If you have an iPhone and prefer to use Google’s own Plus for all of your social networking needs, there’s a picture importer application available for iOS in the iTunes App Store.
It allows you to easily import photos from your Facebook, Instagram, Flickr, or Photobucket account and into your Google+. The application is fast and advertises copying 100 photos in less than a minute. The downside is that this is no official Google tool but made from a third party software maker. Thus, the application is commercial and goes for $0.99 but nonetheless useful if you have a lot of pictures you want to migrate over from a social network to Google+.