Complete dataset of loon productivity for Fuirst et al.

The Common Loon (<i>Gavia immer</i>) is an iconic waterbird of the northern wilderness and an indicator of the health of aquatic ecosystems. We conducted a benchmark comparison of productivity rates and long-term trends in productivity (six-week-old young raised per territorial pair) from 46,401 breeding events across 12 different study populations throughout the southern portion of species’ breeding range in North America. While all regions showed long-term mean productivity rates at or above the threshold considered necessary for population stability (0.48 chicks fledged per territorial pair), we found significant declines in productivity (-0.17− -2.8% per year over 19−48 years) in seven regions, non-significant but downward trends in four others, and a non-significant increase in one region (Maine). Even though productivity is only one of three demographic parameters that dictate the stability of a population, long-term decreases in productivity signal looming population declines in Ontario, the Prairie and Atlantic provinces, New York, Massachusetts, and New Hampshire. We suggest that a variety of region-specific anthropomorphic and natural factors, in addition to increased rainfall secondary to climate change are at fault for such declines. Discovery of causes of productivity decline might lead to successful efforts to mitigate them, thus stabilizing or increasing loon populations.