Land Bird Habitat Association Patterns

A land bird survey in Ivvavik National Park documented 143 different bird species within the Park (Anne C. Holcroft Weerstra Biota Consultants 1997). Part of the analysis carried out by was an analysis of bird-habitat affiliation patterns for Ivvavik National Park. Vuntut National Park shares a border with Ivvavik National Park and a large portion of Vuntut National Park protects similar ecosystems. During June 1998, Parks Canada staff (Henry et al. 1998) tested how a habitat classification system (see MacHutchon 2000) and the bird habitat association patterns described by Holcroft Weerstra (1997) apply to Vuntut National Park. This work was carried out in the area of Thomas Creek and different habitats within a 12 km radius.

To sample bird populations, a standard point count methodology for forested and semi-open environments was carried out (for details see Henry et al. 2000). Point counts were carried out on each of twelve habitat types that appeared to be present in the Thomas Creek study area.

This research suggests that the bird habitat association patterns described by Holcroft Weerstra (1997) largely apply to Vuntut National Park. The point counts carried out by Holcroft Weerstra (1997) and Henry et al. (1998) document that many of the bird species found in Ivvavik and Vuntut National Parks are broad in their habitat requirements and do not specialize in any one habitat type. Birds in Vuntut National Park do associate with different clusters of habitat types, and the bird community does differ across habitat types. Deciduous forests in valley bottoms, spruce forests on mountain slopes, grassy tussocks on pediment slopes, or alpine tundra show different bird densities and support different combinations of bird species.

A summary of bird-habitat association patterns from Henry et al. (2000) is given below, starting with higher elevation, less productive types and proceeding towards lower elevation types that probably exhibit higher productivity. In the following summary, information given for each of the 12 habitat types includes: (1) a brief description of the habitat type (see MacHutchon 2000, for details); (2) the number of bird sightings recorded and estimate of the bird density of this habitat type; and (3) a summary of the bird species most closely associated with this habitat type.

Alpine Slope. Alpine slope is a habitat type that occurs on mountain tops or hill crests. It shows few or no shrubs, and exposed soil normally constitutes 10 to 90 percent of the surface of the ground. Typically low plants constitute more than 10 percent of the ground cover. In this habitat type, 21 bird species were seen. Density of birds appears low, estimated at about 1.65 birds/ha (birds per hectare). Birds that occurred most frequently and in greatest numbers in this habitat type included horned lark and American pipit. Birds seen less frequently in this habitat type included rock ptarmigan, Smith’s longspur and American golden plover.

Birch-Crowberry. This habitat type occurs on mountaintops, hill crests or on south-facing upper slopes. Birch-Crowberry shrub communities on exposed sites usually contain shrubs that are less than 0.5 m tall. Birch-Crowberry grades into Willow-Birch communities as moisture increases, or into Alpine Slope communities as environmental conditions become more severe. Bird density appears to be low, estimated at 1.27 birds/ha, with 35 different birds sighted.

Cottongrass Tussocks. This habitat type occurrs mainly on long, gentle pediment slopes dominated by tussocks. The cottongrass, Eriophorum vaginatum, dominated this wet, cold habitat type. Bird density on this habitat type appears to be fairly high, estimated to be 2.93 birds/ha, with 41 bird sightings. Savannah and white-crowned sparrows were recorded most frequently in this habitat type. American tree sparrows were also commonly observed. Redpolls, whimbrel, ptarmigan, and Smith’s longspur were repeatedly observed. Long-tailed jaegers and short-eared owls were often observed flying over this habitat type, apparently hunting.

Sedge Tussocks. Occurring on exposed pediment slopes where drier conditions persist, this habitat type is dominated by the sedge Carex lugens, which takes the place of cottongrass. Little of this habitat type was observed and no information on birds was recorded.

Graminoid Wetlands. This habitat type is characterized by wet conditions and it usually contains standing water for most of the growing season. It occurs on flat benches near water courses, areas that are not flooded during high water. A diversity of sedges dominates this habitat type, and few or no spruce trees are present. Forty-eight different birds were sighted and density was estimated to be 2.35 birds/ha, a medium density. Mew gulls, lesser yellowlegs and upland sandpipers were observed in this habitat type. Common snipe were observed performing aerial displays overhead. American tree sparrows, redpolls, and savannah sparrows were the most common passerines observed in this habitat type.

