Facebook (Nasdaq: FB) has nabbed another member of Apple’s (Nasdaq: AAPL) original iPhone team, hiring Richard Williamson, the manager who had led Apple’s mapping efforts, according to people with knowledge of the hire.

Williamson joined Facebook in the past couple of weeks to be a manager within its expanding mobile-software group, said two of the people, who declined to be identified because the information isn’t public.

Also this week, Facebook updated its iPhone and iPad applications to let people keep using its chat feature even when they are doing other things, such as reading friends’ updates.

Facebook is bringing its “chat heads” feature to its Apple apps. It’s called chat heads because friends’ profile photos pop up when they send you a message.

Chat heads is part of a broader integration that Facebook is doing with a new Home app on some phones running Google’s Android operating system.

Unlike with Home, iPhone and iPad users will have to stay inside the Facebook application to use chat heads. The update is already available in Apple’s App Store, but Facebook says the chat heads feature will roll out in the coming weeks.

Williamson, who worked at Apple for more than a decade, was one of the engineers assigned by Apple co-founder Steve Jobs to build software for the iPhone. He was later put in charge of the effort to replace Google Inc.’s mapping service for the iPhone and iPad.

Williamson was fired by Apple in November as part of a management shakeup after its mapping product was criticized for misguided directions and inaccurate landmark locations.

Several members of Apple’s iPhone software group have defected to Facebook as Chief Executive Officer Mark Zuckerberg focuses on reaching customers on mobile devices. Apple alumni played a key role in designing Facebook’s recently introduced mobile product, called Home.

Tucker Bounds, a spokesman for Facebook, declined to comment.

Other former Apple employees brought in by Zuckerberg include Greg Novick, a former iPhone manager who helped develop the device’s touch interface; Mike Matas and Kimon Tsinteris, software designers who joined when Facebook acquired their company Push Pop Press; and software engineers Scott Goodson, Tim Omernick and Chris Tremblay.

Twitter Software Designer Joins, too

In a separate move, Facebook has also hired Loren Brichter, the software designer behind Twitter Inc.’s original iPhone app and the word-puzzle game Letterpress, as a consultant, two of the people said. Brichter also once worked at Apple.

Zuckerberg’s hiring of former Apple employees has extended beyond product creation. Facebook’s head of consumer marketing, Rebecca Van Dyck, also worked at Apple.

Facebook isn’t the only company recruiting Apple employees. After the iPhone maker jump-started an era of computing centered around mobile touch-screen devices, companies including thermostat maker Nest Labs Inc. and mobile-payments startup Square Inc. also have lured Apple alumni.