Charadriiformes

The 46 Orders

Paleognaths

Galloanserae

Metaves

Pelecanae

Charadriae

Passerae

CHARADRIAE

CHARADRIIFORMES Huxley 1867

There is a single order in Charadriae, the Charadriiformes. The Charadriiformes include 22 families, with 94 genera and 371 species ranging from shorebirds to gulls to alcids. The Charadriiformes have been carefully studied in recent years and DNA methods have proven especially effective at unraveling the taxonomy. We not only know how most of the various families relate, but we also have a good handle on many of the genera (the large white-headed gulls continue to puzzle).

There is a lot of evidence for monophyly of the Charadriiformes as consituted here (e.g., Ericson et al., 2003a; Paton et al., 2003; Cracraft et al., 2004; Thomas et al., 2004a; Paton and Baker, 2006; Baker et al., 2007; Fain and Houde, 2007). Other than arguments about the Herring Gull complex, the taxonomy of this order is now pretty well worked out. Many studies have found that gulls and alcids are closely related to the shorebirds. Collectively, these analyses have made it quite clear that the sandgrouse (Pteroclidae) and bustards (Otididae) are not Charadriiformes. They have also shown that the buttonquail (Turnicidae) and Plains-wanderer (Pedionomidae) are Charadriiformes. The position of the buttonquail is also supported by morphology (Mayr, 2008).

To help make the taxonomy clear, the Charadriiformes have been divided into 5 suborders: Chionidi, Charadrii, Limicoli, Turnici, and Lari. The 2 page genus-level Charadriiformes tree, shows how it fits together. To improve clarity, the tree includes only the suborders, families, and genera (no subfamilies or tribes).

Click for Charadriiformes tree
Click for Charadriiformes tree

Chionidi Sharpe, 1891

Pluvianellidae: Magellanic Plover Jehl, 1975

1 genus, 1 species Not HBW Family

Chionidae: Sheathbills Lesson, 1828

1 genus, 2 species HBW-3

Burhinidae: Thick-knees Mathews, 1912 (1840)

2 genera, 10 species HBW-3

Charadrii Huxley, 1867

Pluvianidae: Egyptian Plover Reichenbach, 1848

1 genus, 1 species Not HBW Family

Although it is sometimes put in its own family, the Egyptian Plover is typically considered a member of the Glareolidae (pratincoles and coursers). Ericson et al. (2003a), Baker et al. (2007), and Fain and Houde (2007) make clear it is nowhere close to the Glareolidae. All three found it to be basal in the Charadrii (in our sense). Further, all found it to be sister to the remaining Charadrii, which justifies placing it in its own family.

Pluvialidae: Golden-Plovers MacGillivray, 1852

1 genus, 4 species Not HBW Family

One big surprise to come out of the molecular data is that the Golden-Plovers (and Black-bellied) are not so closely related to the rest of the plovers. Several papers have suggested that they are actually closer to the stilts, avocets, oystercatchers, and ibisbill (Ericson et al., 2003a; Baker et al., 2007; Fain and Houde, 2007).

This has been called into question by Baker et al. (2012), who argue that the plovers are a monophyletic group. I find their arugments unconvincing as they seem to ultimately depend on only 2 of 17 genes examined. To make this a bit clearer, suppose we think of the Charadrii as consisting of 4 groups: Egyptian Plover, Golden-Plovers, Avocets and allies, and the main plover/dotterel group. It's clear that the Egyptian Plover is in the basal branch. But which group branches next? Support for any of the three alternatives is relatively weak: One nuclear intron (GAPD3-5) supports the Golden-Plovers. Three genes (ND2, ADH5, and cyt-b) support the main plover group as basal, and two genes support the avocet group. The results from the other 11 genes are too inconclusive to score. Under these circumstances, I think it is best to put the three groups in a trichotomy.

Recurvirostridae: Stilts, Avocets Bonaparte, 1831

3 genera, 9 species HBW-3

Ibidorhynchidae: Ibisbill Bonaparte 1856

1 genus, 1 species HBW-3

Haematopodidae: Oystercatchers Bonaparte, 1838

1 genus, 12 species HBW-3

Charadriidae: Plovers, Dotterels Leach, 1820

13 genera, 63 species HBW-3

Click for Charadriidae tree
Click for Charadriidae tree

The plovers have been reorganized based on Barth et al. (2013). Their data is cobbled together from many heterogeneous DNA sources, and it's possible that some species will move around with more complete data (Little Ringed Plover is one candidate).

