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Field Sparrow (Spizella pusilla)
Nidiologicals-Peck and James (1987) and M.Carey et.al. (1994)
Habitat=field, pastures and second growth forest edges and clearings
Microhabitat=nest built on or near ground; elevated in shrubs and tress later in breeding season.
Average nest height=.2 to .5m
Nest building period=5-8 days in early part of season: 2-3 days in later part
Average # of broods/season= multiple (average of 2.9 in PA study).
Average Egg Date=26 May-21 June
Average clutch size=3-5
Incubation period=average 11-12 days
Egg colour=white or cream colour, heavily spotted on entire surface with denser markings at larger end
Fledgling stage=young leave nest 7-8 days after hatching
Parasitized by cowbirds=yes
The Field Sparrow, a close relative of the Chipping Sparrow (Spizella passerina), remains a common inhabitant of fields and various forms of scrub habitat in the eastern half of the United States, southern Ontario and Quebec. Rare north of the Southern Shield, the Field Sparrow has withdrawn from many areas in southern Ontario due to intensification of agricultural practices as well as the spread and maturation of forest cover in recent decades. They require open areas of dense low ground cover with some woody vegetation for nest support and song perches. It is likely that this species’ population reached its zenith in the 19th century when a low percentage of forest cover and low-intensity agriculture provided great expanses of suitable habitat. Here on the Frontenac Arch, the species remains abundant in rock barren habitats with its shallow till as well as abandoned farms. Forest fires would provide appropriate conditions for this species if not for current forest fire suppression practices.
The nest pictured above was discovered on a recent trip to one of our MAPS sites on crown land in the northern section of the FBS study area. Apart from farm fields, Field Sparrows are ubiquitously found in rock outcrops and in areas burned over in the mid-20th century. Eastern Towhee also occupy these areas and the two are almost always heard singing close together. This nest was actually the second Field Sparrow located at the site, the first of which failed for unknown reasons in early June. In both cases the nest was found elevated in a shrub, although this more recent example is considerably higher than the first, a typical response of the species to the increased growth of vegetation in late summer. The nest itself is similar to the nests of Chipping Sparrow, which are almost entirely constructed with grasses. One difference between the two is that Field Sparrows tend to use a lesser variety of grass types and less animal hair in the nest lining.
The nest is located in a main fork within the crown of an as yet unidentified shrub/sapling. This plant would not not have been suitable for nesting in late spring/early summer as it would would have been exposed to predators in the absence of developed vegetation around it that has now provided dense cover.
This shot of the nest site taken further back shows its position relative to our access trail. The habitat would be best described as a grassy clearing between dense deciduous forest and a large peat bog. To name a few, Yellow-throated Vireo, Scarlet Tanager and Yellow-billed Cuckoo sang from the forest edge throughout the summer, Swamp Sparrow, Common Yellowthroat and Wilson’s Snipe occupied the bog, while Eastern Towhee shared the sunny gap with Field and Song Sparrows.
Fledgling and juvenile Field Sparrows have been encountered throughout the summer period across the study area. This area, with its countless rock outcrops and old fields, has been and continues to be an important region for Field Sparrows in Ontario. The retreat of the glaciers left extensive areas of bare rock and/or shallow vegetation resistant soils, providing open areas for Field Sparrows to prosper. It is plausible however that the suppression of fires, natural succession of fields and conversion to intensive agricultural methods will continue to reduce their numbers in Ontario and beyond.