The most common bird in Stillwater Marsh is a species of marsh hen, yet this species is rarely seen, even by experienced bird-watchers who seek it. In fact, this bird is seen far less frequently than any other bird inhabiting the marsh, including those that are much smaller and much less abundant. Each of the following, if true, helps to reconcile the statements above EXCEPT: ['Although many small marsh birds fly in groups to several feeding areas each day, the marsh hen tends to be solitary and flies only when it is in danger.', "The marsh hen's call is harsh and repetitive, whereas the calls of many other marsh birds are pleasant and melodious.", 'Unlike many small marsh birds, which dash along the banks of the marsh, the marsh hen remains completely still for long periods of time.', 'Many marsh birds are most active during daylight hours, but the marsh hen is usually most active at night.']