Nonetheless, I will treat it at face value. It matches Baker et al. (2007) for the genera that match, and some of its results were prefigured by Christian et al. (1992) and Joseph et al. (1999). Both provided evidence that the old Charadrius was not a natural group. Barth et al. (2013) consider all but 6 species usually considered Charadrius, and the result requires removing most of the “Charadrius” plovers from Charadrius, leaving only 5 species. To emphasize the change, I've divided the plovers into three groups. The basal group is a much reduced Charadriinae. The other two groups are sisters. The lapwings (Vanellinae) are sister to the group of remaining plovers (Anarhynchinae).

Within the new Charadriinae subfamily, the Rufous-chested Dotterel (or Plover) turns out to be sister to the Diademed Sandpiper-Plover. Thus it requires a new genus. Fortunately, Zonibyx (Reichenbach, 1852) is available for it. I have no genetic information on Forbes's and Three-banded Plovers. Livezey (2010) suggests separating them as Afroxyechus and that they are somewhere near Thinornis, hence the placement here in a trichotomy with Thinornis and Charadrius. The genus Thinornis has grown by absorbin Elseyornis and adding the Little Ringed Plover (from Charadrius).

The Vanellinae remain as before as I have insufficient data to justify any changes.

All the other plovers and dotterels are in the third clade, Anarhynchinae. Erythrogonys and Peltohyas are basal. The other species were all formerly in Charadrius. There are several reasonable ways to group them, ranging from 1 genus (Anarhynchus) to 6. There are three or possibily four clades I've chosen to divide them into three genera. There is some uncertainty about how to arrange the Ochthodromus species. They may divide clearly into two clades, but which one the Mountain Plover belongs to is not certain. I've decided to put them all into Ochthodromus (Reichenbach 1852, type wilsonia).

But we have raced ahead with Ochthodromus. Before it, we encounter two other clades. One is the sand-plovers clade, Eupoda (J.F. Brandt 1845, type asiatica). The last clade contains three species. The Wrybill, Double-banded Plover, and New Zealand Plover. These are all somewhat different and could be considered three genera (names are available). However, they are all from New Zealand, and I choose to emphasize that by putting them all in one genus. Anarhynchus (Quoy and Gaimard 1830, type frontalis) has priority.

The taxonomic status of the Kentish-Snowy Plover complex has been controversial. Recent work by Küpper et al. (2009) found that the Kentish, Snowy, and White-fronted Plovers represented independent groups, with little or no evidence of gene flow between them. Not only does this separation appear to be long-standing, but the White-fronted Plover seems to be more closely related to the Kentish Plover than to the Snowy Plover. Accordingly, the Kentish (O. alexandrinus) and Snowy (O. nivosus) Plovers are treated as separate species below.

Rheindt et al. (2011b) provide further evidence in favor of separating Kentish and Snowy Plovers. They also found that the Malaysian Plover, Ochthodromus peronii, is member of the group. It is most closely related to the White-fronted Plover, Ochthodromus marginatus. Both are more closely related to the Kentish Plover than to the Snowy Plover. They also no genetic evidence supporting recognition of White-faced Plover, O. alexandrinus dealbatus, as a separate species.

Charadriinae Leach, 1820

Vanellinae: Lapwings Bonaparte, 1842

Anarhynchinae Baird, Brewer and Ridgway, 1884

Limicoli Garrod, 1873

The term Scolopaci (Strauch 1978?) seems to be the current fashion. However, Limicoli has a lot of priority and a long history of use (often as Limicolae).

Pedionomidae: Plains-wanderer Bonaparte, 1856

1 genus, 1 species HBW-3

Thinocoridae: Seedsnipes Sundevall, 1836

2 genera, 4 species HBW-3

Rostratulidae: Painted-snipes Mathews, 1913-14 (1855)

2 genera, 3 species HBW-3

Jacanidae: Jacanas Chenu & des Murs, 1854 (1840)

6 genera, 8 species HBW-3

Whittingham et al. (2000) found two clades of Jacanas, one containing Hydrophasianus and Jacana, the other consisting of the other four genera.

