Annual Survival of Birds Captured in a Habitat Island
Bordered by the Urban Matrix of Baton Rouge, LA
Jared D. Wolfe, Erik I. Johnson, Philip C. Stouffer, Falyn Owens, Emma Deleon, Eric Liffmann, Kristin Brzeski, Sherri Utley, Dan Mooney, Claire Coco, and Greg Grandy
Southeastern Naturalist, Volume 12, Issue 3 (2013): 492–499
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2013 SOUTHEASTERN NATURALIST 12(3):492–499
Annual Survival of Birds Captured in a Habitat Island
Bordered by the Urban Matrix of Baton Rouge, LA
Jared D. Wolfe1,*, Erik I. Johnson1, Philip C. Stouffer1, Falyn Owens1,
Emma Deleon1, Eric Liffmann2, Kristin Brzeski1, Sherri Utley2, Dan Mooney2,
Claire Coco3, and Greg Grandy3
Abstract - Urban habitat fragments may provide birds the resources necessary to
sustain viable populations in close proximity to human settlement. Conversely, urban
habitat fragments may also act as ecological traps, where birds are lured into habitats
that negatively affect reproduction or survival. In this study, we compared annual survival
estimates of six common resident bird species captured at Bluebonnet Swamp, a
41.7-ha forest fragment bordered by the urban matrix of Baton Rouge, LA, with values
derived from the Institute for Bird Populations’ MAPS program to determine if populations
sampled in the habitat fragment demographically deviated from regional baseline
estimates. We found that three species captured at Bluebonnet Swamp exhibited survival
estimates consistent with regional averages, whereas Cardinalis cardinalis (Northern
Cardinal), Toxostoma rufum (Brown Thrasher), and Poecile carolinensis (Carolina
Chickadee) survival estimates were lower than baseline. Edge effects associated with a
relatively small preserve coupled with disease and semiannual movements in and out of
the study area may be influencing Cardinal and Thrasher survival. We recommend that
other studies focus on measuring avian demographics within habitat fragments to identify
and mitigate factors that limit population sustainability in human-modified landscapes,
as relative density alone may not be an appropriate metric for understanding the value of
habitat fragments to birds.
Introduction
Many scientists believe the onset of the industrial revolution during the latter
half of the 19th century has accelerated the planet’s entry into a new geologic
era, the anthropocene or age of man (Crutzen and Stoermer 2000). The associated
technological advance has, unfortunately, facilitated the Earth’s sixth documented
extinction crisis brought on by relentless ecosystem conversion (Sala et al. 2000),
human population growth (McKee et al. 2003), pollution (Espinosa et al. 2007), resource
extraction (Polidoro et al. 2010), invasive species proliferation (Gurevitch
and Padilla 2004), and climate change (Thomas et al. 2004). According to the Food
and Agriculture Organization of the United Nations (2010), broad-scale changes
associated with human settlement have resulted in 78% of the Earth’s arable land
being converted for agricultural purposes. Rural human settlements and sweeping
agricultural and silvicultural enterprises, interwoven with dense population
1School of Renewable Natural Resources, Louisiana State University, Agricultural Center
and Louisiana State University, Baton Rouge, LA 70808. 2Bluebonnet Bird Monitoring
Project, 10503 North Oak Hills Parkway Baton Rouge, LA 70810. 3The Recreation and
Park Commission for the Parish of East Baton Rouge, 6201 Florida Boulevard, Baton
Rouge, LA 70806. *Corresponding author - jwolfe5@lsu.edu.
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centers, have leveraged intense pressure on many bird species, raising concerns
that isolated and fragmented nature preserves may not provide the necessary resources
for the persistence of many avian populations (Crooks et al. 2001).
