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Abstract: Bart et al (2004a) proposed several approaches for enhancing the considerable value of the Breeding Bird Survey (BBS). Sauer et al. (2005) critiqued some of these approaches, and emphasized alternative goals for the survey. We agree with many of the suggestions of Sauer et al. (2005); notably that multispecies, large-scale surveys such as the BBS are most valuable for bird conservation if they achieve multiple objectives. Nevertheless, we strongly assert that estimation of long-term trends is of fundamental importance for identifying important conservation issues and determining which species represent priorities for conservation efforts, as has been repeatedly demonstrated in the past. We are confident that our recommendations for enhancing the ability of the BBS to detect trends—reducing bias, explicitly recognizing that all bias cannot be eliminated, and increasing sample size in poorly covered areas—can only enhance, and not detract from, the value of the BBS for other purposes.

Abstract: Reliable estimates of trends in population size are critical to effective management of landbirds. We propose a standard for considering that landbird populations are adequately monitored: 80% power to detect a 50% decline occurring within 20 years, using a 2-tailed test and a significance level of 0.10, and incorporating effects of potential bias. Our standard also requires that at least two-thirds of the target region be covered by the monitoring program. We recommend that the standard be achieved for species' entire ranges or for any area one-third the size of the temperate portions of Canada and the United States, whichever is smaller. We applied our approach to North American Breeding Bird Survey (BBS) data. At present, potential annual bias for the BBS is estimated at ±0.008. Further, the BBS achieves the monitoring standard for only about 42% of landbirds for which the BBS is considered the most effective monitoring approach. Achieving the proposed monitoring target for =80% of these species would require increasing the number of BBS—or similar survey—routes by several-fold, a goal that probably is impractical. We suggest several methods for reducing potential bias and argue that if our methods are implemented, potential bias would fall to ±0.003. The required number of BBS or similar routes would then be 5,106, about 40% more than in the current BBS program. Most of the needed increases are in 15 states or provinces. Developing a comprehensive landbird monitoring program will require increased support for coordination of the BBS (currently 2 people) and new programs for species that are poorly covered at present. Our results provide a quantitative goal for long-term landbird monitoring and identify the sample sizes needed, within each state and province, to achieve the monitoring goal for most of the roughly 300 landbird species that are well suited to monitoring with the BBS and similar surveys.