Field Validation of GIS-based Models for Regional and Refuge Bird
Conservation Planning: 2003 Field Season Report

Les D. Murray and Christine A. Ribic, USGS BRD WCWRU, Department of
Wildlife Ecology, University of Wisconsin, 204 Russell Labs, 1630 Linden
Dr, Madison, WI 53706.

# INTRODUCTION

The North American Bird Conservation Initiative (NABCI) is a new bird
conservation effort that seeks to integrate various bird conservation
plans and "deliver the full spectrum of bird conservation through
regionally-based, biologically-driven, landscape-oriented partnerships".
The USGS Upper Midwest Environmental Sciences Center, La Crosse, WI
(hereafter the Lacrosse Lab) and USGS Patuxent Wildlife Research Center,
Laurel, MD, are developing GIS data layers and GIS management tools for
managing and conserving high quality habitat for multiple bird species.
The relationship between bird abundances and local vegetation
characteristics has been well defined by numerous studies. Researchers
also have begun to examine the relationship between landscape variables
and bird abundances. Understanding relationships between abundances of
bird species and landscape factors will help managers to identify areas
of importance for some species of birds. The USGS Upper Midwest
Environmental Sciences Center has begun using Breeding Bird Survey data
to create such predictive models of bird abundances in Bird Conservation
Region (BCR) 23 based on relationships to landscape variables.

This study is being conducted to gather data to be used to validate the
results of the predictive models. The project also will collect data to
compare abundances of grassland birds in landscapes composed of
different amounts of grassland and forest in southwestern Wisconsin. The
information collected by this project will be used to test the accuracy
of predictive models and further understand the relationship between
grassland birds and the surrounding landscape.

# METHODS

[Study Areas]{.smallcaps}

The validation portion of our study was conducted in the Iowa,
Minnesota, and Wisconsin portions of BCR 23. Grids of 3 different scales
(approximately 800 ha, 8,000 ha, 100,000 ha) were then overlayed on a
GIS coverage of the BCR. These scales were defined by the LaCrosse Lab
for their landscape models. To sample the BCR geographically, the BCR
was divided into 5 subregions of equal area and equal sampling occurred
in each of the subregions. Fifteen 8,000 ha landscapes were randomly
selected in each subregion. Within each 8,000-ha landscape, we randomly
chose three 800-ha landscapes that were at least 50% contained in the
8,000-ha landscape. Thus a total of 225 800-ha landscapes were surveyed.

The portion of our study that focused on the relation of grassland
associated birds to landscape composition took place in southwestern
Wisconsin, specifically Dane, Iowa, Green, Lafayette, and Grant
counties. This area was divided into 800-ha landscapes and the
landscapes were classified into 6 landscape types using the National
Landcover Data (Table 1). Five landscapes of each type were then
selected for our study.

Within each selected 800-ha landscape we attempted to locate idle
grassland patches planted to smooth brome (*Bromus inermis*) to compare
local abundances of grassland birds with abundances in the surrounding
landscape. However, we were able to locate and gain permission from land
owners for only 13 fields. All fields used were enrolled in the
Conservation Reserve Program.

[Bird Surveys]{.smallcaps}

### Validation surveys

Roadside surveys consisting of 3 400-m radius point counts were
conducted by volunteers to estimate bird abundances in each selected 800
ha landscape. Surveys were conducted from 1 June to 4 July between ½
hour before sunrise and 4½ hours after sunrise. Most survey routes were
ran twice during the time period, but some routes were only run once
because of weather and lack of volunteers to cover that area. Abundance
information was only collected for species being modeled and species
that we may model in the future (Table 2). Volunteers only counted those
birds seen or heard within 400 m of each point during a 3-minute period.
Observers were careful to try to count each bird only once. A total of
16 observers conducted surveys.

*Landscape level*

Roadside surveys consisting of 3 400-m, 5-minute point counts were
conducted in each of the 30 selected 800 ha landscapes and 3 800 ha
landscapes surrounding each of the selected landscapes (Figure 1).
Roadside surveys were conducted once from 24 May to 12 June and once
between 12 June and 30 June with at least one week between surveys of
the same route. Surveys were conducted between ½ hour before sunrise and
4½ hours after sunrise. Observers recorded the number of birds seen or
heard during each point count for selected species that often occur or
breed in grasslands (Sample and Mossman 1997) and species recorded
during validation surveys (Table 4). Observers recorded whether each
bird was observed during the first 3 minutes of the survey so that
survey results could be compared with validation surveys. Surveys were
conducted by 4 trained observers.

