Gulls, Part 1

The word “gull” probably has the ability to elicit the widest range of emotion among birders and non-birders alike of any bird name. To some birders, “gull” means woe and misery, but to others, it means joy and excitement. To the average non-birder, gulls, or “seagulls,” are a nuisance, “flying rats” that steal food at picnics and eat garbage at the dump. It's also probably one of the few groups that has some of the most sought-after rarities, along with some of the most common “trash” birds.

But, what is a gull? Gulls are part of the order Charadriiformes. Within this large, diverse order, the gulls (part of the family Laridae) are part of the suborder Lari. The Laridae is sister to the skuas/jaegers (Stercorariidae) and the auks (Alcidae). These families are in turn sister to the Crab Plover (Dromadidae) and coursers/pratincoles (Glareolidae). In the Lari, the button quail (Turnicidae) are sister to the rest of the group (Baker et al. 2007, Pereira and Baker 2010).

Hueglin's (Three-banded) Courser (Rhinoptilus cinctus) (Source: Wikipedia)

Within the family Laridae, the gulls are related to the terns and skimmers. While the exact relationships of the gulls relative to the terns and skimmers has not been completely resolved, a recent in depth phylogeny shows the gulls as sister to skimmers, which are in turn sister to most of the terns (Baker et al. 2007). In this study, the noddies (Anous) and white terns (Gygis) fall outside of the “tern” clade, and are sister to the entire group of gulls, terns and skimmers. Other recent studies have found conflicting results to Baker et al. (2007), instead finding the terns as sister to the skimmers, which are then in turn sister to the gulls (Fain et al. 2007), or with the gulls and terns as sister, which are then in turn sister to the skimmers (Ericson et al. 2003). In a phylogenetic study of the terns, Bridge et al. (2005) found the terns to compose a monophyletic group. However, this may not reflect the true phylogeny, as the outgroup (Ring-billed Gull) may have been forced, forcing a monophyletic Sterninae (more on tern phylogeny in another post).

Brown Noddy (Anous stolidus) (Source: Wikipedia)

Long-tailed Jaeger (Stercorarius longicauda), June 2009, Churchill, MB (photo by Jay McGowan)

Parasitic Jaeger (Stercorarius parasiticus), July 2010, Churchill, MB (photo by Andy Johnson)

Within the Laridae, the species level relationships have not been well-resolved. However, the phylogeny been found to consist of several well-supported clades, which renders the traditional Larus (sensu lato) paraphyletic with respect to several of the long-held “unique” genera. This has left two main options, 1) place all gulls in the genus Larus, losing the long recognized unique genera of Rissa, Pagophila, Xema, and Rhodostethia, or 2) break up the traditional Larus. Based largely on the phylogeny of Pons et al. (2005), the AOU and other organizations chose the later, and split up the large and bulky genus Larus into several smaller, distinct genera.

While sampling is not extensive, Baker et al. (2007) recovered different results from Pons et al. (2005) with respect to basal relationships. Baker et al. (2007) found that the Swallow-tailed Gull was sister to Ross’s Gull, which were in turn sister to a clade that includes Sabine’s Gull, Ivory Gull, the kittiwakes, and Larus.

I’ll briefly go through the main highlights (using the “new” genera) of Pons et al. (2005), moving from most basal to most derived.

Figure 1 from Pons et al (2005) showing the phylogeny of the gulls based on mitochondrial DNA sequence data. Note the old names are used in the figure. Click on the figure to make it larger.

Swallow-tailed Gull (Creagrus furcatus) (Source: Wikipedia)

Mixed flock containing Bonaparte's Gulls (Chroicocephalus philadelphia), Sabine's Gulls (Xema sabini), and Little Gulls (Hydrocoloeus minuta), June 2009, Churchill, MB (photo by Jay McGowan)

Mixed flock, including Brown-hooded Gulls (Chroicocephalus maculipennis), Franklin's Gulls (Leucophaeus pipixcan), and Kelp Gulls, January 2010, Chiloe, Chile (Larus dominicanus)

Ross's Gull (Rhodostethia rosea), with a Bonaparte's Gull, June 2008, Churchill, MB (photo by Jay McGowan)

1. Creagrus – 1 species, Swallow-tailed Gull (C. furcatus), endemic to the Galapagos. A truly unique gull, and partly nocturnal, it spends much of its time far from land. The Swallow-tailed Gull has been found to be sister to the rest of the gulls.
   
2. Rissa – 2 species, Red-legged (R. brevirostris) and Black-legged Kittiwakes (R. tridactyla). Both species are colonial nesters, nesting along cliff and rock ledges. The Black-legged Kittiwake is widespread, while the Red-legged Kittiwake is restricted to the Bering Sea. Both are largely pelagic during the non-breeding period. The two kittiwakes are sister-species and are in turn sister to two other species, the Sabine's Gull (Xema sabini) and Ivory Gull (Pagophila eburnea)
   
3. Xema – 1 species, Sabine’s Gull (X. sabini), a gull breeding in the arctic and sub-arctic, and spending the non-breeding period far from shore. A striking gull, it’s forked tail and bold wing pattern make it stunning bird in all plumages. The Sabine's Gull is sister to the Ivory Gull.
   
4. Pagophila – 1 species, Ivory Gull (P. eburnea), a gull that spends nearly its entire life in the arctic and along the edges of the pack ice of the far north, this beautiful species is a much sought after species of southern latitudes, and may be suffering due to changes to its Arctic habitat due to global climate change. The Ivory Gull is sister to the Sabine's Gull, which are in turn sister to the kittiwakes.
   
5. Chroicocephalus – 11 species. This is a well-supported clade of relatively small, mostly hooded gulls. The North American boreal breeder, Bonaparte’s Gull (C. philadelphia) is sister to Slender-billed Gull (C. genei). These two species are sister to the rest of the genus. The remaining Chroicocephalus form a weakly-supported clade, to which Andean Gull (C. serranus) is basal. The Brown-hooded Gull (C. maculipennis) is sister to the remaining members of the clade. Within this clade, Hartlaub’s Gull (C. hartlaubii) is sister to Grey-hooded Gull (C. cirrocephalus). These two species are sister to Black-headed Gull (C. ridibundus) and (C. brunnicephalus). These four species are in turn sister to a group of three Australasian gulls, with Black-billed Gull (C. bulleri) being most closely related to the Red-billed Gull (C. scopulinus) and Silver Gull (C. novaehollandiae).
6. Saundersilarus – 1 species, the Saunder’s Gull (S. saundersi), is found only in East Asia, where it is threatened with habitat destruction. This species is not closely related to any other gull, and its relative position in the phylogeny is not well-resolved, possibly due to its long branch on the tree.
   
