Centronyx bairdii

ADULT: The sexes are similar; length is 5.3 - 5.6 in (13.5 - 14.2 cm). The top of the head and nape are a rich, strong brownish-yellow, striped with black, especially on the sides of the crown and nape. The sides of the head and neck are pale buff and flecked with black with a narrow line of black spots on side of throat. The back feathers are dull black centrally, margined with grayish-white, producing a streaked appearance. The rump is lighter, more buffy. Underparts are white or pale buff on the throat and breast, streaked on the sides, flanks and across the breast with black. The streaks on the breast are sharply defined and form a necklace, those on sides are more diffuse and tinged with rufous. Wing length is 2.75 - 3.0 in (7.0 - 7.6 cm), wing feathers are grayish-brown, coverts are darker centrally, all are edged with pale rufous. There are two not very distinct light wing bars. Tail length is 2.1 - 2.3 in (5.3 - 5.8 cm). It is dull brown or blackish. The middle pair of tail feathers is much narrower and more pointed than the others, outer feathers are narrowly edged with white and dull white terminally; other tail feathers are narrowly tipped with dull white or buffy. The bill is light flesh color, darker at tip; legs are flesh color; feet are darker; the irises are brown. In Alberta, the average weight was 17.8 g for females and 18.9 g for males (Maher 1979).

JUVENILE: The juvenile resembles the adult but markings are more diffuse and the buff of the head and nape is paler (Roberts 1949).

VOCALIZATION: Song consists of two, three, or more "zips" followed by a trill on a lower pitch.

NESTS: The three types of nests are all located on the ground (Cartwright et al. 1937). The first type consists a tuft of grass held up by a shrub. The tuft is hollowed out with a bottom layer of grass, and the sides of up to five in. (12.7 cm) tall are woven with grass. A second type of nest is located underneath an overhanging tuft of grass, with a small opening located on the side. The most common type of nest is built in a depression in the ground with no overhead concealment. All nests are made of woven dead grass and lined with finer grass, hair and moss. The average dimensions for 11 Manitoba nests were 2.5 in (6.3 cm) in diameter and 1.5 in (3.8 cm) deep (Cartwright et al. 1937).

EGGS: The eggs are white and ringed with reddish-brown spots or blotches. The eggs are difficult to distinguish from Savannah sparrow (PASSERCULUS SANDWICHENSIS) and vesper sparrow (POOECETES GRAMINEUS) eggs. The average size is 19.4 x 14.6 mm (Lane 1968).

Field marks include a broad, ochre median crown strip, a narrow band of fine black streaks across the breast, and outer tail feathers that often look white, especially in flight (Godfrey 1966, Peterson 1980).

Nesting habitat includes ungrazed or lightly grazed mixed-grass prairie, prairie with scattered low bushes and matted vegetation (AOU 1983), local pockets of tallgrass prairie, wet meadows, and some types of disturbed habitats. This species most often occurs in tracts of native, mixed-grass prairie that is ungrazed or lightly grazed; it may use wet meadows and tallgrass prairie in dry years. It makes limited use of tamegrass and weedy grain fields (Goossen et al. 1993) but may or may not maintain populations in these altered habitats. Studies in Saskatchewan found equally high frequency of occurrence in native grassland and seeded pasture, slightly lower frequency in hayland, and considerably lower frequency in cropland (Davis et al. 1996). Baird's sparrow was found more frequently (65%) and at higher density in crested wheatgrass than in native (53%) pastures in Sasketchewan (Davis et al. 1996). Relatively dense residual grass may be needed (Sousa and McDonal 1983). Nests are on the ground in dry areas in tangled grass, sometimes under low shrubs (Terres 1980).

In mixed-grass prairies, Baird's sparrow is associated with: blue grama (Bouteloua gracilis), western wheatgrass (Agropyron smithii), little bluestem (Andropogon scoparius), prairie junegrass (Koeleria cristata), needle and thread (Stipa comata), and needleleaf sedge (Carex eleocharis). In wet meadows and tallgrass prairie, some of the associated plants include: northern reedgrass (Calamagrostis inexpansa), prairie cordgrass (Spartina pectinata), switchgrass (Panicum virgatum), big bluestem (Andropogon gerardii), baltic rush (Juncus balticus), and woolly sedge (Carex lanuginosa; Stewart 1975). The birds seem to prefer dense vegetation of medium to tall height (Kantrud and Kologiski 1982; Dryer, pers. comm.).

