Caught red-billed

I attended a conference from home today, but managed to take a few photos out the window during a break:

 

 

 

Small groups of Pine Siskins (Spinus pinus) have been visiting the bird bath in our backyard.

 

Note the bill that tapers to a very sharp point, the notched tail, and the subtle but bright yellow color in the flight feathers (it's more visible in flight):

 

 

 

 

When I was reviewing the photos, I noticed that many of the siskins had something on their bills.  Here are two examples (you can click on the images for larger versions):

 

 

 

 

 

You can see something red on their bills, but I'm not sure what it is.  I have mostly thought about siskins as seed-eaters, but the reddish material looked like it could be berries?  So I read more about the diet of siskins and found one mention of them eating honeysuckle berries.  Perhaps the siskins have found some fruit in the neighborhood?  If you have other thoughts about what they might be eating, let me know!