BIRDS
Daniel F. Brunton
CURRENT BIODIVERSITY
The avifauna of the Mixedwood Plains Ecozone is relatively homogeneous, although concentrations of specific habitat types are marked by concentrations of similar bird species (e.g. colonial waterbirds along the Great Lakes and St, Lawrence River shores, scrub and grassland species in limestone rock barrens (alvars) across southern Ontario).
One distinct breeding bird subgroup is evident within the Ecozone. The complex of southern flora and fauna confined to southwestern Ontario north of Lake Erie and the adjacent northwest Lake Ontario shore constitute the Carolinian Zone (Allen et al. 1990). The distinctive avifauna here includes nationally rare species Acadian Flycatcher, Hooded Warbler, Tufted Titmouse, Prothonotary Warbler (Fig. B-2) and Louisiana Waterthrush. These species are widespread in eastern United States but are restricted in Canada to breeding virtually only within the Carolinian Zone (McColeman & Eagles 1990).
The diversity of birds in the Mixedwood Plains Ecozone has been dramatically influenced by direct and indirect human impact on the landscape since the mid 18th century. Significant impacts in the Mixedwood Plains Ecozone and some examples of the results of these impacts include the following:
- massive clearing of old growth and fragmentation of remaining natural forest
- agricultural and industrial air and water pollution
- commercial exploitation and selective persecution (viz , food gathering, falconry, fashion, religious intolerance, game species management, etc.)
- interference in natural succession and habitat composition (fire suppression, reduction in rates of forest vegetation maturation, infestation of wetland vegetation and woodland edges by non-native plants)
- large-scale creation of artificial and biologically unproductive habitat (pine plantation, urban and agricultural landscapes, etc.)
Equally or more important for many species have been human impacts on the natural landscape in distant areas where many of these species winter or breed.
There are approximately 235 established breeding species in the Mixedwood Plains Ecozone (Appendix A). These are predominately widespread taxa in eastern North America, reflecting the short post-glacial history of the area. No endemic species are known although the Endangered (extirpated ?) Kirtland's Warbler has a significant portion of its very restricted range within the ecozone.
The Mixedwood Plains Ecozone constitutes important winter territory for ca. 80 bird species (Appendix B). Half of these are permanent residents and half are seasonal northern visitors, often present from year to year in wildly irregular population sizes. The Mixedwood Plains Ecozone can provide important winter territory for large numbers of boreal/arctic finches (e.g. Evening Grosbeak, Common Redpoll, Snow Bunting), waterfowl (e.g. Common Golden-eye, Oldsquaw) and raptors (e.g. Rough-legged Hawk, Snowy Owl) in particular years.
A small number of intentionally and accidentally introduced bird species have had a huge ecological impact in the ecozone, especially in urban and agricultural landscapes. Significant non-native introductions include European Starling, House Sparrow, Rock Dove and Ring-necked Pheasant. Recent non-native arrivals showing rapidly increased populations, particularly in and around urban centers are Mute Swan and House Finch (Fig.B-3).
Direct introductions and particular alterations of habitat have favoured the invasion of this area by bird species from elsewhere in North America. Some of these - particularly the highly competitive Mallard, Canada Goose and the nest-parasitizing Brown-headed Cowbird - have had an impact on native biodiversity equal to or greater than that of introduced species.
The Passenger Pigeon is the one extinct breeding species of the Mixedwood Plains Ecozone. Its destruction within and beyond was largely the result of human actions outside of the ecozone (hunting, habitat destruction). Such activities within the ecozone may have accelerated that rate of extinction, however.
Three and possibly four breeding species have also been extirpated from the ecozone within the last century, Golden Eagle, Piping Plover, Greater Prairie Chicken and possibly Kirtland's Warbler. Their loss is primarily a consequence of human harassment and/or habitat alteration.
Most rare species in the Mixedwood Plains Ecozone are southern taxa at the northern periphery of their widespread eastern North American ranges. The breeding of most of these is primarily confined in Canada to the Carolinian area of southwestern Ontario. Several others represent widespread or northern species. The following list of rare taxa reflects their COSEWIC national designation as of February 1996:
Endangered Species:
Harlequin Duck (wintering species)
Peregrine Falcon (anatum race)
Northern Bobwhite
King Rail
Acadian Flycatcher
Loggerhead Shrike
Kirtland's Warbler
Henslow's Sparrow
Threatened Species:
Hooded Warbler
Vulnerable Species:
Least Bittern
Cooper's Hawk
Red-shouldered Hawk
Caspian Tern
Common Barn Owl
Great Gray Owl (wintering species)
Short-eared Owl
Eastern Bluebird
Prairie Warbler
Cerulean Warbler
Prothonotary Warbler
Louisiana Waterthrush
Yellow-breasted Chat