Just moments earlier, all the pigeons were on the platform above. The roof has bird spikes near the edge to help prevent the birds from pooping on visitors. Well, the pigeons can spot a birder from miles away and they love to hang out on the top platform and then jump like they are going to land on the spikes and skewer themselves. They miss the spikes at the very last second. Pigeons love the concerned look on birder's faces as they narrowly miss the spikes!
The above story is fictitious except the part about missing the bird spikes. They don't always miss.