Scolopacidae: Sandpipers, Snipes Rafinesque, 1815

16 genera, 96 species HBW-3

Scolopacidae tree The overall treatment of the sandpipers relies heavily on Baker et al. (2007) and Gibson and Baker (2012). It is generally consistent with the results in Ericson et al. (2003a), Fain and Houde (2007), Paton et al. (2003), and Thomas et al. (2004a) as well the more heterogeneous evidence assembled by Thomas et al. (2004b). The Tringa sandpipers use the arrangement in Pereira and Baker (2005), which was also adopted by the AOU and BOU lists in 2007, and is consistent with Gibson (2010). The arrangement within Numenius is based on Raty's reanalysis of Gibson and Baker (2012).

The curlews and Upland Sandpiper form the basal group (Numeninae), followed by the godwits (Limosinae). After this come the turnstones and stints (Arenariinae), phalaropes and shanks (Tringinae), and finally dowitchers, snipe, and woodcock (Scolopacinae) as in the diagram.

Cibois et al. (2012) found that Aechmorhynchus and Prosobonia are very closely related, enough so to merge Aechmorhynchus (Coues 1874, type parvirostris) into Prosobonia (Bonaparte 1850, type leucoptera). They also found that the expanded Prosobonia belongs in the Arenariinae, possibly close to the turnstones.

It has long been suspected the Surfbird is close to the knots (e.g., Jehl, 1968). This is exactly what Bororwik and McLennan (1999) found in their DNA tree. Indeed, their results suggest the Surfbird and knots are congeneric. The recent analysis by Gibson (2010) and Gibson and Baker (2012), using additional data, concured. Based on this, I've merged Aphriza into Calidris.

I had previously elected to restrict Calidris to the knots and surfbird. The other “Calidris” are more distantly related, and the old genus name Ereunetes has been applied to them, including the Buff-breasted and Spoon-billed Sandpipers (Tryngites and Eurynorhynchus, respectively). However, now that the AOU, BOU, and H&M 4th ed. have all merged them into Calidris, as in Banks (2012), I've decided to follow their treatment.

The treatment of Calidris is based on Gibson (2010) and Gibson and Baker (2012). Note that the Sharp-tailed Sandpiper groups with the former Limicola and Philomachus. The remainder of Calidris is fairly closely related, and although there are some well-supported groups, their relationships are not. The case of the Sanderling is particularly uncertain as some analyses have it sister to the Little Stint, while Gibson and Baker (2012) put it sister to the Dunlin/Rock/Purple Sandpiper clade, as Livezey (2010) does with traditional methods.

The New Zealand Snipes (Coenocorypha) are now considered to include 5 exant and recently extinct species based on Baker et al. (2010) and Worthy et al. (2002). The Snares and South Island Snipes are quite closely related, with an estimated divergence time of about 50,000 years. Their status as separate species rests on the lack of an aerial display for the Snares Snipe, as well as genetic and plumage differences. The other Coenocorypha are somewhat more distant relatives.

Gibson (2010) and Gibson and Baker (2012) found that Imperial Snipe is more closely related to the New Zealand snipes than to the other snipes. The Imperial Snipe and two other snipes have sometimes been separated as Chubbia (Mathews 1913), and that is how I treat them here. It is clear that this arrangement of the snipes is not fully satisfactory, and they deserve further study.

Numeniinae: Curlews G.R. Gray, 1840

Limosinae: Godwits G.R. Gray, 1841

Arenariinae: Turnstone and Stints Stejneger, 1885 (1840)

Tringinae: Phalaropes and Shanks Rafinesque, 1815

Scolopacinae: Dowitchers, Snipe, and Woodcock Rafinesque, 1815

Turnici Huxley, 1868

Turnicidae: Buttonquail G.R. Gray, 1840 (1831)

2 genera, 17 species HBW-3

Lari Sharpe 1891

Dromadidae: Crab Plover G.R. Gray, 1840

1 genus, 1 species HBW-3

Pereira and Baker (2010) found that Dromas is sister to the Glareolidae, as represented by Glareola and Cursorius.

Glareolidae: Coursers, Pratincoles Brehm, 1831

4 genera, 17 species HBW-3

Stercorariidae: Skuas, Jaegers G.R. Gray, 1870 (1831)

1 genus, 7 species HBW-3

The skuas were formerly separated in the genus Catharacta, but a genetic study by Cohen et al. (1997) found the Great Skua and Pomarine Jaeger were sister species. This has been called into question by Braun and Brumfield (1998), who argued that all the skuas might be sister to the Pomarine Jaeger. Either way, the 2-genus treatment was untenable, and most have decided to merge Catharacta into Stercorarius. If Braun and Brumfield are right, an alternative would be to put the Pomarine Jaeger by itself in Coprotheres and the skuas in Catharacta.

