Not only Bing, from their docs:

"In fact, DuckDuckGo gets its results from over four hundred sources. These include hundreds of vertical sources delivering niche Instant Answers, DuckDuckBot (our crawler) and crowd-sourced sites (like Wikipedia, stored in our answer indexes). We also of course have more traditional links in the search results, which we also source from a variety of partners, including Oath (formerly Yahoo) and Bing."

(Regarding search results + instant answers: https://help.duckduckgo.com/duckduckgo-help-pages/results/so...)