2010 NORTHEASTERN NATURALIST 17(1):125–134
Nest-site Fidelity in Grassland Birds on Mowed Versus
Unmowed Areas on a Reclaimed Surface Mine
Danny J. Ingold1,*, James L. Dooley1, and Nicole Cavender2
Abstract - We monitored return rates of 324 color-banded Ammodramus savannarum
(Grasshopper Sparrow), 138 Passerculus sandwichensis (Savannah Sparrow),
and 49 Dolichonyx oryzivorus (Bobolink) on mowed and unmowed areas on a reclaimed
surface mine during seven breeding seasons. We observed 61 returns among
Grasshopper Sparrows, 40 returns among Savannah Sparrows, and 11 returns among
Bobolinks. Grasshopper Sparrows and Savannah Sparrows returned to mowed and
unmowed areas at about equal rates (21 vs. 18% and 26 vs. 31%, respectively), while
Bobolinks returned to unmowed areas at a higher rate than mowed areas (28% vs.
17% respectively). When hatching-year birds were excluded, overall return rates
increased slightly for Grasshopper Sparrows and Bobolinks (19 to 20% and 22 to
23%, respectively), but more substantially for Savannah Sparrows (from 29 to 36%).
Sixteen of 51 returning Grasshopper Sparrows (31%), 12 of 27 Savannah Sparrows
(44%), and 2 of 10 Bobolinks (20%) were observed during multiple years. These
observations support previous findings that reclaimed surface mines provide suitable
nesting habitat for these species. Early-season mowing did not appear to influence
the return rates of Grasshopper Sparrows or Savannah Sparrows, although it may
have influenced Bobolink returns.
Introduction
Populations of several grassland bird species in the Appalachian region
of the eastern United States are declining (Helzer and Jelinski 1999, Sauer
et al. 2005, Swanson 1996), largely as a result of habitat loss and fragmentation
(Askins 2002, Vickery et al. 2005). Reclaimed surface mines, although
heavily disturbed systems, are often vast and secluded and provide potentially
suitable nesting habitat for several obligate-grassland bird species
which might not be able to persist in regions otherwise lacking in extensive
grasslands (Bajema et al. 2001, DeVault et al. 2002, Ingold 2002, Swanson
1996). The nesting success of several grassland bird species on reclaimed
surface mines has been shown to be comparable to that on a variety of
unmined lands (Galligan et al. 2006, Monroe and Ritchison 2005). Populations
of Dolichonyx oryzivorus (L.) (Bobolink), Passerculus sandwichensis
(Gmelin) (Savannah Sparrow), and Ammodramus henslowii (Brewster)
(Henslow’s Sparrow), which have steadily declined in the glaciated portions
of Ohio (Sauer et al. 2005), have increased in the southeastern, unglaciated
1Department of Biology, Muskingum College, New Concord, OH 43762. 2The Wilds,
14000 International Road, Cumberland, OH 43732. *Corresponding author - ingold@
muskingum.edu.
126 Northeastern Naturalist Vol. 17, No. 1
counties where reclaimed surface mines are common (Peterjohn 1989, Peterjohn
and Rice 1991).
In addition to demography and habitat association (see DeVault et al.
2002, Galligan et al. 2006, Monroe and Ritchison 2005), nest-site fidelity
can also be used to assess habitat quality of reclaimed surface mines for
breeding grassland birds. Nest-site fidelity, the proclivity for individuals to
return to breed at a previous breeding site, has been documented in several
species (Bollinger and Gavin 1989, Gavin and Bollinger 1988, Greenwood
1980), and its presence in grassland birds has been positively associated with
hatching and/or fledging success of breeding individuals during the previous
year (Gavin and Bollinger 1988). There are few studies that focus on nestsite
fidelity in grassland birds, and even fewer that have examined the return
rates of grassland birds on reclaimed surface mines. Among the nest-site
fidelity studies that have been conducted, reports for grassland bird species
seem to indicate highly variable return rates which may, in some cases, vary
as a function of habitat quality (Balent and Norment 2003, Bollinger and
Gavin 1989, Gill et al. 2006, Perlut et al. 2008, Wheelwright and Mauck
1998) or geographic area (Jones et al. 2007). Two studies have specifically
quantified nest-site fidelity in grassland birds on a reclaimed surface mine.
Skipper (1998) found that 5 of 27 (18.5%) color-banded male Henslow’s
Sparrows and 0 of 7 color-banded females returned to nest in the same location
as in the previous year in Maryland. Monroe and Ritchison (2005)
reported that 2 of 9 (22%) marked male Henslow’s Sparrows returned to the
same location on one study site and that 2 of 18 (11%) males returned to a
second study site, both in Kentucky. Both of these studies, however, were
relatively short-term (two and four years, respectively).