7. Rhodostethia – 1 species, the Ross’s Gull (R. rosea), is a breeder in Arctic Russia, Canada, and Greenland, is a sought after bird when it ventures to southern latitudes. This species put Churchill, Manitoba on the map in terms of birding, as the most accessible location in the world to see this bird on its breeding grounds. While no longer reliable (seen in June 2008 once, and not at all in 2009 or 2010 while I was in Churchill), many people still travel there every June hoping to see this beautiful gull. Pons et al. (2005) proposed to lump Rhodostethia into Hydrocoloeus based on strong genetic and morphological support. While it has been accepted that Ross’s and Little Gulls are sister species, the AOU chose to retain Ross’s Gull in its own monophyletic genus. The Ross's Gull is sister to the Little Gull. However, the relative position of these two species with respect to the rest of the phylogeny of gulls is not well-supported.
   
8. Hydrocoloeus – 1 species, the Little Gull (H. minutus), is fairly widespread in Eurasia, and breeds in small pockets in North America. This bird is sister to Ross’s Gull (Rhodostethia rosea), and shares a suite of morphological and behavioral characters.
9. Leucophaeus – 5 species; an entirely New World group of gulls. This clade appears to be sister to the remaining two genera of gulls, the Ichthyaetus and Larus. Within the genus, the Grey Gull (L. modestus) is sister to the bizarre and intriguing Dolphin Gull (L. scoresbii). These two South American species are sister to the remaining three species, with Franklin’s Gull (L. pipixcan) being most closely related to the Lava Gull (L. fuliginosus) of the Galapagos, which are in turn sister to the Laughing Gull (L. atricilla).
   
10. Ichthyaetus – 6 species; an entirely Old World radiation of gulls. This clade is sister to the large and confusingly specious Larus. None of the relationships within this group are well resolved. The topography within Pons et al. (2005) places the Mediterranean Gull (I. melanocephalus) as sister to the rest of the genus, which includes Audouin’s Gull (I. audouinii), Relict Gull (I. relictus), White-eyed Gull (I. leucophthalmus), Great Black-headed Gull (I. ichthyaetus), and Sooty Gull (I. hemprichii).
11. Larus - the rest... the dreaded “large, white-headed” gulls (LWHG) of the genus Larus. Within the genus Larus, the “black-tailed” gulls, which includes Belcher’s Gull (L. belcheri) and Black-tailed Gull (L. crassirostris), form a distinct clade that is sister to the remaining LWHG. The rest of the juicy details about this messy genus will be coming in later posts.
    

Black-legged Kittiwake (Rissa tridactyla), June 2008, Churchill, MB (photo by Jay McGowan)

Ivory Gull, February 2010, Rouses Point, NY (Pagophila eburnea)

Mixed flock containing Bonaparte's Gulls (Chroicocephalus philadelphia) and Sabine's Gulls (Xema sabini), June 2009, Churchill, MB (photo by Jay McGowan)

Mediterranean Gull (Ichthyaetus melanocephalus) (Source: Wikipedia)

And, finally, here is a taste of what is to come...

Heermann's Gull (Larus heermanni), September 2009, Pacifica, CA

Thayer's Gulls (Larus thayeri), June 2009, Churchill, MB (see this post for more on these Thayer's Gulls and other gulls of Churchill)

Glaucous Gull (Larus hyperboreus), with Herring Gulls (Larus argentatus), June 2009, Churchill, MB

References:

Baker, A.J., S.L. Pereira, T.A. Paton. 2007. Phylogenetic relationships and divergence times of Charadriiformes genera: multigene evidence for the Cretaceous origin of at least 14 clades of shorebirds. Biology Letters 3: 205-207

Bridge, E.S., A.W. Jones, A.J. Baker. 2005. A phylogenetic framework for the terns (Sternini) inferred from mtDNA sequences: implications for taxonomy and plumage evolution. Molecular Phylogenetics and Evolution 35: 459-469

Ericson, P.G.P., I. Envall, M. Irestedt, J.A. Norman. 2003. Inter-familial relationships of the shorebirds (Aves: Charadriiformes) based on nuclear DNA sequence data. BMC Evolutionary Biology 3(16)

Fain, M.G. and P. Houde. 2007. Multilocus perspectives on the monophyly and phylogeny of the order Charadriiformes (Aves). BMC Evolutionary Biology 7(35)

Pereira, S.L and A.J. Baker. 2010. The enigmatic monotypic crab plover Dromas ardeola is closely related to pratincoles and coursers (Aves, Charadriiformes, Glareolidae). Genetics and Molecular Biology 33(3) 583-586

Pons, J.M., A. Hassani, P.A. Crochet. 2005. Phylogenetic relationships within the Laridae (Charadriiformes: Aves) inferred from mitochondria markers. Molecular Phylogenetics and Evolution 37: 686-699

Bird species discovery odds and ends

Here are a couple more neat graphs about the rate of discovery of new bird species that I couldn't fit well into my previous two posts about the subject (10,000 birds? Part 1 and Part 2).

In Part 1 I briefly introduced the species accumulation curve as a means of comparison of rates of discovery between different groups. Here, I wanted to parse apart any broad-scale patterns in the bird data. I started by splitting the birds into their two broadest groupings - passerines (5927 species) and non-passerines (4100 species) - and then I split passerines again into two more broad classes - oscines (4668 species) and suboscines (1259 species). These new species accumulation curves are plotted against the overall bird curve (in black):

(click to enlarge)

The non-passerine curve falls generally to the left of the passerines and birds overall, indicating that non-passerines were generally described earlier than passerines and fewer non-passerines have remained undescribed until recently. The passerine, oscine, and suboscine curves are generally similar in slope and position, although suboscines lag in the last 100 years or so. The suboscine curve is also the only one with a noticeable uptick - a bunch of new species described - in the last few decades.

