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Nature Notes: Tracking a Harpswell Heron

Ed Robinson
May 7, 2019

Thanks to Maine’s coastal location, and the wide variety of habitats on offer, we are blessed with hundreds of different birds. Over 460 species have been documented in Maine, with around 330 species seen regularly. Some are residents and others are passing through on their annual migration. Although a small community, Harpswell is a popular location for birds of all sorts, and for the birders who track them with binoculars in hand. One of the species of special concern along the coast is the beautiful great blue heron.

Great blue heron (Ed Robinson photo)

The largest of more than a dozen North American herons, Ardea herodias can reach four feet in height, with powerful wings that stretch up to six feet. Despite their size, the birds generally weigh only five to six pounds, thanks to hollow bones in their compact bodies. They are readily identifiable with long necks and legs, a grayish blue body, a white and black crown and yellow eyes and bills. You will often see them standing quietly in still ponds or slowly stalking marshes and mud flats. With a quick strike from the sharp bill, herons feed on a wide variety of fish, amphibians, insects and crustaceans. In the wild, these herons live up to 15 years.

The great blue herons range from the Canadian Maritimes to Alaska during spring breeding season, but winter may find them throughout the Caribbean and in Central and South America. Their nesting sites in Maine are often in dead or live trees near water, with up to 100 pairs nesting in clusters known as a heronry. The birds protect their eggs and fledglings from a range of predators including raccoons, snakes, eagles and great horned owls.

While the population of herons has been reasonably stable across the state, breeding bird surveys have shown a roughly 80 percent decline in coastal breeding pairs since the mid 1980s. In response, biologists from the Maine Department of Inland Fisheries and Wildlife (IFW) have partnered with concerned citizens to set up the Heron Observation Network. Volunteers monitor heron colonies during breeding season to record active nests, while avoiding disturbance to the birds. Using state and volunteer data, in 2015 it was estimated that 1,593 breeding pairs were active in Maine.

IFW bird biologist Danielle D’Auria has been working for ten years to understand the decline in coastal regions. The study is intended to learn more about home ranges, habitat preferences, forage activity, migration routes and more. Since it is impossible to keep up with birds that can hit 80 miles per hour during high altitude migration flights, Danielle and her teams are using innovative solar powered tracking devices that are carefully attached to the back of captured herons with durable Teflon straps.

Salin Bachor holds a captured mummichog minnow at Long Reach in Harpswell in 2016. The minnows are used as bait in a project to track great blue herons. (Walter Wuthmann photo)

To date, five herons have been captured and outfitted with trackers. The devices can be traced using mobile phone technology and GPS location data. With luck, the trackers and the birds packing them will last three to four years while delivering a wealth of data to the research teams. Those research teams include not only professionals like Danielle, but also volunteer bird enthusiasts and school age children. The students are able to participate in following the heron’s activities with computers, and in the field work involved in catching the herons in the first place. (Click here for an article about Harpswell Community School students involved with this project in 2016.)

For more about the project, click here, or follow the project on Facebook here. The public can access data on the tracked herons.

It won’t surprise you that herons are not easy to capture, since they are by nature rather solitary and wary of human disturbance. Danielle and her team learned how to use small bait fish to get a heron accustomed to feeding in a particular area and then use humane traps to capture them. Once captured, the herons are carefully weighed and measured and small blood samples are taken for vital DNA analysis (for instance, it is impossible to determine the sex of herons by physical examination). Leg bands are attached to help identify the birds if they meet with tragedy and are recovered. And they are outfitted with their GPS backpacks.

The school children involved with each heron tagging project are allowed to name the bird, and are encouraged to study the bird’s movements over time. Some students have used the data for science fair and Capstone projects.

The really cool news is that Danielle is bringing her project to Harpswell again in 2019, working with students from the Harpswell Coastal Academy. The team is already scouting possible locations for trapping bait fish and identifying sites known to be favored by herons for feeding. Harpswell Heritage Land Trust (HHLT) is assisting Danielle by matching her with volunteers and sharing knowledge of the area. HHLT will be publishing articles over time so the community can learn more as the study progresses.

Danielle’s goal is to begin capturing bait within the next two weeks and, if all goes well, to have a heron captured by early to mid-June. She is hoping the heron will decide to remain in the area after being outfitted with a GPS device, since there are several known nesting sites within our town. As autumn progresses, we may be able to follow the migration flight of the Harpswell heron as she flees the impending cold season here. Other herons in the study have found comfortable winter homes in warm spots like Cuba and Haiti. With good fortune, “our” heron will wend her way back to Maine early in 2020 for another season of breeding and feeding in our beautiful town. We will keep you posted!!

If you would like to volunteer with Danielle to regularly catch bait and stock a bait bin to lure a great blue heron (equipment and guidance provided), you can reach her at danielle.dauria@maine.gov.

Click here for more information about great blue herons.

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