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Nest Searching: We devote the majority of our research hours to searching
for the nests of grassland birds. The species that we target are those characteristic
of Illinois prairies: namely, Upland Sandpiper, Bobolink, Eastern Meadowlark,
Grasshopper Sparrow, and Dickcissel. Our search method varies according to the
vegetation composition of a particular field, and the particular species targeted.
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Rope Dragging: We employ this technique in fields with short to medium
grass height and containing few, if any, shrubs. As two people drag a
30 meter rope across the width of a field, several others follow behind
to watch for birds flushed from their nests.
The rope passes directly over the low nest without harming either its
contents or the incubating adult. This technique is most effective for
species that will flush directly off their nests, such as the
Eastern Meadowlark and the Upland Sandpiper.
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"Sticking": The goal of this technique is the same as for the rope dragging:
to flush birds off their nests while transversing the entire area of a field.
In fields with shrubs that will snag the rope, we employ meter sticks as
nest-searching tools. Several people walk back and forth across a field in a line,
swinging the meter stick in an arc across the grass and gently prodding small shrubs.
Human footsteps and the motion of the sticks serve to flush incubating birds.
This method is effective for shrub-nesting species such as the Dickcissel,
hard-to-find species, such as the Grasshopper Sparrow, and
those species that also are found by rope-dragging.
For both of these search methods, a bird flushed off its nest will return to
it soon after we leave the area.
- Stalking: Some species, such as the Grasshopper Sparrow and the Bobolink, will flush off their nest and run through the grass before they fly into the air. Often, these nests are well-concealed and cannot be found without knowing their precise location. The best way to find these nests is to follow the birds. Feeding adults or an incubating female will reveal the location of a nest if they are watched patiently from a distance.
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Rope Dragging: We employ this technique in fields with short to medium
grass height and containing few, if any, shrubs. As two people drag a
30 meter rope across the width of a field, several others follow behind
to watch for birds flushed from their nests.
The rope passes directly over the low nest without harming either its
contents or the incubating adult. This technique is most effective for
species that will flush directly off their nests, such as the
Eastern Meadowlark and the Upland Sandpiper.
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Marking the Nest: Once we find a nest, we want to be able to relocate it.
We mark a nest with an 24-inch wooden stake, painted orange or red for visibility.
At approximately five meters from each nest we pound this stake into the ground
and take a bearing. Next, we record the bearing and distance to the stake from a
known reference point, such as a census point or fence row.
Although a few stakes have been swallowed by the field or knocked around by cows,
we are able to relocate the vast majority of our nests.
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Nest Monitoring: In order to document reproductive success or failure,
we monitor the nests we find on a three-day cycle. Monitoring more often
would disturb the birds excessively. Monitoring less frequently
would be less accurate in determining nest fate.
At each visit, we record the contents of the nest,
whether or not an incubating adult was present,
and the behaviors of adults in the vicinity of the nest.
If the nest is empty, we determine if the nest has been depredated
or has fledged young. We describe the appearance of the nest and any eggshells,
if present. Fledged birds will remain near the nest and will continue to be
fed by their parents for some time. Adults carrying food,
the sounds of begging calls and "chips"
in nearby grass, or even just agitated behavior by the parents are
strong indicators of a successful nesting attempt.
- Vegetation Analysis: At each census point, we measure grass height and litter density in order to characterize the vegetation composition of the different fields. Historically, the encroachment of woody vegetation into the native prairie ecosystem was prevented by wildfires. Many of our study sites, however, contain scattered shrubs or fence rows that divide the fields. In order to quantify shrub density, we count the number of shrubs greater than two meters tall, within 100 meters of each census point. In order to determine the effect shrubs may have on nesting success, we categorize the distance of different types of shrubs from each nest. In addition, we record the species of plant supporting the nest, as well as the height of the nest off of the ground.
Field Research Techniques
The following are the techniques used for data collection as part of the study:
For Further Information
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For further information on this research send correspondance to:
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Dr. Scott Robinson
Illinois Natural History Survey
607 East Peabody Drive
Champaign, IL 60820
scottr@mail.inhs.uiuc.edu
