Rookery Blues

Empty nests spur efforts to bring back Peltier Lake's beloved great blue herons.

By Gustave Axelson

The great blue herons of Peltier Lake have no idea how much they're admired. They adorn the city seal in their hometown of Lino Lakes, just north of the Twin Cities. When they leave their nests on fishing expeditions, they sometimes fly over Blue Heron Elementary School.

Herons have been a part of this community since 1945, when they established a breeding place, or rookery, in what is now Rice Creek Chain of Lakes Regional Park Reserve in Anoka County. Generations of local residents have watched the long-legged, gray anglers stalking along quiet shorelines.

Art Hawkins enjoyed watching these herons and their compatriots, great egrets, fly back and forth from the rookery during the spring of 1999. From his post in a farmer's field a half-mile away, he set up his spotting scope to monitor hundreds of heron and egret nests on a 30-acre island at the north end of Peltier Lake.

Hawkins, a retired U.S. Fish and Wildlife Service biologist, volunteered to help the Minnesota Department of Natural Resources keep watch over these herons because of concerns over growing disturbances in this area. In March and April, he watched the herons and egrets gather sticks to repair their ramshackle nests atop the island's basswood and maple trees. In May the birds turned their attention to foraging for frogs and fish for their young. By August the chicks fledged, and the raucous rookery quieted down.

In March of 2000, Hawkins returned to the farmer's field for a second season of watching herons. Everything seemed to be going fine until one June day when he peered through his spotting scope and saw . . . nothing. No silhouettes of six-foot wingspans with gangly legs dragging in the wind. Hawkins heard no calls from chicks hungry for regurgitated fish. The air around the rookery was empty.

When the DNR sent in tree climbers to investigate the nests, they found them empty. Cracked eggshells on the ground indicated there had been a hatch. But all that was left was a pile of feathers in some of the nests.

Hawkins watched this scenario play out again in 2001 and 2002. For three consecutive years, the herons prematurely abandoned their nests in June.

"Only something unusually drastic could account for the abandonment of a colony of birds sitting on eggs or young," Hawkins wrote in his notes after the 2000 failure.

In his mind, that most likely meant human disturbance.

Vagabond Birds

It was, in large part, human disturbance that pushed the herons to this island in the first place, according to DNR nongame wildlife specialist Joan Galli.

"These herons are victims of urban sprawl and our love of living on lakeshores," says Galli. "The only place these herons could get away from people was on this island."

Around the Twin Cities, it appears heron rookeries are facing similar pressure on their habitat. Of the 11 known active heronries in the seven-county metro area, nine are on islands.

"We don't have the resources to properly analyze great blue heron populations," says Galli, "but the Minnesota heron population isn't growing by leaps and bounds, that's for sure. There are certainly fewer colonies."

In 2002 herons abandoned another island rookery north of the Twin Cities, along the Mississippi River. Unlike the Peltier Lake herons, these did not return the following year. The DNR determined teenagers holding island beer parties and shooting off fireworks caused the abandonment. In other words, human disturbance.

Citizens Meet

On Peltier Lake the suspected source of human disturbance was a slalom water-ski course, set up in 1998 in the shallow and quiet northern end of the lake. Even though the course had a permit from Anoka County, the DNR and some lakeshore homeowners were concerned that high-speed boating would disrupt sensitive herons on their nests.

After receiving phone calls from residents who said they were seeing fewer herons around the lake, Peltier Lake Association president Wayne LeBlanc called a meeting in April 1999 to discuss the rookery issue with officials from Anoka County, as well as Lino Lakes and Centerville-the two towns that straddle Peltier Lake. Also present was one of the ski-course permit holders, Jerry Lindner.

According to Anoka County park operations manager Jon Oyanagi, the consensus was to "voluntarily keep any water-skiing to the main body of the lake south of the island. There was agreement to avoid skiing in the area north of the island."

Yet, according to some people who live on the lake, water-skiing continued.

