06-15-2007, 04:32 AM
[url "http://www.spinalcolumnonline.com/1editorialtablebody.lasso?-token.searchtype=authorroutine&-token.lpsearchstring=Josh%20Jackett&-nothing"]Josh Jackett[/url] ![[Image: z.gif]](http://www.spinalcolumnonline.com/images/z.gif)
June 13, 2007 - Nature has run its course in the West Bloomfield Woods Nature Preserve, where great blue herons are no longer nesting, according to a West Bloomfield Parks and Recreation official.
"I don't like to say there's a population decline, because that makes it appear that there's a drop in heron populations or that there's something negative going on with the great blue herons," said West Bloomfield Parks and Recreation Naturalist Laurel Zoet. "That's not the case at all. The fact is that our rookery has dissolved, which is part of the natural cycle with great blue herons."
The former rookery site is located inside the Nature Preserve. A quarter-mile trail starting at a kiosk near preserve's the parking lot, which is accessible from Arrowhead Road, leads to the rookery's outlook platform.
A rookery, according to Zoet, refers to a colony of birds nesting together. She said this is the first year that almost no herons are nesting in the preserve.
"Very early on in the season, we had one heron hanging out in a nest," she said. "Herons will come back to the same rookery year after year. However, that was probably the last holdout, probably perched there waiting for others to arrive, and when no others did, that one moved on."
Zoet said the birds likely moved to another nesting site because of natural changes within the nature preserve.
"They're a bird that likes to take over trees that are sometimes almost all dead, or at least on their way to decline," she said. "They have a wingspan of almost 6-feet, so they need trees that are easy to get in and out of. Unfortunately, these kinds of trees aren't very stable for the long run because they're dead or dying."
She said also that guano, whitewash buildup, and half-eaten fish parts from the herons — all things they drop down from their nesting area — change the nitrogen makeup of the soil the trees are growing in, which helps kill the trees and make them vulnerable to wind and ice damage.
"It's called 'trashing'," Zoet said. "And once the herons have trashed it beyond its usefulness, they'll move on to a different site. It was only a matter of time before our rookery would dissolve on its own."
The process was accelerated about four years by a large ice storm that destroyed a lot of the nature preserve's nesting trees.
"With fewer trees to nest in, few herons could come together," she said. "Some birds started moving on at that point."
After that, the number of nests in the nature preserve dropped from about 100 to 30.
The drop in numbers also likely encouraged the remaining herons to move on.
"There's safety in numbers for great blue herons," Zoet said. "Predators like raccoons, great horned owls, turkey vultures, red tailed hawks, crows, and other things will raid nests. And aside from the herons' size, where they can flap their wings and convince predators to leave them alone because of how big they are, it's really better for them to have a bunch of their buddies around to watch out for the nests. With the fewer nesting sites, they couldn't get that strong concentration of numbers."
Where the herons move on to nest is still a question as the township Parks and Recreation Department didn't have a bird banding or other tracking program in place.
Herons will still occasionally visit the preserve to eat, and some nests from previous years are still visible, according to Zoet.
She said there are no efforts to bring the herons back, and that the nature preserve's focus will be on other species, like the threatened Blanding's turtles at the site.
"It would be incredibly expensive to (try to bring the herons back)," she said. "Plus, there's no guarantee that just because you make the investment in nesting platforms that you get herons to use them.
"I think we have an obligation to the Blanding's turtle. Herons have the capacity to change the makeup of the environment beneath their nests. We would have to do some long-term investigation into how that would impact the turtles that are there. Plus, great blue herons are the most common heron species in the world, while Blanding's turtle is an underprotected species."
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June 13, 2007 - Nature has run its course in the West Bloomfield Woods Nature Preserve, where great blue herons are no longer nesting, according to a West Bloomfield Parks and Recreation official."I don't like to say there's a population decline, because that makes it appear that there's a drop in heron populations or that there's something negative going on with the great blue herons," said West Bloomfield Parks and Recreation Naturalist Laurel Zoet. "That's not the case at all. The fact is that our rookery has dissolved, which is part of the natural cycle with great blue herons."
The former rookery site is located inside the Nature Preserve. A quarter-mile trail starting at a kiosk near preserve's the parking lot, which is accessible from Arrowhead Road, leads to the rookery's outlook platform.
A rookery, according to Zoet, refers to a colony of birds nesting together. She said this is the first year that almost no herons are nesting in the preserve.
"Very early on in the season, we had one heron hanging out in a nest," she said. "Herons will come back to the same rookery year after year. However, that was probably the last holdout, probably perched there waiting for others to arrive, and when no others did, that one moved on."
Zoet said the birds likely moved to another nesting site because of natural changes within the nature preserve.
"They're a bird that likes to take over trees that are sometimes almost all dead, or at least on their way to decline," she said. "They have a wingspan of almost 6-feet, so they need trees that are easy to get in and out of. Unfortunately, these kinds of trees aren't very stable for the long run because they're dead or dying."
She said also that guano, whitewash buildup, and half-eaten fish parts from the herons — all things they drop down from their nesting area — change the nitrogen makeup of the soil the trees are growing in, which helps kill the trees and make them vulnerable to wind and ice damage.
"It's called 'trashing'," Zoet said. "And once the herons have trashed it beyond its usefulness, they'll move on to a different site. It was only a matter of time before our rookery would dissolve on its own."
The process was accelerated about four years by a large ice storm that destroyed a lot of the nature preserve's nesting trees.
"With fewer trees to nest in, few herons could come together," she said. "Some birds started moving on at that point."
After that, the number of nests in the nature preserve dropped from about 100 to 30.
The drop in numbers also likely encouraged the remaining herons to move on.
"There's safety in numbers for great blue herons," Zoet said. "Predators like raccoons, great horned owls, turkey vultures, red tailed hawks, crows, and other things will raid nests. And aside from the herons' size, where they can flap their wings and convince predators to leave them alone because of how big they are, it's really better for them to have a bunch of their buddies around to watch out for the nests. With the fewer nesting sites, they couldn't get that strong concentration of numbers."
Where the herons move on to nest is still a question as the township Parks and Recreation Department didn't have a bird banding or other tracking program in place.
Herons will still occasionally visit the preserve to eat, and some nests from previous years are still visible, according to Zoet.
She said there are no efforts to bring the herons back, and that the nature preserve's focus will be on other species, like the threatened Blanding's turtles at the site.
"It would be incredibly expensive to (try to bring the herons back)," she said. "Plus, there's no guarantee that just because you make the investment in nesting platforms that you get herons to use them.
"I think we have an obligation to the Blanding's turtle. Herons have the capacity to change the makeup of the environment beneath their nests. We would have to do some long-term investigation into how that would impact the turtles that are there. Plus, great blue herons are the most common heron species in the world, while Blanding's turtle is an underprotected species."
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