Those who know me when I get into projects like this know I like to take things to ridiculous excess. In this case, I decided to investigate family-level patterns of description. To get fairly smooth accumulation curves requires a fairly large number of taxa, so I picked the bird families recognized by Birdlife that contain more than 150 species. These twenty families are:

Family name	Species
Tyrannidae	414
Psittacidae	374
Trochilidae	337
Timaliidae	326
Columbidae	318
Emberizidae	313
Sylviidae	293
Muscicapidae	286
Thraupidae	256
Furnariidae	241
Accipitridae	238
Picidae	218
Thamnophilidae	218
Strigidae	186
Phasianidae	181
Meliphagidae	177
Fringillidae	177
Turdidae	173
Anatidae	164
Rallidae	156

And their species accumulation curves, plotted against the all-bird curve in black:

(click to enlarge)

I don't expect anyone to actually tease apart that rainbow coalition of squiggles in detail, especially because they form such a tight column of similarly-sloped curves. That in itself is a pretty neat result - the family-level differences aren't as noticeable as I thought they would be, and teasing them apart in detail is fairly pointless. There are, however, two curves that stand apart from the rest.

On the far left in pale blue is Anatidae. 50% of the currently known ducks were described by 1800, decades before any other family, and 90% were described by 1870. Ducks are big, obvious birds with common interaction with humans (in the form of hunting) and often bold, distinct male plumages in each species. It is thus not surprising that ducks were described comparatively early in history and very few new species have been described in the last 100 years.

In contrast, on the right side of the curves, the pale reddish curve for Strigidae falls below the others in the last 100 years or so. The slope is pretty similar to the other curves for this time period, so I don't think the overall rate of discovery in owls is much lower. Instead, the curve is displaced lower by the flush of new species described in the last few decades - remember in my last post that owls had the highest number of new species described of any family since 1942.

That's all I have for now - have fun staring at those colorful squiggles.

10000 birds? Part 2

In Part 1, I looked at the history of bird species discovery, and found that new bird species have been described at a fairly steady rate of an average 4.9 species per year since the 1940s. Here, I'll review what species have been discovered since the 1940s, where they are found, and why it took so long to find them.

From 1942 until 2008, 330 species encompassing 76 families and 213 genera were described:

(note: I accidently included 1 2009 datapoint, but 2009 is incomplete and more than 1 were described that year)

Among the top families, five (Tyrannidae - tyrant flycatchers, Thamnophilidae -antbirds, Furnariidae - ovenbirds, Rhinocryptidae - tapaculos, Formicariidae - anthrushs) represent the diverse suboscine lineages of South America. Two other top families (Sylviidae - old world warbles and Timaliidae - babblers) are similarly diverse lineages from the old world (I don't think Birdlife carves up these families into smaller groups as other checklists do in the last few years). My gut impression before seeing this data was that these two broad groups of birds would be the leaders for multiple reasons - they compose many of the species I could remember seeing described in the last few years, they contain many cryptic groups and are receiving active taxonomic treatment with new input from DNA and song, and they are found in the tropical areas of the world still receiving new exploration and documentation of fauna. However, the winner in the family category by a large margin was a surprise for me: Strigidae (owls). It makes sense that cryptic nocturnal birds would contain a lot of previously undocumented diversity, but I was surprised at the scale. The top genera track the top families as expected (Glaucidium - Pygmy-Owls, Otus - Scops-Owls, Scytalopus - Tapaculos, Grallaria - Antpittas, Phylloscartes - Tyrannulets, etc).

There are a myriad of historical and unquantifiable reasons that bird species persist until the present day undiscovered or unrecognized by science. However, I made several simple, straightforward predictions about recently discovered species that can be quantified and tested:

1) New species are likely to be found in underexplored tropical countries
2) New species are likely to be single-country endemics
3) New species are likely to have small ranges
4) New species are likely to have small populations and thus more likely to be endangered

Using Birdlife International's online database, I was able to extract relevant bits of information regarding these new species - where they are found, whether they are country endemics, their estimated range size, and their Birdlife conservation status. I tested my predictions by comparing the species described from 1942-2008 with random samples of species described earlier in history: 100 species described by Linnaeus in 1758 and 200 described in the 1840's-1860's.

1) New species are likely to be found in underexplored tropical countries

Here is a summary of where the new species (1942-2008) are found. The first column is overall country listings, which sums to well over 330 because of species ranging across many countries. The second column of results is for single-country endemic species.

As expected, the South American and Southeast Asian tropics top both lists, with Peru and Brazil leading both categories by a good margin.

2) New species are likely to be single-country endemics

I didn't tally the country-by-country data for my 1758 and 1800's sample groups, because so many of them span a huge range of countries. This difference is apparent when you compare the proportion of single-country endemics for each category:

6% of species described in 1758 are found in a single country
24% of species described in the 1840s-1860s are found in a single country
72% of species describe 1942-2008 are found within a single country

This confirms that recently described species are more likely to be restricted to within a single country, and are thus easier to overlook, than those species described earlier in history.

3) New species are likely to have small ranges

I binned the Birdlife range size data by order of magnitude for each of the three time periods and calculated the proportion of the sample in each:

(click to enlarge)

The species described by Linnaeus in 1758 (blue bars) are overwhelmingly species with huge ranges in the millions of square kilometers. Species described in the mid-1800's still have ranges mostly in the hundreds of thousands to millions of square kilometers, but there is a wider distribution of species among the size classes.

For new species described 1942-2008, the distribution among size classes is much wider than in the other time periods. Less than 4% of these species have ranges in the millions of square kilometers - these include species like Cryptic Forest Falcon (Micrastur mintoni) and Amazonian Pygmy-Owl (Glaucidium hardyi) which have large Amazonian ranges. The largest proportion of new species have ranges sizes that are fairly small - 1000s to tens of thousands of square kilometers.

The most stunning category is for range sizes of less than 100 square kilometers - an area only 5 times bigger than my hometown of North Tonawanda, NY. 12.5% of new species (32 total) fall into this category, with some absurdly small known ranges. Four species have a known range of less than ten square kilometers - Munchique Wood-Wren (Henicorhina negreti, 8 sq. km), Poo-uli (Melamprosops phaeosoma, 3 sq. km), Calayan Rail (Gallirallus calayanensis, 2 sq. km), and Bugun Liocichla (Liocichla bugunorum, 2 sq. km). Words fail me in trying to describe how mind-boggling, fascinating yet even heart-breaking it is to see species with ranges like this. The only species with ranges this small in the other categories are a fruit-dove and a honeyeater described in the mid 1800s from tiny South Pacific islands with range sizes around 25-50 sq. km.

