Throwback Thursday: Strange Swallows from 1902

It’s Thurday! So, let’s dive into the avian hybrids literature and fish out a golden oldie. Today: hybrid swallows.

On June 14, 1893, in El Paso County (Texas, US) Edgar A. Mearns found a pair of swallows that were building a nest on an old building. He noticed that ‘the nest was similar to that of Barn Swallow, having the entrance at the top.’ And as any good ornithologist those days would do, he shot both birds.

The male turned out to be a Barn Swallow (Hirundo rustica), while the female was a hybrid between Barn Swallow and Cliff Swallow (Petrochelidon lunifrons). In a short article, published in The Auk, Mearns describes this peculiar cross, but unfortunately without any pictures or drawings. Luckily, I found some recent pictures online (click here for more):


barn x cliff

Barn Swallow (left), Cliff Swallow (right) and a presumed hybrid in the center.



Mearns, E. A. 1902. Description of a hybrid between the Barn and Cliff swallows. The Auk, 19: 73-74.



Some Hybrid Woodpeckers from North and South America

Today, I would like to discuss two papers on hybridization in woodpeckers. The first paper provides the description of a cross between two species in Paraguay. The second study concerns a genomic analysis of hybrid zones between three Sphyrapicus species.


Paraguayan Peckers

Andrés Oscar Contreras Chialchia and Paul Smith provide a detailed description of a hybrid between Cream-backed Woodpecker (Campephilus leucopogon) and Crimson-crested Woodpecker (C. melanoleucus), two species that co-occur along the banks of the Paraná River in Paraguay. Because one picture says more than a thousand words: here is the hybrid specimen alongside the parental species. You can clearly recognize traits of both species. For example, the black-and-white spot on the cheek and the creamy back of the Cream-backed Woodpecker and the striped belly of the Crimson-crested Woodpecker.

Hybrid Woodpecker.png

Top: the hybrid specimen. Left: Cream-backed Woodpecker. Right: Crimson-crested Woodpecker


Sapsucker Hybrid Zones

Three species of Sphyrapicus woodpeckers – Red-breasted Sapsucker (S. ruber), Red-naped Sapsucker (S. nuchalis) and Yellow-bellied Sapsucker (S. varius) – interbreed in several hybrid zones. Red-breasted and Red-naped Sapsucker are more closely related to each other compared to the third species. This situation provides an excellent setting to study the build-up of reproductive isolation and genetic differentiation over time.

Christine Grossen and her colleagues examined over 30 000 genetic markers (Single Nucleotide Polymorphisms or SNPs) along hybrid zones in the Coast Mountains and Rocky Montains. The genomic analyses showed that the tree species are clearly distinct with a small number of hybrids in each hybrid zone. This indicates that there is moderately strong reproductive isolation between them.


hybrid sapsuckers

The three species: Red-naped Sapsucker, Red-breasted Sap-sucker and Yellow-bellied Sapsucker (from left to right)


There were no large regions of differentiation in the genome (so-called ‘genomic islands of differentiation’). However, the authors uncovered 19 small regions of differentiation, some of which were shared between species. One of those regions contained a candidate locus associated with plumage, which could contribute to reproductive isolation.

The authors conclude that ‘[o]ur comparative analysis of species pairs of different age and their hybrid zones showed that moderately strong reproductive isolation can occur with little genomic differentiation, but that reproductive isolation is incomplete even with much greater genomic differentiation, implying there are long periods of time when hybridization is possible if diverging populations are in geographic contact.’



Chialchia, A. O. C. & Smith, P. (2014). A notable hybrid woodpecker (Campephilus leucopogon x C. melanoleucus)(Aves: Picidae) from Paraguay. ORNITOLOGIA NEOTROPICAL 25, 459-464.

Grossen, C., Seneviratne, S. S., Croll, D. & Irwin, D. E. (2016). Strong reproductive isolation and narrow genomic tracts of differentiation among three woodpecker species in secondary contact. Molecular ecology 25, 4247-4266.


Both papers have been added to the Piciformes page.

