By:
And
The
landscape of North Carolina has changed dramatically since the first European
settlers arrived over 400 years ago.
Thousands of acres of bottomland hardwoods along major river systems,
vast longleaf savannas, shrub-like pocosins, open oak-hickory forests, cove,
northern hardwood, open pine and spruce-fir systems in the mountains and even
large prairies greeted early explorers.
All of these areas held a great diversity of birds and other
wildlife. Natural fires and frequent
burning by Native Americans helped create a mosaic of open areas of all types
and sizes interspersed within large tracts of woodlands throughout the state.
As
Europeans settled the state in the 17th and 18th
centuries, the natural landscape began to change drastically. Vast tracts of land were cleared to provide
lumber for homes and ships, start farming operations or create livestock
grazing ranges. This broke up the
continuity of many of our natural systems.
As the population of North Carolina grew and expanded, more habitats
were permanently cleared or altered.
Extensive logging operations that were not done in a sustainable manner
cleared huge amounts of cypress-gum swamps, bottomland hardwoods and longleaf
pine savannas. Fire suppression in the
20th century greatly reduced and altered many other natural
communities. Many wetland systems were
drained and filled to support farming, pine plantations, new towns and other
development.
As
a result of all these land-altering events, many habitats in North Carolina
today are highly fragmented. This means
they have become isolated into smaller pieces and often no longer function in
an ecologically sound manner for many species of birds. Forests, shrubland and grasslands are now
often broken up into distinct, smaller units that no longer meet the needs of
many migratory or even resident birds.
They are separated by large agricultural operations, sprawling towns and
cities, roads, housing developments and shopping malls. Some species of wildlife thrive in these situations. Many do not.
Neotropical migratory birds in particular seem sensitive to these
smaller patches of habitat in which they are forced to nest and raise
young. These are the birds that nest in
North America, but spend our winter in Mexico, the Caribbean, and Central and
South America.
Habitat
fragmentation reduces the size of patches of forest, shrubland, wetlands and
grasslands. This reduces the total area
of contiguous habitat available to birds and increases the isolation of the
habitat. It also leads to an increase in
“edge” habitat that is successfully exploited by a variety of predators that
eat bird eggs and young. An “edge” is
basically where two different habitat types meet, and in agricultural, suburban
and even rural areas this edge is often very abrupt. Opportunistic and adaptable animals operate
well in fragmented habitats such as raccoons, foxes, skunks, opossums,
squirrels, rat snakes, crows, bluejays, grackles and feral and pet dogs and
cats. They all impact bird populations by eating eggs, young birds and even
adults. Other non-native birds like
European Starlings common in urban and suburban areas compete with native
cavity nesting birds for nest sites.
Brown-headed Cowbirds parasitize some birds in fragmented habitats by
laying their own eggs in the nests of other birds (see the fact sheet on
cowbirds for more information).
Non-native invasive plants like Japanese honeysuckle (Lonicera japonica), Chinese privet (Ligustrum sinense) and Japanese grass (Microstegium vimineum) encroach into
smaller habitat fragments, limiting the growth of native plants, disrupting
natural succession and limiting vegetative and structural diversity. This in
turn impacts bird populations.
All
of these problems together along with direct loss of habitat can put
considerable pressure on landbird populations in our state and throughout the
region. Overall in the southeast,
predation seems to be the primary cause of bird nest failure, especially among
neotropical migrants. Birds forced to
compete for nesting sites in smaller and smaller fragments of habitat cause
some to raise young in undesirable locations with reduced food supplies or even
abandon nesting efforts altogether.
These same problems are also occurring not only in breeding habitats,
but also in migration stopover sites and wintering areas throughout the
Americas for migratory landbirds.
Characteristics of the surrounding landscape often influence affects of
habitat fragmentation on bird populations.
Following is a list of scientific papers to help you learn more about fragmentation of forests, shrubland, grasslands or other habitat types and the associated impacts on birds:
Annand,
E.M., and F.R.Thompson III. 1997. Forest bird response to regeneration
practices in central hardwood forests. Journal of Wildlife Management 61:
159-171.
Askins,
R.A. 1994. Open corridors in a heavily forested landscape: Impact on shrubland
and forest-interior birds. Wildlife Society Bulletin22: 339-347.
Askins,
R.A. 2001. Sustaining biological diversity in early successional communities:
the challenge of managing unpopular habitats. Wildlife Society Bulletin 29:
407-412.
Bayne,
E.M., and K.A. Hobson. 1997. Comparing the effects of landscape fragmentation
by forestry and agriculture on predation of artificial nests. Conservation
Biology 11:1418-1429.
Bayne,
E.M., and K.A. Hobson. 2001.Effects of habitat fragmentation on pairing success
of ovenbirds: Importance of male age and floater behavior. Auk 118(2):380-388.
Blake,
J.G. and W.C. Hoppes. 1986. Influence of resource abundance on use of tree-fall
gaps by birds in an isolated woodlot. Auk 103: 328-340.
Blake,
J.G., and J.R. Karr. 1987. Breeding birds of isolated woodlots: Area and
habitat relationships. Ecology 68: 1724-1734.
Blake,
J.G., and B.A. Loiselle. 2001. Bird assemblages in second-growth and old-growth
forests, Costa Rica: Perspectives from mist nets and point counts. Auk 118:
304-326.
Burke,
D.M., and E. Nol. 1998. Influence of food abundance, nest-site habitat and
forest fragmentation on breeding Ovenbirds. Auk 115:96-104.
Bollinger,
E.K., B.D. Peer, and R. W. Jansen. 1997. Status of Neotropical migrants in
three forest fragments in Illinois. Wilson Bulletin 109:521-526.
Brawn,
J.D., and S.K. Robinson. 1996. Source-sink population dynamics may complicate
the interpretation of long-term census data. Ecology 77:3-12.
Buehler,
D.M., D.R. Norris, B.J.M. Stutchbury and N.C. Kopysh. 2002. Food supply and
parental feeding rates of hooded warblers in forest fragments. Wilson Bulletin
114: 122-127.
Burhans,
D.E. and F.R. Thompson III. 1999. Habitat patch size and nesting success of
Yellow-breasted Chats. Wilson Bulletin 111: 210-215.
Darveau,
M., P.Beauchesne, L. Belanger, J. Hout, and P.LaRue. 1995. Riparian forest
strips as habitat for breeding birds in the boreal forest. Journal of Wildlife
Management 59: 67-78.
De
La Zerda Lerner, S., and D.F. Stauffer. 1998. Habitat selection by Blackburnian
Warblers wintering in Columbia. Journal of Field Ornithology 69: 457-465.
Dessecker,
D.R.,and D.G. McAuley. 2001. Importance of early successional habitat to ruffed
grouse and American woodcock. Wildlife Society Bulletin 29: 456-465.
Doherty,
P.F., and T.C. Grubb. 2000. Habitat and landscape correlates of presence,
density and species richness of birds wintering in forest fragments in Ohio.
Wilson Bulletin 112: 388-394.
Donovan,
T.M., F.R. Thompson III, J. Faaborg, and J.R. Probst. 1995. Reproductive
success of migratory birds in habitat sources and sinks. Conservation Biology
9:1380-1395.
Donovan,
T.M., P.W. Jones, E.M. Annand, and F.R. Thompson III. 1997. Variation in
local-scale edge effects: Mechanisms and landscape context. Ecology
78:2064-2075.
Dos
Anjos, L. and R. Bocon. 1999. Bird communities in natural forest patches in
southern Brazil. Wilson Bulletin 111: 397-414.
Fauth,
P.T. 2000. Reproductive success of Wood Thrushes in forest fragments in
Northern Indiana. Auk 117 (1): 194-204.
Ford,
T.B., D.E. Winslow, D.R. Whitehead and M.A. Koukol. 2001. Reproductive success
of forest-dependent songbirds near an agricultural corridor in south-central
Indiana. Auk 118: 864-873.
Frederickson,
T.S. 1998. Impacts of logging and development on central Appalachian forests.
Natural Areas Journal 18: 175-178.
Friesen,
L.E., V.E. Wyatt and M.D. Cadman. 1999. Pairing success of Wood Thrushes in a
fragmented agricultural landscape. Wilson Bulletin 111: 279-281.
Gale,
G.A., L.A. Hanners, and S.R. Patton. 1997. Reproductive success of Worm-eating
Warblers in a forested landscape. Conservation Biology 11:246-250.
Gibbs,
J.P., and J. Faaborg. 1990. Estimating the viability of Ovenbird and Kentucky
Warbler populations in forest fragments. Conservation Biology 4:193-196.
Graves,
G.R. 2001. Factors governing the distribution of Swainson’s Warbler along a
hydrological gradient in Great Dismal Swamp. Auk 118: 650-664.
Hagan,
J.M., P.S. McKinley, A.L. Meehan and S.L. Grove. 1997. Diversity and abundance
of landbirds in a northeastern industrial forest. Journal of Wildlife
Management 61:718-735.
Hanski,
I.K., T.J. Fenske, and G.J. Niemi. 1996. Lack of edge effect in nesting success
of breeding birds in managed forest landscapes. Auk 113:578-585.
Harris,
R.J., and J.M. Reed. 2001. Territorial movements of Black-throated Blue
Warblers in a landscape fragmented by forestry. Auk 118: 544-549.
Hobson,
K.A., and E.M. Bayne.2000. Effects of forest fragmentation by agriculture on
avian communities in the southern boreal mixedwoods of western Canada. Wilson
Bulletin 112:373-387.
Holmes,
R.T., T.W. Sherry, P.P. Marra, and K.E. Petit. 1992. Multiple brooding and
productivity of a Neotropical migrant, the Black-throated Blue Warbler (Dendroica caerulescens), in an
unfragmented temperate forest. Auk 109:321-333.
Holmes,
R.T., and T.W. Sherry. 2001. Thirty-year bird population trends in an
unfragmented temperate deciduous forest: Importance of habitat change. Auk
118:589-609.
Hoover,
J.P., M.C. Brittingham, and L.J. Goodrich. 1995. Effects of forest patch size
on nesting success of Wood Thrush. Auk 112:146-155.
Hunt,
P.D.1996. Habitat selection by American Redstarts along a successional gradient
in northern hardwood forest: Evaluation of habitat quality. Auk 113:875-888.
Johnson,
D.H. and L.D. Igl. 2001. Area requirements of grassland birds: A regional
perspective. Auk: 24-34.
Jones,
J. and R.J. Robertson. 2001. Territory and nest-site selection of Cerulean Warblers
in eastern Ontario. Auk 118: 727-735.
King,
D.I., C.R. Griffen, and R.M. DeGraaf. 1996. Effects of clearcutting on habitat
use and reproductive success of the Ovenbird in forested landscapes.
Conservation Biology 10:1380-1386.
King,
D.I., C.R. Griffen, and R.M. DeGraaf. 1997. Effect of clearcut borders on
distribution and abundance of forest birds in northern New Hampshire. Wilson
Bulletin 109:239-245.
Krementz,
D.G. and J.S. Christie. 1999. Scrub-successional bird community dynamics in
young and mature longleaf pine-wiregrass savannahs. Journal of Wildlife
Management 63: 803-814.
Kuehl,
A.K., and W.C. Clark. 2002. Predator activity related to landscape features in
northern Iowa. Journal of Wildlife Management 66: 1224-1234.
Lambert,
J.D., and S.J. Hannon. 2000. Short-term effects of timber harvest on abundance,
territory characteristics, and pairing success of Ovenbirds in riparian buffer
strips. Auk 117(3): 687-698.
Lent,
R.A., and C.E. Capen. 1995. Effects of small-scale habitat disturbance on the
ecology of breeding birds in a Vermont (USA) hardwood forest. Ecography
18:97-108.
