the birds can be described by a phylogenetic network. When hybridization is not an issue, this network reduces to a tree. The root of the tree is the common ancestor of all living birds. There is a standard procedure that allows us to translate this tree into a linear order.
Much of the information in the tree is lost in translation. For this reason we include genera, families, orders, and other ranked groups to help show which birds are more closely related. The tree view shows the underlying phylogenetic tree that I have used in this list, down to family level. In many cases the actual order given is based on a genus or species level tree. The notes and references in the annotated list show where to find further information on this.
We construct a linear order by finding the oldest division in the tree, and then placing one group first and the other last. This procedure is repeated for every branch of the tree. It is completely arbitrary which group goes first at any point. This means that very many linear orderings can represent the same tree. I generally use the convention of putting the smallest group first, but sometimes the weight of tradition pushes me the other way. Sometimes, the splits seem to be than two-way. In that case the order may reflect a guess of what the underlying two-way splits are. You shouldn't infer that families listed sooner are somehow older than families listed later. An equal amount of time has passed for both since their common ancestor. Which is actually genetically closer to their common ancestors depends on details of their history, details which we do not know.
Acknowledgements
I thank Gustav Asplund, Stefan Ericsson, Peter Kovalik, Marek Kuziemko, Lothar Lorenz, Stephen P. Nawrocki, Jonas Nordin, Daniel Philippe, Stephan Pickering, Sandy Rae, Laurent Raty, and Kristof Zyskowski for their helpful comments and suggestions.