When we think about a "birds-eye view" we generally think about the view from above. I've been talking to my friend Neil Gore and I got some new perspectives on the way birds see things from him. Neil has been watching the birds for many years. Whenever we get together I ask him how the migration is going and he always has some very specific things to tell me.
For example, last week there was a zone of intense high pressure off the East Coast of United States. The heavy descending air acted as a barrier to birds who would have migrated up from the south. The ridge of high pressure extended roughly from east to west forming an invisible atmospheric wall. This kept the weather cool up here in New England but more important the prevailing wind blowing off the ocean slowed down the progress of the northward migration. So things have been pretty quiet for Neil during what is normally the busiest season of birdwatching. Right after I last saw him last week a frontal boundary moved north, and with it I'm sure came the birds.
I spend a lot of time in my diverse garden, which boasts almost 60 plant families in a small space. There are all sorts of plant forms and insects to go with them, which I expect would be a smorgasbord for our feathered friends. I'm curious why I don't see more birds there. I see some sparrows, some cardinals, some bluejays, some juncos, some chickadees, some robins, and some mockingbirds. But I don't see the amazing kind of diversity that Neil talks about; wrens and warblers and all kinds of little surprises. Neil doesn't just look for birds in his garden but the diversity he sees right by his house is remarkable. I asked him if he could look at my garden and diagnose why there aren't more bird species there. He explained what should've been obvious to me, that the birds need some very specific kinds of conditions. Not too much shade and not too much light. Not too much closed in area but not too much right out in the open. A way to escape from potential predators. All of these subtle, almost intangible factors add up to a landscape where birds can thrive or a landscape that at least some birds will avoid. Of course it may be that I'm not looking effectively. It could also be that horrible yapping dog next door.
So the birds-eye view of the landscape is perhaps more complicated than we thought. It involves movement and activities and process in three dimensions. There is a spatial aspect and a temporal aspect, which involves timing. Atmospheric conditions are important and the basic landscape, its contours, and plants make a difference. The birds are looking for specific features in which to nest as well as specific kinds of food, insects, seeds, or whatever.
The migration is something like 10,000 years old. At least as old as the last ice age. Yet every year and in every place there are subtle complexities that determine which bird will be in which spot and when. For the birds, just like for us, the landscape is a dynamic entity. It's a lived-in space, one that accommodates our activity and one that is altered by our activity. For the birds evolution or extinction may be determined by landscape. We humans depend on landscape too, something to think about and study.