The bird was named after officials in the Roman Catholic Church known as the protonotarii, who wore golden robes.
New kingdoms for little birds in golden robes
Biologists are enticing prothonotary warblers to Wisconsin's swampy forest lowlands. You can do it too.
Avon Bottoms, along the lower Sugar River in southwest Rock County is easier to appreciate on paper than in fact. Its lowland, hardwood forest in a meandering riverbottom floodplain offers an important corridor for biodiversity. It encompasses both a state wildlife area and a natural area. Rare tree and plant species thrive here with diverse wetland dependant wildlife. So do mosquitoes and poison ivy. Mosquitoes here seem so thick that no amount of netting or repellant can keep them at bay, and poison ivy covers the forest floor.
The bites and itching were just two of the challenges facing DNR biologists who have launched a pilot project to determine if artificial nest boxes can help augment breeding populations of the prothonotary warbler (Protonotarea citrea), a Species of Greatest Conservation Need for Wisconsin.
The small songbird is a mid-distance migrant that breeds in the eastern United States and spends the winter in mangrove swamps and wet forests of the lowland forests of southern Mexico, Central America, Columbia and Venezuela.
PROW, the nickname given by biologists for the prothonotary, has an olive back with blue-grey wings and tail, yellow underbody, a long pointed bill and black legs. Adult males have a bright orange-yellow head while females and immature birds are duller with yellow heads. The bird was named after officials in the Roman Catholic Church known as the protonotarii, who wore golden robes, according to the Cornell Lab of Ornithology.
Prothonotaries are the only eastern wood warblers that nest in cavities over water near or around mature trees. They breed in moist bottomland forests that are seasonally flooded or are permanent wetlands. They are sensitive to changes in water depth and flow as their nests suffer much higher rates of predation from raccoons, other predators and parasitism by brown-headed cowbirds when not placed over water, said Andy Paulios, Wisconsin Bird Conservation Initiative (WBCI) Coordinator with DNR's Bureau of Wildlife Management.
"Their nest success and life history are very closely tied to the Ďhealth' of the floodplain forest ecosystem," he added.
In Wisconsin, PROWs nest in floodplain forests along the Mississippi, Chippewa, Black, Wisconsin, Sugar, Wolf and other large river systems. Many of these systems no longer have intact floodplain forests, and warblers, red-shouldered hawks, yellow-crowned night herons and other important bird species have likely declined from historical numbers due to this habitat loss, according to Paulios.
That's why 13 DNR wildlife staffers and volunteers got together in the spring of 2009 and, in assembly-line fashion, constructed PROW nest boxes as part of a pilot project to see if the boxes could augment breeding success in floodplain forest areas that have lost a lot of tree cover.
Most of the boxes were placed in Avon Bottoms, but "we ended-up making so many houses that we also put some along the Sugar and Little Sugar rivers in Albany Wildlife Area in Green County and along the Bark River at Princess Point Wildlife Area in Jefferson County," noted DNR Wildlife Biologist Mike Foy, Fitchburg.
Much of the nest box is made from four-inch diameter PVC drain pipe adapted by Foy from a similar design developed by Steve Gilbertson for bluebird boxes. The nest boxes are sprayed with textured light-color plastic paint and insulated to help keep the boxes cool.
"Our goals were to come up with cheap, durable houses that would be acceptable to warblers, easy to construct and mount in the field. The nest boxes are built to withstand the elements, last for multiple seasons, mount on electrical conduit poles, allow for drainage and have entrance holes that are too small for cowbirds, a major warbler competitor. It took only a few minor changes to come up with the design we're building now," Foy pointed out.
The project's objectives are two-fold: determine if the nest boxes are effective in enhancing PROW populations, and assess whether warblers can be used as a "flagship" species to interest people in floodplain forest conservation, said Paulios.
Biologists are looking to find out if warblers will use the boxes and if so, increase both their productivity and the population in the study area. Secondly, researchers seek to answer questions such as:
"Our goal is to engage citizens in PROW nest box trails similar to the enthusiasm generated for bluebird projects," explained Paulios. "Our hope is that PROW can be a window into the larger world of floodplain forest ecosystems. Once folks engage in this (project), we think they will start thinking like warblers."
DNR staff and volunteers placed over 90 boxes in southern Wisconsin floodplain forests during April 2009 in appropriate habitats offering shade or moving water. All offered ready access by canoe, although checking them for activity during early June and early July was challenging, said Paulios. Besides the omnipresent mosquitoes and poison ivy, canoeing to the sites was at times difficult due to snags and fallen timber blocking the river channel that sometimes necessitated portaging around or cutting trails through the logs and branches using a chainsaw.
Monitoring the boxes entailed inspecting nest contents, finding evidence of male or female prothonotaries in the area, and taking notes on general habitat around the box, including water depths. All boxes and poles were removed in October to prevent damage from high water flow.
Almost 40 percent of nest boxes were used by prothonotary warblers in 2009 and another 50 percent were used by native birds including wrens, warblers and tree swallows. There was no evidence of nest parasitism in the artificial boxes compared to 27 percent losses in nests established in natural cavities along the Lower Wisconsin River, according to a 1996 study by Dave Flaspohler, said Paulios.
"Personally, it was fun and gratifying to see warblers using nest boxes. Now we need to learn if boxes of this sort really have potential for helping warblers by providing more secure nesting sites. Our understanding from the literature is that prothonotary warblers using natural cavities for nesting are very vulnerable to both predation and cowbird parasitism," noted Foy.
The two biologists saw no evidence that either presented a problem for warblers using these boxes during the trial's first year. If these early observations hold, then the biologists believe that ramping up to place more PROW boxes throughout suitable habitat in southern Wisconsin could significantly benefit the species.
"Although monitoring was limited, we estimate (that) as many as 25 PROW nests could have produced 50 to 90 chicks. Previous research suggests that chicks that survive their first year will settle in the area where they are fledged. So we expect to see more birds using the boxes in 2010," Foy added.
And early observations indicate they are!
"Upon placing some nest boxes (in Avon Bottoms) during the first week of May 2010,Mike (Foy) and I saw a number of males and a couple pairs immediately fly to the box and start building nests. Instant gratification. One wonders if they were waiting for us to arrive," surmised Paulios.
Working with volunteers and DNR staff, nest boxes were also placed in April 2010, at River Falls, Hustisford, along the Lower Baraboo River, Outagamie County and in the Lake Koshkonong area.
Last May, during a field trip to Avon Bottoms, Paulios observed numerous active nests, including at least one nest with a complete clutch of eggs and a female brooding the nest.
"This is the earliest reported PROW nest for Wisconsin," he said. Field trip participants watched one female building a nest at a PROW box return every three to five minutes with a beak full of moss.
Citizen volunteers can get advice on setting up a prothonotary warbler nest box trail. Andy Paulios can offer more information about PROW habitat, box placement and box construction. E-mail Andy Paulios, or write to him at:
Wisconsin Department of Natural Resources
Monitoring intensity is up to the volunteers, but Paulios encourages two to three visits a year during the June-July nesting season.
"This helps us understand when and how often the boxes are being used. Monitoring helps volunteers better gauge where to place boxes and also gives land managers an idea of the health of their floodplain forest ecosystems," said the biologist.
The WBCI Southern Forests Committee is working on a strategic plan that will set population and wildlife habitat goals for floodplain forests. The Committee will consider using prothonotary warblers and the bird's demographics as a performance measure for managing and restoring this lowland habitat, he added.
Greg Matthews is the public affairs manager for DNR's 14-county South Central Region based in Fitchburg.