*(MOVIE)*
Buffalo Gap Dickcissels, 2012
Distinctive Calls of Male Dickcissels
If you have Dickcissels in your pastures or if you pass their field with your window down there will be little doubt of it, for the males take their bright colors and loud voices to their advertisement perches and sing and counter-sing, hardly taking a breath break. They arrive as a group and seize the grassland acoustics. Breeding males are loud and obvious and they generate a territorial din. This year the Dickcissels arrived at Wheatlands Farm at Buffalo Gap in Virginia’s Shenandoah Valley on June 1 and for the next 66 days they dominated the rap.
In our last post we noted the connection Kenn Kaufman sees between recent eastern breeding appearances of the Dickcissel and the stresses from drought and fire the bird faces in its traditional prairie nesting range. In 2011 drought choked the southern prairies, engulfing Texas plus a 200-mile margin, and arguably accounted for the Dickcissel irruption east of the Allegheny Mountains as the birds sought alternate breeding opportunities. This year the drought expanded northward, toasting crops and pastures across Nebraska, Iowa, and Wisconsin and compromising grassland nesting over an enlarged dry zone. And in 2012 the Dickcissel chorus at Buffalo Gap grew by many voices; upward of a dozen males sang on this farm of 160 acres of grassland, more than double the 2011 numbers. That level of Dickcissel breeding density is characteristic of the grassland sweet spots in Missouri and Kansas but is uncommon in the East. (Check Lang Elliot's comments and recordings at www.birdtunes.com)
The U.S. Drought Monitor, maintained at the University of Nebraska in association with NOAA and USDA, observes regarding the 2012 episode,
" The drought has inflicted, and is expected to continue to inflict, catastrophic economic ramifications for the affected states."
So, the drought sequence will likely continue, seemingly a component of global climate change. If 2013 is comparably dry in the prairie states and if the Dickcissels again seek nesting relief in the East, there will be little doubt of the Kaufman correlation. Would a record search show that eastward Dickcissel irruptions in earlier years were also the result of western weather stresses? At this point we are on notice of a likelihood that the Dickcissel will be needing welcome in such grasslands as remain in the East (after the massive twentieth-century abandonment of eastern farmland). In seeking breeding refuge to the east of its principal historic range, is the Dickcissel an early indicator species of climate change?
The Dickcissel has problems in the east which it did not have in its pre-Colombian prairie range where the main perils to nesting were bison hooves and fires; worse, of course, in dry years. Arriving in Virginia's Shenandoah Valley on June 1st of this year, the Dickcissels set up shop a month or more behind the Bobolinks and Meadowlarks. Eastern farmers cut hay in late May and early June. Hay made in early June on this farm this year would have contained Dickcissel nests; some other nests as well, but many of the other grassland obligates have brought off a brood by then and could better afford the loss than could the Dickcissels.
Most of the eastern grasslands available for breeding are those which farmers maintain for pasture or hay and the Dickcissels arrive at the wrong moment in the farming schedule. If they choose hay ground the nests go through the cutter. If they select lightly-grazed pasture, that is likely to be clipped for weed control in early July. A Dickcissel's best hope is to find a spot inaccessible to cutting equipment -- a wet or rocky place -- large enough to accommodate a territory.
That is another problem. Grassland birds including Dickcissels and Bobolinks are, in the terms of researchers, "area sensitive"; they need tracts of suitable habitat large enough to accommodate not just one territory, but several, perhaps many. You don't often find one pair of Dickcissels or Bobolinks (like many grassland birds, both are polygamous and sometimes polyandrous so the term "pair" applies loosely), you find a nesting cohort which requires a large tract of grassland; research suggests a minimum of 60 acres for Bobolinks. Dickcissels migrate together, claim adjacent territories, winter together, and perhaps know one another as individuals across their lives. A migrating group in search of accommodations doesn't just shed one or two pairs at each promising weed patch; the entire group stops when it finds a tract suitable to the tribal need. When nesting is finished, they decamp for Venezuela en masse as abruptly as they arrived. At Wheatlands Farm they departed on August 5th this year.
In 2012 this farm gave up a cutting of hay on 45 acres of alfalfa and orchard grass to accommodate the Dickcissels’ relaxed schedule. By the coincidence of a mild previous winter there was enough hay left over for the coming winter, assuming average weather, meaning no back-to-back three-foot snows. Such hospitality would normally be beyond the means of many farms, this one included, even with all hearts in the right place and all awarenesses attuned. Few farms can offer the largesse Dickcissels require of the eastern yeoman -- on the order of ten large round bales of hay per nest. By that crude estimate, a farm would sacrifice 250 cow days of winter feed in hosting one Dickcissel nest. But -- you don't get one nest; you get some nests or none.
The Dickcissels at Buffalo Gap outline a conservation challenge. The bird is persecuted with surfactants and other chemicals on its wintering grounds in Venezuela where grain farmers consider it a pest, as we once viewed the Carolina Parakeet. The Dickcissel is under pressure from drought and fire on its traditional North American grassland breeding grounds. So, we surmise, it has turned eastward for a chance to recruit and to sustain viable numbers. Here it runs into an adverse farming schedule in its principal nesting habitat. We must think of a way to accommodate all parties.
