Because they stand about 5 feet tall and bugle loudly, cranes make an indelible impression. Their courtship dances inspired early human dancing and, some historians say, their form in flight influenced shapes in the Roman alphabet. Sandhill cranes draw a particularly devout audience in California, where thousands of people swarm the vast Central Valley each winter to ogle its famous flocks. Although most cranes leave the state in spring, 40 to 60 pairs linger behind to breed in the remote marshes of the Modoc National Wildlife Refuge of northeastern California. There they stride elegantly through tall grasses, keeping a watchful eye on their fuzzy chicks.