| Using BBIRD Methodology in a
Logistically Constrained Study Sallie
J. Hejl1,2 and Jennifer A. Holmes1
| ABSTRACT— One of the goals
of the Breeding Biology Research and Monitoring Database (BBIRD) program is to examine the
effects of management and other anthropogenic disturbances on avian breeding productivity.
The BBIRD program relies on a network of cooperators using standardized sampling protocols
to find and monitor the nests of all species or a subset (focal group) of species in an
area. In a study of fragmentation effects on forest birds, we initially used the
community-level BBIRD approach, finding and monitoring nests of as many species as we
could. From 1992-1994, we found twice as many nests in the second year (154 nests of 27
species) and third year (141 nests of 23 species) as in the first year (65 nests of 15
species), but in most cases, we found insufficient numbers per species to make good
inferences. In general, we found more nests of common than of uncommon species, but we
could not easily find nests of all of the common species. Cavity nests and enclosed nests
generally were easier to find than open-cup nests, but nests of most species took large
amounts of time to monitor. Each observer was able to monitor from 10 to 15 nests per day.
In 1995, we realized that to get good information on nesting productivity in these
habitats, we either had to hire more people to cover more plots, or to focus on fewer
species. We decided to focus on two old-growth associates, with a primary emphasis on
Winter Wrens (Troglodytes troglodytes) and a secondary emphasis on Brown Creepers (Certhia
americana), resulting in our finding 51 wren and 13 creeper nests. We also colorbanded
these species to obtain data on pairing success, probability of renesting, number of
broods per season, and return rates. In addition, colorbanding helped us confirm that we
had obtained most of the wren nests in each area and were able to minimize a potential
bias in nest success studies: that of discovering only easy-to-find nests. We obtained
good information on Winter Wrens, and minimal information on Brown Creepers. Our study
illustrates that breeding productivity studies are labor intensive and often encounter
budgetary and other logistical constraints (e.g., low nest densities and difficult habitat
in which to work). In addition, when trying to address landscape-level questions, such as
the effects of fragmentation, locating accessible replicate plots of rare habitat can be
difficult. Even for the most common species in cedar/hemlock old-growth forests, replicate
plots are essential for obtaining sufficient sample sizes of nests to test hypotheses. We
agree with current BBIRD recommendations that suggest eight 35-50 ha plots/treatment for
areas with low nest density. We found that our habitat required one person/50-ha plot to
find most nests of focal species and to monitor those nests. Thus, we would need 16 field
assistants for an ideal expanded study comparing nesting success in fragmented and
continuous forests, in which we would expect to find about 20 nests per treatment per year
for each of five focal species. When limited by constraints such as ours, we suggest that
researchers focus on one to five focal species. If focusing on a few species, then
colorbanding individual birds to examine additional aspects of population dynamics also
may be possible. |
1 USDA Forest Service
Rocky Mountain Research Station
P. O. Box 8089
Missoula, MT 59807
2Current address:
715 South 4th St. West
Missoula, MT 59801 |