A number of extrinsic factors that influence grassland habitat structure
(e.g., mowing, hay-cropping, burning, and grazing) could affect reproductive
success and/or nest-site fidelity on reclaimed surface mines. Numerous
studies have shown that mowing and hay-cropping, particularly between
May and August, adversely affect reproductive success of several grassland
bird species in the Midwest and northeastern United States (Bollinger et
al. 1990, Frawley and Best 1991, Ingold 2002). However, Ingold (2002)
reported that Ammodramus savannarum (Gmelin) (Grasshopper Sparrow)
and Savannah Sparrows on a reclaimed surface mine frequently nested on
plots that were mowed in mid-April prior to onset of nesting. In general, few
studies, particularly on reclaimed surface mines, have examined the effects
of early- (prior to 1 May) or late-season (after 1 Aug) mowing on grassland
bird breeding density, reproductive success, or return rates (but see Herkert
1994a, b; Ingold 2002; Ingold et al. 2009). Our objective was to quantify and
compare long-term return rates of Grasshopper Sparrows, Savannah Sparrows,
and Bobolinks on areas mowed in mid-April versus unmowed areas on
reclaimed surface mine habitat.
2010 D.J. Ingold, J.L. Dooley, and N. Cavender 127
Methods
Study area
The Wilds (International Center for the Preservation of Wild Animals)
is a 3700-ha center for conservation research and education located
on reclaimed mined land overlapping portions of Muskingum, Guernsey, and
Noble counties in southeastern Ohio. The landscape was initially mined for
coal by the Ohio Power Coal Company in the 1940s and 1950s. After a 10–
15 year hiatus, the land was again mined from 1969–1984 and subsequently
reclaimed. Today, the landscape is comprised of hilly non-native grasslands
with scattered wood lots, drainage ponds, lakes, and a large wetland area.
See Ingold (2002) for a description of the predominant vegetation types that
comprised our study site.
Field methods
We established eight 210- x 90-m rectangular plots in 1999 along
the western boundary of the Wilds. Four plots were mowed during mid-
April each year from 2000 to 2007, and four plots were left undisturbed.
After our first year of data collection, we determined that our sample size
of marked birds on these plots would be limited. Thus, during the subsequent
six field seasons (2001–2006), we captured and color-banded birds
not only on the plots, but on several unmowed areas between them. Each
plot, as well as the areas between them, was surrounded on at least three
sides by a minimum of 10 ha of additional open grasslands with some scattered
Elaeagnus umbellata Thunb. (Autumn Olive) trees. The same plots
were mowed each year in most cases; however, there were some years in
which a few previously mowed plots were left unmowed, and a few previously
unmowed plots were mowed. Because of our decision to expand the
sampling area, our intention shifted from conducting an inferential experiment,
to reporting return rates of these species on readily available mowed
and unmowed areas.
Grasshopper and Savannah Sparrows and Bobolinks were captured using
2.6- x 12-m mist nets and play-back tapes. Captured individuals were
fitted with 3 plastic color bands (randomly chosen color combinations) and
a US Geological Survey aluminum band (2 color bands on one leg and a
color band and an aluminum band on the other leg) to facilitate individual
identification in subsequent breeding seasons. Netting and searching for
color-banded birds was conducted on each mowed and unmowed area on a
weekly or biweekly basis between 0800 and 1200 hrs (EDT) from early May
through mid-July 2000–2007. The amount of time spent netting birds was
relatively uniform across each area. Typically, four nets were placed in an
area, usually near one or more singing males. We were fairly thorough in our
capture efforts, but did not attempt to capture every individual in every area,
nor did we spend much time netting in those portions of study areas in which
birds were consistently absent. Captured birds were classified to gender and
128 Northeastern Naturalist Vol. 17, No. 1
as hatching year or adult. Location and general habitat attributes associated
with the capture site were recorded. Recaptured or resighted birds were
identified from previous records, and returning individuals were considered
to have exhibited site fidelity if they were sighted or captured within 100 m
in any direction of the original point of capture.
Analyses
Return rates were calculated by dividing the total number of returns
we observed in a given species in a particular habitat (mowed vs. unmowed)
by the total number of individuals that were banded in that
habitat. Detection and survival probabilities were estimated for Grasshopper
and Savannah Sparrows using Pradel routines (Pradel 1996) available
within Program MARK (White and Burnham 1999) and are reported
± SE. Small sample sizes precluded estimating detection and survival
probabilities for Bobolinks. Birds that returned to plots in which the
treatment had inadvertently been changed between years (e.g., unmowed
plots that were mowed or mowed plots that were left unmowed) were not
included in our return-rate calculations or in our detection and survivorship
probability estimations.
Results
We captured and color-banded 324 Grasshopper Sparrows, 138 Savannah
Sparrows, and 49 Bobolinks from 2000–2006 and documented 112 total
returns across all species from 2001–2007 (Table 1). We documented 61
returns among Grasshopper Sparrows (Table 2), 40 returns among Savannah
Sparrows (Table 3), and 11 returns among Bobolinks (Table 4).
