Are you ready, birders? September is peak migration season for our long-distance migrants that feed heavily on insects and winter in the tropics. Every oriole, hummingbird, and swallow you see now may be your last until next spring, especially in the north, while grosbeaks, tanagers, catbirds, and buntings continue their exodus as well.
Nighthawks moved through the state over the past seven to 10 days but are fewer now in all but far southern counties. Bobolinks, all the flycatcher species, and most of the vireos are also on their way out.
Warbler migration is now firing on all cylinders statewide, with the best numbers and diversity to come around mid-month. Look for Swainson’s and gray-cheeked thrushes around the same time. The first short-distance migrants are also on the move, including species such as white-throated, swamp, chipping, and Lincoln’s sparrow, purple finch, and cedar waxwing.
Flocks of grackles, red-winged blackbirds, and American robins are common, though most haven’t begun southward flights yet.
Raptor migration is getting underway. American kestrels, broad-winged hawks, and ospreys are especially known for early-season movements, but nearly all species, such as vultures, eagles, harriers, and red-tailed, sharp-shinned, and Cooper’s hawks can be seen. The best hawk watching days usually occur from mid-September to late October and often feature at least partial sunshine and cool west or northerly winds.
Although shorebird numbers are past peak, diversity can be excellent this time of year. Some Great Lakes beaches are hosting sanderlings, semipalmated plover, ruddy turnstone, and even a couple red knots. Other uncommon species reported this week were Hudsonian godwit and whimbrel. Wetlands continue to host good numbers of great blue herons, green herons, great egrets, belted kingfishers, blue-winged teal, wood ducks, and mallards. A few horned grebes have shown up a bit earlier than average.
The week’s rarest find was a magnificent frigatebird photographed on August 28 in Milwaukee County, furnishing Wisconsin’s sixth record of this elegant seabird typically found nearer the Gulf of Mexico. Milwaukee also hosted a laughing gull and yellow-crowned night-heron, while a black-crowned night-heron in Ashland was rare for Lake Superior.
Expect high migration activity and turnover this week as several cold fronts sweep through the state and provide the weather conditions birds prefer for these long flights. Help us track them and their movements by reporting your observations to www.ebird.org/wi.