Visualizing Data

Colophon

The animal on the cover of Visualizing Data is a Northern hawk owl (Surnia ulula). They are called Northern hawk owls because they are largely found in the boreal forests of North America and Eurasia, and because of their behavioral similarities to the hawk; they fly, hover, and soar low over open areas searching for prey. Also, more like hawks than owls, they predominantly use their sight, rather than their hearing, when hunting.

They are widely dispersed geographically, found from Eurasia to Norway, Sweden, and Finland; east through Siberia to Kamchatka; and in North China and Central Asia as far south as Tien Shan. In North America, they can be found from Alaska east to Labrador, Canada. They breed wherever food is plentiful; when food is scarce, they (mostly the young owls) may fly south of their normal distribution.

Medium-size owls, they are usually between 36–41cm long with a wingspan between 22–25cm wide. Typically, males weigh between 273–326g and females weigh more, between 306–392g. The sexes are very similar in appearance and can be most easily distinguished by their calls. The typical male call is a fast, melodious, purring trill; although the female call is similar, it has a higher pitch and is less clear.

Their heads are round and their faces whitish, bordered on each side with a thick black stripe. The upper half of their body is generally dark gray and black, with a densely spotted forehead and crown. Their tails are long with white stripes. Their bills are ...