By Antonio Del Valle
Sunrises over the tallgrass praire were a wondrous daily event to behold while surveying at Nachusa Grasslands.
This summer, as part of my graduate research project at Northern Illinois University, I had the opportunity of studying some of the many bird species that call Nachusa Grasslands home. Luckily, surveying birds is an activity that you can do by yourself, which was a key factor in being able to safely conduct my research project in the midst of a global pandemic.
The focus of my research is to determine how birds that breed on the prairie are impacted by some of the large scale disturbances on the prairie landscape—mainly bison herbivory and prescribed fire. Different bird species prefer different types of prairie. Species such as killdeer (Charadrius vociferous) and upland sandpiper (Bartramia longicauda) prefer shorter prairies that, at Nachusa, are maintained through the eating of plants by bison and frequent prescribed fires. In contrast, species such as Henslow’s sparrow (Centronyx henslowii) and sedge wren (Cistothorus platensis) prefer dense, tall prairies that are maintained through infrequent disturbances.
A figure describing the relationship between different grassland bird species presence and months since a disturbance event has occurred on the prairie.
Grassland birds are a suite of species that specialize in using prairie habitat as their preferred place to breed and raise young. These species are of particular interest to me because grassland birds have experienced drastic population declines. A recent paper published in Science shows just how serious this decline has been.
Bird populations in North America have declined by three billion individuals since 1970. Grassland birds in particular have declined more than any other group of birds.
But it is not all doom and gloom for these grassland birds. Thanks to the hard work put into the restoration, management, and conservation of the tallgrass prairie habitat at Nachusa Grasslands, there are bountiful places for these types of birds to breed during the summer. My research aims to help us understand more about these declining species. Preserves such as Nachusa Grasslands give me an opportunity to observe them in areas where they are still relatively prevalent.
High quality prairie restorations take a lot of hard work but provide great habitat for many declining and rare plants and animals.
A typical morning of surveying birds starts out by waking up well before sunrise. I set my schedule to arrive to Nachusa around 5:30 AM in order to start surveying during peak bird activity. Coming prepared with coffee and waterproof clothes were key factors in staying awake and dry while traversing the dew-soaked prairie. Upon arriving to a survey point at the preserve, I begin surveying birds via sight with my binoculars, as well as by sound. I record all of the birds I see and hear into my field notepad for five minutes. While surveying, I record the number of individuals of each species, estimate their distance from me, and record any breeding behaviors that are displayed. Surveying in this systematic fashion allows me to look at the data later and compare what birds were seen in what areas, how many were present, and whether I can confirm that they were breeding (according to eBird’s breeding bird behavior codes). Additionally, this format allows me to compare my data to other data sets across different years and potentially different preserves/sites.
The depth of the thatch layer covering the ground is measured by using a ruler. This layer of dead plant material is important for certain species that require cover.
In addition to surveying birds, I also survey vegetation and bison density through dung counts. Vegetation surveys involve measuring vegetation height, thickness of thatch layer, and percent cover of plant species. These measurements give me quantitative values to describe the vegetation structure within different areas of the preserve. Bison density is calculated through systematically counting units of dung at my survey locations. Looking at bison density in different areas of the preserve can help show where bison are spending most of their time (and eating more plants).
One of my favorite birds to observe this summer was the Henslow’s sparrow. This secretive sparrow is rarely seen on the prairie, as it spends most of its summer down low in the grasses and only pops up once in a while when singing or flying. The Henslow’s sparrow song is unique as well. Cornell University’s All About Birds online field guide describes it as the simplest and shortest song of any North American bird, and to me it sounds like a faint hiccup. These sparrows have a greenish wash on their face and fine streaks on their flanks, which help to distinguish them visually from other sparrow species if you have the pleasure of catching a glimpse of them. They, along with many of the other grassland breeding birds, are now on their way back to their overwintering grounds in Central and South America. The prairies will be noticeably quieter until they begin to return in the spring again.
I’m looking forward to analyzing the data collected this summer and preparing for next year’s field season over the next few months. I hope that my research can help provide knowledge to aid in the continued conservation of these grassland bird species. Nachusa Grasslands is a wonderful place to observe these birds and many other plants and animals in their native habitat.
Citations & Resources:
Fuhlendorf, S.D., et al. (2009). Pyric herbivory: Rewilding landscapes through the recoupling of fire and grazing. Conservation Biology 23:588–598.
Rosenberg, K.V., et al. (2019). Decline of the North American Avifauna. Science 366(6461):120-124.
