A Four-year Summary of Breeding Bird Surveys in TFL 48 ... - BIOD

Variation in abundance among transects within a species is most likely attributedto differences in habitat quality and availability, whereas variation among years isprobably attributable to other factors (e.g., climatic variation, annual fecundity). Forexample, among the first six transects that were established in 2002, the abundance ofSwainson's Thrush was usually greatest on the West Utah-Johnson Creek transect, buthighly variable among the four years surveyed (Figure 8). From 2002 – 2004, theabundance of Tennessee Warbler and Wilson's Warbler was relatively consistentamong the same six transects. The abundance of Chipping Sparrow, Ruby-crownedKinglet, and Yellow-rumped Warbler were variable among both transects and years,with synchrony in relative abundance occurring in some years, and asynchrony inabundance occurring in other years. Both Gwillim (in 2005) and Wolverine contributemore to the variability than other transects because of lower sample sizes.14