About equal percentages of Grasshopper and Savannah Sparrow
returns were to mowed versus unmowed areas (21% vs 18% and 26%
vs. 31%, respectively; Table 1), while a slightly higher percentage of
Bobolink returns were to unmowed vs. mowed areas (28% vs. 17% respectively;
Table 1).
Mean (±SD) estimated detection probabilities were largely similar
between habitats for Grasshopper Sparrows (x̅ = 0.786 ± 0.048 and 0.693
± 0.077 in mowed vs. unmowed plots, respectively). Detection probabilities
were higher in mowed relative to unmowed habitats for Savannah
Table 1. Numbers of Grasshopper Sparrow (GH), Savannah Sparrow (SA), and Bobolink (BO)
returns to the same location (within 100 m2) and habitat type (mowed vs. unmowed) in which
individuals were originally banded.
Number of individuals Number of returns Returns to Returns to
banded (2000–2006) observed mowed areas unmowed areas
GH 324 61 (19%) 26/126 (21%) 35/198 (18%)
SA 138 40 (29%) 14/53 (26%) 26/85 (31%)
BO 49 11 (23%) 4/24 (17%) 7/25 (28%)
2010 D.J. Ingold, J.L. Dooley, and N. Cavender 129
Sparrows (x̅ = 0.869 ± 0.066 and 0.594 ± 0.119, respectively); however,
in many cases, the variation around estimates for particular years was large
(ranging from near zero to 0.9999).
Mean annual apparent survival probabilities for Grasshopper Sparrows
were higher in mowed areas (x̅ = 0.81 ± 0.055 and 0.676 ± 0.095 in mowed
vs. unmowed plots, respectively), while mean annual apparent survival
probabilities for Savannah Sparrows were similar in mowed and unmowed
habitats (x̅ = 0.733 ± 0.079 and 0.773 ± 0.118, respectively).
Table 4. Number banded (n) and recaptures/resightings of all Bobolinks banded from
2000–2006 on a reclaimed surface mine (the Wilds) in Ohio.
Recaptures/resightings by breeding season (habitat types combined)
Year
banded n 2000 2001 2002 2003 2004 2005 2006 2007
2000 4 - 0 0 0 0 0 0 0
2001 3 2 0 0 1 0 0
2002 6 1 0 1 0 0
2003 9 1 1 0 0
2004 5 0 0 0
2005 13 2 0
2006 9 2
Table 3. Number banded (n) and recaptures/resightings of all Savannah Sparrows banded from
2000–2006 on a reclaimed surface mine (the Wilds) in Ohio.
Recaptures/resightings by breeding season (habitat types combined)
Year
banded n 2000 2001 2002 2003 2004 2005 2006 2007
2000 18 - 7 2 1 0 0 0 0
2001 23 1 5 2 1 0 0
2002 18 5 2 2 2 0
2003 35 3 2 1 0
2004 14 0 0 0
2005 8 1 1
2006 22 2
Table 2. Number banded (n) and recaptures/resightings of all Grasshopper Sparrows banded
from 2000–2006 on a reclaimed surface mine (the Wilds) in Ohio.
Recaptures/resightings by breeding season (habitat types combined)
Year
banded n 2000 2001 2002 2003 2004 2005 2006 2007
2000 18 - 6 3 2 0 0 0 0
2001 29 7 0 1 0 0 0
2002 43 4 2 2 1 0
2003 47 4 3 2 0
2004 61 5 3 1
2005 61 8 3
2006 65 4
130 Northeastern Naturalist Vol. 17, No. 1
Eleven, twenty-six, and four percent of the Grasshopper Sparrows,
Savannah Sparrows, and Bobolinks, respectively, were captured during
their hatching year (Table 5). Return rates of these individuals were low
(6% Grasshopper, 8% Savannah, and 0% Bobolinks), and when excluded
from our calculations, the overall return rates of each species increased
(Table 5).
Sixteen of 51 (31%) returning Grasshopper Sparrows, 12 of 27 (44%)
Savannah Sparrows, and 2 of 10 (20%) Bobolinks were observed during
multiple years (Tables 2–4). Four Grasshopper Sparrows were seen during
three consecutive years, and two Savannah Sparrows were observed
during four consecutive years.
Discussion
Our findings suggest that reclaimed surface mines provide suitable
nesting habitat for Grasshopper Sparrows, Savannah Sparrows, and Bobolinks.
