A Natural Heritage Review of the Thousand Islands
Table of Contents
St. Lawrence Islands National Park lies on the Frontenac Axis in southeastern Ontario; it lies in a "tension zone" between more northern and southern forest regions. A great diversity of habitats here attracts a wide variety of birds; as of early spring, 1980, 241 species of birds have been recorded in Leeds County, where the park is found. Species more typical of areas to the north such as the Hermit Thrush, Purple Finch and Junco nest alongside typically southern species like the Yellow-throated Vireo, Orchard Oriole, and Henslow's Sparrow. Certain other landbirds, such as the Pine Warbler, are common in the Thousand Islands area because of local pockets of suitable habitat.
Each season has its interesting highlights. One can witness tremendous waterfowl migration and the arrival of colonially nesting species (gulls, terns, herons, and blackbirds). During winter, the park supports waterfowl and gull populations and large numbers of passerine birds. Winter is the best time for observing Turkeys on Hill Island. Bald eagles can often be seen in the vicinity of the Thousand Islands Bridge, where the water pouring over the sill of Lake Ontario usually keeps the river from freezing.
This publication is a summary of studies into the bird life of the Thousand Islands to date. Hopefully, it will provide the reader with a brief background regarding the resident and migrant birds in our area.
THROUGH THE SEASONS [Top]
Each spring, large numbers of waterfowl migrate through the St. Lawrence Islands National Park area, a spectacular annual highlight for birders in the area. In late March and early April, up to 10,000 waterfowl may be present along the river between Gananoque and Brockville; as many as 18 waterfowl species nest and feed here in late March (See Table 1). In late April and early May, the calling of Canada Geese overhead and on the river is heard night and day. It is fascinating to realize that they are on their way from their wintering area along the coasts of Delaware and Maryland to their breeding grounds on the Belcher Islands and in Ungava.
The best localities for observing waterfowl during spring migration are first Ivy Lea and the 5 km stretch of river between Mallorytown Landing and Brown's Bay and then later the Mallorytown Landing to Jones Creek area, Landon Bay, and Ivy Lea.
Fewer waterfowl migrate here in fall; about 11 species of waterfowl are present along the river between Gananoque and Brockville in late October.
Many other birds stage (rest and feed during migration; the area so used is referred to as the staging area) here during spring and fall. The species diversity of birds in the St. Lawrence Islands National Park area is probably greatest during spring and falls.
In spring, Lakes Erie and Ontario act as a barrier to the northward movement of raptors (birds of prey) and funnel most raptors north-eastward along the southern shorelines of these water bodies (Figure 2). Some cross between Lake Erie and Ontario, but most follow the southern Lake Ontario shoreline east-northeast. Peak numbers occur at the southeastern corner of Lake Ontario at Derby Hills, New York and disperse north and east of there. The most common spring raptor migrants in the Thousand Islands are Marsh Hawks, American Kestrels, and Red-tailed Hawks.
Fall migration is generally the reverse of the spring pattern. Raptors move southwest along the north shores of Lakes Ontario and Erie (Figure 2). The major feature of raptor migration in the Thousand Islands region is, therefore, the barrier effect that Lake Ontario has on the spring and fall migration of these birds.
Interested observers have many other landbirds to look for during migration in February to May and August to November.
February and March [Top]
The first flocks of migrant crows and starlings begin to arrive in the St. Lawrence Islands National Park area during late February and early March just as Snow Buntings, Tree Sparrows and Lapland Longspurs are leaving the St. Lawrence Islands National Park area, where they have wintered, for their northern nesting grounds. The occasional robin or male red-wing may also be seen, but these birds do not become common until mid-March (female red-wings not until mid-April). Towards the end of the month, Mourning Doves, Loggerhead Shrikes, bluebirds, meadowlarks, grackles, cowbirds, Song Sparrows, phoebes and Tree Swallows arrive.