Since the mid-1980s, conservationists have advocated local solutions for
global problems by formulating public and federal programs that reconcile
the preservation of native biodiversity in close proximity of human enterprise,
such as the Natural Resources Conservation Service’s Farm Bill Conservation
Programs (Cain and Lovejoy 2004, Zinn 2001) and the National Wildlife
Federation’s “Garden for Wildlife” program (Rosenzweig 2003), which focus
on conservation and education in urban and rural environments. Small nature
preserves strategically located within urban centers may also serve as essential
habitat for vulnerable bird populations. However, small nature preserves may
instead undermine conservation efforts by acting as ecological traps, where birds
are lured into habitats that negatively affect survival and population growth
(Robertson and Hutto 2006). Bird-monitoring efforts should be employed to
differentiate between the potentially positive and negative influences of small
nature preserves on local bird populations. In this study, we used 22 months of
bird-capture data to generate survival estimates of six resident bird species in a
41.7-ha habitat fragment surrounded by an urban matrix in Baton Rouge, LA. Our
survival estimates were compared with values from the Institute for Bird Populations’
(IBP) Monitoring Avian Productivity and Survivorship (MAPS) program
for the south-central region of the United States to determine if bird populations
residing within the habitat fragment demographically deviated from regional
baseline survival estimates. Our year-round volunteer-based monitoring effort is
the first of its kind in Louisiana and represents a model program for assessing the
value of fragmented habitats to resident birds within an urban landscape.
Study Area
The Bluebonnet Swamp Nature Center is located within the city limits of
Baton Rouge, LA (see Appendix A in Supplemental File 1, available online at
https://www.eaglehill.us/SENAonline/suppl-files/s12-3-1117-Wolfe-s1, and, for
BioOne subscribers, at http://dx.doi.org/10.1656/S1117.s1), and comprises 41.7
ha of seasonally inundated Taxodium distichum L. (Bald Cypress) and Nyssa
aquatica L. (Water Tupelo) forest bordered by a diverse upland component comprised
of Quercus nigra L. (Water Oak), Liquidambar styraciflua L. (Sweetgum),
Quercus virginiana Mill. (Live Oak), Fagus grandifolia (American Beech),
Magnolia grandiflora L. (Southern Magnolia), and other hardwoods. The understory
of the upland forest contains many native and nonnative species such as
Ligustrum sinense Lour. (Chinese Privet), Toxicodendron radicans (Poison Ivy),
and Rubus spp. (blackberry). The study site was a small floodplain prior to the
construction of Highland Road, which served as a supply road for 18th-century
plantations; Highland Road subsequently blocked drainage outlets resulting in
the present-day swamp. The study area came under threat of development during
rapid urban expansion throughout the latter half of the 20th century, prompting
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its purchase by the Nature Conservancy and subsequent donation to the Parks
and Recreation Commission of Eastern Baton Rouge Parish (BREC), which
designated the site as a conservation area in 1997. The seasonally inundated
Bald Cypress-Water Tupelo swamp at Bluebonnet represents a small portion of
a once-dominant forest type in East Baton Rouge Parish (DeWeese et al. 2007).
Currently, Bluebonnet is characterized as an isolated patch of protected upland
forest and swamp surrounded by the dense urban matrix of Baton Rouge (Appendix
A). The Bluebonnet Bird Monitoring Project was started in March 2010 as
a volunteer-based bird initiative focused on measuring bird demographics within
the preserve. Additional activities include intensive community outreach, educating
biology students from local universities, and studying avian natural history
(Johnson et al. 2012, Wolfe 2011, Wolfe and Pyle 2011).
Methods
Since March 2010, volunteers have operated fifteen 12- x 3-m (36-mm mesh)
mist-nets twice per month, for five hours per session beginning at sunrise; each
net was typically located between 20 and 50 m from each other in upland forest
at Bluebonnet Swamp. Captured birds were marked with unique USFWS metal
bands (Wolfe and Ralph 2010). Banding data for the six most common resident
bird species captured between March 2010 through December 2011, Cardinalis
cardinalis L. (Northern Cardinal), Thryothorus ludovicianus Latham (Carolina
Wren), Poecile carolinensis Audubon (Carolina Chickadee), Vireo griseus
Boddaert (White-eyed Vireo), Tufted Titmouse L. (Baeolophus bicolor), and
Toxostoma rufum L. (Brown Thrasher) were chosen for survival analyses.
