Lesser Prairie-Chickens in Southeastern New Mexico

Male lesser prairie-chicken (Tympanuchus pallidicinctus)
near Milnesand, New Mexico, March, 2001.

The lesser prairie-chicken, Tympanuchus pallidicinctus, is a member of the grouse family Phasianidae.  Grouse are chicken-like birds that are often hunted for sport or food.  The lesser prairie-chicken is a handsome bird, with sandy brown barring over most of the body, and paler barring below.  The sandy color and barred pattern enable the lesser prairie chicken to blend in well with the sandy-soiled grasslands in which it lives.  The body is 16-18 inches long, and the wingspan is about two feet.  Lesser prairie-chickens weigh about 1.6 pounds.
             The mating system of lesser prairie chickens is centered on their display grounds, which are called leks.  A lek is an area in which several males gather to perform their elaborate mating display.  The males have orange-colored sacs on their necks, which they inflate to make them more conspicuous.  At the same time, they lower their heads, raise feathers on the backs of their necks, fan their tail feathers, make short jumps into the air, flap their wings, and rapidly stamp their feet on the ground.  The males face off with each other in display contests and sometimes are aggressive toward each other.  All of this activity is accompanied by a warbling gobble that is somewhat reminiscent of a turkey, and may be audible for over a mile.  Presumably, the female lesser prairie-chickens find all of this attractive, and they come to the lek and select a male.  The mating takes place on the lek, usually in April, and the female then leaves to begin nesting.
              Males may live for five years, and they usually use the same lek throughout their lives.  Leks are used by several generations of males, and some leks have been known to remain active for fifty years.  The lek is a large open area with little or no vegetation.  Lesser prairie-chickens sometimes use abandoned oil well drill pads or little-used dirt roads as leks.
              The female makes her nest in grass left over from the previous summer.  The nest is usually within two miles of the lek.  The female lays 12-15 eggs and incubates them for 24 days.  Young lesser prairie chickens are downy and precocial, and leave the nest soon after hatching.  Although the mother watches over them, young lesser prairie chickens feed themselves.  They can make short flights in one to two weeks, and are fully grown after several weeks.  Lesser prairie-chickens eat grasshoppers and other insects, seeds, leaves, waste grain, and the acorns and catkins of shinnery oak.
             Lesser prairie-chickens spend their winters feeding and loafing in the residual grasses, usually within a few miles of their lekking grounds.  During deep snows they may burrow into the snow for warmth.  Lesser prairie-chickens are strong fliers, and when disturbed they fly off toward the horizon, often not landing until they have flown a mile or more.  Lesser prairie chickens are well-camouflaged and wary of humans.  This makes them difficult to find during most of the year, but during mating season males become somewhat oblivious to everything except possible mates and competitors.  Birdwatchers and researchers observe lesser prairie-chickens by arriving at a lek well before sunrise.  As long as the observers remain in their vehicles or in blinds, the males begin their display before first light, ignoring the trucks and their occupants.  However, the lekking grounds of most lesser prairie-chickens are now protected, and every effort should be made to avoid disturbing displaying birds.  In some areas, such as Milnesand, New Mexico, Lesser Prairie-Chicken festivals are held which celebrate the annual breeding displays.  These festivals allow birders to observe lesser prairie-chickens in their natural habitat under closely controlled conditions, and often include demonstrations of research on other animals as well as on lesser prairie-chickens.
             Predators of lesser prairie-chickens include foxes, coyotes, badgers, and many kinds of raptors, especially northern harriers, golden eagles, and great horned owls.  Many lesser prairie-chicken nests are destroyed by egg predators, including foxes, coyotes, skunks, ground squirrels, ravens, and even snakes.  Nests may be trampled by cattle.  There is some evidence that nests of lesser prairie-chickens may be destroyed when discovered by ring-necked pheasants.  If the nest is destroyed, the female lesser prairie-chicken may attempt to renest, although when this occurs, it usually results in a smaller clutch.
