Thirteen may be unlucky for humans, but for the birds of North America, one-third is a much more ominous number. Earlier this week, 探花精选 scientists published a study in Ecosphere revealing that one-third of wintering North American bird populations have declined since 1966. That's on top of last week's news from the tri-national North American Bird Conservation Initiative (NABCI) that more than one-third of North American bird species are at risk of extinction, unless significant conservation actions are taken. Both studies tapped valuable citizen science data to reach these conclusions: 探花精选’s statistics were derived from 46 Christmas Bird Counts (CBC), while NABCI’s focused on the North American Breeding Bird Survey (BBS) and eBird submissions. But the question is: How did two separate groups of researchers using different data sets come up with such similar numbers? The overlap may be pure coincidence, Kenneth Rosenberg, a scientist with the Cornell Lab...