From 1989 to 2007, Walt Sakai from Santa Monica College did mist net surveys of birds at the James Reserve. Each year in the spring for 4 days, he netted and banded birds. Over the years, he captured 1,500 individuals representing 47 species found on the James. Walt has allowed us to present some of his results here to provide an insight to the changing diversity of the avian community at the James.
Upon looking at Walt’s results, the first thing we notice is the number of individuals caught per year varied from less than 30 to as high as 138 birds (Figure 1). Although the trapping effort was conducted at the same time each year, some of this variability in captures can be attributed to different weather conditions, early or late arrival of spring, experienced each year. However, overall, as we know from wildlife population biology in general, population abundance of any species cycles, primarily with climate patterns. Thus, the highs and lows in numbers caught probably reflects these annual changes of abundance of individuals of the species captured. This can be seen relative to the three most abundant species (Mountain Chickadee, Dark-eyed Junco, and Western Bluebird; Figure 2).
As for the number of species captured per year, like total abundance, this too varied per year (Figure 3). Of interest, however, is that although the number of species captured went up and down, it did gradually increase in the later year, reaching a high of 22 species in 2006 (Figure 3). The one predictable effect of increasing richness of species captured is a corresponding increase in the diversity of the species captured per year (Figure 4). When compared to the overall diversity index for the total sample (red star in Figure 4), the last 5 years of the capture effort were above average. The possible reason for this trend might be deduced from further analyses of the data, especially regarding possible climate effects and vegetational changes. Overall, these data, thanks to Walt’s efforts, indicate the benefit and the potential of the James Reserve for investigating a myriad of aspects of the highly diverse avian community at the James.
