Conservation and Management

Effects Of Human Activity

Collisions

Like other nocturnal migrants, White-throated Sparrows are killed by impact with tall structures such as towers, lighthouses, and lighted buildings. The Field Museum of Natural History collected 335 White-throats that died from hitting McCormack Place Building in Chicago from 1980 to 1992 in spring and fall migration. This is a major problem in cities. In Toronto volunteers from the Fatal Light Awareness Program (FLAP) patrol the downtown core; although unable to cover the area adequately, they collected 3176 dead and injured birds in 2007 alone, of which 455 were White-throated Sparrows. Most White-throats are found at night or early morning at the ground floor of lighted buildings, having fluttered down from above or directly struck the lower windows. Deaths are usually caused by head trauma. The White-throated Sparrow is among the top 3 of 164 species taken in Toronto window/building kills, and has a similar rank in other major cities (M. Mesure, pers. comm.).

Research Activity

Experimental handling of free living birds has little effect on survival rate. Muscle biopsy of wintering birds has no effect on condition or return rate, and biopsied birds show less weight loss than controls (Westneat 1986). Similar results for laparotomy on wintering birds. Laparotomized birds differ from controls only in their tendency to remain as winter residents (Piper and Wiley 1991).

White-throated Sparrows exposed to microwaves exhibit gaping, panting, crouching, and loss of muscular coordination at sublethal power levels; microwave exposure correlates with changes of dominance relative to birds of higher rank (Wasserman et al. 1984).

Prone to nest desertion if disturbed during nest-building or egg-laying. Repeated handling of nestlings causes premature fledging; such young are extremely vulnerable to predators and hypothermia. Birds that have been captured become wary of humans, are easily alarmed by presence of humans near nest, and are less responsive to song playback (JGK, JBF).

Pesticides

No effect of DDT on adult life expectancy, based on birds banded prior to 1946 (pre-DDT) and since 1949 (DDT era) (Franks 1973). Further life-expectancy in both groups estimated at 1.1 yr for individuals successfully reaching Jan 1 after hatch year. DDT in diet delays onset of premigratory fattening and nocturnal restlessness. Prolonged exposure leads to increased nocturnal restlessness correlated with body concentration of DDE (DDT metabolite) (Mahoney 1972). Premigratory fattening inhibits accumulation of DDT and its metabolites in brain (Mahoney 1974); birds treated with a high dosage of DDT experienced a decrease of DDT residues in brain. Kendeigh (1947) found little effect of aerial spraying of DDT in a spruce budworm outbreak in Ontario.

Aerial spraying of Fenitrothion over clear-cuts (used to control forest insects) causes significant reduction of brain cholinesterase activity, which provides a measure of spray impact (Busby et al. 1983a). Repeat spraying after 8 d leads to chronic cholinesterase activity reduction from exposure to Fenitrothion metabolites. Reproductive success also affected by spraying; normal incubation disrupted, clutch desertion increased, and fledging success reduced (Busby et al. 1990). Spraying reduces adult populations, primarily through mortality and territory abandonment. Aerial spraying of both Fenitrothion and Aminocarb over closed-canopy forests has less impact on White-throated Sparrows than on other forest species (Busby et al. 1987, Busby et al. 1983b), owing to tendency of White-throated Sparrows to occupy lower strata. LC50 (median lethal concentration) of Fenitrothion fed to captives for 5 d is 49.8 ppm (Forsyth and Martin 1993). Inhibition of brain cholinesterase activity in birds that die ranges from 57.2 to 81.3%. Song rates during exposure decline because of early death of dominant individuals; song rate may not be an accurate method of assessing effects of spraying on wild populations. Hopping and chasing are significantly reduced because of exposure. MacKinnon (1989) reported a 55 % drop in numbers in the second year following treatment of regenerating forest clearcuts in Nova Scotia with the herbicide 2,4,5-T.

Dietary exposure of White-throats to the organophosphorus pesticide acephate depressed cholinesterase acrtivity in three brain regions (basal ganglia, hippocampus, hypothalamus) important to migratory behavior. Exposure of migratory adults prevented them from establishing a preferred orientation, perhaps by affecting memory of the migratory route. Treated juveniles did display a seasonally correct orientation. Results imply adverse effects to wild birds exposed to low pesticide levels (Vyas et al. 1995, 1996).

Blood tests showed that White-throated Sparrows ingested significant amounts of lead from spent shot at a trap and skeet range (Vyas et al. 2000).

Habitat Alteration

Prefers forest edge habitat and may benefit from some forestry practises, as long as some conifers remain standing (Clark et al. 1983). Has declined with extensive removal of forest for agriculture or closure of forest by regeneration (JBF).

Management

No efforts made to manage species directly. Efforts to manage other species and forestry practices may indirectly affect White-throated Sparrow. To minimize collisions with buildings, FLAP and other organizations promote a lights-out policy for tall buildings, as well as deterrents or coverings for windows.