The species boundaries in the southern skuas (all but S. skua) are somewhat uncertain. See Ritz et al. (2008).

Alcidae: Auks Leach, 1820

11 genera, 25 species HBW-3

The taxonomy follows Baker et al. (2007) and Pereira and Baker (2008). The time scale in Pereira and Baker should be taken with a grain of salt. Considering that some of the fossils used as calibration points are distantly related, or of controversial affinities, perhaps with a whole trunkload of salt would be better.

Humphries and Winker (2010) clarified some details about Aethia. For the split of Scripps's Murrelet, Synthliboramphus scrippsi, from Xantus's Murrelet, Synthliboramphus hypoleucus, see Birt et al. (2012). Further, Synthliboramphus hypoleucus takes the name Guadalupe Murrelet.

Laridae: Gulls, Terns, Skimmers Rafinesque, 1815

24 genera, 105 species HBW-3

The exact placement of several genera (Rynchops, Anous, Procelsterna, Gygis) remains somewhat problematic. It's clear that they are relatively basal within Laridae, but exactly how basal, and their order remains uncertain.

There are four relevant papers: Bridge et al. (2005), Baker et al. (2007), Ödeen et al. (2010), and Jackson et al. (2012). They successively analyze more genes, but Baker et al. has better taxon sampling in the terns. It is clear that the skimmers are by themselves, the gulls group together, and the terns other than Anous, Procelsterna, and Gygis also form a clade. Whether all of the terns are monophyletic, or whether the core terns plus Gygis are monophyletic, remains less than clear.

Basal Larids

Bridge et al. (2005) placed Anous and Gygis in the Sternidae. In contrast, Baker et al. (2007) found Anous and Gygis to be basal to the gulls, terns, and skimmers. In their combined analysis, Ödeen et al (2010) group Anous, Gygis, and presumably Procelsterna basally in Laridae, with a trichotomy between the skimmers, gulls, and remaining terns. They note that this arrangement is weakly supported. They also give a somewhat better supported mitochondrial tree which puts Gygis with the other terns and Anous with the gulls and skimmers. Finally, Jackson et al. (2012) consider more genes, but leave out the noddies. The resulting combined analysis puts the white terns sister to the terns, and the skimmers as basal group. The mitochondrial DNA results are a bit different, and put the white terns as basal, then skimmers, then gulls and terns.

This suggests that we think of the larids as consisting of five main groups: gulls, terns, skimmers, noddies, and white terns. There's no consensus about how they fit together, so I'm treating them as a five-way polytomy. I emphasize this by ranking them as subfamilies and ordering them by subfamily size.

Gyginae: White Terns Verheyen, 1959

Rynchopinae: Skimmers Bonaparte, 1838

Anoinae: Noddies Bonaparte, 1854

Sterninae: Terns Vigors, 1825

There are differences in the tern taxonomy in Bridge et al. (2005) and Baker et al. (2007). I've adopted the Bridge et al. framework because they sampled many more tern species than Baker et al.

The American Sandwich Terns are split under the old name Cabot's Tern, Thalasseus acuflavidus. Efe et al. (2009) found that Cabot's Tern is more closely related to Elegant Tern than to Old World Sandwich Terns. They also found that no systematic genetic distinction between Cayenne and Cabot's Terns and question whether eurygnathus is distinct from acuflavidus.

Larinae: Gulls Rafinesque, 1815

At the generic level, the taxonomy of the gulls follows Sternkopf (2011) and Pons et al. (2005). Sternkopf uses a wider variety of genes that Pons et al., but cuts back a bit on taxa considered. Their results are generally consistent with each other and with Crochet et al., (2000). The Pons et al. treatment was quickly accepted by AOU and BOU.

The use of Sternkopf (2011) means that the Little/Ross's Gull clade is one of the basal groups, that Heermann's Gull groups with the other band-tailed gulls, and that the Ring-billed and Mew Gulls are sister species. It's also led to some minor reordering within genera. Unfortunately, Sternkopf did not consider Saunder's Gull, and its new position is somewhat uncertain (Pons et al. had it on a branch between Chroicocephalus and the now moved Little/Ross's Gull group). I've moved it to just before Chroicocephalus, but not in with the most basal groups.

