occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) BREEDING: se Manitoba east to Maritime provinces and south to eastern Texas, central Louisiana, and western North Carolina and Virginia. Isolated populations in western and northeastern Lower Peninsula of Michigan, southern Ontario, and south-central Pennsylvania. Extirpated from New England and Maritime provinces (AOU 1957, 1983, Yosef 1996). Recent data indicate that populations in Maryland and Virginia are subspecies LUDOVICIANUS (see Bartgis 1992). NON-BREEDING: southern half of breeding range south to northeastern Mexico, Gulf Coast, and Florida.

Length: 23 cm

Weight: 47 grams

Differs from subspecies LUDOVICIANUS of the southeastern U.S. in that the gray of the upperparts averages slightly paler and the underparts less purely white; also, the bill is much smaller and the tail is decidedly shorter than the wing (rather than the reverse) (Ridgway 1904).

Comments: See files for L. LUDOVICIANUS.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

See files for L. LUDOVICIANUS.

Comments: See files for L. LUDOVICIANUS.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: Number of occurrences has not been determined.

1000 - 10,000 individuals

See files for L. LUDOVICIANUS.

See files for L. LUDOVICIANUS.

Canada

Rounded National Status Rank: NNR - Unranked

United States

Rounded National Status Rank: N3B,N3N : N3B: Vulnerable - Breeding, N3N: Vulnerable - Nonbreeding

Rounded Global Status Rank: T3 - Vulnerable

Reasons: Spotty distribution and precipitous declines throughout range.

Other Considerations: In extreme south of winter range, MIGRANS may overlap temporally with LUDOVICIANUS breeding season in February/March; perhaps should not be tracked separately from LUDOVICIANUS because of difficulty in differentiation.

Global Short Term Trend: Decline of 50-70%

Comments: Difficult to compare historical and current distribution given the changes in effort to locate shrikes. Was abundant but population decline noted in midwest prairie populations since late 1940s and in New England by 1960s. Population decline affected this subspecies most, especially from Virginia to Florida (Yosef 1996). North American Breeding Bird Survey (BBS) shows current decrease 3.5 - 5 percent per year across range. Only Colorado, Montana, North and South Dakota, Louisiana, and Texas had stable or increasing populations (Peterjohn and Sauer 1995, cited in Yosef 1996). Christmas Bird Count (CBC) shows similar trends. Largest declines in North Carolina, Maryland, Virginia, and South Carolina (Yosef 1996).

Degree of Threat: B : Moderately threatened throughout its range, communities provide natural resources that when exploited alter the composition and structure of the community over the long-term, but are apparently recoverable

Comments: HABITAT: Forest clearing in central and eastern North America may have allowed range increase before 20th century. Conversion from small farm fields to large crop fields, and farms to woodlands or suburbs later in the 20th century, however, reduced available habitat. Removal of hedgerows, shrubs and trees and the draining of potholes and sloughs have reduced available habitat in the prairies. Slow population decline in Quebec from 1940's to 1970's associated with loss of pastureland (Yosef 1996). In Illinois, slow decline from 1900 to 1950 attributed to loss of habitat (Graber et al. 1973, cited in Yosef 1996). In New York, total land area in farms declined from 9.16 million hectares in 1900 to 3.72 hectares in 1982; area in hay crops and pasture also declined. PESTICIDES: Role of contaminants remains unclear; concentrations required to reduce populations are unknown. Pesticides, however, may have been an important factor in the decline; population decline coincides with the use of organochlorines. May be responsible for slowing the development of young shrikes, for reducing eggshell thickness, and for reducing the size of clutches and broods. Despite ban of these chemicals, populations continue to decline. The effects of new pesticides have not been identified. PARASITISM: Nest parasitism by brown-headed cowbird (Molothrus ater) has been reported in Iowa (DeGeus and Best 1991, cited in Yosef 1996) but appears uncommon. PREDATION: Most carnivores, including feral cats and raptors are predators (Yosef 1996). Low nest success is associated with roadside habitat that is attractive to predators and favored by shrikes. COMPETTITION: Potential competitors with other species that are better adapted to human-induced habitat changes include: American kestrel (Falco sparverius), European starling (Sturnus vulgaris), and red fire-ant (SOLENIPSIS INVICTA; Yosef 1996). COLLISION: Fledgling, juvenile, and adult mortality caused by collisions. In Virginia, 29 percent of observed fall and winter mortality due to collisions with automobiles, second only to predation. Increase in vehicular traffic since 1940 may have contributed to major population decline (Flickinger 1995, cited by Yosef.

Biological Research Needs: Further research using banding and radiotelemetry necessary to determine limiting factors for populations esp. during winter (sources of mortality and relative importance of habitat loss or fragmentation); determine degree of winter range overlap with LUDOVICIANUS.

Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: Species was proposed as a candidate (Category 2) under review for possible federal listing (USFWS 1991, cited in Yosef 1996). This subspecies was designated threatened in 1986 and uplisted to endangered in 1991. The subspecies is classified as Endangered by Committee on the Status of Endangered Wildlife in Canada.

Needs: Protect and maintain large pastureland in heavy rotational grazing; decrease use of pesticides; maintain hedgerows in farm and pasture lands.

Comments: There is a relatively broad zone of intergradation between subspecies MIGRANS and LUDOVICIANUS (Miller 1931).