*Patch level*

Two observers conducted 100-m radius point counts to estimate grassland
bird abundances in idle grass patches. Observers recorded all birds of
all species seen or heard with 100 m of the point during a 5-minute
period. Surveys were conducted once from 28 May to 4 June and once from
13 June to 14 June. The distance from the observer to each bird also was
recorded. To allow more time to accurately count other species of birds,
only a simple tally of the number of red-winged blackbirds seen or heard
was recorded because red-winged blackbirds were very abundant. Birds
overhead were recorded if they were searching for food, defending a
territory, or displaying. As many 100-m radius points were placed in
each field as possible. The center of each point was at least 125 m from
all field edges to reduce the number of nongrassland species recorded.
The center of the point counts were at least 300 m apart. Two fields
were too small for any points to fit, thus no data was collected. A
total of 16 point counts were conducted in 11 fields.

[Nest Searching and Monitoring]{.smallcaps}

We searched for nests of bobolinks in the 8 fields in which Bobolinks
were observed. We searched for nests by watching the behavior of the
birds and trying to pinpoint the location of the nest. If the nest was
not found after the first attempt, the area near where the nest was
believed to be was marked with flagging tape and we attempted to find
the nest at a later date. All found nests were marked using a surveyor
flag 5 m north of the nest and a Global Positioning System. Nests were
monitored every 2-3 days until the nest fledged or failed. Nests of
other species were monitored if found incidentally while searching for
bobolink nests.

Daily survival rates were calculated using the Mayfield method for
bobolink nests. We used an 11 day incubation period and 10 day nestling
period to calculate nest success for the entire nesting period (Baicich
and Harrison 1997).

[Red-headed Woodpecker Sightings]{.smallcaps}

In addition to the validation surveys, we recorded the approximate
location of all red-headed woodpeckers observed by 9 researchers from
May to July. The landscape characteristics of the locations of these
observations will be compared to random points in the study area.

[Vegetation]{.smallcaps}

Vegetation height, density, and cover were measured at 3 points for each
point count placed in a field once in June . The points of vegetation
measurements were located a random direction and random distance,
between 0 and 100 m, from each point count location. In fields too small
to contain a point count, vegetation points were a random distance and
direction from the center of the field for comparison with nest sites
within the field.

At each point, height-density was measured using a Robel pole and canopy
cover was measured using a Daubenmire frame. Height-density was recorded
as the lowest decimeter of the Robel pole visible from 4 m away at a
height of 1 m from the four cardinal directions and then the values were
averaged. Cover estimates were made at the same point and estimated to
the nearest 5% for the following categories: grass, forb, woody, dead
vegetation, litter (dead plant material lying flat on the ground), and
bare ground. Litter depth was measured to the nearest mm from the soil
surface to the upper surface of the litter. Vegetation height was
measured to the nearest cm as the tallest piece of vegetation within 1
cm of the Robel pole.

# RESULTS

[Bird Surveys]{.smallcaps}

##  Validation surveys

Common yellowthroat and Savannah sparrow were the species of interest
observed most often followed by bobolink, eastern meadowlark, and sedge
wren (Table 3). The maximum number of birds of one species observed on a
single route was 17 bobolinks followed by 14 Savannah sparrows. Cerulean
warblers were the species least observed with only five observations.

##  Landscape level

Eastern meadowlark, brown-headed cowbird, common yellowthroat,
ring-necked pheasant, and Savannah sparrow were the five most often
observed species during surveys (Table 4). Eastern meadowlark and
savannah sparrow were most abundant in high-grass and supergrass
landscapes (Figure 2). Grasshopper sparrow was seen at higher numbers in
the high grass-low forest landscape (Figure 2). Killdeers were observed
more often in landscapes with low amounts of forest (i.e., \<10%).
Brown-headed cowbird and common yellowthroat were most abundant in the
low grass-high forest, high grass-high forest, and high grass-medium
forest. Bobolinks (Figure 2) and ring-necked pheasants had their highest
abundances in the high grass-high forest and high grass-medium forest.

