Birder’s Notebook: The Northern Wheatear – Another World Traveler
Fall migration is underway. Many birds have long journeys ahead of them, but few are as epic as that of the northern wheatear – a threemonth, 9,300-mile migration across the entire continent of Asia to East Africa.
Singly or in small flocks, these eye-catching, sparrow-size songbirds are making their way west towards Wales. They travel over open country, especially along our beaches and coastal lowlands. Their flashy white rumps and tails stand out among the many small brown passerines on the move.
It may seem that there are more wheatears migrating than were nesting here, and there are. Much of Alaska and western Canada’s wheatear population funnels through the Seward Peninsula to cross over the Bering Strait to Asia.
During fall migration, the western tip of the peninsula is a staging area for northern wheatears. In the last half of August, groups of up to 300 wheatears have been reported, feeding voraciously on insects before crossing the Strait.
People living in Wales in 2010 may remember German ornithologist Heiko Schmaljohann, who did ground breaking research there on wheatear migration.
Schmaljohann placed dishes of mealworms on electronic scales to attract and weigh the birds, reading their weights through a spotting scope. He weighed over 100 northern wheatears and captured some to fit with tracking devices.
This research documented many interesting aspects of northern wheatear biology, including the route and timing of the wheatear’s remarkable migration.
The tracked birds traveled an average of 93 days to reach their African wintering grounds, including an average of 44 layover days. When traveling, they averaged 115 miles per day.
It was shown that they increase their body weight by 50 percent before crossing the Bering Strait to Asia.
Such a large weight gain is not needed for the short flight across the Strait at Wales, but it gives the birds a cushion of reserves on their long migration, allowing them to bypass traditional stopovers if weather or conditions are unfavorable.
Most of the birds took off just after midnight on August nights. Many bird species migrate at night when cooler temperatures and more stable air make flight easier. By landing for rest during daylight hours, insect eating birds such as wheatears have an easier time finding food. Night flight may also lessen risk of predation.
Many of the wheatears Schmaljohann tagged were birds that had hatched earlier that summer. They were making their first great journey only a month after learning to fly! Traveling alone, the youngsters have innate knowledge of where to go to find food at traditional stopovers and how to reach their wintering grounds in East Africa.
The northern wheatear is a regular breeder on the Seward Peninsula. They nest widely across the uplands and foothills in open, dry-tundra habitats where rocks, rocky outcrops or boulder fields provide nesting sites.
In mid-May, males arrive first on the breeding grounds to establish and defend their territories by singing. Wheatears are exceptional mimics and their territorial songs can include mechanical sounds and vocalizations of other birds and animals, particularly their alarm calls.
Sometimes singing isn’t enough to defend a territory and males resort to aerial displays or even long and fierce fights.
Courtship begins as soon as the females arrive and involves various flight and ground displays that all incorporate flashing of the striking white-and-black tail pattern. In a common flight display, the male flies high with rapid wing beats and “dances” in place before gliding back to the ground.
When a pair-bond is established the female selects a nest site and builds a nest of vegetation on dry tundra, under a rock or in a rock crevice or sometimes in an old ground squirrel burrow.
The female lays an average of seven eggs which she incubates while the male defends the territory by song. The young hatch in 13 to 14 days which in our region is often around June 20.
Only the female broods the nestlings, but both parents feed the young. Typically in early July, or 15 days after the hatch, the bob-tailed youngsters leave the nest, some still unable to fly. The young depend on their parents for food for at least two weeks after they leave the nest.
Northern wheatears eat a variety of adult and larval insects and spiders and some berries in the fall. They are drawn to dung and decomposing animal matter which are sources of flies and larvae.
Wheatears forage for insects mostly on the ground, hopping and running in short bursts over short tundra vegetation with much tail bobbing. These bursts of movement are thought to startle insects out of hiding. Wheatears are often seen standing erect to scan for prey from the ground or a low perch. Sometimes they flutter up and snatch insects out of the air.
Northern wheatears are adapted to extremes, enduring freezing temperatures and occasional snowstorms on their northern breeding grounds, and sweltering heat on African savannahs. In the north they actively forage throughout the day, while in Africa they must escape extreme heat by sheltering in the shade for much of the day. For six months of the year they travel between these extreme environments.
In three months, the northern wheatears now leaving the Seward Peninsula will take up winter residence on the hot savannahs of East Africa.
Then, in late February, migratory restlessness will lure them out of their shady hideouts and into the air to retrace their flight path back to the far north. The return journey is a couple weeks faster with less time spent at stopovers.
In mid-May, spring migrants will again fly over the ice of the Bering Strait to tundra regions of the Seward Peninsula and beyond, rejoining musk oxen and grizzly bears after a winter in the company of lions and rhinos.