Our return rates, in some cases, are comparable to those reported for
these species on unmined lands. Our 21% overall Grasshopper Sparrow return
rate is lower than the 28% overall return rate reported for this species
during a three-year study in western New York (Balent and Norment 2003),
and notably lower than the rates reported from a six-year study on Conservation
Reserve Program fields in Maryland (Gill et al. 2006). In contrast,
our return rates for Grasshopper and Savannah Sparrows were substantially
higher than those reported for these species during a nine-year study in
Montana, which was conducted on a large, undisturbed native prairie landscape
(Jones et al. 2007). Our overall return rate for Bobolinks (24%) was
lower than those reported by Gavin and Bollinger (1988) and Bollinger
and Gavin (1989) on low-quality sites (44% male returns and 25% female
returns). We concur with Bollinger and Gavin (1989), who suggested that
Bobolink return rates at a particular location are likely influenced by their
density at that location, and therefore return patterns should not be generalized
across sites. Densities, in turn, are likely influenced by habitat quality
and patch size (Herkert 1997). Patch size on our study site was comparable
to those in Bollinger and Gavin’s (1989) study, but it is possible that the
quality of habitat on our site (a highly disturbed reclaimed surface mine)
Table 5. Numbers of Grasshopper Sparrows (GH), Savannah Sparrows (SA), and Bobolinks
(BO) captured during their hatching year (HY) on all areas, and overall return rates (2001–
2007) of these species when hatching-year birds are excluded.
Number banded during Total return rates Return rates with
HY (2000–2006) with HY birds HY birds excluded
GH 34/324 (11%) 61/324 (19%) 59/290 (20%)
SA 36/138 (26%) 40/138 (29%) 37/102 (36%)
BO 2/49 (4%) 11/49 (22%) 11/47 (23%)
2010 D.J. Ingold, J.L. Dooley, and N. Cavender 131
was lower than that in central New York (unmined pastures and meadows;
Bollinger and Gavin 1989).
That observed return rates were similar and apparent survival rates
actually higher on mowed vs. unmowed areas for Grasshopper Sparrows
suggests that our spring mowing regime did not adversely affect this species.
That return rates and apparent survival rates for Savannah Sparrows
were also comparable between habitats also suggests April mowing was
not detrimental. Similarity in return rates of Grasshopper Sparrows and
Savannah Sparrows to mowed vs. unmowed areas in this study were likely
in part a result of their generalized habitat requirements (Madden et al.
2000, Vickery 1996, Warren and Anderson 2005, Wheelwright and Rising
1993), and the preference of both species to nest in medium to short
vegetation (Balent and Norment 2003, Gill et al. 2006, Ribic and Sample
2001, Whitmore 1979).
The return rates for Bobolinks to mowed vs. unmowed areas across this
seven-year period contrasted slightly (28% vs. 20%, respectively), although
our sample sizes were small. These results are consistent with those reported
by Ingold (2002), in which Bobolink densities on mowed plots were lower
and nests were uncommon. Bobolinks are generally associated with tall
grasses and legumes (Herkert 1997, Madden et al. 2000, Renken and Dinsmore
1987), and the extent to which vegetative growth occurred between the
time of mowing and the onset of nesting likely influenced whether Bobolinks
returned to mowed plots in this study. This growth, in turn, was likely in part
a function of plant species composition, which varied somewhat across our
study area.
Relatively few Grasshopper and Savannah Sparrows and Bobolinks (6%,
8%, and 0%, respectively) banded during their hatching year were observed
to return to their natal area in subsequent years. Return rates of hatching-year
individuals among these species in other studies have generally been low as
well (Balent and Norment 2003, Jones et al. 2007, Wheelwright and Rising
1993), although Gill et al. (2006) reported a 12% return rate in hatching-year
Grasshopper Sparrows in Maryland.
Results from this investigation are consistent with previous work suggesting
that reclaimed surface mines can provide useful habitat for these
species of grassland birds (Bajema et al. 2001, DeVault et al. 2002, Monroe
and Ritchison 2005, Galligan et al. 2006). Nonetheless, developing longterm
strategies for successful conservation of these species will likely
require addressing a number of additional questions. Though mowing did
not appear to negatively impact return rates for Grasshopper and Savannah
Sparrows, there are other management strategies that might prove important
in enhancing habitat quality for these species, as well as for Bobolinks (e.g.,
providing perch sites, particularly in situations in which restoration work
may involve removing invasive shrubs; see Gill et al. 2006).
132 Northeastern Naturalist Vol. 17, No. 1
Acknowledgments
We are indebted to Evan Blumer for encouraging and promoting conservation
research of native species at the Wilds. Jason Larson, Richard Yost, Charlotte
Worstall, Aaron Binckley, Daniel Hollenbaugh, John Treasure, Jarrod Girod,
Ashley Campbell, Paul Gledhill, Elena Gledhill, Lauren Harding, Jessica Turner,
Adam Cirone, and Don Ingold all assisted in the field work. Funding was provided
through Muskingum College and the Homer A. Anderson Distinguished
Professor of Natural Sciences Endowment.
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