Willow-Birch. Willow-Birch is generally found at lower elevations, but occasionally occurs in sheltered sites at higher elevations. It is characterized by an abundance of shrubs usually more than 0.5 m tall. Dwarf birch, willow, and blueberry are common. This type had a total of 55 bird species and a high bird density, estimated to be 3.08 birds/ha. White-crowned sparrows, savannah sparrows, and redpolls were the most frequently observed birds in this habitat type. Fox sparrows, American tree sparrows, ptarmigan, American robin, and yellow warbler were also observed.

Willow-Horsetail. This habitat type usually occurs on moist to wet slopes where shrubs tend to grow less than 0.5 m in height. Willow-Horsetail sites are dominated by willows and are characterized by shallow permafrost, cold soils and high exposure. Density of birds in this habitat type appears to be medium, estimated to be 2.42 birds/ha with 28 different species recorded. White-crowned sparrows, American tree sparrows, redpolls, and American robins were the most frequently recorded birds in this habitat type. Other species observed include savannah sparrow and, in one instance, a willow ptarmigan female with chicks.

Willow Floodplain. Willow Floodplain sites occur on low, flat areas that are adjacent to streams and rivers. These sites lack poplar trees and are periodically flooded. They are usually dominated by willows that often grow 2 m or taller in height. With 53 bird species recorded, this habitat type exhibits the highest bird density of the 12 habitats studied, estimated at 3.47 birds/ha. White-crowned sparrows, American tree sparrows, redpolls, American robins, yellow warblers, Wilson’s warblers, and yellow-rumped warblers were frequently observed in this habitat type. Other species recorded include gray-cheeked thrush, fox sparrow, and willow ptarmigan. Spotted sandpipers, solitary sandpipers and lesser yellowlegs were observed in this habitat type in areas adjacent to Thomas Creek.

Willow Terrace. Willow Terrace occurs on flat benches near streams that are not flooded during high water. This habitat type is usually found on drier sites and often shows a well developed shrub layer. Shrubs frequently include willow, rhododendron, and soopolallie. Although 34 species were sighted, the birds recorded were usually beyond the boundaries of the point counts, with the result that the estimated bird density for this habitat type is very low, estimated to be 0.68 birds/ha. These results suggest that birds may use the boundary zone between Willow Terrace and other habitat types more frequently in comparison to the interior portions of this habitat type. Savannah sparrows, American robins and fox sparrows were frequently observed. White-crowned sparrows and redpolls were also observed in this habitat type.

Spruce-Birch. This habitat type is typically found on south-facing slopes. These sites are characterized by spruce trees and dwarf birch shrubs. Other shrubs such as willow and blueberry are frequently associated with these sites. Similar to the situation for Willow Terrace, most of the bird sightings (34 of 42 sightings) in Spruce-Birch occurred immediately beyond the boundaries of the point counts. This pattern results in a very low density for this habitat type, estimated to be 0.78 birds/ha. Birds occurring on or adjacent to this habitat type include yellow-rumped warblers and American robins, the most frequently sighted species. Other species recorded included dark-eyed juncos, ruby-crowned kinglets, gray jays, Bohemian waxwings, gray-cheeked thrushes, varied thrushes and boreal chickadees.

Spruce-Horsetail. This spruce forest typically grows on moist to wet south-facing slopes. This habitat type is common in areas adjacent to Thomas Creek. Although there were 104 bird species sighted, the habitat type shows low bird density, estimated to be 1.43 birds/ha. Birds frequently sighted in this habitat type include yellow-rumped warblers, American robins and white-crowned sparrows. Other bird species sighted on this habitat type included boreal chickadee, gray jay, gray-cheeked thrush, varied thrush, ruby-crowned kinglet and American tree sparrow.

Spruce-Rhododendron. This habitat type usually occurs on flat benches near streams and it is found on sites that are usually not flooded during high water. The habitat type exhibits a high density, estimated to be 3.01 birds/ha and featured 49 bird sightings. Yellow-rumped warblers, white-crowned sparrows, American robins and gray-cheeked thrushes were most frequently recorded in this habitat type. Other species observed were American tree sparrows, varied thrushes, ruby-crowned kinglets and fox sparrows.