Robins and crossbills. How odd to have both robins and two species of crossbills having wintered in our region in such impressive numbers. In the case of white-winged and red crossbills, a simply unprecedented irruption of these delightful finches. Maybe even phenomenal.
How come? Available food is probably the reason. Last year’s spring and summer weather helped bushes, shrubs and trees produce a truly bumper drop of fruits and berries. These sustained the flocks of robins. (The pickings must be getting sparer by now.)
Speculating about all those crossbills is a lot shakier. Both white-winged and red crossbills began to be recorded in unusual numbers last autumn by Dr. Thomas Hahn, UC Davis, in Jackson Hole, who studies these birds here and elsewhere.
Now then, the continent is suffering a catastrophic loss of coniferous trees to insects and an introduced blister rust. Consequences from this will be many and significant and with us for a long time. Animals and birds dependent in part or in whole on cone seeds are just some of affected organisms.
Crossbills are not exclusively cone eaters, for they eat seeds of fruit (discarding the pulp) and insects and seeds, even suet. In fact, they eat these non-cone foods using their specialized bills just as other birds do. However, those crossed bills are indeed unusual, intended to pry open the scales of closed coniferous cones.
In fact, the entire bird seems to have evolved to open unripe cones. Its crossed bill’s upper (longer) mandible wedges between two cone scales so that the tip of the lower mandible is fixed on the inside surface of a scale. The bird then twists its head and forces the two mandibles apart by special jaw muscles. Then the unusually large parrot-like tongue extends into the newly opened scales and “eats off the unripe seed using a special cartilaginous cutting tool which forms the tongue tip.” (Christopher Leahy in The Birdwatchers Companion). During this activity the crossbill’s unusually powerful large feet secure the pine cone and the bird.
Not to mention they’re cute. And tame. Possibly tame because crossbills are usually coniferous arboreal forest dwellers and not used to human presence. Thus, they sport a variety of plumages, from red to orange to yellow. Darn cute.
Couple of days ago, there were eight red crossbills and two white-winged crossbills in my feeder tray at once. The two white-wings were surprisingly and quite noticeably smaller birds. Further, their bills did not look entirely crossed. Mandible crossing on these cute little birds doesn’t show itself for about a month after hatching. Crossbills can breed at any time of year when ripe cones are available. They will at times breed even during an “irruption,” such as the one we’re witnessing now. So many crossbills or other species south of their expected wintering ranges are termed an irruption of that species.
Robins not having left the region is not considered an irruption. But, have you noticed the abundance not only of crossbills but also of red-breasted nuthatches.
If you’re not feeding birds yet, you can. There’s lots of time to get in on the fun.
Field Notes: April Fool’s Day, but I kid you not: This is springtime in the Rockies. Enjoy it.
Birds know it’s spring. Some species have already bred. Others – owls and ravens – are audible and visual examples of bird courtship. Robins, too, were in the mood before this latest exhibition of spring snows. Of course, some migrants have retreated south but shall return.
A spotted towhee, quite unusual here, was down near the Hoback Junction around March 17 (Andy Angstrom) and it or another was on the west bank on Friday (Connie Leavell). Also now on Crane Creek Ranch, Wendy Morgan, Sunday. Probaby the same bird. It’s really great to be able to follow one bird on its wanderings in the valley, thanks to careful observers.
Around mid-March, Andy Angstrom hit the big time! Harris’s sparrow, Savannah sparrow, Lincoln’s sparrow and song sparrow.
Those pesky crossbills are surprising folks all over the place (Alice Richter, Roger Watson, Francesca Rice and lots of others). On March 23, Roger Watson heard two boreal owls conversing plus a saw whet owl calling. Pine grosbeak numbers increased (Deborah Linn, Tammy Christel). Evening grosbeaks turning up (Steve Kilpatrick, Ron and Jen Gessler).
Sandhill cranes were back beginning on about March 18 (John Kerr, Mike Maples). Prairie falcons were back by March 19 (Bob Martin, Mike Maurer). An influx of rosy finches (Bruce Hayse, Claudia Gillette). Clark’s nutcrackers were noticed, as were red-breasted nuthatches. Red-tailed hawks came back, probably wondering why so soon. Juncoes in groups and flocks and a few Cassin’s finches. Clark’s nutcrackers, in town, Julie McLauren.
Sally Haubert welcomed a lone bull bison (Thursday, in Kelly). On Friday, Joel Lopez spotted a group of eight moose at the Gros Ventre Junction on U.S. 89.
Oh ... on March 22, Kirby and Stephanie Williams were enjoying spring beauties. Hope those wildflowers are cozy today under their white covering.
© Bert Raynes 2009
Bert Raynes writes weekly on whatever suits his fancy with a dash of news on nature and its many ways.