Throwback Thursday: A Hybrid Quail That Tried to Phone Home

Numerous papers on avian hybridization are published each month, applying the newest genomic and statistical techniques. But occasionally, one needs to escape to simpler times. That is the idea of this Throwback Thursday section on the blog: I dive into my huge collection of literature on avian hybridization and pick out a remarkable paper. Today concerns a short piece by M.E. Peck, published in The Condor in 1911. The short title almost says it all: A Hybrid Quail.

The bird in question is probably a cross between Mountain Quail (Oreortyx pictus) and California Quail (Callipepla californicus, in the paper referred to with the older generic name Lophortyx). The hybrid was found in Oregon, where it ‘was killed, apparently, by flying against a telephone wire.’ Mr. Peck himself collected the bird and mounted it ‘while fresh’. The morphological analysis shows that ‘[i]f this hybrid be compared point by point with the two parent forms, there will be found a remarkably even balance of characters derived from each; this is especially true of the coloration.’ Here is a – unfortunately black-and-white – picture of the mounted specimen:

Hybrid Quail

And for comparison, the two species that produced this fine specimen.


Mountain Quail (left) and California Quail

Finally, I would like to share the title page of this short paper. It is amazing how nice the old editions of these journals, such as The Condor, looked those days.



Peck, M. 1911. A hybrid quail. The Condor, 13: 149-151.

The Superb Bird-of-Paradise and the ‘Dancing Species Concept’

Time for something different, but actually closely related to hybridization: species concepts. Today, I came across a press release from the Cornell Lab of Ornithology. It concerns the Superb Bird-of-Paradise (Lophorina superba), a bird species endemic to New Guinea and known for its peculiar mating display. It can be best described as a jumping black and fluorescent blue smiley-face (click on the picture to see the courtship display in action or click here).




Scientist Ed Scholes and photographer Tim Laman documented this courtship display for two populations: the western population in the Arfak Mountains and the more common population that occurs all across the island. They noted striking differences between birds from these populations. Scholes remarks: “The courtship dance is different. The vocalizations are different. Even the shape of the displaying male is different.” Pictures show that the shape is indeed different. The Western male has a crescent shape, while the common male is more oval-shaped.


superb pictures

Differences in shape between Western male (left, crescent shape) and widespread male (right, oval shape).


Based on their observations, Scholes and Laman both believe that the Western population should be considered a separate species. When I read this, I had to frown. Can you really describe a new species based on dancing? Then taxonomists could add an extra species concept to the long list already available: the Dancing Species Concept. According to this species concept, I would be considered member of a separate species compared to some of my fellow Homo sapiens. My dancing moves are – euphemistically speaking – not so good…

Of course, I am writing this jokingly.  The distinct dancing behaviors of Superb Birds-of-Paradise fit within the Species Recognition Concept. The display ensures that females chose the ‘right’ species. It would be interesting to see how females from the Western population respond to displaying males from the widespread population. If they ignoring the jumping smiley, it would provide extra evidence for the description of a new species.

In fact, a recent genetic study showed that the Western population is genetically distinct from the widespread population. “The timing of this DNA-based study is perfect,” said Ed Scholes, “because it is great to have our field observations supported by solid genetic evidence. We really appreciate this in-depth study of the evolutionary relationships among the different forms of Superb Bird-of-Paradise.” To be continued.




Irestedt, M., Batalha-Filho, H., Ericson, P. G., Christidis, L. & Schodde, R. 2017. Phylogeny, biogeography and taxonomic consequences in a bird-of-paradise species complex, Lophorina–Ptiloris (Aves: Paradisaeidae). Zoological Journal of the Linnean Society.

The Songs of Tree Finches (and their hybrids)

Floreana Island, one of the islands in the Galápagos archipelago, is home to the critically endangered Medium Tree Finch (Camarhynchus pauper). This small passerine coexists and hybridizes with the common Small Tree Finch (C. parvulus). Estimating the population sizes of these species is extremely difficult because they are morphologically similar. Therefore, Katharina Peters and Sonia Kleindorfer relied on acoustical surveys. In other words, they compared the songs of these finches.

