Since 1948, birds have been counted in winter in a 65 acre study plot in Rock Creek Park, a large forested area in Washington, D.C. The deciduous upland forest habitat has harbored 41 different kinds of birds.
However, only 5 kinds of birds have been found in every year. They are pictured below, from left to right: Carolina chickadee, tufted titmouse, white-breasted nuthatch, downy woodpecker, and brown creeper. These birds often occur together in small flocks.
The most common birds are the chickadee and the titmouse. In the chart below, you can see that their numbers fluctuate quite a bit from year to year. Year is the x-axis and count is on the y-axis. The nuthatch, woodpecker, and creeper numbers have been fairly stable.
It can be difficult to spot bird population changes over the short-term so long-term surveys like this one, and the Breeding Bird Census, help us to monitor the state of birds.
This census was restarted in the winter of 2010 after having last been surveyed in 1979.
As can be seen in the picture below, the study plot is a deciduous forest on a slope heading toward Rock Creek. The upper section is dominated by oak trees while the lower section favors tuliptrees.
Several ravines cut through the forest but only one has permanent water. The understory is comprised of saplings and a few shrubs.
Wintering birds subsist on a diet of nuts and seeds provided by the trees as well as overwintering insects and their eggs. There is little fruit in the plot available.
The forest area was likely cut during the Civil War (1860s) and continues to regrow. When the study plot was first set up in 1948 there were scattered Virginia pines but these have died out as hardwoods have taken over.
Young beech trees, with their smooth white trunks, are quite visible in the photo and when they mature, will likely be the final stage of the forest's succession.
Deer have become more common in the park since 2000 and their browsing on low vegetation has opened up the forest understory.
Exotic shrubs from Asia, such as barberry and doublefile viburnum (Viburnum plicatum), have taken root in some areas of the plot and threaten to spread widely and displace native plants. Their spread may be speeded up by birds dispersing their winter fruit.
Bird Abundance Table
Average is the average number of birds (per 100 acres) divided by the total number of years. A '*' indicates less common species.
Years is the number of years the bird was observed.
|Great Horned Owl||*||1|