4) New species are likely to have small populations and thus are more likely to be endangered

I wasn't able to easily pull data on population sizes for a large range of species from the Birdlife database, so instead I used a proxy - Birdlife conservation status. I calculated the proportion of species from each time period that fall into the six Birdlife categories:

DD = Data Deficient
LC = Least Concern
NT = Near Threatened
VU = Vulnerable
EN = Endangered
CR = Critically Endangered

(click to enlarge)

Just as the 1758 and mid-1800s samples were overwhelming skewed towards species with large range sizes, these categories are both over 80% composed of species ranked Least Concern. Only one of the 1758 species (Bald Ibis, Geronticus eremita) and one of the 1800s species (Cuban Kite, Chondrohierax wilsonii) are recognized as Critically Endangered. A plurality of the new species are Least Concern, but there is a very wide distribution of rankings, with 8.5% (28 species) being Critically Endangered.




Well, that about covers it. If you weren't keeping a running tally, all of my predictions were validated by the data! While I love playing with this data and learning more about the patterns of discovery of new species, I realized in the end that these findings are rather disturbing. A depressingly large proportion of bird species that have remained unknown to science until recently have very tiny ranges and are endangered. In this era of exceptional environmental destruction, how many more species like these have slipped away into extinction unnoticed? That is a number we can never know.

10,000 Birds?

"You think you know every bird in the world, and then someone shows you a Curl-crested Aracari"

David Quammen, The Song of the Dodo

An oft-cited figure for the diversity of birds in the world is around 10,000 living species, a reasonable rule of thumb although estimates vary - Birdlife International currently recognizes 10,027 while the IOC list is currently at 10,396. Duncan Wright says the number should be closer to 12,000 if recently extinct birds are included (and he also coincidentally begins with a David Quammen quote). Pinning down an exact number is an impossibility because differing opinions on species limits in species and subspecies complexes create a near-infinite number of list permutations. Pinning down a number is also impossible because the bar keeps getting raised by the new bird species discovered every year.

New species of bird often receive a small splash of press when discovered or described, because birds are regarded as an exceptionally well described group of vertebrates and we've long reached the point where new birds are few in number. Additionally, the hunt for new species has been romanticized in such good reads as A Parrot Without A Name or this more recent Birding article (pdf) by Joseph Tobias. Tobias quotes Mayr (1946) as proclaiming the general end of new bird discovery - “I doubt that in the entire world even as many as 100 new species remain to be discovered” - but states that a yearly trickle of new species have been described since then. Just how many new birds are discovered every year? How much has the trickle of new birds declined? How many new birds are left to discover?

I can't answer the last question, but I can find data for the first two. It is a logistical nightmare to track down this data by finding every new species description in the primary literature. Instead, I picked a world checklist to find what I needed. The formal way to list species in literature includes a citation for the description of the species, such as Puffinus griseus (Gmelin 1789). By using these dates, you can quickly extract the year by year data for species descriptions. This method also only counts newly described species, not splits through the elevation of previously recognized subspecies.

The only quickly downloadable checklist I found with data like this is Birdlife International's checklist, so I used their most recent version (v3, June 2010) and plotted out the data. Here is the number of new bird species described each year, beginning in 1758 with Linnaeus and ending in 2008 (the Birdlife checklist is incomplete for new species in 2009 and 2010):

(click to enlarge)

The early decades show relative inactivity in bird taxonomy punctuated by massive monographs (like the 400+ that Linnaeus described in one work). The golden age of bird taxonomy peaks in the mid-1800's, with several decades of 50+ species described every year. The number of new birds described then generally declines to the present day.

Another way to present this data - the most useful for comparison - is to create a species accumulation curve. This represents, for each year, what percentage of the total number of known species was described at that point. This allows you to examine what those small numbers of new species each year mean in the context of the total number of known bird species. The slope of the curve is a proxy for the rate of discovery of new species, and you can easily eyeball the differences in slope representing different rates of species description over time.

Here is the species accumulation curve for birds:

(click to enlarge)

This represents a typical curve for a well-described fauna - the middle range is steepest, and the curve plateaus as new species become increasing hard to find. Compare the curve for birds with that of a very different fauna, another favorite of mine, geckos:

(click to enlarge)

In stark contrast to birds, the rate of discovery of geckos has only accelerated through time, and the last few years have seen the highest yearly rates of gecko discovery ever - but that's another post. The point is that geckos are a representative of an under-described group with lots of new species to be found and taxonomic description left to be done. Birds are comparatively well-described and have relatively little left to be found.

We can estimate how little is left to be found by studying the decline in new species found. So how about that decline? Zooming in to the last 120 years, we get this:

(click to enlarge)

At about the time Mayr proclaimed the end of bird discovery in the 1940s, the overall rate of description of new birds had been trending steeply downward for decades. After the rate reached rock bottom - 1941 is the last year with more than ten bird species described - there is indeed a steady trickle of new species every year, averaging 4.9 species per year and varying from zero (in 1954 and 1978) to ten (1960, 1974, 1997) new birds yearly.

However, this trickle does not seem to show any sign of stopping, even decades after Mayr's prediction. In fact, if you take just the data from 1942-2008, look at the general trend line:

(click to enlarge)

That's right, that is a (very weakly supported) POSITIVE trend line for the discovery of new species in the last seven decades. Given the overall wide variance in discovery from year to year in these decades, I double-checked this trend my making a moving ten-year average of new birds per year:

(click to enlarge)

This is a really fascinating result! Despite the fact that the overall description rate of birds has plummeted and won't ever get back up to the rate it was 100 years ago, discovery of new birds has stabilized and shows no signs of slowing since the 1940's. That means that, while the species accumulation curve has plateaued, it is not exactly drifting towards zero and the total number of remaining bird species can't be extrapolated. Who knows what is left to find?

In part 2 of this post, I'll outline what new species have been discovered in the last few decades, where they are being found, and some reasons for their late discovery. Stay tuned.

