The Joys of Visible Migration in Fall

By Adam Dudley

Western Kingbird, all photos by Adam Dudley

I always find the fall migration season immensely exciting. Millions of birds are on the move, heading south or arriving for the winter from the north. Many birds are nocturnal migrants with their journeys beginning an hour or so after dusk and usually finishing well before dawn, so it is impossible to witness their migratory flights. However, in recent years it has become clear that the migratory flights of some birds can be observed in the early mornings by anyone armed with a pair of binoculars. And I’m out to persuade you to give it a try!

The phrase “visible migration” accounts for those days when birds are on the move in the right conditions and can be seen in daylight. The observation of bird migration during the day was pioneered by the Dutch in the 1940s, and now there are thousands of birdwatchers around the world who take great pleasure standing in one spot identifying flying birds pushing south when the weather cooperates. Regular observations have revealed that both the topography of the landscape and the local weather are primary influences on the pattern, timing and numbers of migrants moving through an area. By selecting a suitable location, it is therefore possible to enjoy the magic of bird migration, not only at close quarters, but also right on your doorstep!

Blue Grosbeak

 
Visible migration is most obvious where natural land features act as a barrier to movement, channeling birds along their edges, and/or where favorable habitats or land features act as leading lines. Luckily for us, the Tucson area is particularly good for visible migration! The Catalina and Rincon mountains tend to act as barriers as the birds are completing their overnight flight, causing many songbirds to engage in migratory flights just after sunrise. These morning flights often involve birds flying in directions other than those aimed toward their ultimate destination, helping them correct any “off route” displacement they have experienced overnight, as well as to search for suitable habitat to stop for the day and refuel.

So, how to get started? In Tucson, what is traditionally known as the ‘fall’ migration starts in July. A great way to witness daytime southbound migration is to stand on open ground, a hill, or even a rooftop with a good view of the sky and horizon. From here, during the first few hours of daylight, you should be able to scan with your binoculars or scope and pick up any migrants as they come past. After a couple of visits, you’ll gradually begin to 'tune in' to both the pattern and direction of movement through the site. On a good morning you could see a great number and variety of birds passing by. But by mid-morning it will all be over, and the skies will be quiet again.

Black-throated Gray Warbler

Lark Sparrow

 
Around Tucson, birds as varied as grosbeaks, warblers, flycatchers, kingbirds, shorebirds, and sparrows can wing their way across the sky. Although getting out into the field and observing visible migration can at first appear rather daunting, it is worth remembering that the identification of what may initially appear as small, fast moving 'blobs' takes a little time and perseverance. When starting out, it pays to accompany more experienced birders who know the calls and flight behavior of each species. And a fast-focusing camera is a great tool for identifying fast-flying birds!

The best days for seeing visible migration are when there is a light to moderate headwind or crosswind, with good visibility. Days when the weather changes for the better after rain are also good. So, watch out for a sudden rise in pressure after the passage of a front or a storm. It seems that the birds are desperate to get on with migration, and the first available migration window often triggers the most exciting movements.

Vesper Sparrow

Plumbeous Vireo

Nashville Warbler

From mid-July until mid-October, I usually start watching around dawn, standing in my front yard with a cup of coffee. My yard has a good view of the sky, and within 30 minutes or so it becomes apparent whether the morning is going to be a terrific one or not. Generally, I hear birds before I see them, especially warblers and sparrows, although others don’t call at all as they fly past. On hearing a flight call, I get my camera ready, and then snap photos at full speed as the bird flies over. Birds can be either skimming fast over the tops of trees or flying at a height that gives me a better chance of getting a photo for identification purposes. Some birds fly quite slowly (mockingbirds, kingbirds, Phainopeplas) and others whiz past! Birds can be on their own (flycatchers), in flocks (tanagers, kingbirds), and sometimes they land in nearby bushes to allow a closer look.

In 2021 I branched out and decided to try out a different location. I chose the Southeast Houghton Area Recharge Project (SHARP) because it is relatively close to my house, and not that heavily birded. My first visit confirmed my suspicions that this location is great for visible migration! Within a few minutes of arriving, I heard the distinctive call of Solitary Sandpiper, and two birds flew over. They circled and eventually came down to the only flooded pool where they spent the next few minutes feeding and bathing, before taking flight once again. On my next visit, I saw Least Sandpiper, White-faced Ibis, Hooded and Bullock’s Orioles, Lark Sparrow, Western Tanager, and Black-headed Grosbeak.

Solitary Sandpiper

Western Tanager

Black-headed Grosbeak

One of the most fulfilling parts of watching visible migration is that you never know what might fly past. One memorable August morning a calling Dickcissel zipped by my yard at full speed. In September, a Clay-colored Sparrow flew past, and then in October a Bald Eagle drifted by! The time is now. Grab your coffee, your binoculars, head outside, and look to the skies!

Adam Dudley is a keen birder and naturalist who has lived in Tucson for 5 years. Originally from the UK, he and his wife Jane have spent 25 years in the USA, living on the east and west coasts before moving to Arizona. His passion is birding local patches in Tanque Verde.