*Patch level*

A total of 14 species were observed during point counts in Conservation
Reserve Program fields. Six of the 14 species observed are considered
grassland obligates by Sample and Mossman (1997) (Table 5), and field
sparrow require grassland during the breeding cycle. Red-winged
blackbird was the most abundant species observed during point counts
followed by bobolink, Henslow's sparrow, and sedge wren (Table 5).

[Nest Searching and Monitoring]{.smallcaps}

A total of 30 nests of 3 species (bobolink \[24\], field sparrow \[4\],
meadowlark \[2\]) were found on 5 fields. Five of the 24 bobolink nests
were found with eggs. Three of the five nests with eggs hatched young.
Seventeen of the 22 nests found that hatched young fledged at least one
host young. All bobolink nests that failed were depredated. Two field
sparrow nests were successful, one nest was abandoned, one was
depredated. Both meadowlark nests were depredated.

The daily survival rates for bobolink nests were 0.9000 (SE = 0.0045, n
= 4) for the incubation stage and 0.9647 (SE = 0.0002, n = 22) for the
nestling stage. Overall survival was 0.313 for incubation and 0.698 for
the nestling stage. These values were multiplied to get an overall
success rate for bobolink nests of 22%. The small sample size of nests
during incubation could bias this estimate low. Thus we combined
exposure days from incubation and nestling and calculated a daily
survival rate and overall success rate for the entire nesting cycle
regardless of stage. The daily survival rate for the entire nesting
cycle was 0.9567 (SE = 0.0003, n = 22) and the overall success rate
estimate was 39%.

[Red-headed Woodpecker Sightings]{.smallcaps}

Fifty-four observations of red-headed woodpeckers were made including
those that occurred during landscape-level road side surveys (Figure 3).
Some of these observations are probably the same bird or breeding pair
seen on different days and will be considered a single territory for
future analyses.

[Vegetation]{.smallcaps}

Vegetation in CRP fields was relatively homogeneous with grasses and
litter comprising most of the canopy (Table 6).

# FUTURE WORK

Future work will include continuation of roadside surveys for the
landscape and validation portions of the study. We will use the same
roadside routes for the landscape level surveys so that a higher
resolution GIS database can be constructed for the areas being surveyed.
For the validation surveys, we will use some of the same routes (the
number yet to be determined), but also will include some new survey
routes so that we have abundance information from more locations. We
also will study the arrival time in the spring, territory distribution,
and nest placement of bobolinks in grassland patches of different sizes
to examine the relationship between patch size, patch selection, and
territory placement.

# Acknowledgements

We would like to thank Wayne Thogmartin for constructing the predictive
bird abundance models, supplying comments on our study design, and all
his help with GIS and calculating landscape metrics. We also would like
to thank Melinda Knutson, Stan Temple, Dave Mladenoff, Jun Zhu, Dave
Sample, Doug Johnson, John Sauer, and Mike Guzy for feedback on the
study design. Special thanks to Sonya Knetter for her help with GIS
problems. Aaron Rea, Nathan Hurst, Peter Ruppert, Dawn Trick, and a slew
of volunteers provided the field assistance that made the project
possible.

# LITERATURE CITED

Baichich, P. J., and C. J. O. Harrison. 1997. A guide to nests, eggs,
and nestlings of North American birds. Second edition. Academic Press,
San Diego.

Sample, D. W., and M. J. Mossman. 1997. Managing habitat for grassland
birds: a guide for Wisconsin. Wisconsin Department of Natural Resources,
Madison. 154 pp.

Table 1. Definitions of landscapes surveyed in southwestern Wisconsin.

  ------------------------------ --------------------- ------------------
  Landscape                      %grass in landscape   %forest in
                                                       landscape

  low grass-low forest           30-45%                \<10%

  low grass-high forest          30-45%                \>20%

  high grass-high forest         60-80%                \>20%

  high grass-medium forest       60-80%                10-20%

  high grass-low forest          60-80%                \<10%

  supergrass                     \>80%                 \<20%
  ------------------------------ --------------------- ------------------

Table 2. Bird species of interest for the validation surveys.

  ------------------------- ---------------------- -----------------------
  Forest                    Grassland              Generalist

  Black-billed cuckoo^a^    Bobolink^a^            Common yellowthroat^b^

  Blue-winged Warblers^b^   Eastern meadowlark^b^  

  Cerulean warbler^a^       Grasshopper sparrow^a^ 

  Golden-winged warbler^a^  Henslow\'s sparrow^a^  

  Red-headed woodpecker^a^  Savannah sparrow^b^    

  Wood Thrush^a^            Sedge wren^a^          

                            Upland Sandpiper^a^    

                            Western Meadowlark^b^  
  ------------------------- ---------------------- -----------------------

^a^ Priority species in BCR23 that have been modeled.

