Ornithological Summary

The
importance of North Heron Lake
to birds has been known since the early 1900s. In June 2007; the Minnesota Biological
Survey (MBS) conducted breeding bird surveys at North Heron Lake as part of a
broader survey of Jackson, Cottonwood, Martin, and Watonwan counties. 

 

Those
familiar with North
Heron Lake
know that it is much more than just open water. 
A diverse mix of habitats surrounds the lake, including emergent marsh,
shrubby willow thickets, wet grasslands, and scattered patches of trees and
small woodlots.  Diverse habitat means high
bird diversity.  The final tally for MBS
bird surveys was an impressive 77 bird species. 
Almost all of the typical marsh birds were found, including 10 duck
species, nesting Western Grebes, American White Pelican, the secretive Least
Bittern, Virginia Rail, American Coot, Black Tern, Marsh Wren, Swamp Sparrow,
Red-winged and Yellow-headed Blackbirds. 
Rarer species found included Trumpeter Swan (a state-threatened
species), American Bittern (relatively rare in southern Minnesota), Forster’s Tern (a state special
concern species).  Also observed was the
Great-tailed Grackle, a large cousin of the Common Grackle that has recently
moved into Minnesota
from the south.  Great-tailed Grackles
were first documented nesting in Minnesota in
southernmost Jackson
County in May 2000.  In our area, this species is a relatively
secretive, marsh-nesting bird.

 

Grasslands
around North Heron Lake support species such as Red-tailed Hawk, American
Kestrel, Sedge Wren, Clay-colored Sparrow, Savannah Sparrow, Grasshopper Sparrow,
Dickcissel, Bobolink, and Western Meadowlark. 
Shrubby thickets are home to species like the Willow Flycatcher, Yellow
Warbler, Common Yellowthroat, and Song Sparrow. 
Woodlots and others areas of trees and shrubs provided suitable habitat
for species like Great Horned Owl, Yellow-bellied Sapsucker, Great Crested
Flycatcher, House Wren, Rose-breasted Grosbeak, and Indigo Bunting.  The Red-headed Woodpecker and Blue Grosbeak
have also been documented within this IBA.

Conservation Issues

Heron Lake has become one of the most popular walleye fisheries in
southern Minnesota. With a shallow lake depth and ideal vegetation for this
species, recreational fishing has become popular. With high boat traffic
colonial Waterbirds such as Franklin’s Gulls and Black Terns are fighting human
interaction as well as common natural factors. Over the past years a decrease
in vegetation has been noted. These colonial water nesters often return to the location
from which they fledged. Returning individuals are finding scarce availability
of nesting sites. Factors such as high precipitation levels and large waves
caused by boaters flood the nests of these birds. With fewer gulls and terns
fledged at the colony locations fewer birds are returning to the breeding
grounds. Less vegetation also means less food stores for these birds. High wave
activity can also prevent the establishment of emergent vegetation.

 

Tilling and drainage of nearby farmlands is also a concern to water
quality and the drainage effects on water level. The Heron Lake system is prone
to extreme water level fluctuation because of the amount of drainage into the
watershed. A heavy rainfall event in the watershed results in very rapid water
level increases which greatly affect the waterbirds nesting in the system.