             Shinnery oak (Quercus havardii) is the dominant plant in the habitat of the lesser prairie-chicken.  Shinnery oak is unlike most familiar oak trees.  The largest part of the plant is the root mass, which occurs under the sand.  This mass sends out shoots which rarely protrude more than a foot above the surface of the sand.  Much of the rest of the vegetation is grass, such as bluestem and gramma grasses.  These grasses are subject to periodic fires, and these fires can destroy the shoots of the shinnery oak.  When this occurs, the root mass simply sends out new shoots.  Shinnery oaks may live for thousands of years and reproduce very slowly, but they sporadically produce large quantities of acorns, which serve as food for many kinds of animals, including lesser prairie-chickens.  During certain times of the year, leaves of shinnery oak are toxic to cattle.  Shinnery oak also may reduce the amount of grass where it occurs.  Because of this, cattlemen often try to destroy shinnery oak, but it is difficult to kill.  Effects of destruction of shinnery oak on populations of lesser prairie-chickens are not completely understood.
             Most species of grouse are not considered to be endangered, despite declines in populations over the last one hundred years.  However, species of the genus Tympanuchus have undergone severe declines since the settlement of North America by Europeans.  The sharp-tailed grouse, Tympanuchus phasianellus, has been extipated from much of the southern part of its original geographic range.  The heath hen, Tympanuchus cupido cupido, which formerly lived in New England and the Mid-Atlantic states, is extinct.  Attwater’s prairie-chicken, Tympanuchus cupido attwateri, is extinct in the wild.  Most other populations of the greater prairie-chicken, Tympanuchus cupido, have declined dramatically during the last century.  Conversion of habitat to farmland is usually cited as the reason for these declines.
              Like other members of the genus, the lesser prairie chicken has undergone severe declines in population.  This bird originally ranged over much of western Texas, eastern New Mexico, western and central Kansas and Oklahoma, southwestern Nebraska, and eastern Colorado.  Populations still exist in all of these states except Nebraska, but total numbers may have declined by 97% since the 1800s, and lesser prairie-chickens only occupy about 8% of the total land area in which they were once found.  A concurrent decline has occurred in southeastern New Mexico.  Recent surveys in Lea and Eddy counties have resulted in only a few sightings of lesser prairie-chickens in an area in which a seemingly healthy breeding population existed just 15 years ago.
              Although loss of habitat has been blamed for declines in populations of lesser prairie-chickens throughout the range, land use patterns in Lea and Eddy Counties have not changed much during the last twenty years.  Other suggested causes for declines in this area include predation, overhunting, destruction of habitat due to overgrazing, loss of necessary vegetation due to efforts to control shinnery oak, noise and other disturbance due to activity associated with extraction of oil and natural gas, increased mortality due to collisions with power lines, and increased habitat fragmentation.  Populations of prairie-chickens naturally undergo periodic fluctuations due to variation in climatic conditions.  Any of the previously mentioned human-caused problems occurring at a low point in the population cycle could push the lesser prairie-chicken toward extirpation.
             In 1998, the lesser prairie-chicken was listed as a candidate for threatened status by the United States Fish and Wildlife Service.  The Bureau of Land Management, which manages most of the federal lands in Lea and Eddy counties, provided funding for my research, which is an attempt to better understand the reasons for the decline in populations of the lesser prairie-chickens.  My research focuses on the leks of lesser prairie-chickens and is proceeding in several directions.  I am measuring the structure and composition of the vegetation on active leks, abandoned leks, and in the pastures where they occur.  Differences in the vegetation may indicate that grazing by cattle has negative effects on lesser prairie chickens.  I am measuring sound levels at active and abandoned leks.  High noise levels may interfere with mating calls during lekking activities.  If females cannot hear males, reproductive behavior may be disrupted.  I am also determining the extent of oil and gas activity near active and abandoned leks.  All of these measurements, along with climatic and other habitat data, will be used as variables in a multivariate statistical analysis in an attempt to determine which factors were most important in the decline of lesser prairie chickens in southeastern New Mexico.  This information will be useful to Bureau of Land Management personnel as they try to preserve the remaining birds, and perhaps to rebuild populations in Lea and Eddy counties.  It should also be helpful to those trying to protect populations in other areas.