All survival analyses and goodness-of-fit tests were conducted in Program
MARK (White and Burnham 1999). Bimonthly banding occasions were collapsed
into single monthly time intervals in Cormack-Jolly-Seber (CJS) models used to
estimate apparent monthly survival for the six study species. Nine candidate models
were formulated for each of the six species (Table 1). In addition to varying
apparent annual survival (φ) and apparent annual recapture probability (p) by time,
we included two time-since-marking models (TSM) to vary with φ (Cooch and
White 2011). TSM models can account for survival deflation due to the effects of
transient individuals moving through the study area (Pradel et al. 1997).
The overdispersion factor (ĉ) was calculated for each species by dividing the
deviance of each species’ global model by deviance estimated via a boot-strapping
goodness-of-fit routine (using 1000 iterations; Cooch and White 2011). The resulting
ĉ values were used to determine model goodness-of-fit whereby any species
exhibiting a ĉ value less than 3 was considered exhibiting adequate fit (Cooch
and White 2011). Top models were chosen based on associated corrected Akaike
information criterion (AICc) values (Table 1), and all monthly survival estimates
from top models were multiplied to the power of 12 to generate annual survival
estimates. Annual survival values from the six study species were compared to
estimates from the IBP MAPS program to identify demographic deviation from
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regional baseline survival rates (DeSante and Kaschube 2009). IBP operated 116
MAPS stations from 1996 through 2006 in the south-central region of the United
States; each MAPS station used a variable number of mist-nets, which were
operated from 26 April until 13 August. The 116 MAPS stations throughout the
south-central region represented 41 habitat types (see Appendix B in Supplemental
File 1, available online at https://www.eaglehill.us/SENAonline/suppl-files/s12-3-
1117-Wolfe-s1, and, for BioOne subscribers, at http://dx.doi.org/10.1656/S1117.
s1); the three most common habitat types included: tall-grass prairie/cross timbers,
bottomland hardwoods, and oak-gum bottomland forest: 2000 harvest (DeSante
and Kaschube 2009). Importantly, IBP and Bluebonnet Swamp used the same CJS
and TSM models to generate estimates of annual survival.
Results
Between March 2010 and December 2011, a total of 1419 birds were captured
at Bluebonnet Swamp, including 736 captures representing the six study species.
The most commonly captured species was Northern Cardinal (365 captures representing
183 individuals), and the least commonly captured species used in the
analysis was Tufted Titmouse (39 captures representing 20 individuals) (Fig. 1).
Each study species had associated ĉ values below 3, indicative of adequate
model fit, and yielded top model monthly survival estimates with constant time
Table 1. Descriptions of Cormack-Jolly-Seber (CJS) and time-since-marking (TSM) models used
to estimate survival of six species of birds between March 2010 and December 2011 at Bluebonnet
Swamp Nature Preserve. Notations and descriptions include the survival parameter (Surv.), recapture
probability parameter (Recap.), number of parameters associated with each model (Par.) and
species for which the associated model had the lowest AIC value (Species).
Surv. Recap. Par. Species Model description
φ(·) p(·) 2 Brown Thrasher, CJS model with constant survival; constant
Carolina Chickadee, recapture.
Tufted Titmouse,
White-eyed Vireo
φ(2./.) p(·) 3 none TSM model with two classes for survival ( first
and subsequent intervals after marking) with
survival constant for each class; constant
recapture.
φ(·) p(t) 23 none CJS model with constant survival; timedependent
recapture.
φ(t) p(·) 23 none CJS model with time-dependent survival;
constant recapture.
φ(2./.) p(t) 24 Northern Cardinal, TSM model with two classes for survival ( first
Carolina Wren and subsequent intervals after marking) with
survival constant for each class; timedependent
recapture.