Those species that first appeared in March become increasingly common in April and many begin to nest. Flickers, Brown Creepers and Golden-crowned Kinglets appear early in the month, and are followed by Yellow-bellied Sapsuckers, Ruby-crowned Kinglets, Winter Wrens, Hermit Thrushes and White-throated Sparrows. White-throats become quite abundant in thickets and hedgerows in late April but are still present in good numbers into mid-May. From mid- to late April, Barn Swallows, Purple Martins, Whip-poor-wills, House Wrens, Thrashers, towhees, and Chipping and Field Sparrows begin to arrive. In late April, the Yellow-rumped Warbler arrives, the first warbler species of the year.
All of the remaining landbirds that migrate to or through the St. Lawrence Islands National Park area do so in May; the majority arrive (or begin to arrive) in the first two weeks of the month. Flycatchers, catbirds, thrushes, vireos, warblers, orioles, tanagers and Rose-breasted Grosbeaks dominate the early May period and often arrive in large migratory waves. White-crowned Sparrows are present in good numbers for most of the month. By the third week in May, most resident species have begun to nest and only a few late migrants have not yet begun to arrive. Nighthawks and Tennessee and Blackpoll Warblers appear in late May, just as the populations of most transient warblers are decreasing. Blackpolls are some of the latest migrants in the region; some birds linger through much of June.
August and September [Top]
In late May and throughout August, swallows gather throughout the St. Lawrence Islands National Park area in large flocks; most have departed by the second week of September. Tree Swallows, however, remain in the Thousand Islands region until early October. Kingbirds gather in loose flocks towards the end of August and depart early in September. Great Crested Flycatchers have also left by this time and Least Flycatchers and peewees depart shortly afterwards.
Veeries are the first thrushes to leave the park area and most are gone by the second week of September. Swainson's Thrushes return at about this time and their fall migration through the Thousand Islands region lasts for about a month. Wood Thrushes depart towards the end of September and migrant Hermit Thrushes begin to arrive from the north.
Migrant Brown Creepers pass south through the St. Lawrence Islands National Park area beginning the first week in September and although most have left by late October, some remain for the winter. Kinglets arrive later in September and remain common into early October.
Other early fall migrants are the vireos and warblers. Most non-resident species of these two families arrive from mid to late August and their migrations continue for about a month. Many of the warblers have moulted their bright spring plumage and their fall plumages are often very difficult to separate.
The Yellow Warbler, the most common nesting warbler in the St. Lawrence Islands National Park area, is the first to leave, usually by the first week in September. Most other warblers and vireos have departed by the end of September, but Orange-crowned Warblers do not begin to arrive until this time.
The non-resident species of sparrows are another important feature of fall landbird migration. Migrant White-throated Sparrows arrive in mid-September and Dark-eyed Juncos and White-crowned Sparrows arrive a little later in the month. Peak fall numbers of these three sparrows occur in mid to late October.
October and November [Top]
Flickers leave the St. Lawrence Islands National Park area by early October and their departure is closely followed by that of crows. However, a few of both species may winter in the area. Other species that depart by early to mid-October include the phoebe, catbird, Brown Thrasher, Yellow-rumped Warbler, Ovenbird, yellow-throat and American Redstart. By mid-month, the only warblers to be found in the St. Lawrence Islands National Park area are orange-crowns and Nashvilles.
The main southward migration of finches and sparrows takes place in October. The last Rose-breasted Grosbeaks depart early in the month and are soon followed by the last Savannah and Chipping Sparrows. Most towhees, Field Sparrows and Swamp Sparrows have departed by the third week in October. Blackbirds have gathered into large flocks by October and most have left the St. Lawrence Islands National Park area by early November. Robins and Hermit Thrushes leave in late October.
Most of the migrant landbird species that winter in the St. Lawrence Islands National Park area arrive in late October and November.
THE NESTING SEASON [Top]
Habitat types greatly influence the number of birds of a given species in an area as well as the diversity of species. During the summer months more birds are seen as one moves from evergreen habitat through mixed, open, and deciduous forests. A 1977 study in the park revealed that the five most widely distributed common species were Eastern Wood Peewee, Brown-headed Cowbird, Great Crested Flycatcher, Red-winged Blackbird and Red-eyed Vireo.
TYPICAL HABITATS AND SPECIES [Top]
The study also showed that the birds species typical of each of the four categories are as follows: (The species listed as characteristic for each habitat are those that were more abundant in the habitat than in any of the other three habitats. Within the list for each habitat, the species are listed in decreasing order of dependence on that habitat.)
