White-winged Crossbill (Loxia leucoptera)
- Offers photos, range maps, and facts about this songbird's breeding and diet.
- http://www.mbr-pwrc.usgs.gov/id/framlst/i5220id.html

Red Crossbill (Loxia curvirostra)
- Photo of this species.
- http://www.birdsofoklahoma.net/Redcrossbill.htm

Crossbills Audiovisual Guide
- Lists the different types of North American crossbills and provides sound files and facts for each type.
- http://research.amnh.org/ornithology/crossbills/contents.html