φ(t) p(t) 44 none CJS model with time-dependent survival; timedependent
recapture.
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or TSM dependency (see Appendix C in Supplemental File 1, available online
at https://www.eaglehill.us/SENAonline/suppl-files/s12-3-1117-Wolfe-s1, and,
for BioOne subscribers, at http://dx.doi.org/10.1656/S1117.s1). Our averaged
annual survival estimate across all six study species at Bluebonnet Swamp (φ =
0.360, SE = 0.050) was lower than the averaged regional baseline estimate for the
same species (φ = 0.455, SE = 0.034). Tufted Titmouse, White-eyed Vireo, and
Carolina Wren exhibited similar annual survival estimates relative to the regional
baseline. Brown Thrasher (φ = 0.108, SE = 0.087), Northern Cardinal (φ = 0.370,
SE = 0.021), and Carolina Chickadee (φ = 0.234, SE = 0.177) survival estimates
were substantially lower than regional baselines, although Carolina Chickadee
survival estimates had large associated standard error causing overlap with the
regional baseline survival estimate, hindering subsequent inference (Fig. 1).
Discussion
In this study, we have provided the first annual survival estimates of common
bird species residing in a forest fragment within a Louisianan urban matrix. Our
Figure 1. Annual survival estimates with standard error bars of six resident bird species,
and there average estimates, from Bluebonnet Swamp and the Institute for Bird Populations/
NBII Bird Conservation Node for the south-central region of the United States
(Institute for Bird Populations 2012). Numbers in parentheses on the x-axis associated
with Bluebonnet estimates represent number of individuals followed by number of total
captures from March 2010 through December 2011.
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averaged survival estimate pooled across all study species was slightly lower
than regional baseline estimates for forest passerines indicating that, on average,
landbirds residing in Bluebonnet Swamp exhibit slightly lower annual survival
relative to counterparts in the broader south-central region. White-eyed Vireo,
Tufted Titmouse, and Carolina Wren exhibited annual survival rates similar to
regional estimates, whereas Brown Thrasher, Carolina Chickadee, and Northern
Cardinal showed relatively low annual survival. Differences in annual survival
estimates between Bluebonnet Swamp and MAPS may be influenced by two inherent
methodological discrepancies. First, MAPS collected data only during the
breeding season, while Bluebonnet Swamp collected data year-round. Second,
MAPS and Bluebonnet Swamp annual survival estimates were calculated from
data collected between 1994 through 2006, and 2010 through 2012, respectively.
We believe differences in capture effort are mitigated by unique recapture probabilities,
generated for each dataset in Program MARK, which make annual
survival estimates comparable between MAPS regional baseline and Bluebonnet
Swamp values. Therefore, we believe that deviations in annual survival between
Bluebonnet Swamp and regional estimates represent real differences, except for
Carolina Chickadee, which suffered from large standard errors that probably resulted
from the low number of recaptures (Fig 1).
Northern Cardinals may have exhibited lower survival relative to regional
baseline estimates as a consequence of potential seasonal movements between
our study site and the urban matrix. For example, Northern Cardinals capture rates
peaked during winter months followed by a steady decline throughout the spring
and summer (Wolfe 2011). Cardinals were routinely captured during the winter,
after which many individuals apparently left the study area, as has been confirmed
in some cases by reading band numbers from photographs taken at feeders in the
urban matrix, only to be recaptured the following winter. Presumably, during the
winter when food became scarce in the urban matrix and cardinals become more
gregarious, they returned to Bluebonnet, which provided predictable crops of Chinese
Privet fruit (J.D. Wolfe, unpubl. data). Semiannual movements of Cardinals
may account for actual decreases in survival relative to baseline estimates, or it
may be a statistical artifact associated with a partially nomadic behavior. More
study focused on the local movements of resident birds is warranted given our preliminary
findings. Northern Cardinals, Tufted Titmouse, and Carolina Chickadee
all commonly use bird feeders, and each species exhibited survival estimates equal
to or lower than baseline values, suggesting that feeders available to Bluebonnet
birds do not noticeably increase annual survival. The harsh 2010/2011 winter resulted
in rare February snowstorms in Louisiana that may have further impacted
Cardinal populations; however, one would presume other resident species (e.g.,
Carolina Wren and Tufted Titmouse) would respond in a similar fashion if harsh
weather limited annual survival.