^b^ Species that we may model in the future.

Table 3. Mean number of birds seen per survey route and associated
standard error, maximum number of birds seen on a route, and total
number of observations for roadside survey routes conducted by
volunteers for use to validate predictive models of bird abundance in
BCR 23.

  ---------------------------------- ------- -- ------ -- ------ -- ---------
  Species                            Mean       SE        Max       Total

  Black-billed cuckoo                0.05       0.01      2         19

  Bobolink                           0.81       0.12      17        264

  Blue-winged warbler                0.07       0.02      3         31

  Cerulean warbler                   0.01       0.01      1         5

  Common yellowthroat                1.86       0.11      10        551

  Eastern meadowlark                 0.39       0.06      7         128

  Grasshopper sparrow                0.15       0.03      4         60

  Golden-winged warbler              0.02       0.02      2         8

  Henslow\'s Sparrow                 0.02       0.01      2         9

  Meadowlark spp.                    0.02       0.01      1         8

  Red-headed woodpecker              0.07       0.02      3         30

  Savannah sparrow                   1.28       0.12      14        409

  Sedge wren                         0.32       0.05      7         120

  Upland sandpiper                   0.02       0.01      3         8

  Western meadowlark                 0.07       0.02      5         23

  Wood thrush                        0.12       0.02      4         44
  ---------------------------------- ------- -- ------ -- ------ -- ---------

Table 4. Mean number of birds seen per roadside route from 24 May to 30
June 2003 in 800-ha landscapes in southwestern Wisconsin classified into
six landscape types (see Table 1 for definitions).

  --------------- -------- -- -------- -- -------- -- ---------- -- -------- -- --------
  Species of      Low         Low         High        High          High        Super-
  interest        grass-      grass-      grass-      grass-        grass-      grass
                  low         high        high        medium        low         
                  forest      forest      forest      forest        forest      

  Baltimore       0.1         0.8         1.1         0.4           0.1         0.8
  oriole                                                                        

  Black-billed    0.0         0.0         0.0         0.0           0.0         0.0
  cuckoo                                                                        

  Brown-headed    1.5         2.5         4.4         2.5           1.1         0.9
  cowbird                                                                       

  Bobolink        0.2         1.1         1.9         2.2           0.9         1.0

  Blue-winged     0.0         0.0         0.0         0.1           0.0         0.0
  warbler                                                                       

  Clay-colored    0.0         0.1         0.0         0.0           0.0         0.0
  sparrow                                                                       

  Cerulean        0.0         0.0         0.0         0.0           0.0         0.0
  warbler                                                                       

  Common          1.2         3.0         2.7         3.4           1.6         0.6
  yellowthroat                                                                  

  Dickcissel      0.3         0.0         0.0         0.1           1.0         0.7

  Eastern         0.4         0.2         0.1         0.6           0.0         0.2
  bluebird                                                                      

  Eastern         1.0         1.1         2.8         3.5           3.0         4.0
  meadowlark                                                                    

  Field sparrow   0.2         1.8         0.3         1.3           0.6         0.2

  Grasshopper     0.4         0.5         0.3         0.7           1.1         0.2
  sparrow                                                                       

  Golden-winged   0.0         0.0         0.0         0.0           0.0         0.0
  warbler                                                                       

  Henslow\'s      0.1         0.2         0.2         0.1           0.0         0.0
  sparrow                                                                       

  Horned lark     1.1         0.0         0.0         0.7           0.9         0.3

  Killdeer        1.7         0.2         0.4         0.4           1.7         0.7

  Meadowlark spp. 0.1         0.0         0.2         0.4           0.5         0.5

  Northern        0.0         0.0         0.0         0.0           0.0         0.0
  harrier                                                                       

  Red-headed      0.1         0.1         0.2         0.1           0.0         0.3
  woodpecker                                                                    

  Ring-necked     1.0         1.4         2.5         2.7           1.2         1.1
  pheasant                                                                      

  Savannah        0.7         1.0         1.3         1.8           2.2         2.5
  sparrow                                                                       

  Sedge wren      0.2         0.2         0.4         0.1           0.3         0.0

