First Records for the Boreal Owl in New Mexico

Abstract

In North America the Boreal Owl (Aegoliusfunereus) was long believed to breed only in Canada and Alaska (AOU 1957). A juvenile of this species collected in August 1963 in north-central Colorado (Baldwin and Koplin 1966) was the first indication that the species might breed much farther south, particularly in the Rocky Mountain chain. Increased efforts by biologists and birdwatchers led to the discovery of nests in Minnesota (Eckert and Savaloja 1979), Idaho (Hayward and Garton 1983), and Colorado (Palmer and Ryder 1984). Fledged young have been seen in Washington (Batey et al. 1980) and Montana (Rogers 1973). Spring records of singing males indicate that breeding populations are widespread in Idaho, Montana (Hayward et al. 1987a), and Colorado (Ryder et al. 1987). The accumulation of breeding season records in recent years is more likely the result of greater human penetration of Boreal Owl habitat during the peak singing period, generally March through early May, rather than an increase in owl numbers or a range expansion into the region (Palmer and Ryder 1984). Summer and autumn records in eastern Washington and Oregon indicate that the species is resident there (Whelton 1989). Autumn records from 1896, 1903, and 1929 in Colorado (Bailey and Niedrach 1965) suggest that the species has been resident there historically in suitable habitat (Baldwin and Koplin 1966). The Boreal Owl had not been reported in New Mexico since the arrival of Europeans, but bones attributed to Crypotoglaux (=Aegolius) funerea richardsoni were found among Pleistocene bones in Shelter Cave, Dona Ana County, New Mexico (Howard 1931). Since the species had been documented in Colorado only 56 km north of the New Mexico border in 1985 (Ryder et al. 1987), we initiated surveys for the Boreal Owl near Cumbres Pass on the Colorado/New Mexico border in the spring of 1987 and expanded our efforts south into New Mexico in succeeding seasons. Most Boreal Owl records for Colorado are from elevations in excess of 2,700 m and in climax Engelmann spruce-subalpine fir (Picea engelmanni-Abies lasiocarpa) forests interspersed with meadows and other small openings (Ryder et al. 1987). We conducted surveys between April 1987 and April 1989 in the Sangre de Cristo, San Juan, and Jemez mountains (Fig. 1), concentrating on this habitat type. Breeding season surveys (18 nights) were conducted as described by Ryder et al. (1987) while autumn surveys (16 nights) followed the protocol of Palmer and Rawinski (1986). Both surveys involved playback of the Boreal Owl staccato song (Bondrup-Nielson 1984) for 5-min intervals at stations spaced 200 to 800 m apart. Documentation required a vocal response (staccato song) or a sighting in the spring. We report only sightings of Boreal Owls in the autumn because the Northern Saw-whet Owl (A. acadicus) has similar call notes, though Whelton (1989) also reported summer and autumn Boreal Owls based on calls. Boreal Owls were recorded at five locations in New Mexico and three locations in adjacent southern Colorado (Fig. 1, Table 1). Two autumn sightings were made more than 45 km south of Colorado and one spring sighting occurred 107 km to the south of the state line. A photograph of the first New Mexico record was published (Hubbard 1987) and photographs of it and two other owls were deposited in the New Mexico Ornithological Society Archives. We heard six Northern Saw-whet Owls and saw another. All these owls sang their typical courtship song; five were heard in the spring. Unidentified Aegolius respondents were seen or heard at seven other New Mexico locations during autumn surveys (Fig. 1). These may also have been Boreal Owls; at two autumn locations (B and C; Fig. 1) we saw Boreal Owls in the same vicinity where Aegolius owls responded during earlier surveys. Whelton (1989) had 40 contacts with Boreal Owls, but saw only seven of those perched. He identified the remainder by physical and flight characteristics (eight) or their calls (25). He recorded only three saw-whet owls, or only 11% of a total of 28 unseen 'Received 13 June 1989. Final acceptance 22 January 1990.