Differences in Brown Thrasher survival estimates between regional baselines
and Bluebonnet may reflect edge effects associated with a relatively small
preserve (e.g., increased mesocarnivore predation and resource instability), or,
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alternatively, local disease outbreaks. For example, approximately 40% of all
Brown Thrashers captured during the spring and summer of 2010 and 2011 had
moderate to severe avian pox infestations, representing the most prolific pox infection
rate in our cumulative experience banding birds (see Appendix D in Supplemental
File 1, available online at https://www.eaglehill.us/SENAonline/suppl-files/
s12-3-1117-Wolfe-s1, and, for BioOne subscribers, at http://dx.doi.org/10.1656/
S1117.s1). Disease prevalence may have lowered Thrasher survival, especially
during the harsh winters of 2010 and 2011, and may not accurately reflect longterm
demographic trends at Bluebonnet. Sustained monitoring will determine if
our estimates represent actual departures from baseline demographic values, or
statistical vagaries associated with 22 months of constant effort capture data.
We recommend that other studies focus bird-monitoring efforts in urban
habitat fragments to determine the value of isolated forests to bird populations.
Furthermore, an increase in sustained monitoring efforts will provide insights
into metapopulation dynamics between multiple habitat fragments, which can be
coupled with demographic estimates from studies such as this one, to forecast the
number and size of reserves necessary to sustain viable bird populations.
Acknowledgments
Special thanks to the Institute for Bird Populations for publishing uniquely important
demographic data and to Jim Saracco for insightful edits. Thanks to all the volunteer
bird banders of the Bluebonnet Bird Monitoring Project. This project would not be
possible without the support of the Parks and Recreation Commission of the Parish of
Eastern Baton Rouge, Louisiana State University’s School of Renewable Natural Resources,
and the Baton Rouge Audubon Society. Funding was provided by the Western
Bird Banding Association Research Grant and revenues from the Peter Pyle Advanced Bird
Banding Workshop. This is a contribution of the Bluebonnet Bird Monitoring Project.
Literature Cited
Cain, Z., and S. Lovejoy. 2004. History and outlook for Farm Bill conservation programs.
Choices: The Magazine of Food, Farm, and Resource Issues 4:37–42.
Cooch, E., and G.C. White. 2011. Program MARK: Analysis of data from marked
individuals—“A gentle introduction”. Available online at http://www.phidot.org/
software/mark/docs/book/. Accessed 1 November 2012.
Crooks, K.R., A.V. Suarez, D.T. Bolger, and M.E. Soulé. 2001. Extinction and colonization
of birds on habitat islands. Conservation Biology 15:159–172.
Crutzen, P.J., and E.F. Stoermer. 2000. The “Anthropocene”. Global Change Newsletter
2000 41:12–13.
DeSante, D.F., and D.R. Kaschube. 2009. The Monitoring Avian Productivity and Survivorship
(MAPS) program 2004, 2005, and 2006 report. Bird Populations 9:86–169.
DeWeese, G.G., H.D. Grissino-Mayer, and N. Lam. 2007. Historical land-use/land-cover
changes in a bottomland hardwood forest, Bayou Fountain, Louisiana. Physical Geography
28:345–359.
Espinosa, F., J.M. Guerra-García, and J.C. García-Gómez. 2007. Sewage pollution and
extinction risk: An endangered limpet as a bioindicator? Biodiversity and Conservation
16: 377–397.
2013 Southeastern Naturalist Vol. 12, No. 3
J.D. Wolfe, et al.
