Alaska Bird Observatory

Creamer’s Field Migration Station: Fall Report, 1998.

15 December, 1998

Anna-Marie Benson, Migration Program Manager
Alaska Bird Observatory, Box 80505, Fairbanks, AK, 99708

The Alaska Bird Observatory (ABO) has operated a large standardized mist-netting station at Creamer’s Field Migratory Waterfowl Refuge in Fairbanks, Alaska from 1992-1998. The objectives of the netting program are to capture and band migrating passerines to examine: 1) population dynamics; 2) the phenology of migration; 3) timing of life history events (e.g. migration, reproduction, molt, juvenile dispersal, and seasonal differences in body condition); 4) habitat use; and 5) to provide public education programs relating to avian ecology and conservation.

Approximately 150 migration-monitoring sites are located throughout North America. Creamer’s Field Migration Station (CFMS) is the northernmost station in the Western Hemisphere. The location of this study site provides crucial information for studying population trends in Nearctic-Neotropical migrants. The migration station has become a popular destination for local school groups, naturalists, bird enthusiasts, and international visitors. 

Field methods have remained constant during seven years of migration banding at CFMS. Nets were opened at sunrise and closed seven hours later or as late as 1400 h, between 15 July and 30 September (weather permitting). For a detailed description of the methodology see Pogson et al. (1996).

Relative abundance

I used first-time captures of individuals in the analysis of abundance (newly banded birds, returns, foreign recoveries, and unbanded dead birds). Birds banded in spring or summer and recaptured in fall were not included, as they were assumed to be local breeders. Captures prior to 25 July were excluded, as they were likely breeding birds or local dispersing juveniles (based on molt and plumage) rather than migrants.

I calculated a daily capture rate (birds/1000 net hours) for each species. The annual population index was calculated as the geometric mean (arithmetic mean of the transformed counts, back transformed) of all daily migration counts for 19 abundant species . A constant (one) was added to each daily capture rate to compensate for counts of zero. Geometric mean (compared with arithmetic mean) is relatively insensitive to occasional unusually high counts while still reflecting small increases or decreases that are consistently present in daily counts across the entire migration season (Dunn and Hussel 1995).

Summary 1998

We banded 5,753 birds of 37 species (Table 1) during fall migration of 1998. Myrtle Warblers, Orange-crowned Warblers, American Tree Sparrows, and Slate-colored Juncos comprised 75% of the birds banded. Rare captures included a Northern Harrier, two Merlins, two Common Snipes, a Yellow-bellied Flycatcher, and a Golden-crowned Kinglet.

Relative Abundance

I calculated population indices for species in which more than 10 individuals were captured each fall (Table 2). We recorded the highest population index for six species in 1998 (Black-capped Chickadee, Gray-cheeked Thrush, Myrtle Warbler, Fox Sparrow, Gambel’s White-crowned Sparrow, and Slate-colored Junco). We recorded the lowest index of Alder Flycatcher and Yellow Warbler in 1998. Eight of 19 species had their lowest index in 1993, which Pogson et al. (1996) hypothesized was the result of a hot, dry summer. The 1992 population indices should be used with caution as the nets were not operated between 17 July and 4 August, which may be a critical time for capturing long-distance migrants such as the Alder Flycatcher.

Education

School groups were organized through Andrea Swingley, ABO education coordinator and Mark Ross, Alaska Department of Fish and Game (ADFG). Children were presented with a standardized curriculum designed by ABO. Unscheduled guests were greeted by staff, interns, and volunteers and presented with a banding demonstration relating to avian ecology and conservation. See the enclosed education report for more details.

Volunteers

In 1998, 50 volunteers, including seven youth, assisted with the operation of CFMS. Volunteers received training in removing birds from mist nets, net maintenance, bird identification, recording data, and holding birds for public demonstrations. During our annual volunteer survey, 100% of the respondents stated their volunteer expectations had been met, the level of training and assistance they received was sufficient, the atmosphere of the banding lab was professional and courteous, and the conditions for volunteers were safe. When they asked what they liked best about volunteering for ABO, responses included:

• Feeling fulfilled about doing something to further science and our awareness of the role and status of songbirds.
• The sense of awe I get holding a tiny bird that just made, or is about to make, a long journey.
• A chance to talk and "do" birds with the other volunteers and staff, but what I like best is something active to do out of doors with birds.

