Here are the answers to the quiz from the last post:
a. Type 4
Type 4 is believed to specialize on the cones of Douglas-fir. It is widespread but somewhat irregular in its distribution: it is usually common in moist forests of the Pacific Northwest and can be frequently found in dry forests there also. It is regular in southeast Arizona, and indeed this particular recording was made at Barfoot Junction in the Chiricahuas in May 2009. It appear to be absent some years from Colorado, but fairly common in other years; 2009 saw a decent influx of this type into the state.
Ken Irwin (unpubl.) has proposed that hidden inside Type 4 there is another call type, Type 10, that specializes on sitka spruce in coastal California. It’s still unclear to me whether Type 10 is a separate call type or just a variation on Type 4. Whatever the case, Type 10 seems to wander widely, at least across the northern states, out to New England and Maryland.
The Type 4/10 group, as a whole, sounds very distinctive because of its upslurred calls. It may be a little hard to hear that they are upslurred because they are delivered so fast, but the rising, flicking quality of the calls is pretty distinctive, reminding some people of the “whit” calls of Empidonax flycatchers.
b. Type 9, the South Hills Crossbill
This type is sedentary and restricted to the South Hills and Albion Mountains of Idaho, where it feeds on the local variety of lodgepole pine. It sounds kind of like Type 2, clear, simple, and downslurred, but it is noticeably low-pitched. I think it is kind of “dull-sounding,” without much ring or resonance, but I’d be interested to hear how other people describe the difference. I recorded this in the South Hills in September 2009.
c. Type 2
Here’s a Type 2. This is probably the most numerous crossbill in North America; it is common almost everywhere Red Crossbills can be found. It is surmised to specialize on ponderosa pines. Across its range its calls are variable, but the high-pitched, clear, downslurred quality is fairly distinctive. This recording was made in Boulder County, Colorado, in July 2007.
d. Type 3
This is one of the smallest crossbills (only Irwin’s proposed Type 10 is similarly small) and is one of the most common crossbill types in moist northwestern forests, apparently specializing on western hemlock. It also can be found across the boreal forest, occasionally into New England, and it wanders rarely into the southern Rockies — there are now two certain records for Colorado and more in the “probable” category. There are also recordings from Arizona.
Types 3 and 5 sound similar to my ear: they are more complex than the types we heard above, less clear and less obviously upslurred or downslurred. Type 3 is the duller-sounding of the two, but I must admit I need practice with this identification. This particular recording, the second-ever for Colorado (from the Grand Mesa, February 2009), was made by Andrew Spencer when I was right beside him–and I didn’t turn on my microphone because I thought they were “just” Type 5s. To be fair, Andrew recorded them because he thought they were White-winged Crossbills. :) He didn’t identify them until days later when he looked at the spectrogram.
e. Type 5
This is the “other” common crossbill in Colorado (besides Type 2), a widespread bird of high elevations in the West, apparently adapted to feed on lodgepole pine but also very fond of Engelmann spruce. In direct comparison I think it sounds more “metallic” than Type 3, but it’s a tough call in the field. A distant flock can sound a lot like a bunch of crickets. This recording was made in Larimer County, Colorado, in June 2009.