499
Food and Agriculture Organization of the United Nations (FAO). 2010. 2010 statistics.
Available online at http://www.fao.org/economic/ess/ess-publications/ess-yearbook/
ess-yearbook2010/yearbook2010-reources/en/. Accessed 10 February 2012.
Gurevitch, J., and D.K. Padilla. 2004. Are invasive species a majorcause of extinctions?
Trends in Ecology and Evolution 19:470–474.
Johnson, E.I., J.D. Wolfe, and J. Hartgerink. 2012. Barred Owl preys upon Sharp-shinned
Hawk. Journal of Louisiana Ornithology 9:22–23.
McKee, J.K., P.W. Sciulli, C.D. Fooce, and T.A. Waite. 2003. Forecasting global biodiversity
threats associated with human population growth. Biological Conservation
115:161–164.
Polidoro, B.A., K.W. Carpenter, L. Collins, N.C. Duke, A.M. Ellison, J.C. Ellison, E.J.
Farnsworth, E.S. Fernando, K. Kathiresan, N.E. Koedam, J.H. Primavera, S.G. Salmo,
III, J.C. Sanciangco, S. Sukardjo, Y. Wang, and J.W.H. Yong. 2010. The loss of
species: Mangrove extinction risk and geographic areas of global concern. PLoS ONE
5:1–10.
Pradel, R., J. E. Hines, J.-D. Lebreton, and J.D. Nichols. 1997. Capture-recapture survival
models taking account of transients. Biometrics 53:60–72.
Robertson, B.A., and R.L. Hutto. 2006. A framework for understanding ecological traps
and an evaluation of existing evidence. Ecology 87:1075–1085.
Rosenzweig, M.L. 2003. Win–win Ecology: How the Earth’s Species can Survive in the
Midst of Human Enterprise. Oxford University Press, Oxford, UK.
Sala, O.E., F.S. Chapin, J.J. Armesto, E. Berlow, J. Bloomfield, R. Dirzo, E. Huber-
Sanwald, L.F. Huenneke, R.B. Jackson, A. Kinzig, R. Leemans, D.M. Lodge, H.A.
Mooney, M. Oesterheld, N.L. Poff, M.T. Sykes, B.H. Walker, M. Walker, and D.H.
Wall. 2000. Biodiversity: Global biodiversity scenarios for the year 2100. Science
287:1770–1774.
Thomas, C.D., A. Cameron, R.E. Green, M. Bakkenes, L.J. Beaumont, Y. Collingham,
B.F.N. Erasmus, M.F. de Siqueira, A. Grainger, L. Hannah, L. Hughes, B. Huntley,
A.S. van Jaarsveld, G. F. Midgley, L.J. Miles, M.A. Ortega-Huerta, A. Townsend
Peterson, O. Phillips, and S.E. Williams. 2004. Extinction risk from climate change.
Nature 427:145–148.
White, G.C., and K.P. Burnham. 1999. Program MARK: survival estimation from populations
of marked animals. Bird Study 46:120–138.
Wolfe, J.D. 2011. Bluebonnet Bird Monitoring Project annual report. 2011. Available
online at http://braudubon.org/pdf/BBMP_AnnualReport2011.pdf. Accessed 10 February
2012.
Wolfe, J.D., and P. Pyle. 2011. First evidence for eccentric prealternate molt in the Indigo
Bunting: Possible implications for adaptive molt strategies. Western Birds 42:23–26.
Wolfe, J.D., and C.J. Ralph. 2010. Bluebonnet Bird Monitoring Project operational
protocol [BRAS]. Available online at http://braudubon.org/pdf/BBMP_protocol.pdf.
Accessed 10 February 2012.
Zinn, J.A. 2001. CRS issue brief for Congress report: IB96030: Soil and water conservation
issues. Available online at http://cnie.org/nle/crsreports/agriculture/ag-18.cfm.
Accessed 10 February 2012.