Table 1. Number of birds banded during fall at Creamer’s Field Migration Station, Fairbanks, AK: 1992-1998.

Table 2. Population index using geometric mean of daily migration counts (birds/1000 nh) of 19 species (n>10 individuals each year) at CFMS during fall migration: 1992-1998.

Recent analyses of data from standardized mist-netting stations confirm the usefulness of this method for studying the abundance and survivorship of migratory bird populations (Chase et al. 1997, Dunn et al. 1997, Johnson and Geupel 1996). The northern location of Creamer’s Field Migration Station allows us to examine the initial phase of autumn migration in Nearctic-Neotropical passerines. A more in-depth analysis of these data will answer questions relating to passerine migration that cannot be answered elsewhere in North America.

Management Implications

Understanding movements and population dynamics of passerines has become an international concern due to recent documentation of population declines throughout North America (Rappole and McDonald 1994, Askins et al. 1990). The importance of establishing baseline data for species has been recognized (usually after a species is threatened or endangered) (O’Connor 1992). Baseline monitoring allows land managers to set management priorities (e.g. habitat preservation) based on scientific data. Long-term data collected at ABO is important for understanding population dynamics of migratory songbirds in interior Alaska.

This research was funded primarily by: ABO membership; ABR, Inc.; Alaska Conservation Foundation; Arco Alaska, Inc.; Arctic Audubon Society; BLM (Cooperative Agreement #1422L320A7-2005); Exxon Co., U.S.A; Lawson-Valentine Foundation; and the Skaggs Foundation. The Alaska Department of Fish and Game and U.S. Fish and Wildlife Service provided significant in-kind support.

We gratefully thank all ABO interns and volunteers for their time and dedication. The ABO Scientific Advisory Council has provided invaluable expertise and guidance in research design and data analyses. We also thank John Wright and Mark Ross of the Alaska Department of Fish and Game for their time and support. Keith Larson provided technical support in database management.

Askins, R.A., J.F.Lynch, and R. Greenberg. 1990. Population declines in migratory birds in eastern North America. Curr. Ornithol. 7: 1-57.

Chase, M.K., Nur, N. and G.R. Geupel. 1997. Survival, productivity, and abundance in a Wilson’s Warbler population. Auk in press.

Dunn, E.H., D.T. Hussell, and R.J. Andams. 1997. Monitoring songbird population change with autumn mist netting. J. Wildl. Manage. 61(2):389-396.

Dunn, E. H., and D.T. Hussell. 1995. Using migration counts to monitor landbird populations: review and evaluation of current status. in Current Ornithology, Vol.12, (D.M. Power, ed.). Plenum Press, New York.

Hagan, J.M., III, T.L. Lloyd-Evans, J.L. Atwood, and D.S. Wood. 1992. Long-term changes in migratory landbirds in the northeastern United States: evidence from migration capture data. in: Ecology and Conservation of neotropical Migrant Landbirds, (J.M. Hagan and D.W. Johnson, eds.), Smithsonian Institution Press, Washington, pp. 115-130.

Hussell, D.J.T., M.H. Mather, and P.H. Sinclair. 1992. Trends in numbers of tropical and temperate-wintering migrant landbirds in migration at Long Point, Ontario, 1961- 1968, in: Ecology and Conservation of neotropical Migrant Landbirds, (J.M. Hagan and D.W. Johnson, eds.), Smithsonian Institution Press, Washington, pp. 101-114.

Johnson, M.D. and G.R. Geupel. 1996. The importance of productivity to the dynamics of a Swainson’s Thrush population. Condor 98: 133-141.

O’Connor, R.J. 1992. Trends in Population: Introduction. in: Ecology and Conservation of neotropical Migrant Landbirds, (J.M. Hagan and D.W. Johnson, eds.), Smithsonian Institution Press, Washington, pp. 23-25.

Pogson T.H., A-M. Barber, S.L. McDaniel, and S.K. Springer. 1996. Creamer’s Field Migration Station fall summary report. Unpublished report.

Rappole, J.H., and M.V. McDonald. 1992. Cause and effect in population declines of migratory birds. Auk 111: 652-660.