Range Expansion of the Bronzed Cowbird with the First Missouri Record

Arizona. The Bronzed Cowbird was first observed in Arizona in 1909 (Phillips et al. 1964) and breeding populations of the species apparently became established throughout much of southern Arizona during the next 45 years. In 1957, the A.O.U. Check-list indicated that the winter range extended "north, rarely to southern Arizona (Tucson)" (p. 542). Bronzed Cowbirds were not reported west of Wickenburg (Maricopa Co.) until 1951 when Monson (1954) found them along the Colorado River near Parker (Yuma Co.). By the mid-1960's, they were regular but uncommon winter residents of southern Arizona (Johnson and Roer 1968). The species now commonly breeds throughout southern and central Arizona (M. Robbins, pers. observ.), but is still an uncommon summer resident along the Colorado River (J. Dunn, pers. comm.). Wanderers have also recently appeared in Prescott (Yavapai Co.), Carrizo (Navajo Co.), and Clifton (Greenlee Co.) (Witzemann et al. 1976). New Mexico. Phillips et al. (1964) indicated that Bronzed Cowbirds first appeared in New Mexico, in Guadalupe Canyon (Hidalgo Co.), during July 1947. The species was breeding there on 21 June 1968 (Niles 1970). It was primarily confined to the extreme southwestern corner of the state until the early 1960's, when it was detected in the Gila River Valley near Redrock (Grant Co.) on 6 June 1962. By 1968, it had reached the Cliff area (Grant Co.) and was subsequently found breeding just north of there (Hubbard 1971). The species was observed in the San Francisco Valley near Pleasanton (Catron Co.) on 10 June 1975 (Witzemann et al. 1975); in central New Mexico at the Bosque National Wildlife Refuge (Socorro Co.) on 6 June 1973 (Parker 1973); and again in the Socorro area during May 1977 (Witzemann et al. 1977). At present, its range continues to expand slowly northward in the state. California. The first report of the Bronzed Cowbird in California was of a male at Whipple Point above Parker Dam (San Bernardino Co.) on 29 May 1951 (Monson 1951). Monson (1958) obtained the first specimen near Bard (Imperial Co.) on 12 May 1955. Cardiff (1961) collected a second specimen, a female, about 110 km farther west, at Westmoreland (Imperial Co.) on 22 April 1956. Cowbirds were reported at Brock Ranch (Imperial Co.) on 10 May 1968 and at Mecca in the desert north of the Salton Sea (Riverside Co.) on 13 July 1968. A pair lived near Jacumba (extreme southwestern San Diego Co.) between 1973 and 1976, but their breeding status is uncertain; however, a juvenile was seen there on 13 July 1974 (J. Dunn, pers. comm.). Strays were seen as far west as Whittier (Los Angeles Co.) on 12 June 1963 and 9 April 1964 (J. Dunn, pers. comm.); and as far north as Kelso (San Bernardino Co.) on 25 May 1977 (McCaskie 1977). McCaskie et al. (1966) provided the first evidence that Bronzed Cowbirds were breeding in California when they saw a pair copulate near Laguna Dam (Imperial Co.) on 2 June 1962. Currently, the species is an uncommon summer resident along the Colorado River, primarily in park-like settings (J. Dunn, pers. comm.). Texas. In the early 1900's, the Bronzed Cowbird was restricted to the lower Rio Grande Valley. Its range incr ased significantly in southern Texas after the Great Freeze of 1951, when most of the remaining forest was cleared for agriculture (Oberholser 1974). The earliest record of its presence in the Big Bend area (Brewster Co.) dates 9 June 1969 (Easterla and Wauer 1972). In July 1970, at least two young cowbirds were in the company of Hooded (Icterus cucullatus) and Orchard orioles (I. spurius) at this same locality (Snider 1970). The species also appeared in the Davis Mountains (Jeff Davis Co.) of West Texas during the summer of 1969 (Easterla and Wauer 1972), and large numbers were there during the summer of 1973 (Parker 1973). By 1972, the species was breeding as far north as San Angelo (Tom Green Co.; Williams 1972). Wintering individuals occasionally appear as far north as Brazos Co. and east to Houston (Texas Ornithol. Soc. 1974). There is also a probable record for Fort Worth (Tarrant Co.; K. Arnold, pers. comm.). Louisiana. R. B. and M. A. Moore et al. observed six Bronzed Cowbirds at Little Cheniere (Cameron Parish), Louisiana on 31 December 1961. The first specimen collected in Louisiana was obtained on 14 March 1964 just west of Port Allen (West Baton Rouge Par.; Lowery 1974); this specimen is in the State University Museum of Zoology (LSUMZ 33861). All subsequent records have been confined to the extreme southern parishes. An additional specimen of unknown sex (LSUMZ 94224) was taken at Belle Chasse (Plaquemines Par.) on 11 August 1978. Although this species may have bred in New Orleans as early as 1974, positive evidence of this was not obtained until 1976 (Stewart 1976). The number of breeding individuals in the New Orleans area has increased steadily since then (N. Newfield and others, pers. comm.). Florida. The first record was of three birds in Sarasota (Sarasota Co.) on 15-21 April 1962 (Paulson and Stevenson 1962). Matteson (1970) subsequently collected a male on 8 November 1968 at Lake Alice (Alachua Co.) in northern Florida. Additional specimens were seen or obtained in southeastern Florida (Alachua Co.) on 18 November 1971 (Robertson 1972) and at Boynton Beach (Palm Co.) on 7 and 11 November 1976 (Edscorn 1977). An "invasion" of cowbirds followed in south Florida during the winter of 1977-78, where as many as ten may have been present (Stevenson 1978); three wintered near St. Petersburg (Pinellas Co.) during 1978-79 (Stevenson 1979). To date there is no evidence of breeding in the state. Mississippi. Bronzed Cowbirds were first noted in Mississippi on 6 January 1979 at Pascagoula River Flats (Jackson Co.). In March, more than 15 were seen in huge flocks of blackbirds (Hamilton 1979). Missouri. Berlin Heck first reported the presence of a Bronzed Cowbird in Missouri on 5 January 1979 at a bird feeder in the Squaw Creek National Wildlife Refuge (Holt Co.). We and others (Tim Barksdale, Leo