One noteworthy feature is the use of separate genera for masked gulls (Chroicocephalus), hooded gulls (Leucophaeus), and black-headed gulls (Ichthyaetus). The large white-headed gulls remain in Larus. Within Larus, the band-tailed gulls (pacificus, belcheri, atlanticus, and crassirostris) may also deserve generic recognition (Gabianus?), although the evidence is less strong here. It has been strengthened a bit by Sternkopf (2011), who includes the other band-tailed gull (heermanni) as the basal member of that group.

Starting with Western Gull, we run into a taxonomic maze, the large white-headed Larus gulls — the herring gull clade. The herring gull clade involves over 30 very closely related taxa, not all of them treated as separate species. They seem to have differentiated quite recently, with the common ancestors of all herring gulls living perhaps 300,000 years ago. Some of these taxa may still be in the process of speciation, and the genetic differences between them are very small. In fact, the genetic distances are small enough that the basal member of the clade, the Western Gull, hybridizes fairly freely with one of its most distant relatives, the Glaucous-winged Gull. In spite of this, many of the other taxa either do not interbreed, or do so only infrequently, and hence represent distinct biological species.

The papers by Liebers et al. (2001, 2002, 2004), de Knijff et al. (2001), Crochet et al. (2002), Pons et al. (2004), and Gay et al. (2005) focus on the big white-headed gulls. Gull relationships are somewhat obscured by past and recent hybridization, and species limits within the herring gulls remain controversial. In spite of this, a coherent picture is being teased out.

The Yellow-footed Gull and Western Gull (both races) are likely sisters, and are likely sister to the main group of herring gulls. The Ring-billed Gull appears to be the closest relative to the whole clade, including Western and Yellow-footed. This suggests that the ur-herring gulls originated in North America. A group found its way east into Europe and split into two clades, possibly corresponding to glacial refugia (clades I & II in Liebers et al., 2004). The west European clade includes the Great Black-backed, European Herring, Armenian, and Yellow-legged Gulls. The rest are in an Aralo-Caspian clade.

The Caspian Gull (cachinnans only) is basal in the Aralo-Caspian clade, which again splits into two. The first includes Lesser Black-backed Gull (including heuglini, taimyrensis, and barabensis). The Kelp Gull apparently derives from the Lesser Black-backed. The other clade spread eastward into Siberia. This is as far as Liebers et al. give detailed information, as their sampling had very limited coverage of East Siberian and North American species.

Crochet et al. (2002), Pons et al. (2004), and Gay et al. (2005) did sample the North American species. As all three analyzed the same two genes, the results are not independent. None included vegae, and several taxa remain poorly resolved. They all show Glaucous Gull in the North American group. However, due to past hybridization, it remains unclear which clade the Glaucous Gull belongs to—whether it is part of the North American group or close to argentatus. I'm guessing the argentatus relationship is recent hybridization, but my confidence in this is pretty low. In fact, my confidence in this section of the tree is low enough that I leave it unresolved on the diagram.

It had once been thought that the Herring Gull was a ring species that had spread around the world. However, the herring gulls are actually a number of biological species, making the ring species story incorrect. However, some of the herring gulls do interbreed (promiscuously in the case of occidentalis and glaucescens), and the ring species story has a kernel of truth in it. In fact, as the herring gulls spread from North America (occidentalis) around the world we get to glaucescens, completing a ring of many species. In the ring species story, the birds interbreed locally around the ring, with the ends infertile. Ironically, reality gives us a bizzaro-world version of the ring species, where the steps of the ring interbreed infrequently or not at all, and the two endpoints interbreed freely.

A second ring may be forming in the other direction between graellsii Lesser Black-backed and American Herring Gulls as graellsii invades North America.

Some of the species limits among the herring gulls remain contentious. E.g., see Pittaway (1999) and Weir et al. (2000) concerning whether glaucoides, kumlieni, and thayeri are one, two, or even three species. For the present, I am following AOU on this (two). Other named taxa in Liebers's clade II sometimes considered species include (West) Siberian Gull (heuglini and maybe taimyrensis), Baltic Gull (fuscus), Steppe Gull (barabensis), and Mongolian Gull (mongolicus). They also suggest two types of Glaucous Gull, which may not match traditional subspecies, and two types of European Herring Gulls that definitely don't match traditional subspecies. There's also a question concerning whether the Yellow-legged Gull should be split into Mediterranean Yellow-legged Gull (michahellis), Atlantic Yellow-legged Gull (atlantis) and possibly even Cantabrican Yellow-legged Gull (lusitanius?).

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