Imagine that you are an ornithologist in Colorado, and you want to investigate the population status of every bird in your state. You could use any of the three surveys to examine the status of year-round resident species, such as the Mountain Chickadee and the Steller’s Jay, and each survey would probably indicate the same changing population trends. Only the Breeding Bird Survey, however, allows you to examine species (such as many warblers and the Western Tanager) that migrate farther south than Colorado in winter. But taken alone, the Breeding Bird Survey does not provide information on species such as redpolls and Snow Buntings that breed north of Colorado. Only a winter bird survey, such as Project FeederWatch or the Christmas Bird Count, fills in the gaps for species that breed farther north.

Do the Christmas Bird Count and Project FeederWatch provide identical information? Although they overlap in many respects, each of these surveys provides unique information (Figure 1). The Christmas Bird Count, for example, records nearly a century’s worth of information on bird abundance and includes many species rarely sighted at bird feeders. Therefore, it is better able to detect long-term population trends in species such as the Short-eared Owl that don’t visit backyard feeders. On the other hand, Project Feeder-Watch takes place throughout the winter and thus detects bird population trends within a single season, as well as across many years. Project FeederWatch is excellent for tracking species such as the Evening Grosbeak, whose late-winter irruptions in some years may go undetected by the Christmas Bird Count.

Figure 1. Project FeederWatch, Christmas Bird Count, and the Breeding Bird Survey are all continentwide bird-populations monitoring surveys. Although the surveys share many characteristics (see the areas of overlap in the diagram above), each has unique characteristics that set it apart from the others (see the nonoverlapping areas in the diagram above). For example, each of the three surveys provides an index of species abundance for year-round resident species (such as the Tufted Titmouse), but only FeederWatchers survey their backyard birds throughout the winter.

Figure 1 illustrates the areas of overlap and distinction among these three continental surveys. Each survey provides an index of abundance of year-round resident (non-migratory) bird species. Yet they differ in when and where they take place. Project FeederWatch and the Christmas Bird Count take place during winter, and they include many feeder birds and birds that breed in the northern boreal forest but winter farther south. In contrast, the Breeding Bird Survey takes place in summer and thus includes all those fabulous migratory species (such as warblers) that winter south of the United States. FeederWatchers count birds all winter long, whereas Christmas Bird Count and Breeding Bird Survey participants survey birds on a single day early in their respective seasons.

Whereas FeederWatchers survey birds at backyard feeding stations, Christmas Bird Count participants survey birds they observe within a 15-mile-diameter area, and Breeding Bird Survey participants survey birds they observe along fixed 24.5-mile sections of road. The 15-mile count circles and the 24.5-mile transects contain a variety of habitats, including some feeders. Christmas Bird Count participants, in fact, often make use of feeder areas.

Bird population scientists at the Cornell Lab of Ornithology and Bird Studies Canada (our Canadian partner in Project Feeder-Watch) have conducted studies to determine how closely Project FeederWatch results correlate to the results of the other two surveys.

Scientists at Bird Studies Canada, for example, recently examined how FeederWatch data compared to Christmas Bird Count data (Lepage and Francis. 1998. "Does FeederWatch Really Track Bird Populations?" BirdWatch Canada 7:8–9). Although FeederWatch has been running as a continental program since 1987, it began in 1976 as the Ontario Feeder Bird Survey. Therefore, the Canadian researchers had more than 20 years of data to analyze. Using sophisticated statistical methods, the researchers analyzed indices of population abundance for 56 Ontario bird species. They discovered that population trends for FeederWatch and the Christmas Bird Count were similar for nearly three-fourths of the common feeder species. These included many species (such as the irruptive winter finches) with large year-to-year fluctuations, but also a few species (such as the Downy Woodpecker) with more subtle population changes.

Likewise, scientists at the Lab of Ornithology recently compared the abundance indices of nine common feeder species over seven years across the northeastern states (Wells et al. 1998. "Feeder Counts as Indicators of Spatial and Temporal Variation in Winter Abundance of Resident Birds," Journal of Field Ornithology 69(4):577–586). Each of the nine species spends the entire year in the Northeast. They found that both surveys provided similar results, especially when looking at geographic variations in bird abundance within a single winter season. They suggested that Feeder- Watch was good for tracking species with extreme population changes, such as the Carolina Wren, whereas the Breeding Bird Survey was better for tracking species with more subtle population changes.

So why should you participate in Project FeederWatch? Besides being fun and relatively easy, FeederWatch is the only continental survey that can track populations for an entire winter. Also, whereas extreme weather or other circumstances may significantly affect results obtained by annual, one-day snapshot surveys, Feeder- Watch data are less affected by extraordinary, short-term events. No single survey is perfect, but if we find similar patterns among several independent surveys, we can feel more confident about the results.

Thus, Project FeederWatch is important because it adds to the arsenal of bird-conservation tools. By comparing and contrasting data from two or more continental bird surveys, you, as an ornithologist from Colorado (or anywhere else), can gain a more complete picture of North America’s ever-changing bird populations.