



meadowland a mile south of the marsh. A robin almost always flies to the 

 same fencepost in my yard before dropping to the lawn. When children 

 frighten the Yellow Warbler from her nest by the hatchery door, she departs 

 the same way every time. The Yellow-headed Blackbirds that steal grain 

 from the duck pen generally use a routine approach. Day after day the 

 Marsh Hawk that nests near the channel may be seen on its regular course 

 down the north side of Cadham Bay. 



Here is an orderly pattern of movement. The waterfowl of the Delta 

 Marsh respond to the physical design of their environment in much the 

 same way as elk or mice follow their earth-worn trails. But unlike the mam- 

 mals, whose feet mark the paths for all to see, the bird leaves no record of 

 its passing. These waterfowl must obey the natural shape of the land and 

 water when moving from one area to another, responding to visual cues as 

 these are presented by points and bays, channels and islands, reeds and 

 willows. 



Here is a rule of order, a design of habit. Free as the winds to fly when, 

 where, and how they might choose, wildfowl hold almost as closely to lanes 

 of passage as do earthbound mammals. Such habit, such conservation of 

 energy, is probably a universal trait of animals. The game trails of larger 

 mammals are well known to hunters ; and who is there who has not seen the 

 Meadow Mouse path in an old field? Our own lives we know to be influ- 

 enced by habit. This permits us to accomplish complicated acts with the 

 least expenditure of energy; it simplifies our world. Daily we take the same 

 route to school or office, although many variations of the trail might be fol- 

 lowed. We walk along the same streets, over regular short cuts to shop at 

 the usual stores, and pick up the morning paper at the same corner because 

 it is easier to follow an established pattern than to pioneer a new trail every 

 day. 



13 