New Wood-Warbler Taxonomy

The July issue of The Auk contained the AOU North American Checklist Committee's 51st supplement to the AOU checklist (pdf), a variety of splits and changes to taxonomy at the genus level and higher. Sibley handily summarizes the name changes to North American species, and Michael Retter reviews the whole supplement, and I'm sure it has been plastered elsewhere on the blogosphere by now so I am not going into a full review here (plus, I blogged about one of the splits two years ago - everyone else is late to the party). Instead, I'm breaking my long self-imposed blog exile to talk about warblers. Actually, mostly about warbler names.

The 51st supplement makes two changes to genera in New World wood-warblers (Parulidae): the waterthrushes are split from the Ovenbird (Seiurus) and placed in a new genus, Parkesia, and most of the genus Vermivora is split and removed into a new genus, Oreothlypis . These changes are based on results that have been in the phylogenetic literature for some years now, but have not resulted in comprehensive taxonomic updates. While Klein et al. (2004) presented a phylogeny for the family and documented many problems with generic limits, they did not present many taxonomic solutions and their sampling of the diversity of Central and South American Parulids was very slim. In general, while there have been several papers addressing phylogeny in the overall family (Klein et al 2004, Lovette and Hochachka 2006) and in certain groups (Dendroica: Lovette and Bermingham 1999; Myioborus - Perez-Eman 2005; Geothylpis and Oporornis - Escalante et al. 2009), a comprehesive phylogeny of the group with solid sampling of species (there are over 110 in the whole family) and a complete update of Parulid taxonomy has been lacking ... (drumroll)... until now.

Lovette et al. (2010) present a comprehensive picture of the evolution of the wood-warblers, sampling all but three species and addressing the phylogenetic analyses with a good array of loci and methods. Their main result is a phylogenetic hypothesis for comparative studies and a proposal for complete revision to generic boundaries. I just want to step through the warbler tree and possible taxonomic disagreements as a guide for when taxonomic authorities eventually get to addressing them.

Phylogeny of the Parulidae (Fig. 5 from Lovette et al. 2010) with proposed taxonomic changes. You'll definitely want to click to enlarge and read

Parulidae is a large family with ~110 species concentrated in several large genera, but the early branches of the tree are composed of 7 different species-poor lineages. The first branch in the tree is in all analyses the Ovenbird (Seiurus aurocapillus) - the dull, chunky warbler of forest floors in the Eastern US. Other lineages represent monotypic genera, the odds and sods of the Parulidae that have been recognized as distinct - the Worm-eating Warbler (Helmitheros vermivorus), Black-and-White Warbler (Mniotilta varia), Prothonotary Warbler (Protonotaria citrea), and Swainson's Warbler (Limnothlypis swainsonii). The final two lineages in this group represent some of the generic reassignments already made by the AOU. The Northern (noveboracensis) and Louisiana (motacilla) are moved from the genus Seiurus, which they shared with the Ovenbird (a relationship that never made sense to me, given how different they are in plumage and habits), to their own genus, Parkesia (created for them by Sangster 2008). Three species of Vermivora - Bachman's (bachmanii), Blue-winged (pinus, now cyanoptera), and Golden-winged (chrysoptera), are found to not be closely related to the remaining members of the genus. These lineages are all found in Eastern North America, but represent a variety of plumage and ecological specializations. The exact relationships among them change depending on analyses (except the placement of Ovenbird at the base of the tree), but it is clear that they are all old and distinct, and I don't foresee anyone attempting to lump some of these monotypic genera.

Worm-eating Warbler (Helmitheros vermivorous) from Wikipedia

The remaining members of what was Vermivora - Tennessee (peregrina), Orange-crowned (celata), Colima (crissalis), Lucy's (luciae), Virginia's (virginiae), and Nashville (ruficapilla) - get their own branch of the warbler tree. These ex-Vermivora are a pretty cohesive and closely related group - they are all North American, either greenish (northern and eastern species) or grayish (southwestern species), most with an orange or rufous crown patch and yellowish vent. However, they share their branch with two oddballs - Crescent-chested Warbler (superciliosa) and Flame-throated Warbler (gutturalis), formerly in the genus Parula. Both of those are Central American species with plumage very similar to that of Northern and Tropical Parulas, Crescent-chested especially - check this photo out - but Flame-throated is a bit more distinctive and I'm not surprised it is not related to other Parulas.

The ex-Parula group is pretty closely related, the ex-Vermivora group is pretty closely related and the two groups are each others closest relatives on the big warbler tree, but already opinions differ on how to assign new genus names. Sangster (2008b) saw this result in earlier phylogenetic literature and took the step of naming each group separately - Crestent-chested and Flame-throated Warblers get the resurrected genus name Oreothlypis, and the ex-Vermivora get a newly created genus name Leiothlypis. Lovette et al. (2010) decided to give a genus name to the whole group, meaning Leiothlypis gets subsumed by Oreothlypis as the name for the group. The AOU voted the same way in the 51st supplement, merging all eight taxa into Oreothlypis, with many of the voters citing one genus as marginally better than two, even though it is totally arbitrary. I personally think keeping Leiothlypis and Oreothlypis as separate makes more sense, given their distinctiveness from each other, but both options are valid.

Lucy's Warbler (Oreothlypis luciae) from Wikipedia

The next branch in the warbler tree contains the yellowthroats (Geothlypis), species found throughout the New World united by black masks and another feature you might never guess from their name, the gray or black hooded North American warblers in the genus Oporornis, and an unusual, little-known, likely extinct species endemic to St. Lucia in the Lesser Antilles - Semper's Warbler (Leucopeza semperi). However, generic limits are all mixed up in this group, necessitating change. There is a tight-knit little group of closely-related yellowthroats, including the widespread Common (trichas) and the similar Belding's, Bahama, Altamira, and Hooded, and the slightly more distantly related Olive-crowned and Black-polled. Their closest relative is not, however, other yellowthroats but instead Kentucky Warbler (Oporornis formosus), which with its black mask and yellow underparts looks more like a yellowthroat than the other Oporornis anyway. The two gray-hooded species, Mourning and MacGillivray's, are closest relatives (and a hybrid zone has recently been described in Canada), but instead of being closest to the other gray-hooded species, Connecticut, they are related to two more unusual yellowthroats - Masked (aequinoctialis, which may actually be a species complex) and Gray-crowned (poliocephala). The two final species in this group are old, distinct genetic lineages - Connecticut (agilis) and Semper's Warbler. Escalante et al. (2009) and Lovette et al. (2010) both choose, because of how mixed up the traditional genus limits are, that it makes most sense to contain this whole group within one genus - Geothlypis has priority. An alternative treatment has already been made by John Boyd's TiF Checklist - he retains Leucopeza, allows Connecticut to retain the genus Oporornis, and leaves the rest as Geothlypis. I also tend to prefer retaining Leucopeza for the very distinctive Semper's Warbler, but Connecticut isn't all that different from others and I'm not sure it should get its own genus. I guess I'm undecided on this point.

