Sunday, June 19, 2011

A new hybrid hummingbird from Honduras

Our monthly bird monitoring pulse in Monte Uyuca, Honduras, yielded a surprise this week in the form of this hummingbird, an apparent hybrid of Azure-crowned Hummingbird x Berylline Hummingbird. Although hybridization is relatively common in hummingbirds, we believe this to be the first report of this particular combination. We're preparing a short paper documenting this remarkable find.

Roselvy, Lya and I had just started our bird banding Thursday morning and this was the very first bird I pulled out of the nets. Not recognizing the species, I was excited that we captured yet another new hummingbird for the station, after three new hummingbird species last month! A review of the Howell & Webb guide, however, quickly made us realize that none of the species found in the region fit this bird, and that we were holding in our hands either a vagrant or a hybrid.

The second possibility seemed the more obvious, and once we figured that out, it didn't take us long to arrive at the most likely parental candidates.

In this partial side view, the bird looks much like a regular Azure-crowned Hummingbird, a locally abundant species.

Turning the bird a little, however, reveals a heavily spotted throat and breast, where Azure-crowned has more white. The crown is not blue ("azure"), but green. (Go back a few blog posts for shots of a regular Azure-crowned Hummingbird.) Berylline Hummingbird has a green throat and crown.

The tail of this individual is not at all like an Azure-crowned tail, but a lot like a fresh Berylline tail. The purple gloss in the tail of Berylline hummingbird tends to fade to rufous on more worn individuals, usually notable on the outer rectrices especially.

Beautiful tail!

Here's a view of the underside of the bird, showing a mix of characters of Azure-crowned and Berylline Hummingbirds.

Berylline Hummingbird has a large rufous flash in the wings, absent in Azure-crowned. This individual has a weak rufous flash.

This weak rufous flash is also visible on the upperside of the wing.

What a lovely bird!

There's an extensive body of literature on hybridization of hummingbirds, handily summarized here. Intra- and intergeneric hybrids have been described for various Amazilia species, including Berylline, but apparently not Azure-crowned. The latter is common at the study site, Reserva Biológica Monte Uyuca near Tegucigalpa, Honduras, while the former has never been recorded there - at least not by us, during monthly banding pulses that started in January of 2010. Berylline does occur in Honduras, reaching the eastern edge of its range in the area of the study site.

We took photographs and measurements, before we released it back into the wild.

Postscript 2 July 2011:
It seems this hybrid has been reported once before, by a French ornithologist who sorted through the specimen collection of the British Museum, encountered what he thought was this combination, and published his notes. See Jacques Berlioz, 1932, Notes critiques sur quelques Trochilidés du British Museum, Oiseau 2: 530-534. Berlioz describes his find as the probable result of a cross between Azure-crowned and Berylline Hummingbirds, showing a perfect mix between the two parent species. He notes that this individual was collected near Jalapa, the capital of the Mexican state of Veracruz, where both species occur.

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