=+7.43 ● Ecologists have long been interested in factors that might explain how far north or south particular animal species are found. As part of one such study, the paper

“Temperature and the Northern Distributions of Wintering Birds” (Ecology [1991]: 2274–2285) gave the following body masses (in grams) for 50 different bird species that had previously been thought to have northern boundaries corresponding to a particular isotherm:

7.7 10.1 21.6 8.6 12.0 11.4 16.6 9.4 11.5 9.0 8.2 20.2 48.5 21.6 26.1 6.2 19.1 21.0 28.1 10.6 31.6 6.7 5.0 68.8 23.9 19.8 20.1 6.0 99.6 19.8 16.5 9.0 448.0 21.3 17.4 36.9 34.0 41.0 15.9 12.5 10.2 31.0 21.5 11.9 32.5 9.8 93.9 10.9 19.6 14.5