Gray-crowned Yellowthroat (Geothlypis poliocephala) from Wikipedia

Masked Yellowthroat (Geothlypis aequinoctialis) from Wikipedia

The remaining warblers - fully two-thirds of the diversity of the family - form two broad groups. One contains almost all the remaining North American species, mainly the bright colorful migratory species in Dendroica that are what most come to mind when wood-warblers are mentioned. The other contains almost all warbler diversity in Central and South America in several distinct genera.

The North American Dendroica radiation of warblers is pretty amazing - they are the eye candy of the family. They underwent an early burst of speciation that declined through time, likely as ecological niches were filled. They have diversified to the extreme in plumage (and to a degree in song as well), so much so that virtually no plumage characters unite them, but they have not diversified much morphologically. This may constrain them ecologically, but they also adapt by behaviorally partitioning their ecological niches - the subject of some classic ecological studies. Check out this poster on the North American members of the group. Lovette et al. (2010) confirm earlier phylogenetic studies that Dendroica represents one big cohesive group. However, taxonomic changes come from other species found nested within the genus. The American Redstart (in the monotypic genus Setophaga), the two remaining Parula - American (americana) and Tropical (pitiayumi) - and the Hooded Warbler (Wilsonia citrina) are all firmly embedded within Dendroica. The strange Whistling Warbler (Catharopeza bishopi) - seen here - from St. Vincent in the Lesser Antilles is also closely related to this radiation, but represents the earliest branch. Lovette et al. (2010) choose to rename the whole group into one genus - Setophaga has priority, unfortunately removing the name Dendroica associated with much of the literature on the group. I agree with this move, except perhaps on lumping Catharopeza in with the rest. I like minimizing taxonomic changes necessary, and the position of Catharopeza as the oldest branch does not mandate that it be lumped in with the rest of the group. It is pretty unique in plumage, but on the other hand, few species in Dendroica look alike - it is their heterogeneity that unites them. John Boyd has taken an alternative approach to the taxonomy, choosing to preserve all of the other genera that were found lumped within Dendroica. This necessitates making some odd changes - three West Indian Dendroica (Arrow-headed (pharetra), Plumbeous (plumbea), and Elfin Woods (angelae)) would require their own new genus to be described, and Kirtland's (kirtlandii), Cape May (tigrina) and Cerulean (cerulea) would need to be lumped into Parula to preserve that genus. I completely disagree with this approach - it creates much more taxonomic change than the alternative, it relies on the exact branching pattern of species within the overall group which is likely to change depending upon the analysis, and I see no real distinctiveness to these genera - especially the bizarre new Parula.

Cerulean Warbler (Setophaga cerulea) from Wikipedia

Blackburnian Warbler (Setophaga fusca) from Wikipedia

Most warbler diversity in the Neotropics falls within a large genus, Basileuterus. While containing almost as many species as the newly expanded Setophaga, plumage in this genus is much more conservative, consisting most often of yellow underparts, green or grayish upperparts, and striping on the face. Lovette et al. (2010) find that Basileuterus is actually two distinct groups occupying different portions of the tree, and it needs to be split into two genera. One group is primarily South American species, and also includes embedded within it two species often given their own genus Phaeothlypis - River Warbler (rivularis) and Buff-rumped Warbler (fulvicauda). Phaeothlypis is merged into this genus and the South American group is given the resurrected genus name Myiothlypis. The other clade of Basileuterus retains that genus name and consists mostly of Central American species with a few closely related South American forms. In with the new reduced Basileuterus clade is the Fan-tailed Warbler, often split as its own genus Euthlypis lachrymosa. It represents the earliest branch in Basileuterus, and like Catharopeza could continue to be recognized because taxonomic change is not abolutely necessary, but Lovette et al. (2010) include it in Basileuterus.

Black-crested Warbler (Myiothlypis nigrocristatus) from Wikipedia

Pirre Warbler (Basileuterus ignotus) from Wikipedia

Buff-rumped Warbler (Myiothlypis fulvicauda) from Wikipedia

The final two Neotropical lineages are related to Myiothlypis. One lineage is the redstarts/whitestarts in the genus Myioborus. This is actually the only large genus in the Parulidae not affected by taxonomic changes. The other lineage contains a motley assortment - Canada Warbler (Wilsonia canadensis), Wilson's Warbler (Wilsonia pusilla), Red-faced Warbler (Cardellina rubrifrons), and the two reddish warblers in Ergaticus: Red (ruber) and Pink-faced (versicolor). A close relationship between Cardellina and Ergaticus is hardly surprising: these species are some of the only warblers to utilize bright reds in their plumage, and they are all restricted to Mexico and adjacent areas. The inclusion of two Wilsonia species here is bizarre - the genus never made any sense to me, but I expected them all to be thrown in with Dendroica. Instead, it looks like two species from the broad Neotropical radiation of warblers have reinvaded North America, become migrants, and are perhaps as similar to some Dendroica in plumage as they are to Neotropical species. As weird as this group appears, Lovette et al. (2010) lump Ergaticus, Cardellina, and the two Wilsonia into one genus - Cardellina has priority. The alternative, retaining Ergaticus, would necessitate the creation of two new monotypic genera for Wilson's and Canada Warblers - not really a very desirable solution.

