Figure 309. Indigo Buntings have been colonizing California for the past half-century but still occur mainly as rare spring and fall transients. This scruffy migrant, a first-spring male, was photographed during May 1984 at Corn Spring in Riverside County (Herbert Clarke).

 

 

 

 

 

INDIGO BUNTING Passerina cyanea (Linnaeus, 1766)

Accepted: 16 (94%)	Treated in Appendix H: no
Not accepted: 1	CBRC review: 1972 records1
Not submitted/reviewed: 1	Large color image: see Figure

This bunting’s northern breeding limit extends from eastern Saskatchewan east to Maine. The southern limit stretches from central Texas east to Florida and from the central Great Plains region southwest—locally and irregularly—to southern Arizona and very rarely to southern California. The species breeds rarely in southern British Columbia, sometimes paired with the Lazuli Bunting, and mixed pairs have also been recorded in Oregon and California. The species winters in Bermuda and the northern West Indies and from central Mexico south to Panama and northwestern Colombia; rarely north to southern Texas, the Gulf coast, and Florida; and casually elsewhere within the breeding range, including along the Pacific coast. Vagrants are regularly found in the Maritime Provinces but occur only casually or accidentally in northern Alaska, the Northwest Territories, northern Manitoba, southern James Bay, Newfoundland, Iceland, and on the Islas Revillagigedo. Several European records may represent escapees (e.g., AOU 1998), but a small number from Ireland and the United Kingdom are regarded as acceptable (e.g., BOU 1999), and a vagrant was found on the Azores (Alfrey 2006).

California’s first Indigo Bunting, a first-spring male collected on 11 April 1908 at Mecca in Riverside County, was properly identified in due time (Thompson 1964, MVZ 811). The species has been doggedly pioneering westward since at least the 1940s, competing with Lazuli Buntings on their breeding grounds and often pairing with them. Rowe and Cooper (1997) concurred with Johnson (1994), who concluded that “humans have played no obvious role” in this expansion. Grinnell and Miller (1944) considered the species’ occurrence in California to be unverified, but by 1956 the state had its first nesting attempt, involving a male Indigo Bunting and a female Lazuli in Soledad Canyon, Los Angeles County (Bleitz 1958). Their nest held two infertile eggs plus the egg of yet a third species, the Brown-headed Cowbird, and the pair abandoned it. A territorial male Indigo collected at the same location on 10 June 1957 (LACM 29045) was found by Sibley and Short (1959) to show “possible effects of hybridization in the lightness of the rump color and in the length . . . of the wing.” Kroodsma (1975) later clarified that head and rump color are relatively variable in these species and further cautioned that the Indigo’s “adult winter plumage includes white abdominal feathers, and frequently not all of these are molted until late summer.” Concerns raised by Sibley and Short regarding the potential prevalence of Indigo × Lazuli hybrids in the zone of overlap were defused, to some degree, by Emlen et al. (1975) and Kroodsma (1975), who found only limited hybridization between these species in the Great Plains zone of overlap. The CBRC had little time to ponder such complications, once a flood of 16 accepted records in 1972 alone effected the Indigo’s prompt removal from the review list.

The Indigo Bunting occurs in California primarily as a rare, regular, and widespread spring and fall migrant. Because of the species’ increasing incidence in summer (see below), timing of migration is perhaps best examined in areas where many migrants occur but few birds oversummer. From 1966 to 1998, Southeast Farallon Island hosted 141 migrant Indigo Buntings: 93 in spring (7 May–14 July) and 48 in fall (18 July–13 December), a ratio of nearly 2:1 (Richardson et al. 2003). On San Clemente Island, Sullivan and Kershner (2005) reported 15 in spring (28 April–30 June) and eight in fall (16 September–13 October), a comparable ratio. Inland, at the oases of eastern Kern County, records average about five or six per spring (mostly mid May to mid June) and about one or two per fall (7 September–1 November; M. T. Heindel unpubl. data, May 2000).

Most parts of California now claim nesting records, although such behavior is most regular and widespread along riparian corridors in the interior of southern California. In the Kern River Valley of northeastern Kern County, Rowe and Cooper (1997) considered the species “an uncommon but regular summer resident, with as many as 20 singing males on territory between early May and mid-August.” Unitt (2004) reported numerous breeding records from San Diego County’s “inland valleys to the desert edge” but none from the coastal lowlands or desert floor. Rosenberg et al. (1991) regarded the species as an uncommon but local summer resident in the lower Colorado River Valley, but surprisingly the Arizona Breeding Bird Atlas project yielded no probable or confirmed nesting along the Arizona side of the river during field work that took place primarily between 1993 and 2000 (Corman and Wise-Gervais 2005). Even as the state’s incipient breeding population expands and grows, the number of “pure” Indigo Buntings in California remains so small compared with the widespread Lazulis that most pairings continue to be mixed.

Indigo Buntings occur casually in winter along the length of the coast, becoming more prevalent than Lazulis by late October or early November. A first-year male banded on Southeast Farallon Island on 13 December 1985 turned up on 21 December at Inverness on the nearby Marin County coast and was last seen on 15 April 1986 (AB 40:328, 521). In the interior, winter males have twice been recorded in Brawley, Imperial County: 18 March 1978 and 19–20 January 1991 (Patten et al. 2003).

¹On the review list 1972–1973