Manolis,
J.C., D.E. Anderson and F.J. Cuthbert. 2002. Edge effect on nesting success of
ground nesting birds near regenerating clearcuts in a forest-dominated landscape.
Sauk 119: 955-970.
Marzluff,
J.M. and K. Ewing. 2001. Restoration of fragmented landscapes for the
conservation of birds: A general framework and specific recommendations for
urbanizing landscapes. Restoration Ecology 9:280-292.
Matlock,
G.R. 1993. Microenvironment variation within and among forest edge sites in the
eastern United States. Biological Conservation 66:185-194.
Moorman,
C.E. and D.C. Guynn. 2001. Effects of group selection opening size on breeding
bird habitat use in a bottomland forest. Ecological Applications 11: 1680-1691.
Moorman,
C.E., D.C. Guynn and J.C. Kilgo. 2002. Hooded Warbler nesting success adjacent
to group-selection and clearcut edges in a southeastern bottomland forest.
Condor 104: 366-377.
Norment,
C. 2002. On grassland bird conservation in the northeast. Auk 119: 271-279.
Ortega,Y.K.,
and D.A. Capen.1999. Effects of forest roads on habitat quality for Ovenbirds
in a forested landscape. Auk 116:937-946.
Paton,
P.W.C. 1994. The effect of edge on avian nest success: How strong is the
evidence? Conservation Biology 8:17-26.
Pearson,
S.M. 1993. The spatial extent and relative influence of landscape-level factors
on wintering bird populations. Landscape Ecology 8:3-18.
Petit,
L.J., and D.R. Petit.1996. Factors governing habitat selection by Prothonotary
Warblers: Field tests of the Fretwell-Lucus models. Ecological Monographs
66:367-387.
Peterjohn,
B.G. 2003. Agricultural landscapes: Can they support healthy bird populations
as well as farm products? Auk 120: 14-19.
Porneluzi,
P., J.C. Bednarz, L.J. Goodrich, N.Zawada, and J. Hoover.1993 Reproductive
performance of territorial Ovenbirds occupying forest fragments and a
contiguous forest in Pennsylannia. Conservation Biology. 7:618-622.
Porneluzi,
P., and J. Faaborg. 1999. Season-long fecundity, survival and viability on
Ovenbirds on fragmented and unfragmented landscapes. Conservation Biology
13:1151-1161.
Probst,
J.R., and J.P. Hayes. 1987. Pairing success of Kirtland’s Warblers in marginal
vs. suitable habitat. Auk 104:234-241.
Pulliam,
H.R., and B.J. Danielson. 1991. Sources, sinks and population regulation.
American Naturalist 137:550-566.
Rappole,
J.H., and M.V. McDonald. 1994. Cause and effect in population declines of
migratory birds. Auk 111:652-660.
Ricketts,
M.S., and G. Ritchison. 2000. Nesting success of Yellow-breasted Chats: Effects
of nest site and territory vegetation structure. Wilson Bulletin 112: 510-516.
Roberts,
C., and C.J. Norment. 1999. Effects of plot size and habitat characteristics on
breeding success of Scarlet Tanagers. Auk 116: 73-82.
Robinson,
S.K., F.R. Thompson III, T.M. Donovan, D.R. Whitehead, and J.Faaborg. 1995.
Regional forest fragmentation and the nesting success of migratory birds.
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Robinson,
S.K. 1998. Another threat posed by forest fragmentation: Reduced food supply.
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A.D., and R.H. Yahner. 2000. Bird communities associated with harvested
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A.D. 2002. Nest predation in forested regions: Landscape and edge effects.
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breeding in a forest fragment. Auk 110:37-48.
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T.C., and M.L. Hunter. 1993. Avian nest predation in clearcuts, forest and
edges in a forest-dominated landscape. Journal of Wildlife Management
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pairing success of male Ovenbirds, Seiurus
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T.W., and R.T. Holmes. 1989. Age-specific social dominance affects habitat use
by breeding American Redstarts (Setophaga
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