Wilson's Warbler (Cardellina pusilla) from Wikipedia

Red Warbler (Cardellina ruber) from Wikipedia

Collared Whitestart (Myioborus torquatus) from Wikipedia

Well, that about covers Parulidae - or at least, a guide to the potentially confusing and contentious upcoming taxonomic changes in the group. I haven't even covered many problems with species limits in the group, or any of the interesting aspects of warbler biology that the phylogeny can be used to study. Maybe someday. To close, here is a summary of genera in the taxonomy of Parulidae proposed by Lovette et al. 2010:

Seiurus
Helmitheros
Parkesia (incl. some Seiurus)
Vermivora
Mniotilta
Protonotaria
Limnothlypis
Oreothlypis (incl. some Vermivora, some Parula)
Geothlypis (incl. Oporornis, Leucopeza)
Setophaga (incl. some Wilsonia, Dendroica, Catharopeza, some Parula)
Myiothlypis (incl. Phaeothlypis, some Basileuterus)
Basileuterus (incl. Euthlypis)
Cardellina (incl. some Wilsonia, Ergaticus)
Myioborus

References

Escalante P, Marquez-Valdelamar L, de la Torre P, Laclette JP, and J Klicka (2009) Evolutionary history of a prominent North American warbler clade: the Oporornis-Geothlypis complex. Molecular Phylogenetics and Evolution 53:668-678

Klein NK, KJ Burns, SJ Hackett, and CS Griffiths (2004) Molecular phylogenetic relationships among the wood warblers (Parulidae) and historical biogeography in the Caribbean basin. Journal of Caribbean Ornithology 17, 3-17

Lovette IJ and E Bermingham (1999) Explosive speciation in the New World Dendroica warblers. Proc R Soc Lond B 266:1629-1636

Lovette IJ and WM Hochachka (2006) Simultaneous effects of phylogenetic niche conservatism and competition on avian community structure. Ecology 87(7):S14-S28

Lovette, I., Pérez-Emán, J., Sullivan, J., Banks, R., Fiorentino, I., Córdoba-Córdoba, S., Echeverry-Galvis, M., Barker, F., Burns, K., & Klicka, J. (2010). A comprehensive multilocus phylogeny for the wood-warblers and a revised classification of the Parulidae (Aves) Molecular Phylogenetics and Evolution DOI: 10.1016/j.ympev.2010.07.018

Perez-Eman JL (2005) Molecular phylogenetics and biogeography of the Neotropical redstarts (Myioborus; Aves, Parulinae). Molecular Phylogenetics and Evolution 37:511-528

Sangster G (2008a) A new genus for the waterthrushes (Parulidae). Bulletin of the British Ornithological Club 128:212-215.

Sangster G (2008b) A revision of Vermivora (Parulidae) with the description of a new genus. Bulletin of the British Ornithological Club 128:207-211.

Another New Bird Species for 2009

The December issue of the Oriental Bird Club bulletin BirdingASIA has added a potential new species to the known birds of the world (see the other birds described in 2009 here). In June of 2009 (how's that for turnaround time?), two birders and tour leaders for Field Guides found a flowerpecker species (Dicaeidae) feeding on fruiting mistletoe above the rainforest canopy walkway at the Borneo Rainforest Lodge. It was unknown to them and the ornithologists working in this large primary forest. In sightings over several days, they took pictures of at least two individuals feeding on the mistletoe and heard one sing (too briefly to get a recording). Then they were gone, and the strange flowerpeckers haven't been relocated by the time of publication.

I have no experience or knowledge of flowerpeckers, so I can't comment on this birds' distinctiveness. The authors knew it was something different though, and ended up combing through the literature and 25,000 museum specimens comparing the photos to every possible look-alike, including little-known juveniles of all the flowerpecker species. Nothing matches. The authors speculate that the bird must be a canopy specialist to have avoided previous discovery in a well birder and surveyed area.

With no specimen in hand, a new species cannot be formally described. Instead, the authors gave it the label 'Spectacled Flowerpecker' and published their findings, ending with a plea to birders and ornithologists to help search for this species.

For more information and photos of the new bird, check out the paper, linked below.

Reference

David P. Edwards, Richard E. Webster, and Rose Ann Rowlett (2009) 'Spectacled Flowerpecker': a species new to science discovered in Borneo? BirdingASIA 12:38-41. PDF

New Bird Species of 2009

Welcome to the world! We're sorry we missed you for so many years.

Synallaxis beverlyae, Rio Orinoco Spinetail (Hilty and Ascanio 2009)

Prowling the mighty Rio Orinoco in Venezuela in 1998, Steven Hilty heard something strange singing from a small river island. Since Steven Hilty literally wrote the (excellent!) book on Venezuela's avifauna, this was nothing to dismiss. 11 years and a lot of hard work later, he amassed enough evidence to publish a description of a new spinetail species named for his wife Beverly. The new spinetail is most similar in plumage to S. albescens, a species in the llanos that overlaps S. beverlyae in range, but the song is closer to other species including S. albigularis from other regions of South America.

The new spinetail exhibiting typical spinetail shyness (Source: Hilty and Ascanio 2009)

This spinetail is found only in unique scrubby dense vegetation on river islands that are seasonally flooded. So far it is only known from three widely separated islands (see map below) but the authors guess that it could be distributed on islands in-between, which have been poorly surveyed. See Gunnar's post about this discovery for more as-yet-unnamed potential new species from these river islands (and more pictures of the new spinetail). While the population size and conservation status of these birds is unknown, the authors note that dams on the river threaten the natural flood cycles and the ecology of these islands.

The widely disjunct islands known to have the spinetail (Source: Hilty and Ascanio 2009)

Phylloscopus calciatilis, Limestone Leaf Warbler (Alstrom et al. 2009)

Beginning in 1994, ornithologists began to notice birds thought to be the Sulpher-breasted Warbler (P. ricketti) in breeding condition, singing, in what was their wintering range in Laos. Upon more detailed study, they realized these warblers represented a unique taxon. The plumage was nearly identical to P. ricketti but the Laos birds differed in songs, calls, and morphometrics. Analyzing the genetics, they found this new warbler was actually more closely related to the Yellow-vented Warbler (P. cantator), which is much more distinct in plumage, than P. ricketti, with which it is so nearly identical. Together the three species form a closely related group among Phylloscopus species, and they occupy distinct ranges in southeast Asia that don't quite overlap, as is typical for a closely related species complex. The authors named this new warbler calciatilis ("dwelling on limestone"), the Limestone Leaf Warbler, after the unique limestone karst region it is endemic to.

