Bert attempts to call pigeons...and fails miserably.
Elmo scares the pigeons, and I refrain from making cheap jokes at Elmo's expense.
The first sketch is most notable because it apparently dates from that three-year period after Jim Henson died but before Steve Whitmire was cast to perform Ernie. Perhaps this is the reason why Bert appears by himself with no other recognizable characters--except for that tiger, of course. This is the second time in a week that that tiger has shown up!
I'm not sure when the second sketch was recorded, so I don't know whether they paired Bert with someone other than Ernie because they had to or because they just thought it would be funny. The only thing I can say with some certainty is that, based on Bert's puppet design, this sketch appears to originate from sometime between 1989 and 1997.
Elmo and Bert play off one another reasonably well, but there is a noticeably different dynamic between them. Notice how Bert's reactions tend to the sad/despairing side of the spectrum, rather than getting angry like he does with Ernie.
Bert seems to employ the same naming scheme with pigeons that he does with his goldfish. Or maybe he named his goldfish after the pigeons! Yeah, now that I think of it, that seems much more likely.