After helping band young kestrels last Friday, the Goose Pond summer crew conducted a silphium borer moth survey in Hopkins Road Prairie. During the survey, they not only found evidence of the rare moth, but also discovered a northern harrier nest!
Sarah, Madison Audubon's seasonal Goose Pond restoration intern, stood at a designated point while the Prairie Partners interns spread out along the length of a rope and moved in a circle around Sarah. As they walked, the surveyors called out the number, species, and condition of silphium plants they passed, “one compass plant, unaffected,” “one prairie dock, affected,” etc.
The crew had just finished recording the data at a point when a female harrier rose from the grass very near to where they were standing! Excited, they spread out to examine the area for evidence of a nest. It only took a minute before one of the interns called out, and the group all gathered around the well-hidden, but strangely unprotected-looking nest! Inside the nest were two young harriers, perhaps five days old. Not wanting to cause the young any distress, the crew quickly left the area, but not before entering the GPS coordinates of the site and snapping a few quick photos. It was a great find, and a great end to a day filled with young raptors!
One of the most interesting aspects of harriers is their courtship display. The male courts the females and advertises his territory by performing sky-dancing displays: undulating, rollercoaster-like flights up to 1,000 feet off the ground, sometimes covering more than half a mile. Males are gray in color while females and young are brownish. Northern harriers are the only hawk-like bird known to practice polygamy – one male can mate with several females.
This spring we were very fortunate on a number of days to observe the courting display over the Browne and Lapinski-Kitze Prairies. Many visitors from the Wisconsin Society for Ornithology on tour at Goose Pond also witnessed courtship display.
Harriers, often called “marsh hawks”, nest and hunt in grasslands and marshes. They are the only ground nesting raptor in Wisconsin and prefer to nest in dense vegetation. Nests are made of sticks and are lined inside with grass and leaves. Females incubate 3-5 eggs for 31 days and brood chicks for 36 days until they fledge. The males provide most of the food for the females and nestlings.
The eggs and young are vulnerable for over two months to nest predators that include coyotes, striped skunks, raccoons, red foxes, American crows, and great horned owls. The larger the grassland habitat the more difficult it is for predators to locate harrier nests. Grassland areas that are devoid of scattered trees also help eliminate predation by crows and owls.
Harriers are diurnal, and hunt by gliding low over the grasslands searching mostly for small mammals. They use their exceptionally good hearing to find prey, this hearing being the function of their owl-like facial disc. Their favorite prey is the meadow vole.
Harriers nested at Goose Pond Sanctuary for (perhaps) the first time in 100 years in 2009 in the Wood Family Prairie. In 2010, they nested in the Browne Prairie. No nests were found from 2011-2013. In 2014, Tony Abate and the interns found a nest at Hopkins Road Prairie. They also located a harrier nest at Erstad Prairie that day. Last year, harriers nested in the Lapinski-Kitze Prairie.
This year, the six pairs of American kestrels at Goose Pond fledged 30 young probably due to an abundance of small mammals, mostly meadow voles. A large vole population might also be the reason that we have three pairs of harriers nesting in the local area. In addition to the harrier nest at Hopkins Road Prairie, there is likely a pair nesting in the Browne Prairie, but we now have reason to suspect there is also a pair nesting at Judi Benade’s prairie one mile west of Goose Pond!
Confirmations of harriers in the first year of the Atlas II project were few and far between. There were three additions confirmations in Columbia County (Lodi State Wildlife Area (SWA), Pete Helland SWA, and Schoenberg Marsh Waterfowl Production Area (WPA); no confirmations were reported in Dane, Lafayette, and Sauk counties; one confirmation in Iowa County at Mounds View Grassland, owned by The Prairie Enthusiasts, three confirmations in Jefferson County at the Counties’ Korth Park, Lake Mills SWA – Zeloski Marsh Unit, and Red Cedar Lake State Natural Area and (WPA). It is important to restore large acreages to permanent grassland habitat so that birds like the incredible harrier have breeding habitat.
The North American Breeding Bird Survey records a steady decline of over 1% per year from 1966 to 2014, resulting in a cumulative loss of 47%, with Canadian populations declining more than U.S. populations. Partners in Flight estimates the global breeding population at 1.4 million, with 35% spending some part of the year in the U.S., 17% in Canada, and 10% in Mexico.
By Mark and Sue Foote-Martin, Resident Managers, and Maddie Van Cleve, Land Steward, Goose Pond Sanctuary