Limestone Leaf Warbler compared to similar species (Source: Alstrom et al. 2009)

Pycnonotus hualon, Bare-faced Bulbul (Woxvold, Duckworth, and Timmons 2009)

By far the strangest new bird is a bald, ugly, boring thing, like the Limestone Leaf Warbler, discovered in the limestone karst region of Laos. Observations of strange bald unknown bulbuls in the region were made as far back as 1995, but they were met with "good-natured ribbing". It wasn't until December 2008 that good, repeated observations were made by the authors and birds were captured in mist-nets. This crazy new species was named hualon - a Lao word for bald-head - and is noted in the publication as only found so far on one limestone outcrop. Other sightings are mentioned, and it appears to have been recently independently discovered at another location by this guy, who nicknamed them Khammouane Bulbuls. Check out his page for better photos of the species and the habitat.

Meet the Ugly Bulbul (Source: Woxvold, Duckworth, and Timmons 2009)

The birder who independently discovered these bulbuls seems to feel a little peeved at the original discoverers for not getting a publication out sooner. It is worth pointing out in all of the species here that none of them were first seen in this decade. While new species publications can (and should) happen a lot quicker than this, it is an enormous investment of time and effort for the ornithologists involved. Unless the new bird just serendipitously falls into a researcher's mistnet, it takes repeated observations by birders and researchers just to confirm a new bird has been found. Then you've got to go through the effort of capturing the bird and collecting specimens, getting recordings and characterizing the behavior and range of the new species. It needs a detailed comparison with other closely related species, and sufficient material might not be available for study in museums, necessitating more fieldwork. These new species are also not being found in heavily trafficked areas, and require setting up expeditions to remote areas. But I digress...

So, I could only find three completely new bird species descriptions for the year (Note I said descriptions, not discoveries, because as I've rambled about there is a lag time before publication. If you're wondering how many as yet undescribed birds are floating out there, there is a pretty good Birdforum thread about that) I think three is around average based on my recollection from the past few, but I haven't actually looked at the numbers. One of these days I'll get to that. To bolster this year's total, here are two more that don't quite make the cut as full new species.

Honorable Mentions:

Loxia sinesciuris, South Hills Crossbill (Benkman et al. 2009)

When compiling new species discoveries and descriptions, I try not to count those that were already known as populations or subspecies of another species and then split based on new data. There are lots of those every year, and it is plenty hard to keep track. Plus, completely new species are simply a lot cooler. This crossbill blurs the line.

A resident population of Red Crossbills (Loxia curvirostra) with a distinct call note was discovered in the South Hills of Idaho in 1997. Anyone who knows anything should know that Red Crossbills are one of the craziest and complex examples of adaptive evolution and incipient speciation this side of Darwin's Finches. There are 9 or 10 call types in North America, each with a particular conifer specialization and a bill morphology adapted to that conifer's cones. Many of these call types are nomadic across large swaths of North America, and bill morphology varies enough to make identification without call note difficult or impossible. I am less familiar with old world crossbills, but there are at least as many variants of Red Crossbill on that side of the pond. Basically, crossbill systematics are fubar.

The tiny geographic range of this putative new species (Source: Benkman et al. 2009)

So, that's why when the Idaho crossbills were discovered to be a resident population, crossbill guru Craig Benkman wasted no time getting them studied. Through his lab's work, they documented that the crossbills with the resident call type were almost totally reproductively isolated by assortative mating from other crossbill call types that periodically moved through the area. The other calls would breed in the same area as the South Hills call type, but the two weren't mixing. Because reproductive isolation is one of the strongest criteria for delimiting species, Benkman and colleagues lifted these birds out of the curvirostra morass and named them a new species. I could write a whole lot more about this system and all of its problems (I know because I've had a half-finished post started way back when this paper first came out), but I thought a brief summary was due here.

Geospiza sp. nov.?, Darwin's Finch (Grant and Grant 2009)

Remember two paragraphs ago when I mentioned the only more complex example of adaptive radiation than crossbills? Yup, this is it. The Grants have been studying ground finches in the Galapagos since just after Darwin left the early 1970's, and more than any previous work have made them the true example of Darwinian speciation. They've written whole books about their work, others have written books about them and their work, and countless scientific papers. Their paper this year has to be one of the coolest, though.

The Grant team has been tracking the fate of every medium ground finch on the small island of Daphne Major for 30 years through the use of color bands. In 1981, an odd immigrant from the other islands with hybrid characters from medium ground finch (Geospiza fortis) and cactus finch (G. scandens) arrived and started getting it on with the locals. The Grants monitored seven generations descending from this immigrant. In the forth generation, the lineage was reduced to two siblings, who bred and kept the lineage going. After that event, the lineage remained totally distinct, likely due to their distinct song, and have stayed reproductively isolated from the other finches on the island.

I get it now... the immigrants don't like to breed with bluebands (Source: Grant and Grant 2009)

Basically, the Grants just watched the birth of an incipient species. The immigrant lineage had larger beaks than the island native birds, providing ecological niche differences. When song differences arose through inbreeding, the lineage was able to remain distinct from other ground finches through behavioral isolation. This would have been the ultimate new species discovery, but the Grants refrain from giving it full species status (or any taxonomic status at all) and a name. They note that there is no answer to how many generations of isolated breeding are necessary before the lineage can be called a new species. They also note that many incipient species lineages are likely to fail before achieving full reproductive isolation, and predict that theirs will do so either through behavioral breakdowns leading to re-absorption by hybridization into the parent species or stochastic extinction of their tiny population.

So. Freakin'. Cool.



References

Alstrom, P, P Davidson, JW Duckworth, JC Eames, TT Le, C Nguyen, U Olsson, C Robson, and R Timmins (2009) Description of a new species of Phylloscopus warbler from Vietnam and Laos. Ibis 152: 145-168. Abstract

Benkman, CW, JW Smith, PC Keenan, TL Parchman, and L Santisteban (2009) A new species of the Red Crossbill (Fringillidae: Loxia) from Idaho. The Condor 111(1):169-176. Abstract

Grant, PR, and BR Grant (2009) The secondary contact phase of allopatric speciation in Darwin's finches. PNAS 106(48):20141-20148. Abstract

Hilty, SL, and D Ascanio (2009) A new species of spinetail (Furnariidae: Synallaxis) from the Rio Orinoco of Venezuela. The Auk 126(3):485-492. Abstract

Woxvold, IA, JW Duckworth, and RJ Timmins (2009) An unusual new bulbul (Passeriformes: Pycnonotidae) from the limestone karst of Lao PDR. Forktail 25:1-12. PDF