CHARACTERISTIC SPECIES IN THE THOUSAND ISLANDS [Top]
Below are a few characteristics of those birds considered to be the most common species in the park; these are also common to abundant nesting birds in the Kingston area and New York State.
Yellow Warbler: This is by far the most abundant species. Many visitors on hikes conducted by park interpretive staff soon learn the characteristic song of the Yellow Warbler: "Cheep, cheep, shredded wheat!" It is most often found in deciduous and open communities. The well developed deciduous shrub cover in such areas appears to be an important component of the Yellow Warblers preferred nesting habitat. In open communities, for example, Yellow Warblers appear to be concentrated in the shrub zones, especially along the fringes of woodland. The Yellow Warbler is quite adaptable in its breeding location but deciduous shrubs seem to be the preferred nest sites, especially those in the vicinity of water.
Song Sparrow: This bird is abundant and widespread; the only two habitats in which it is usually not seen are pine and maple. Most are seen in open and deciduous habitats. They are less often detected in the mixed and evergreen forests. The number of Song Sparrows detected increases significantly with increasing ground cover; they are most often found in habitats characterized by relatively dense ground cover and average development of the scrub layer.
They are relatively uncommon in mixed forest, probably in part due to the relatively low ground cover in these communities. In evergreen forest, they are abundant in juniper habitat; probably due to the open nature of this habitat combined with a moderate ground cover and a well-developed and diverse shrub component. They are absent from pine (where shrub and ground cover ranked low).
Red-winged Blackbird: This bird is most common in open habitat, slightly less common in mixed and deciduous forests and nearly absent from evergreen forests; sightings are significantly correlated with increasing ground cover. Its preferred nesting habitats are cattail marshes and open swamps, but it is also common in upland bushy fields, especially in the vicinity of water.
Brown-headed Cowbird: Field studies show the Brown-headed Cowbird to be the second most evenly distributed species among the four broad habitat categories. This is consistent with the idea that this species probably does not select habitat per se but rather locates the nests of various host species in which to lay its eggs.
Eastern Wood Peewee: This is the most evenly distributed species among the four broad habitat categories but it occurs in higher densities in forested than in open habitats. They appear to frequent mature forest and open woodland, both deciduous and coniferous.
Common Grackle: The Common Grackle is most often detected in mixed woodland, and only rarely in coniferous forests.
Red-eyed Vireo: Generally, Red-eyed Vireos are found in mature woodlands with well-developed shrub layers. Red-eyed Vireos seem to make significant use of the understory both in the central and peripheral zones of deciduous woodlands.
Northern Oriole: These are most commonly detected in deciduous woodland, less commonly in mixed forest and uncommonly in the open community. They have not been observed here in evergreen forest.
Warbling Vireo: This bird is most commonly sighted in deciduous forests, about half as commonly in open habitat, infrequently in the mixed community, and not seen in the coniferous community.
Great Crested Flycatcher: Most sightings o this beautiful flycatcher occur in mixed and deciduous communities; they are most common in mature woodlands, preferring deciduous or mixed forests.
American Redstart: It appears that American Redstarts prefer woodland habitats more than do Yellow Warblers and they also tend to nest higher in the understory; often one can get quite close to these birds.
House Wren: House Wrens, found in large numbers in the park, usually nest in tree cavities, but a variety of nest sites may be used. It frequents open woodland, forest clearings deciduous thickets and shrubbery.
Black-capped Chickadee: Most often detected in deciduous forest. Black-capped Chickadee are seldom seen in the open community. Their broad habitat range includes dry and wet deciduous and mixed woodlands of various ages and extents, woodland openings and edges, woodlots and thickets.
Common Yellow-throat: Predominantly seen in open areas, YelIow-throats are usually not observed in mixed or evergreen forests. Generally, they are most common in those habitats with lots of ground cover; it is a ground-nesting species whose nests are extremely difficult to find.
COMMONLY OBSERVED BIRDS [Top]
Many people are not so enthusiastic as bird watchers, that they would rise at dawn to listen to singing woodland birds. For their benefit, below is a list of those birds most likely to occur in picnic, campground and dock areas, and along the Thousand Island Parkway and nature trails.
