There's lots of good information in there, including good descriptions of each flight call type, the new Cassia Crossbill, and even a new flight call type found in Central America in the last couple of years!
There are currently good numbers of crossbills (Types 2, 3, 4, and even 5!) moving across the country west to east. These will add to an already pretty large group of Type 1 and Type 7/10 here currently. As the season unfolds we are hoping for a really good push further east, maybe further south, and maybe even some breeding in the early spring.
Please attempt recordings for any crossbills you encounter in the field. Digital camera video settings or phone voice memo features are perfectly acceptable means of recording to get the birds to flight call type.
If there are any questions, don't hesitate to contact either Matt Young or me (contact information at the end of the article linked above). We will be happy to respond so long as we are not out in the field chasing the birds.