Possible Explanations

As the issue moved to the Lino Lakes and Centerville city councils in March 2002, it ignited a debate that pitted the community's beloved herons against the local passion for boating and water skiing. As the councils considered a proposal to establish a formal slow no-wake zone near the Peltier Lake heronry, Scott Lanyon-a local resident, ornithologist, and director of the University of Minnesota's James Ford Bell Museum of Natural History-presented a list of 10 potential disturbances causing rookery abandonment.

In addition to high-speed boating, Lanyon offered a variety of humanmade and natural reasons. Some were dismissed, such as harassment by the island's resident bald eagles. There has never been a reported incident of an eagle acting aggressively toward a heron on Peltier Lake. One year, four heron nests even shared the same tree with an eagle nest. Other possible reasons only partially explained the abandonment. For example, highway construction on nearby Interstate 35W during spring 2000 could not have caused rookery failure in 2001 and 2002.

Lindner, vice president of the Minnesota Water-ski Association, cited the closing of a nearby fish hatchery and the removal of bullheads and carp from Peltier Lake as possible reasons because both might have been food sources for the birds.

Jeff Perry, natural resources specialist for Anoka County Parks, doubts food scarcity caused the herons to leave. "The whole corridor of wetlands within the Rice Creek chain of lakes provides very high-quality habitat for feeding. It's full of fish, invertebrates, and amphibians," he says. "These herons were documented flying as far away as 20 kilometers to feed."

Herons Come Back

Council meetings deliberated on the slow no-wake zone for two months, and never did unanimously agree on water-skiing as the primary cause for rookery abandonment. But the potential for disturbance from high-speed boating was the cause they acted on.

"Of all the potential causes presented to the council, that was the one we could do something about," says John Bergeson, mayor of Lino Lakes.

The slow no-wake zone measure carried unanimously in both councils, and it was in place just after March. But the buoys were placed by Anoka County Parks in June 2002-too late to save the nesting season for that year.

n 2003, with the slow no-wake zone in place, the herons came back to nest. And this time they stayed.

The DNR estimates more than 300 pairs of great blue herons and 12 pairs of great egrets successfully nested in the Peltier Lake rookery in 2003. That's about half of the rookery's nesting population four years ago. But at least there's hope it will remain active.

Another Season

A sunset clause was included in Lino Lakes' slow no-wake zone ordinance. As a result, the council will reconsider the issue next fall.

Bergeson says he thinks the slow no-wake zone will be extended or made permanent. Lindner agrees, though he hopes the terms are changed.

"I don't have a problem with the great blue herons. I want to protect them like everyone else," he says. "I expect the no-wake zone will stay in effect, but I think it should be moved [north of the island] . . . and it should only be April through July. It doesn't have to be the entire year." Perry disagrees.

"Research shows that herons are flushed off nests when humans come within 300 yards," he says. "The current buffer starts 200 yards south of the island. We've already compromised so there would be minimal impact on recreational activities on the rest of the lake, but the buffer can't move in any more.

"We can't adjust the timing either, because all summer long the no-wake zone also protects sensitive aquatic vegetation in the area. When motorboats rip up those plants, they release phosphorus that degrades the water quality. And that's a regionwide problem, because Peltier Lake is the headwaters for the entire Rice Creek chain of lakes, and it eventually flows into the Mississippi River. So herons aside, clean water throughout the northern Twin Cities is another important reason for maintaining this no-wake zone."

As far as the herons are concerned, Hawkins is optimistic he will see an unprecedented comeback in the rookery.

"In 30 years of monitoring bird colonies, I never saw one that kept coming back after three years of disruption," he says.

That may be because the Peltier Lake herons have no other choice.

"In the Twin Cities and suburbs, our herons have been reduced to literally nesting on islands of suitable habitat," says Galli. "They have nowhere else to go."

Gustave Axelson is a freelance writer who lives in Minneapolis.