Welcome to the first weekend of fall, a wonderful time to be outdoors in Georgia. Leaves are taking on the first tinges of autumn color, migratory birds are passing through and a hint of cooler days and nights is in the air.

As autumn revs up, here are a few things to watch out for:

First, the sun isn’t nearly as high in the sky now as it was in summer. It means that sunbeams are coming in more slanted than a month ago, producing longer shadows at noon. Even though we still might have a few more hot days during the next month or so, the sun won’t beat down as it did in July — and can even be invigorating.

The neighborhood gets quieter. As cooler weather sets in, the singing of katydids, cicadas and crickets slows dramatically and sounds much more tired and worn out. The singing will stop altogether once temperatures drop below 52 degrees.

Fall bird migration, a more leisurely and protracted movement than in spring, goes into full swing. Keep an eye out because you might see some birds, such as some warbler species, coming through that you don’t normally see at any other time of year in Georgia.

Also, look for flocks of highly acrobatic, common nighthawks darting and swooping about as they snatch flying insects in midair. If you’re lucky, you might see huge flocks of chimney swifts swirling and circling about large chimneys at dusk and then plunging into the structures to roost for the night. The last waves of migrating ruby-throated hummingbirds — most of them first-year birds hatched this summer — are coming to feeders, but will be gone soon.

It’s also prime time for hawk migration and, on the coast, shorebird migration.

At the same time, Georgia’s “winter birds” that nested up north during summer — kinglets, yellow-rumped warblers, sparrows, cedar waxwings, yellow bellied sapsuckers and others — are arriving to spend the winter here.

The warm, sunny days of early fall also are great for butterfly watching because this is when many species are more abundant and active. In particular, everybody’s favorites, monarch butterflies, are starting to move through Georgia now.

IN THE SKY: From David Dundee, Tellus Science Museum astronomer: The moon will be last quarter on Tuesday. Mercury and Venus are low in the west just after sunset. Jupiter and Saturn are in the south at dark.

Charles Seabrook can be reached at charles.seabrook@yahoo.com.