Alaska Bird Observatory

Six Years of Banding at Creamer's Field Migration Station

From 1992-1997, the Alaska Bird Observatory (ABO) has operated a large standardized mist netting station at Creamer's Field Migratory Waterfowl Refuge in Fairbanks, Alaska. The objectives of the netting program have been to capture and band migrating passerines to 1) monitor population dynamics, 2) study the timing of life history events (eg. migration, reproduction, molt, juvenile dispersal, and seasonal differences in body condition), 3) examine habitat use of migrants, and 4) 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 landbird migration monitoring station in the western hemisphere. The location of the study site is important for studying population trends among nearctic-neotropical migrants, as it is near the beginning of a migrant's journey during fall migration and near the terminus of spring migration. This is a fascinating location to study aspects of migration, considering migratory distances of the species we capture range from 3,000-6,000 miles.

During six years of migration banding, we banded 24,545 birds of 55 species (Table 1). Fall population indices were calculated as the geometric mean (arithmetic mean of the transformed counts, back transformed) of all daily migration counts (birds/1000 net hours) of 19 species in which more than 10 individuals were captured each fall (Table 2). Range of dates used to calculate population indices was 25 July-30 September. Nine out of 19 species had their lowest index in 1993, which we hypothesized was the result of a hot dry summer. The 1992 population indices should be used with caution as the nets were not operated until 4 August, which may be a critical time for capturing long-distance migrants such as the Alder Flycatcher. In 1992, the lowest index of Alder Flycatchers was measured.

Highlights from fall migration 1997

• During fall migration of 1997 we banded 4,839 birds of 35 species.
• Myrtle warblers comprised 25% of the birds banded.
• American Tree Sparrows and Fox Sparrows had their highest population index in 1997. Thirteen of 19 species had a higher-than-average population index in 1997.
• The proportion of hatch year birds was higher than average in 11 of 19 species.
• These data suggest 1997 was a productive breeding season in a variety of taxa captured at Creamer's Field Migration Station.

We had some unexpected captures of special interest. For example, two hatch year Yellow-bellied Flycatchers, were captured during fall migration. The recent records of hatch-year birds captured in Tok and Fairbanks, along with records of singing males in interior Alaska, indicates we may be at the leading edge of a range expansion of this species. We had one foreign band recovery of a Sharp-shinned Hawk originally banded in Nevada as a HY bird in 1992. This is our first recovery of a bird banded outside of the state of Alaska.

Preliminary data for Total Individuals Captured and Capture Rates for spring migrations 1992-1998 are now available.