That OTHER Red Crossbill Complex

One of the newest, most cutting edge challenges of modern, ABA Area birding is identification of red crossbills to type. For those not aware, it has been shown that red crossbills in North America can be divided into as many as ten “types” which are differentiable in the field mainly by distinctive flight calls. It is thought that the crossbills are radiating to adapt to forage in different species of conifer. This has all become common knowledge in the birding community in the past few years, with many birders actively seeking to record crossbills in the field and then identify the recordings (here‘s a good example of me doing the same thing with a vagrant flock of red crossbills in Pennsylvania). What is considerably less common knowledge is that red crossbills in Europe (typically known as common crossbill) also have types (the first observations of which were made by Magnus Robb in Dutch Birding). If little is known about the types in North America, next to nothing is known about the types in Europe; identification of crossbills here is very much on the cutting edge.

I was lucky enough this week to encounter a couple groups of crossbills in the (awesomely named) Accursed Mountains National Park in Kosovo and, despite being stupid enough to leave my microphone at my hostel, was still able to capture a mediocre iPhone recording of a couple of birds.


Crossbill Land, Accursed Mountains National Park, Kosovo

But before diving into my recording, a brief overview of European crossbill types is in order. To begin with, crossbills typically have two distinct calls, a flight call and an excitement call (typically used for alarm or to call in other crossbills). Both of these call types can typically be identified to type. There are 8 types of crossbill in Europe which are each assigned letters (unlike the numbers used in North America). They are as follows:

Type A- Wandering Crossbill, a common and widespread irruptive type.

Type B- Bohemian Crossbill, specializes in black pine and apparently found in Central Europe, the Balkans, and Turkey.

Type C- Glip Crossbill, seemingly the commonest (at least in Western Europe).

Type X- Parakeet Crossbill, another common Western European type.

Type D- Phantom Crossbill, reminiscent of “Enigmatic crossbill” of the ABA Area in that it is little known and appears to vanish for years at a time.

Type E- British Crossbill, name says it all.

Type F- Scarce Crossbill, only recorded from the Low Countries.

This information has mostly come from the excellent book The Sound Approach to Birding which has a great section on crossbill ID.

Now back to the crossbills in Kosovo. The recording in its mostly unedited entirety can be viewed here. Not surprisingly given the above information, the recording revealed them to be Type B (Bohemian). This is seemingly the resident type in the various Balkan mountain ranges.

The majority of the recording is a lone bird giving excitement calls. As you can see in the below spectrogram, these are multibanded (although the low quality of the recording obscures many of the bands) and high pitched. A listen to the recording itself will show a distinct nasal quality of the notes. These are all characteristics of Type B.

Screen Shot 2017-10-31 at 11.03.25 AM

Excitement Calls

More distinctive to the ear, is the flight calls of the small flock which comes overhead towards the end of the recording. These calls are high, upswept “weet” notes which, again, are distinctive of Type B.


Circled Examples of Flight Calls

Also note the (barely audible) fractions of song in the middle of the recording.

It was really great to get my first experience with European crossbill types. This kind of thing is a fantastic way to broaden your birding skills and also is contributing in a valuable way to science. In this case for instance, this is only the third crossbill recording I can find from the Balkans (with an additional one from Slovenia and one from Bulgaria) and is the only one of the three which has been identified to type. It cannot be stressed enough how little is known about this fascinating complex: for example, eBird output shows no records of Type B at all!!

If I encounter more crossbills here in the Balkans, I hope that I will be able to obtain some better recordings and perhaps see if any other types (namely widespread, irruptive ones) are showing up in the area. But in the mean time, I am content with what might be the first fully identified red crossbills in the Balkan Peninsula.

eBird checklist:

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