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Managing
for Nongame Birds
When managing
forest land for nongame birds, one should consider the needs of
all the birds that will occupy that land. This becomes somewhat
difficult however, when we realize that there are at least three
different populations of birds over the course of a year. There
are year-round residents, winter visitors, and summer visitors.
Their needs are perhaps better understood when their foods are
considered. Year-round residents are the most versatile, and can
sustain themselves on a combination of seeds, fruits, and
insects. However, there are few fruits and insects in winter so
most of our winter visitors depend on seed bearing plants.
Likewise, our summer visitors tend to be those species that have
evolved to feed primarily on insects which thrive in a diversity
of plant types.
By providing
mixed habitats that support all food types over the course of a
year, it is possible to support all bird species that might
occur in that area. If all types of management could not be
undertaken, the next step should then be to assess which group
of birds needs our management help the most. Following are some
general guidelines about different bird groups and what can be
done to benefit them in basic forest management.
Year-round
Residents
These are the
birds that we are most familiar with; cardinals, bluejays,
chickadees, carolina wrens, and bluebirds just to name a few.
They are the residents of small farm woodlots as well as city
parks. Although you can find some of them deep in the forest,
they don't require that habitat. As long as there is food and
available nesting sites, these birds are at home. About half of
our resident songbirds are cavity nesters, so the single biggest
asset to them is a good mixed forest with different sizes of
dead or dying trees, or trees with natural cavities like beeches
and gums. Although some of our residents are at home in pine
forests, most prefer at least a mixture of hardwoods, and tend
to benefit more as the percentage of hardwood increases. This is
largely due to the diversity of seeds and fruits generated by
hardwoods, as well as the potential for cavities.
Mixed
woodlots, a good diversity of tree and shrub species, and a
regular water source such as a creek or stream will greatly
benefit resident forest dwellers. These birds also depend
heavily on cover from hawks, particularly in the winter, so a
sprinkling of holly, sweetbay, or similar plants make for a
valuable midstory component in woodlots or around yards.
Winter
Visitors
Among those
forest dwelling species that spend their winters in Virginia are
kinglets, creepers, juncos and several species of sparrows.
Collectively they occupy almost all forest and field habitats.
The kinglets and creepers surprisingly still manage to find
insects in the winter, utilizing conifer forests, hardwoods, and
brushy edge habitats. The juncos and sparrows, however, are
predominantly seed dependent and benefit from weedy fields,
brushy hedgerows, and forest/field edges. A plan of mixed
forests and idle fields with hedgerows accommodates the needs of
most winter visitors.
Summer
Visitors
Summer brings
about a whole host of birds not seen any other time of year.
There are at least 65 species of forest dwelling birds alone,
that occur in Virginia just during the warmer months. Most of
these species spend their winters in Central and South America
and so are called neotropical migrants. Fortunately, almost all
of them are insect eaters, so they don't destroy crops, and they
help keep a lot of insect pests in check. Unfortunately, some of
them have rather demanding habitat needs and many of them are
suffering significant population declines in Virginia. Looking
at the majority of these species, and with particular emphasis
on the ones in the most trouble, the preferred habitat types are
large blocks of mature hardwoods.
Of course, if
you don't have large blocks of hardwood forest, they are
difficult to create. There are other measures that can be
undertaken to improve songbird habitat. When harvesting timber
out of any size stand, it is best to try to preserve as much of
a core area as possible. In other words, if one is interested in
managing for summer songbirds, one would consolidate cuts into
one large area of clearcut, rather than cutting a number of
smaller blocks out of the middle. One preferred timber
management technique might be a selective cut, where a large
proportion of the overstory is left intact. This would generate
rapid growth of the understory which is also favorable because
it initially produces a number of different types of plants, in
regards to height, amount of foliage, etc. As insect eaters,
these songbirds depend on a variety of plants which will support
a number of different kinds of insects. For each type of forest
habitat there is at least one specialized bird species that can
exploit its resources.
There are at
least two reasons for promoting the management of large blocks
of timber for songbirds. First, some of these species are known
to be area sensitive. That is, they are dependent on a forest
size that is actually much greater than they actually need to
find a nest site or to locate food. This is one of the behaviors
that makes them so specialized and consequently so hard to
manage for.
There is
another problem that relates to small forest size. Birds that
are forced to nest close to an edge are subject to greater
problems from brown-headed cowbirds. Cowbirds are nest
parasites. They lay their eggs in the nest of smaller songbirds.
When the cowbird eggs hatch, the young are so big that they get
all the food that the host parents bring back. The result is
that the smaller songbird young do not survive and the cowbirds
increase in number affecting more and more songbirds each year.
Since cowbirds are not forest dwelling species, they tend to
look for their victims along forest edges. So the bigger the
block of forest is, the more interior space there is for
songbirds to get out of the reach of cowbirds.
Many of the
migrant songbirds prefer transitional habitats, such as
regenerating clearcuts. The only problem with clearcuts is that
they are only useful for about 6-8 years until the regenerating
pine stand closes in and shuts out the hardwood and herbaceous
understory. Once the pines take over there are very few
songbirds that utilize monoculture pine stands as their primary
habitat. It's not until the stand reaches maturity and a
hardwood midstory starts to creep back in that the stand regains
its value to songbirds. Ideal areas for many summer songbirds
would be habitats that could be maintained in a shrubby, mixed
vegetation state as in powerline corridors, or young clearcuts.
Unfortunately, very few landowners own large tracts of timber
that could be managed to the benefit of nesting songbirds.
However, there is a great deal the small landowner can do for
migrating songbirds. Even with all the migrant birds that nest
in Virginia in the summer, there are many more migrating
songbirds that just pass through Virginia on their way to
nesting areas far to the north of us. We see them only as they
travel through in spring and fall. What these birds need is a
safe place to refuel during their journey.
In the
Coastal Plain, birds tend to funnel toward the coast as they
make their start north or south for migration. In order to
accomplish this, they typically use streams, creeks, and rivers
to lead them to the coast. As a result, waterways, swamps, and
riparian corridors tend to be vitally important to migrating
birds. For those landowners who cannot manage large areas for
nesting songbirds, there is a lot that can be done by simply
protecting forested tracts along waterways. Increasing the width
of forested buffers along streams, even to the point of doubling
recommended BMP's when harvesting timber is a highly recommended
management practice for birds as well as other wildlife.
Tree-lined
fencerows and forested roadsides also serve as valuable travel
corridors for migrating songbirds, especially if the corridor
links two larger tracts of forest. These corridors provide a
critical area for safe passage of birds and other wildlife
migrating to nesting sites or just moving from one wooded patch
to another. |