Medium Tree Finch

close-up of a Medium Tree Finch (C. parvulus)

Song differed significantly between Medium Tree Finch and Small Tree Finch, but it was not possible to discriminate between Small Tree Finch and the hybrids. So, the latter two were combined in the ‘C. parvulus/hybrid’ group for further analyses.

Comparing acoustical surveys in 2004, 2008 and 2013, it turned out that the endangered Medium Tree Finch has declines by 52% between 2004 and 2013, while the  ‘C. parvulus/hybrid’ group has increased by 45% during that time period. The decline of the Medium Tree Finch is probably the outcome from an extreme drought event that hit the Gálapagos islands from 2003 to 2007.



Peters, K. J. & Kleindorfer, S. (2017). Avian population trends in Scalesia forest on Floreana Island (2004-2013): Acoustical surveys cannot detect hybrids of Darwin’s tree finches Camarhynchus spp. Bird Conservation International, 1-17.


This paper has been added to the Thraupidae page.

Hybrid Geese in Finnish Hunting Bags

Time to share a paper on hybridization in a bird group that is close to my heart: geese. I obtained my PhD studying the role of hybridization in the evolutionary history of the True Geese (see here for several publications). For some reason, you develop an unbreakable bond with the topic of your PhD thesis. But enough sentimental jibber-jabber, let’s dive into this week’s avian hybrids paper.


Some Taxonomy

The Bean Goose complex is a taxonomic nightmare. The current classification encompasses three species: the Pink-footed Goose (Anser brachyrhynchus), the Taiga Bean Goose (A, fabalis, three subspecies) and the Tundra Bean Goose (A. serrirostris, two subspecies), although some authorities lump Taiga and Tundra Bean Goose together. However, based on analyses of the mitochondrial control region, Ruokonen et al. (2008) identified three distinct lineages: the Pink-footed Goose, the Middendorff’s Goose (currently a subspecies of Taiga Bean Goose), and the Bean Goose (currently split in Taiga and Tundra Bean Goose). Ottenburghs et al. (2016a), on the other hand, reported a sister species relation between Pink-footed Goose and Tundra Bean Goose. The phylogenetic relationships in this complex are highly influenced by rapid speciation and hybridization.


Hybrids in the Hunting Bag

Johanna Honka (University of Oulu, Finland) and colleagues collected Bean Geese that were shot by Finnish hunters between 2010 and 2013. A genetic analysis, based on mitochondrial DNA (mtDNA) and microsatellites, revealed that most shot geese belonged to the Taiga (sub)species.

More interesting (from an avian hybrids point of view), one individual carried mtDNA from a Pink-footed Goose, while another individual had Greater White-fronted Goose (A. albifrons) DNA. This confirms the idea that there is a lot of hybridization going on in geese (see here for an review on hybrid geese; Ottenburghs et al. 2016b).

bean goose x pink-footed goose

A possible Bean Goose x Pink-footed Goose (from


Honka, J., Kvist, L., Heikkinen, M. E., Helle, P., Searle, J. B. & Aspi, J. (2017). Determining the subspecies composition of bean goose harvests in Finland using genetic methods. European Journal of Wildlife Research 63, 19.

Ottenburghs, J., Megens, H. J., Kraus, R. H., Madsen, O., van Hooft, P., van Wieren, S. E., Crooijmans, R. P., Ydenberg, R. C., Groenen, M. A. & Prins, H. H. (2016a). A tree of geese: A phylogenomic perspective on the evolutionary history of True Geese. Molecular Phylogenetics and Evolution 101, 303-313.

Ottenburghs, J., van Hooft, P., van Wieren, S. E., Ydenberg, R. C. & Prins, H. H. T. (2016b). Hybridization in geese: a review. Frontiers in Zoology 13, 1-9.

Ruokonen, M., Litvin, K. & Aarvak, T. (2008). Taxonomy of the bean goose-pink-footed goose. Molecular Phylogenetics and Evolution 48, 554-562.


This paper has been added to the Anseriformes page.