Friends Field Trips 2021
During the Pandemic, we offer Self-Guided Walks each month with the same topics as our regular Naturalist-led Field Trips. They can be taken at your convenience on any day.
Purple Martin Colony in the Preserve
by Gisela Kutzbach
Purple Martin Team 2021: Anna Pidgeon, faculty advisor; Richard Ness, main monitor; Gisela Kutzbach, coordinator; Chuck Henrikson, David Liebl, Seth McGee and Biocore interns, Nicole Miller, Paul Noeldner, Will Vuyk
Follow the trail on the map to reach the Purple Martin house at Biocore Prairie
The flashy Purple Martins, with their deep purple iridescent feathers, are much loved. They chatter and gurgle happy songs, all day long. They display dizzying speeds and acrobatics in the air and then glide smoothly into their homes. They like living in crowded colonies, interacting constantly.
They had disappeared from the Preserve and generally declined in midwestern US because of habitat loss. They are cavities nesters but cannot make their own. Most of them now live in houses and gourds provided and cared for by people. Because they grow very accustomed to our human presence, we can watch them from close by and enjoy them. They prefer open spaces near water, with large amounts of insects to feed on. They are affectionally called PUMAs, using the standard abbreviation of bird names (first two letters of the two words making up their common name).
The Purple Martin Citizen Science project at the Biocore prairie was developed in 2017 to provide habitat opportunities for PUMAs and bring them back to the Preserve, as well as educational opportunities for the public. The last four years have been an amazing learning experience. The house was established in 2017 as part of a continent-wide citizen science project known as “Project MartinWatch.” The Friends of the Lakeshore Nature Preserve have a faculty advisor and a team of 6 monitors who check the house every week, and more often during breeding season. At the end of each season, the team submits reports to Preserve management and the Purple Martin Conservation Association (https://www.purplemartin.org). If you are interested in learning how to help, please email.
On this virtual walk, you will learn about the Purple martins’ appearance and habits, nesting behavior, enemies, and migration patterns. To get a feel for their behavior and vocal social life, watch the movie below, provided by Seth McGhee.
Purple Martins acquire their adult plumage over a period of two years. At that age the male martins achieve their iridescent purple feathers, even under the tail. The two-year old females have dark purple on their heads, but otherwise look more like the 1-year-old subadults with their brownish pin-stripes down the whitish undertails. The very young and subadults also show yellow inside their beaks.
Purple martins are the largest in the family of swallows. They can reach speeds of 40 miles an hour. They are specialists in catching the agile dragonflies, alternating between rapid flapping and then smooth gliding, flying circles up high only to dive down with high speed and then catch their prey in mid-flight. To support their dizzying lifestyle, they consume enormous numbers of insects, including dragonflies, butterflies, moths, and flies.
Purple martins generally stay with the same partner for a season. Nest building begins several weeks after the martins have arrived at the site and might take a few weeks to complete. At the Biocore Prairie, the monitors provide a bed of pine needles for a good start. The martins add some twigs, and after shaping a shallow nest bowl, they will line their nest with green leaves from the nearby apple trees. Soon after, they will begin laying eggs, one every morning for about 5-6 days.
The female starts incubating the day before she lays the last egg. She has a featherless breeding patch which transfers heat to the eggs. Depending on the weather, incubation takes 15-16 days and fledging between 26-32 days. Soon after hatching, the young develop feathers. Because the early arrivals tend to breed a few weeks earlier than the later subadults, hatching and fledging times for the different compartments of a house can vary. In 2017, we had 3 young nestlings fledge. This year, we had the first fledglings on July 9 and the last nestlings are expected to fledge the end of July. Our monitor team is thrilled that in 2021 seven martin pair built nests, with a total of 35 eggs, and after some losses of eggs, 25 fledglings expected.
From the start, the young nestlings devour insects of any size. Both parents feed them, stuffing dragonflies and butterflies, insects high in protein, down their throats, with the tail end of the insect body still sticking out of the gaping beaks, while digestive juices start acting on the front end. Once the nestlings reach adult size, they begin exploring the entrance porch to their home, and eventually they will take off on their first flight. They will stay close to the house for a few more days, often spending the night in the safety of their old home, and still being fed by their parents. But after a week, they have learned to forage for their own food and become independent. The sequence below, photographed by Janis Cooper, shows the moment of fledging.
Enemies and threats
Although martins display strength by their sheer numbers in a colony, enemies are a threat during breeding season. European starlings and house sparrows, both invasive birds not protected by federal law, are strong aggressors. Once a male sparrow sets an eye on occupying a nest site in a martin colony, he will not give is up – he values home over female. If a purple martin house monitor should remove a house sparrow nest, the angered male may become aggressive, and destroy purple martin eggs and kill nestlings. This year, a house sparrow destroyed all four eggs in one nesting compartment.
Parasites are another threat to nestlings. This year, the gourds and house were covered with hundreds of mites, visible with binoculars and crawling up the arms of monitors. These mites attach to the skin of the nestlings and feed on their blood. This being a citizen science project, we decided to observe. It appears that all nestlings survived. .
And of course, hawks are known to rob nests and attack young birds. In 2017, a Coopers hawk was sitting in the corner apple tree, waiting for a good moment to attack the martins at the house. What a sight it was, to see the martins assemble as a group, harass the hawk and chase him off. See the movie below. A guard on the martin house pole protects from snakes, and the half-moon entrance holes and tunnels of the gourds protect from starlings and owls. Bad weather with no insects to feed on is another threat.
Video by Seth McGee.
Watch purple martins chase away a Coopers Hawk in slow motion.
Martins usually return to the same area and house where they spent the previous summer. Subadults often have to find new quarters. The first birds to arrive in late March are adults martins, called scouts. In 2021, our team readied the house in mid-March and the first scouts were sighted in the Preserve by the end of March. They were followed by subadults several weeks later, in May.
After the breeding season, martins begin to assemble in roosts of hundreds and thousands of birds at large bodies of water with reeds and thick brush. From here they migrate in smaller groups to winter quarters in South America, mostly Brazil, approximately 5000 miles. Here in Wisconsin, the largest roost is along the northern edge of Lake Winnebago. A roost at dusk, when hundreds of birds are descending in a short time, is a spectacular sight.
On their way to the south in fall and up north again in spring, martins use several routes. Individual birds have been followed via GPS tags. A major track is via the Yucatan peninsula, central America and Colombia, others take the land route via Mexico, and still others do “island hopping,” crossing via the Caribbean, Cuba and other islands.
We are thrilled to report a total of 26 fledglings from the initial 35 eggs. We look forward to yet higher occupancy of the house next year, as our PUMAs like to return to their nesting locations. What a chatter it will be!!! When you visit this purple martin house this August, you will still be able to spot martins circling the house and feeding above the prairie.
Free public field trips are one of the most valuable contributions the Friends make to the Preserve. They have been organized every spring and fall for over 10 years on various topics and are all led by Friends volunteers. Many are professional naturalists and emeritus faculty and staff. The Friends also partner with other environmental organizations for field trips.
Field trip coordinator: Doris Dubielzig
Bird and Nature Outings
Free, family-friendly walks on the 4thSunday of the month. Bring your binoculars and camera. Meet at the Picnic Point entrance next to the kiosk (2004 University Bay Drive). Sponsored by the Friends of the Lakeshore Nature Preserve, Friends of Urban Nature, and Madison Audubon Society. Meet at the Picnic Point Kiosk, across from UW Lot 130. Contact Paul Noeldner (608-698‑0104).