South Hills Crossbill - Idaho

The March issue of Condor includes: Benkman, C., J.W. Smith, et. al. (2009) "A new species of red crossbill (Fringillidae: Loxia) from Idaho." Condor 111: 169-176.

The South Hills and Albion Mountains of the Sawtooth National Forest of southern Idaho have a resident, Type 9, Red Crossbill that Benkman et. al. describe as a good species, South Hills Crossbill Loxia sinesciuris.  Sinescirius  means "without squirrels".  The South Hills area is surrounded by sage habitat, a natural barrier preventing emigration of pine squirrels. The absence of red squirrels enables Rocky Mountain lodgepole pines and crossbills to engage in a "coevolutionary arms race" with the pines developing larger and thicker scales and crossbills evolving larger and deeper-based bills.  A result is lodgepole pines' serotinous cones remain unopened until a fire sweeps through melting the cone scales.  Without fire or squirrels, tightly closed scales surrounding lodgepole pine seeds are only opened by the seed predator, red crossbills. 

There are two other crossbill types, Type 2 and Type 5, moving in and out of the area.  Those two crossbill types have been recorded breeding with South Hills Crossbills in 12 of 1704 pairings, a frequency of 0.007, an order of magnitude less frequent than the hybridization occurring in other named European crossbill species. Sonograms of "South Hills Crossbill" flight call notes and songs are different than other "type" crossbill sonograms.  Songs of South Hills Crossbills have many buzzy notes, whereas songs of both Type 2 and Type 5 crossbills consist mostly of shorter whistled notes.  The authors suspect this new "species" also occurs north and east of the currently described range.

Scientific evidence seems to favor Type 9 Red Crossbills becoming South Hills Crossbill, but we will wait to see if the AOU Check-list Committee feels the same way. On a global warming note, climate change predictions have forecast the South Hills and Albion pine forests to disappear by the end of the 21st Century and with it this unique crossbill.

Comments

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I would rather not see Red Crossbills split into a bunch of species. Birders/listers will have to have recording equipment to figure out what species they are seeing. I'll give up listing, if this happens.