Wild On The Prairie: Birds
Cowbirds adapted to the Buffalo Prairie
March 2, 2003
Originally cowbirds were called buffalobirds, but the name is forgotten. Cowbirds followed the buffalo. They developed parasitic egg depositing so they could stay with the buffalo. Buffalo grazed on the move, ranging casually, never remaining for long. Buffalo are social animals (except for old bulls). Even a small group exceeded the carrying capacity of the shortgrass and midgrass prairie. They had to move, and the cowbirds followed, their eggs left behind in other birds nests. A female cowbird will lay 40 eggs each year.
Cowbirds not only ate insects disturbed by buffalo, but more importantly by taking advantage of the rich microhabitat of decomposing buffalo dung. They harvested the dung invertebrates. Dung is recycled purposefully by many species of fly larvae, dung beetles, scarab beetles, termites, and ants. Scorpions and centipedes hunt the recyclers.
The dung were also pockets of seed, gathered by the buffalo as if especially for the cowbirds. Did the Cowbirds act as sentinels for the buffalo, with the buffalo interpreting their behavior for advance warning of an approaching predator? Or were they always out of sight of the buffalo, a day or two behind as the buffalo moved along? I have not found mention of the behavior of buffalo birds in the diaries of early settlers and explorers.
Female Cowbirds are masters of observation, able to find the nests of at least 150 species of birdsfrom warbler to thrush in size. Males gather in leks, performing for the wandering females. Males perform a spread wing crouch, and then topple over face forward to impress their prospective mate. The female is secretive, until the egg is laid, when she chuckles, preens, and ruffles her feathers. She sometimes remove an egg from the nest being parasitized, and usually only lays one egg per nest that she finds. Cowbird eggs hatch quicker than the hosts eggs, and Cowbird young grow faster than the hosts young. The young cowbirds will sometimes push their nestmates out.
Normally parasitization does not cause reproductive failure of the host bird. If it did, the technique would be factor in causing the extinction of the host species. Birds near the buffalo prairies adapted to cowbird parasitization, but when European man introduced cattle in places buffalo had not existed, eventually the Cowbird spread to these new locations. Bird species not adapted to parasitization have suffered, for example, the Black Capped Vireo of Central Texas and Oklahoma.
I use the symbolism of cowbirds to represent buffalo because of the vast winter flocks of cowbirds that flock to suburban horselots and edge of town farms. 10,000, 20,000, and more cowbirds, in one great flock, swirling and whipping about like smoke in a windy skyin difficult to count, or even estimate, bringing to mind the countless herds of buffalo of the Llano Estacado and the headwaters of the Concho, Colorado, Brazos and Red Rivers.
Five million buffalo ranged from the Concho River to the Canadian River. Three hundred to five hundred million prairie dogs also utilized that same range, as well as a million pronghorn. Summer heat urged a northward drift, winters blue northers sent each band and clan plodding south.
Two aerial phenomena could direct the daily travel of the buffalo. Smoke and clouds are semaphores of change. On the flat Llano the horizon is fifteen miles away, but a thunderstorm is visible for a hundred miles and more. Grass greens within hours of a rainfall; water swelling plant cells designed to disconnect, to go dormant without the injury of drought stress. In a week bunchgrasses grow six inches. Sideoats grama, sand dropseed, cane bluestem, windmill grass, fall witchgrass. The common names of the grasses beside the trails I walk daily are names I say subconsciously, respectfully, as I recognize these dominant members of the Southern Llano Estacado grassland ecological community.
The irregular spring thunderstorms would catch the prairie on fire, with the insistent southeast and southwest winds herding the fire for days. For miles, flaring up for the windy days and slowly smoldering on calmer nights, the fires burned and burned, until stopped by the broken rocky country of the breaks, or a draw with lush green grass snuffed the flames quiet. For a hundred miles, or two hundred, or even three, the fire rode the will of the winds. Afterwards, remnants of winter moisture fed quick green growth; within two weeks a blackened prairie became green. Buffalo turn and walk towards thunderstorms climbing fifty thousand feet into the sky, and would turn into a wind with the scent of old and traveled grass smoke.
Mesquite was present in the buffalo prairie, but only in the low areas where the moist vegetation stopped the range of fire. Buffalo helped control mesquite as well. Buffalo defeated hopeful mesquite seedlings advancing from their refuges. Mesquite has a weak crown, susceptible to fungus. Buffalo brushhogged the mesquite, stomping it, pulverizing the new growth. Fungus and rot organisms are part of a healthy biotic community, flourishing easily in the microclimate of the grass seas floor. Prairie dogs, of course, did their part, nibbling germinating seeds.
Thousands of hooves broke the hardened soil, tilling grass and forb seeds to planting depth, the litter of old stalks provided subtle niches for the seedlings nourishment. Grazing also forces grasses to send out new tillers - new sprouts from the clump, like offsets of day lilies and iris. Old clumps are recycled quickly by termites, earthworms and the rest of the decomposers.
The buffalo managed the grassland. Ungrazed grass deteriorates, choking itself with litter. The litter gives a protective mulch for the tall weeds Conyza and Sawtooth Daisy. Their six-foot-tall summertime bloomstalks shades the grass, further weakening it. The buffalo prairie was the creation of fire and grazing.
When you see a huge flock of cowbirds, imagine buffalo in even larger numbers. The cowbirds are the ghosts of the vanished buffalo.