Breeding, Migratory, and Wintering Birds of the Northern ... - Eco-Index

were at or near the northern edge of their winter range and other species were found well outside oftheir known winter range. Wintering Neotropical migrants included two Cassin’s kingbirds, 10Cassin’s vireos, 13 orange-crowned warblers, 67 yellow-rumped warblers, 76 black-throated graywarblers, seven Townsend’s warblers, two Wilson’s warblers, 17 Lazuli buntings, and one Scott’soriole. Cassin’s kingbirds, Wilson’s warbler, and Scott’s oriole typically winter south of the reserve.Numbers of black-throated gray and Townsend’s warblers, which winter in low densities north intosouthern Arizona, were especially high on the reserve. Interestingly, Cassin’s vireo was much morecommon during winter (12) than plumbeous vireo (2), yet plumbeous vireo was much more common(15) than Cassin’s vireo (2) during migration in September 2007. We detected >100 individualEmpidonax flycatchers during winter most of which were gray, Hammond’s, dusky, and “western”flycatchers. We observed three least grebes in the same pond in which we confirmed nesting in July2008.In January 2008, we detected several species of birds that nest at higher elevations in oakwoodland, pine forest, and mixed-conifer forest in the surrounding region and that migrant to thelowlands in winter. Presence of several species of these elevational migrants was notable. Wedetected two brown-backed solitaires in Huijalo Abajo on 5 January 2009, which represented the firstwinter records of this species in the region. Presence of brown-backed solitaire was not entirelyunexpected because they occur locally during the breeding season in the Sierra Huachinera (A.Flesch, unpublished data) and in the adjacent Sierra Tabaco (Lammertink et al. 1996) approximately50-60 km north of the reserve. We detected two slate-throated redstarts (see cover photo) in a patchof dense shrubs and vines that overhung the bank of the Río Aros in a sheltered glen approximately1000 m below the confluence of Arroyo los Chinos. These attractive warblers nest in high-elevationconiferous forests in the Sierra Madre Occidental and although there are no summer records fromareas north of the reserve in Sonora (Russell and Monson 1998, Flesch 2008b) they likely nest athigher elevations in the Rio Aros watershed in neighboring Chihuahua. Another elevational migrantthat was not known to winter as far north of the reserve was white-eared hummingbird; we detectedone individual in Huijalo Abajo on 5 January 2009. Other elevational migrants of note were greaterpewee that was present in low numbers in Huijalo Abajo and Babisal Arriba and buff-breastedflycatcher along the Rio Aros and in la Ventana.Several species that were uncommon in summer were much more common in winter whereas forother species we observed the opposite pattern. Nutting’s flycatchers are rare on the reserve insummer yet we detected >30 individuals in winter when they were present on all seven transectsthat we surveyed. In contrast, blue-gray gnatcatchers are extremely local in the summer when breedin oak scrub on Mesa Encinosa yet were common throughout much of the reserve in winter. Blackcappedgnatcatchers, however, which are common during summer, were rare in winter suggestingthey also make seasonal movements between their summer and winter ranges. Similarly, we did notobserve five-striped sparrows during winter despite that fact that they are abundant during summer.We found tall, dense stands of perennial bunchgrasses on Mesa Encinosa on the flats north of upperHuijalo Canyon. These grasslands seem to dominate many of the ridge tops and shallow slopes onthe east side of the Sierra Zetasora. While exploring these grasslands on 5 January 2009, weflushed a single grasshopper sparrow and an unidentified meadowlark. Presence of these speciessuggests these portions of the reserve support small populations of wintering grassland birds thatare extremely uncommon in this region of Sonora. Additional surveys of these areas in summer andwinter would be informative.ConclusionsThe Northern Jaguar Reserve supports a diverse assemblage of breeding, wintering, and migratorybirds and a varied assortment of environments across a wide elevation range. Since 2007, we have9