“I have a bird question for you. In the past week, I have been seeing flocks of cardinals . . . The first time, I pulled my car over on a street near my house and tried to count them (really close up!) and I think there were about 12-15. Today I saw at least 7-9 in my friends’ yards near a small stream, that is not far from the other sighting. There were males and females.

So my questions are-
How many are in a brood? Are they youngsters that have banned together looking for mates and a new house? Were they all juveniles-they didn't look huge, but it wasn't obvious that they were youngsters. And is this unusual? I have never seen this before. Blue Jay's- yes sure, but never this many cardinals together. I thought they were extremely territorial.
Cheers!
Nancy”

Good question Nancy. First, I’ll answer the easy ones: 1) Northern Cardinals lay 1-5 (usually three) eggs in a clutch. 2) They would not be juveniles looking for mates or a breeding territory, as these are both springtime activities. Plus, cardinals do not nest communally, so the flock would split up if breeding was on their minds. 3) They may or may not be juveniles – and there is no way to tell from size: as with most birds, juveniles are essentially the same size as adults by the time they fledge. 4) Is this unusual? Not really, but it’s not seen around these parts that often.

So, what WAS going on here? Nancy, you are correct that Northern Cardinals are extremely territorial – but not necessarily so outside the breeding season. During the breeding season, if you’re another cardinal – or a reflection of a cardinal in the window – WATCH OUT! However, when reproduction is not on a cardinal’s mind, then it’s all about food. Cardinals will form flocks at abundant food sources. Flocks even as high as 60-70 birds have been recorded in the southeastern U.S. If there’s enough food for everyone, then there’s little reason to fight over it. Safety in numbers than becomes a greater benefit than fighting to maintain control of a winter territory. Therefore, birds of various ages and sexes will form small foraging flocks in the fall, and they may be maintained straight through the winter.

Here in Maine, we are approaching the northern limits of the range of the Northern Cardinal so we have fewer Cardinals. We do have more and more every year however – only a few decades ago, Cardinals would of made the Rare Bird Alert in Maine. If we had more Cardinals, we would see cardinal flocks more often. If you lived in the Carolinas, for example, you would see flocks of Cardinals all the time in the winter.

Here’s some more info on cardinals:
1) Cornell’s “All About Birds” Website.
2) More biology stuff from the Animal Diversity Web.
3) Some technical reading on cardinal flock behavior.