Tony’s ongoing graduate research is supported by the following sources:
By Charles Larry
The sound of the sandhill crane seems to echo across an immense gulf of antiquity. Cranes evolved during the Eocene (56-33.9 million years ago). The earth was warmer and wetter during this time, and in North America, with vast areas of prairie, savanna, marsh, and shallow inland seas, it was ideal habitat for the ancient ancestors of modern cranes. This early crane was likely a relative of the crowned crane now found in Africa. Fossil remains of this early crane have been found in North America, dating some 10 million years. But then the climate in North America started to cool, eventually bringing about the Ice Ages. These events saw the disappearance of this early crane on the continent. At some point a relative of the modern crane, one suited for cooler climates, evolved here. The earliest fossil of this later crane was a bone almost identical to that found in modern sandhills. This fossil was found in Florida, dating back 2.5 million years. Modern sandhill cranes (Grus canadensis) are divided among two and six geographical subspecies, depending on sources. Generally, there are the greater and lesser sandhills.
Nachusa Grasslands has had sandhill cranes stop over for brief periods over several years. In August of 2018, even a pair of whooping cranes stopped and then moved on! As far as is known, this is the first time that a pair of sandhills have nested and raised two colts (as the young sandhills are called) at Nachusa. It is usual for sandhill cranes to lay two eggs, a few days to a week apart, but it is rare that both colts will live to fledge. Some reasons as to why only one colt survives are various predators, lack of sufficient food, and sometimes the aggression of the older crane toward its slightly younger sibling. At Nachusa both of the young have fledged and are flying.
Sandhill cranes usually mate for life. They become sexually mature at two years old but four or five years old is more likely to be when mating begins. Sandhills are well known for their "dancing" during mating season. This behavior is not fully understood, as cranes of any age may dance at times not related to breeding season. It is thought to also be a way of working off aggression.
Both sexes participate in the building of the nest, constructed in or near water. Nests are composed of plant material found near the nesting site, such as cattails, sedges, rushes, and grasses.
Nests can be six feet in diameter. At breeding time both sexes "paint" their feathers with clay and mud. The birds are normally gray in color, but the painting changes the feathers to brown. This is thought to be a camouflaging technique to blend in with the nesting site.
Both parents incubate the eggs. While one sits on the nest, the other is either standing guard or gathering food. The female usually sits on the nest during the night. Hatching is about a month after laying. After hatching, the cranes abandon the nesting site, moving to a hidden spot somewhere still near water.
The parents are fiercely protective of the young. Many predators are a danger to either the eggs or the colts. Among them are coyotes, foxes, raccoons, owls, and various hawks, all of which inhabit Nachusa Grasslands.
Sandhills eat a variety of food, from insects such as grasshoppers or dragonflies, to aquatic plants and tubers, to small mammals such as mice, to snakes and worms. They will even eat the eggs of other birds, such as red-winged blackbirds, rails, and ducks. More recently, sandhills have learned to forage in cornfields and will often flock in vast numbers doing this. During breeding season, they are very territorial with an average territory range of about 20 acres. Until the cranes abandon the nesting site, where they are more or less isolated, they will defend this territory from other sandhills and predators by various aggressive displays and even fighting.
By late summer the sandhills will probably move to an area where there is a larger crane population and more abundant food to fatten up for migration, which will happen sometime in the fall. The juveniles will stay with the parents during migration and through the winter. Sometime in the following spring they will separate from their parents and go out on their own. The main winter flyways for migration in this area are either south to Georgia or Florida or over to Texas.
Sandhill cranes are threatened, as is true of cranes the world over. Climate change is one major threat. Droughts have become much more frequent, and wetlands are disappearing. In some states cranes are hunted. In the past, this resulted in the extinction of sandhills from Washington State in 1941. They have now been reintroduced to this state in small numbers. Farming conversion to incompatible crops (soybeans) over crops like corn also threatens cranes. Probably the biggest threat is from loss of habitat from urbanization and development.
The sandhill crane is a magnificent bird. It would be tremendously sad if someday the sandhill crane were to join the thousands of species disappearing from our planet. To hear no more the sound of this bird, which author Peter Matthiessen says is "the most ancient of all birds, the oldest living bird species on earth." Sad indeed.
Johnsgard, Paul A. A Chorus of Cranes: the Cranes of North America and the World.
University of Colorado Press, 2015.
Forsberg, Michael. On Ancient Wings. University of Nebraska Press, 2004.
Matthiessen, Peter. The Birds of Heaven, North Point Press, 2001.
If you would like to play a part in habitat restoration for sandhill cranes at Nachusa Grasslands, consider joining our Thursday or Saturday Workdays, or give a donation to the Friends of Nachusa Grasslands. Donations to Friends can be designated to support the ongoing stewardship at Nachusa.
I am a nature photographer, a freelance graphic designer, and steward at Nachusa's Thelma Carpenter Prairie. I have taken photos for Nachusa since 2012.
I have been a high school French teacher, registered piano technician, and librarian. In retirement I am a volunteer historian at Lee County Historical and Genealogical Society.