Species That Will Be Commonly Observed in Areas that are Frequented by Park Visitors
RARE AND THREATENED LANDBIRDS [Top]
Two landbird species that are currently protected under Ontario's Endangered Species Act formerly nested in Leeds County. One, the Peregrine Falcon, nested at two sites in the Charleston Lake area until about 1942. Except in arctic regions, the peregrine has been virtually extirpated as a nesting species in eastern North America (Peakall, 1976).
The Bald Eagle is a second endangered landbird that formerly nested in Leeds County. Its numbers have decreased alarmingly throughout southern Ontario and elsewhere; human disturbance, habitat loss and pesticides are the principal causes for the decline (Sprunt, 1969). The locations of at least six former nest sites are known in the St. Lawrence Islands National Park area; they were usually situated in large trees near water. The Bald Eagle presently occurs only as a winter visitor in the Thousand Islands region, occurring near Ivy Lea.
A number of species that are not officially endangered may in fact be threatened with extinction in the St. Lawrence Islands National Park area. Ospreys and Red-shouldered Hawks formerly nested commonly in Leeds County, but they are now scarce nesting species both in the county and in other areas. Ospreys nest in trees near water and their diet is exclusively fish. Again, the link between present population declines and toxic chemical levels is strong (Bull, 1974). Reasons for diminishing numbers of Red-shouldered Hawks have not yet been fully documented. Swampy woodlands and river bottoms are the preferred nesting habitats of this species although it also nests in dense woodlots. These natural habitats are becoming less common.
Several other landbird species are considered rare, either at a regional or local level. Some of these species are restricted to certain habitats (e.g., Pine Warbler); others are on the fringes of their normal range (e.g., Turkey, Carolina Wren, certain wood warblers, etc.).
RARE AND THREATENED WATERBIRDS [Top]
One species of waterbird that is protected under Ontario's Endangered Species Act the Piping Plover formerly nested in the St. Lawrence Islands National Park area. However, none are known to have nested since 1894. Piping Plovers may still occur along the St. Lawrence as very rare migrants during spring and fall
Fish-eating waterbirds are presently common in the St. Lawrence Islands National Park area but their populations may be threatened nonetheless. Although Great Blue Herons seem to be reproducing well, other colonial waterbirds nesting in the St. Lawrence Islands National Park area face varying degrees of reproductive failure.
Reproductive success of Herring Gulls in eastern Lake Ontario has been poor in recent years. This is thought to be due to pollution. Colonies of Common Terns here have had greater reproductive success than any other Lower Great Lakes tern colony, according to recent reports.
SELECTED REFERENCES [Top]
BELLROSE, F.C., 1976. Ducks, Geese and Swans of North America. Stackpole, Harrisburg, PA. 544 pp.
BRADSTREET, M.S.W., and J.D. McCracken, 1978. Avifaunal Survey of St. Lawrence Islands National Park. Prepared for Parks Canada by L.G.L. Limited, Environmental Research Associates. Toronto, Ontario. 343 pp.
FYFE, R.W., S.A. Temple, and T.J. Cade, 1976. The 1975 North American Peregrine Falcon Survey: Canadian Field Naturalist. 90: 228-273
GILBERTSON, M., and R. Hale,
1974. Early Embryonic Mortality in a Herring Gull Colony in Lake
Ontario. Canadian Field Naturalist. 88: 354-356.
HENNY, C.J., F.C. Schmid, E.M. Martin and L.L. Hood, 1973. Territorial Behaviour, Pesticides and the Population Ecology of Red-shouldered Hawks in Central Maryland, 1543-71. Ecology 54: 545-554.
QUILLIAM, H.P., 1973. History of the Birds of Kingston, Ont. Kingston Field Naturalist, Kingston, Ont. 209 p.
TONER, G.C., W.E. Edwards and M.W. Curtis, 1942. Birds of Leeds County, Ontario. Canadian Field Naturalist 56: 8-12, 21-24, 34-44, 50-56.
WEHKES, F. 1974. A Survey of Bald Eagle Nesting Attempts in Southern Ontario, 1969-1973. Canadian Field Naturalist. 88: 415-519.