Indicator Species - A Closer Look

Indicator Species - A Closer Look

Grassland Birds - If you plant it, they will come
photos and text by P. Allen Woodliffe, MNR District Ecologist, Aylmer District
Bluestem Banner - Summer 2005

The Dickcissel (Spiza americana) is a sparrowsized bird that, because of its black and yellow bib, has been described by some as a smaller version of a meadowlark. Its core breeding range is the mid-western part of the continent, from Texas to southern Manitoba so it is not a species that most Ontario birders encounter very often.

The native grasslands of the tallgrass prairie region have always been its preferred habitat, adapting to hayfields and pastures as those original natural habitats disappeared. However in years of drought in the core of its range, they tend to move away to where moisture conditions provide for better vegetation growth. It is during those drought years when they sometimes show up in southwestern Ontario. The current year is such an example. Even though it is relatively dry here, it is still more lush than parts of the midwest. As a result southwestern Ontario has experienced a moderate invasion of this species.

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	Small White Lady's-slipper

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In May of this year a Dickcissel was reported from a grassland site at Bronte Creek Provincial Park. In mid-June this species was detected initially at two different sites in Chatham-Kent, with numbers ranging from approximately seven birds at one site to as many as twenty at the other.

As of early July, they had been recorded from at least six different areas of Chatham-Kent, and been confirmed as breeding with the discovery of at least two nests, one of which was situated in a well-developed clump of Virginia Mountain-mint (Pycnanthemum virginianum). The site with the largest number of birds is a privately owned area of grassland. The one where nests have been found is on crown land, and interestingly it had been planted as a prairie nursery site in 1996. There is a profusion of prairie wildflowers and grasses at this site, and in addition to Dickcissel, hosts at least 20 Bobolink, four Eastern Meadowlark, and a number of Savannah, Song and Field Sparrows.

Even more exciting than the occurrence of Dickcissel is the appearance of two Henslow’s Sparrow (Ammodramus henslowii)! This diminutive and secretive species has declined drastically in most of the northeastern U.S. states where it has been known to occur. In the core of its mid-western range, it experienced severe declines. For example in the state of Illinois, Breeding Bird Survey results indicate it had declined by ~94% from 1958-1993. However since then it appears to have increased in numbers somewhat in its core range.

Henslow’s Sparrow was declared Endangered by the Committee on the Status of Endangered Wildlife In Canada (COSEWIC) in 1993 and added to Ontario’s Endangered Species Act in 1994. Due to the Endangered status of this species in Ontario and Canada, the specific location of its occurrence in Chatham-Kent is not being divulged. The second Ontario Breeding Bird Atlas is just completing its fifth and final field season.

Results after the first four years of data collection indicate that the species showing the most drastic decline are those that require grassland habitats. It is therefore a glimmer of encouragement to see that some of these tallgrass prairie creation sites are being used by a good diversity of typical grassland birds, and occasionally by some of the rare and endangered species!

To date many people are content to see the vegetative results of such prairie plantings, and there has been little formal monitoring of the success of them. It is important to document the impacts of such activities, and more specific efforts at conducting breeding bird surveys in tallgrass prairie creation and restoration sites are being planned for the future.