Red crossbill (Percna) COSEWIC assessment and status report: chapter 7
Habitat
On the basis of their morphology and foraging requirements, Red Crossbills are extremely specialized for conifer habitats. The most important habitat requirement for Red Crossbills percna subspecies is conifer seed availability. Habitats that provide this on a large scale are mature Black Spruce and Balsam Fir (Abies balsamea) stands, and on more restricted scales across the island, Red Pine, White Pine and White Spruce (Picea glauca) stands. A key habitat feature for Red Crossbills is a mosaic of conifer seed availability across a large (near island-wide) scale, so that when conifer seed is not abundant in a specific geographic area (or type of conifer), there will be other areas (and/or species of conifer) that offer more abundant seed resources. The Red Crossbill, despite its extreme level of specialization, does not have a restricted distribution. Conifer stands are necessary habitat for foraging, roosting, and nesting percna. Foraging sites can be distant from roosting/nesting sites.
The percna subspecies is not expected to tolerate habitat disturbance well. Fragmentation of old growth conifer stands and reduced stand rotation ages can result in patterns of cone loss over large areas that would not be able to be escaped by a population that may be relatively sedentary compared to some other North American Red Crossbills. Critical habitat for Red Crossbill percna subspecies, will likely be difficult to distinguish, because these areas might not be used on an ongoing basis over successive years (Benkman 1993b), particularly by a small and possibly fragmented population. Current and on-going disturbances to the habitat of the Red Crossbill could be threatening the viability of the small remaining population.
Forest Harvesting
Habitat for Red Crossbills is becoming increasingly fragmented. Harvesting regimes have shortened rotation lengths for conifer stands in Newfoundland (Thompson et al. 1999, 2003), resulting in restricted fragments of mature stands, which have been shown to be the most productive habitat for Red Crossbills in other locations (e.g., Alaska; Holimon et al. 1998) within a matrix of younger age stands and clear-cuts. Remnants of mature forest are currently sparse in Newfoundland (see Figure 4).
Global Forest Watch Canada 2000.
Fragmented habitat negatively impacts crossbills(Helle 1985), as fragments may have lower cone production than contiguous stands. Current harvesting regimes are increasing the fragmentation of Black Spruce and Balsam Fir stands (Flight and Peters 1992). Red and White Pines exist only in tiny isolated fragments scattered about the island (Roberts 1985; Rajora et al. 1998) due to historical harvesting, other landscape changes and disease (Page et al. 1974; Whitaker et al. 1996). It is possible that Red Crossbill numbers declined as White and Red Pines declined, as has been observed in other locations (e.g. Dickerman 1987; Erskine 1992).
Insects and Fungi
Outbreaks of insects and fungi defoliate large areas of forests in Newfoundland. During the 1970s, softwood forests in Newfoundland had extensive outbreaks of Spruce Budworm (Choristoneura fumiferana). Cone production can be significantly reduced by even slight defoliation by budworms. During the past several decades, Spruce Budworm and Hemlock Looper (Lambdina fiscellaria fiscellaria) have defoliated millions of hectares of Newfoundland forests (see references in Carroll 1996). Since 1967, Hemlock Looper has been estimated to have killed approximately 14 000 km2 of Balsam Fir, and Spruce Budworm has been estimated to kill approximately 5 250 km2 of Balsam Fir and about 750 km2 of Black Spruce (Carroll 1996). Pines are also threatened from outbreaks such as those caused by fungi. White Pine Blister Rust (Cronartium ribicola) devastated the small number of surviving White Pine trees and is still preventing regeneration. Red Pines are currently threatened by Scleroderris canker (Gremmeniella abietina; Whitaker et al. 1996). Tree loss from insect and fungi damage is higher than loss from harvesting and is an order of magnitude higher than loss from fires.
Forest Fire
Fire has had a major cumulative influence in changing and shaping forest composition on insular Newfoundland, particularly in the central and eastern sections of the island. Soon after European incursion in the early 17th century, fishers used fire to clear large tracts of land along the coasts. These uncontrolled fires removed many tens of thousands of km2 of boreal coniferous forest, much of which has never regenerated and remains as bog and barrens habitat today (Wilton and Evans 1974; Damman 1983). During the 20th century, extensive fires were often started by cinders from locomotive engines (Wilton and Evans 1974; Montevecchi and Tuck 1987). In 1960 - 1961, fire destroyed 4165 km2 in central and eastern Newfoundland (Hayward et al. 1960, 1961), eliminating cone sources over these areas. This fire, as well as others around the turn of the 20th century, and in 1946, 1977, and 1979, contributed to the decline of Red Pines across the island (Roberts 1985). Fire promotes the regeneration of Black Spruce, which tends to predominate in central and eastern coniferous forests, but not in western Newfoundland where precipitation is greater, forest fire is less frequent and extensive and where harvested Black Spruce forests tend to be replaced by Balsam Fir (Damman 1983). Recent fire suppression activities likely tend to inhibit the regeneration and spread of Black Spruce. A controlled burn in Terra Nova National Park in 2002 was designed to help simulate a natural ecosystem process.
Ninety-nine percent of the forest resource of Newfoundland and Labrador is owned provincially. On insular Newfoundland, however, the timber and property rights for 69% of the Crown land has been granted to forestry companies under 99 year licences that were issued in 1905 and 1935 (Natural Resources Canada 2002). The primary forestry companies that hold these licences are Abitibi Consolidated Inc., which manages approximately 18 000 km2 of forests, and Corner Brook Pulp and Paper Ltd. (a division of Kruger Inc.), which manages 20 620 km2 of forests. The percentage of provincially and federally protected land is 7.8% of the land and freshwater area of insular Newfoundland. Some potentially important habitat for Red Crossbills could be secured and protected in the Little Grand Lake Provisional Ecological Reserve in western Newfoundland that is currently under consideration by the government of Newfoundland and Labrador for permanent status.
Page details
- Date modified: