Can you guess what these are?

[BjornBee]

I have one can among my mason bee colonies that have tubes filled and plugged with long pieces of grass sticking out.

http://s186.photobucket.com/albums/x236/BjornBee/?action=view&current=Beepictures108.jpg

I have had alfalfa and other bees before make use of the tubes, but not sure what these would be. I'm thinking of a type of wasp, as I had seen a few around this can but did not take the time to investigate last summer.

Anyone have this before? Any guesses?

Thank you

[vajerzy]

My guess is a bird plugging the openings...I have Carolina Wrens and other Wrens stuffing grass and branches in all sorts of places.

[BjornBee]

My guess is a bird plugging the openings...I have Carolina Wrens and other Wrens stuffing grass and branches in all sorts of places.

I hadn't even thought about birds.... :) Thank you.