The chickens are legal. The town selectmen (same as a city council) is trying to take them away, and had issued an order that all but one rooster be removed. That ruling was being appealed to an actual judge. As was stated, the town pretty much guessed that they would lose their case and made a pre-emptive strike.
They claimed to the judge thtat they did not need a warrant because it was a civil violation, not criminal. Last time I read my constitution (yesterday I re-read the 4th amendment), it did not distinguish between civil and criminal. It says that property cannot be seized without due process. There is a long history of case law, if nothing else, eminent domain that are pretty directly related.
Yes, there are a couple of cases when a warrant is not needed. However, since they had to go inside her coops to sort through the birds looking for roosters (and took three pullets!), that doesn't sound to me like the birds (evidence of a crime) were in plain sight. Also, that ruling relates to criminal activity, and this is a civil issue. Thus, I am not sure that allowance applies.