  Upland          0.0         0.0         0.0         0.0           1.0         0.0
  sandpiper                                                                     

  Vesper sparrow  0.3         0.0         0.0         0.0           0.0         0.0

  Western         0.3         0.0         0.0         0.1           0.6         1.1
  meadowlark                                                                    

  Wood thrush     0.0         0.6         0.0         0.0           0.0         0.0
  --------------- -------- -- -------- -- -------- -- ---------- -- -------- -- --------

Table 5. Mean number and mean maximum number of birds seen per point
count and associated standard errors (in parentheses) in Conservation
Reserve Program fields in southwestern Wisconsin in May and June 2003.

+------------------------------+------+----------+---+--------+----------+
| Species                      | Mean |          |   | Mean   |          |
|                              | nu   |          |   | m      |          |
|                              | mber |          |   | aximum |          |
+------------------------------+------+----------+---+--------+----------+
| American Crow                | 0.03 | (0.03)   |   | 0.06   | (0.06)   |
+------------------------------+------+----------+---+--------+----------+
| Brown-headed Cowbird         | 0.06 | (0.06)   |   | 0.13   | (0.13)   |
+------------------------------+------+----------+---+--------+----------+
| # Bobolink^a^                | 2.25 | (0.68)   |   | 3.00   | (0.83)   |
+------------------------------+------+----------+---+--------+----------+
| Common yellowthroat          | 0.13 | (0.07)   |   | 0.25   | (0.14)   |
+------------------------------+------+----------+---+--------+----------+
| # Eastern meadowlark         | 0.31 | (0.10)   |   | 0.44   | (0.13)   |
+------------------------------+------+----------+---+--------+----------+
| Field sparrow                | 0.03 | (0.03)   |   | 0.06   | (0.06)   |
+------------------------------+------+----------+---+--------+----------+
| # Grasshopper sparrow        | 0.03 | (0.03)   |   | 0.06   | (0.06)   |
+------------------------------+------+----------+---+--------+----------+
| # Henslow\'s sparrow         | 1.38 | (0.26)   |   | 1.94   | (0.35)   |
+------------------------------+------+----------+---+--------+----------+
| Mallard                      | 0.06 | (0.06)   |   | 0.13   | (0.13)   |
+------------------------------+------+----------+---+--------+----------+
| Meadowlark spp.              | 0.28 | (0.12)   |   | 0.56   | (0.24)   |
+------------------------------+------+----------+---+--------+----------+
| Red-winged blackbird         | 5.47 | (1.18)   |   | 6.88   | (1.36)   |
+------------------------------+------+----------+---+--------+----------+
| # Savannah sparrow           | 0.03 | (0.03)   |   | 0.06   | (0.06)   |
+------------------------------+------+----------+---+--------+----------+
| **Sedge wren**               | 1.34 | (0.23)   |   | 1.81   | (0.29)   |
+------------------------------+------+----------+---+--------+----------+
| Song sparrow                 | 0.06 | (0.04)   |   | 0.13   | (0.09)   |
+------------------------------+------+----------+---+--------+----------+

^a^ Obligate grassland species defined by Sample and Mossman 1997 are
shown in bold.

Table 6. Mean vegetation structure and canopy cover measurements taken
during June 2003 for points in Conservation Reserve Program fields
planted to smooth brome in southwestern Wisconsin.

  ------------------------------------------ -- -------------- -- --------
  * *                                           Mean              SE

  Structure                                                       

  Height-density (dm)                           4.4               0.3

  Height (cm)                                   70.5              2.9

  Depth (mm)                                    51.4              6.4

  Canopy cover (%)                                                

  Grass                                         54.8              3.1

  Forb                                          4.5               1.8

  Woody                                         0.2               0.2

  Dead                                          5.9               1.4

  Litter                                        34.2              3.2

  Ground                                        0.4               0.3
  ------------------------------------------ -- -------------- -- --------

![](media/image1.jpeg){width="6.495833333333334in"
height="4.972916666666666in"}

![](media/image2.wmf){width="4.509722222222222in"
height="2.6055555555555556in"}

Figure 2. Abundances of 4 obligate grassland birds (Sample and Mossman
1997) in landscapes with various amounts of forest and grassland in
southwestern Wisconsin during May and June 2003.

![](media/image12.jpeg){width="6.495833333333334in"
height="4.972916666666666in"}