The breeding range and preferred habitat may shift from year to year, depending on whether the breeding season is wet or dry (Kantrud and Faanes 1979, Kantrud and Kologiski 1982). In dry years or in drier portions of the range, breeding occurs in grassy slough bottoms, alkali flats and depressions in low lying grasslands (Salt and Wilk 1958, Kantrud and Kologiski 1982). At Sheyenne Lake, North Dakota in 1980 (a very dry year), the density in wet meadows was 55% greater than in upland mixed-grass native prairie, the normal breeding habitat in this area (Faanes 1982). In North Dakota,these birds are often associated with saline or freshwater habitats (Dryer, pers. comm.), such as temporarily flooded emergent vegetation at Chase Lake National Wildlife Refuge and dense brome grass adjacent to saline lakes at Palermo Wetlands, Grenora Wetlands, and North Lake.

It was previously believed that Baird's sparrow would not nest in any type of disturbed or cultivated habitats (Cartwright et al. 1937). In Alberta, Owens and Myres (1973) found breeding only in undisturbed grasslands. Dryer (pers. comm.) and Kantrud and Kologiski (1983) reported that it may be found in disturbance habitats such as alfalfa, brome and wheatgrass hayfields, weedy stubble fields and tracts of retired croplands. It has been located in wheat fields in Manitoba and Saskatchewan (Lane 1968). Both Dryer (pers. comm.) and Berkey (pers. comm.) noted that it is found in alfalfa fields in North Dakota, although haying in early July probably destroys most of the nests. It is also found in dry wetland basins (Goosen, pers. comm.). The greatest densities typically occur in idle or lightly grazed native prairie (De Smet and Miller 1989).

Some bunches of dead grass and litter may be necessary as a nesting substrate (Kantrud and Kologiski 1982; Berkey, pers. comm.). In North Dakota, dense heavy litter accumulation is not preferred habitat (Smith, pers. comm.). A critical component of optimal breeding habitat is a lush understory of vegetation (De Smet and Miller 1989). This species usually is not associated with a high density of shrubs (Cartwright et al. 1937; Berkey, pers. comm.). Sousa and McDonald (1983) include details of habitat requirements.

Nonbreeding habitat includes open grasslands and overgrown fields (AOU 1983). In Arizona, it includes dense stands of grass, usually in extensive expanses of grasslands. The birds seem to prefer areas of taller, denser grass. They can also be found on south-facing slopes of mixed-oak grassland where the oaks are on the north slope.

Breeding density can range from 0.13 pairs/hectare (Stewart and Kantrud 1972) to 0.41 pairs/ha (Johnson 1974); density in Saskatchewan was up to 0.27 pairs/hectare (Pylypec 1991). Breeding pairs favor larger patches of remaining grassland to smaller ones (McMaster and Davis 1998, as cited by Johnson and Igl 2000; Johnson and Igl 2001).

In North Dakota, mammalian predators probably include: white-footed deermouse (Peromyscus leucopus), thirteen-lined ground squirrel (Spermophilus tridecemlineatus), short-tailed weasel (Mustela erminea), long-tailed weasel (M. frenata), least weasel (M. rixosa), striped skunk (Mephitis mephitis), and coyote (Canis latrans; Lane 1968). The remains of a Baird's sparrow was found by the nest of a northern harrier (Circus cyaneus) and in the stomach contents of a merlin (Falco columbarius; Lane 1968).

This species does not form winter flocks.

Baird's sparrow is very rarely parasitized by brown-headed cowbird (Molothrus ater). In Manitoba, 2 of 13 nests were parasitized (De Smet and Miller 1989). The effect of brood parasitism on nesting success is not known.

This species tends to nest in semicolonial groups of a few pairs. The breeding season extends from late May through mid-August in North Dakota, with the peak in early June through late July (Stewart 1975). Males arrive on the breeding grounds first and immediately set up their territories; females arrive three to seven days later. Eggs are laid mostly in June-July. Normally, four or five eggs are laid, although three- and six-egg clutches are possible (Lane 1968). Incubation, by the female, lasts 11-12 days. The female does all brooding and for the first two to four days does all feeding of the nestlings. The young are well-feathered when they leave the nest but are not able to fly and are fed almost exclusively by the male. Young leave the nest at 8-10 days, hide in grass, first fly at 13 days, and begin to leave parents' territory at 19 days. Two broods are often raised. The length of the interval between nests depends on whether or not the pair stays together for both nests. Cartwright et al. (1937) found three double-brooded females: two retained the same mate for both nests and one female switched mates. The females that retained their first mates began laying the second clutch one day after the first brood left the nest; the female that switched mates began laying the second clutch eight days after the first brood left.

Nests are difficult to locate (Cartwright et al. 1937, Lane 1968). Females do not flush from the nest until they are almost stepped on, and in one instance, a female did not flush even when a rope was dragged over her (Cartwright et al. 1937).

Cartwright et al. (1937) reported that 15% (6/40) of the nestlings on his study area did not live to leave the nest. The major predators were probably small mammals and birds (Cartwright et al. 1937).