Four New Migrants for Costa Rica

Abstract

Sightings of four species of migrant passerines not previously recorded from Costa Rica (Slud 1964; Orians and Paulson 1969; Dickerman 1971) are reported here. Vireo solitarius. Solitary Vireo. George V. N. Powell saw a bird of this species at Monteverde, Puntarenas Province, in the Cordillera de Tilarin in northwestern Costa Rica on 8 January 1971. The site was at 1540 m in Lower Montane Rain Forest (Holdridge 1967). The vireo attended a small mixed flock containing Golden-crowned Warblers (Basileuterus culicivorus) and Common Bush-Tanagers (Chlorospingus ophthalmicus). I saw a lone bird, perhaps the same individual, at the same location on 15 March 1971. The bird had a gray helmet, white lores and eye-ring (= spectacles), white throat, olive back, yellow wash on the flanks, and a heavy Vireo bill. This species has not previously been reported south of Nicaragua (Eisenmann 1955), where it is rarely encountered (T. R. Howell, pers. comm.). Dendroica occidentalis. Hermit Warbler. Peter Feinsinger and I observed a single individual foraging low in a planted row of Guatemalan cypress (Cupressus Benthami Endl.) along a wood's edge in Monteverde on 20 October 1971, elevation 1450 m. The bird fed alone though several other migrants, including Townsend's Warblers (Dendroica townsendi) and Black-throated Green Warblers (Dendroica virens), were nearby. The bird was in immature or female plumage and was identified by its gray crown, nape, and back; yellow cheeks with hint of dark auriculars; unmarked white throat, chin, and underparts. Numerous other North American migrants were present on this date. Dendroica townsendi. Townsend's Warbler. I saw this species frequently at Monteverde between 20 October and 5 April. Largest numbers (as many as six seen on 20 October 1971) and most frequent sightings occurred during the fall though a few birds were seen throughout the winter months. F. G. Stiles (pers. comm.) first observed the species at Monteverde on 16 September 1968. This is the earliest Costa Rican fall record. The bird was an adult male foraging in second growth. Edmund Stiles found a bird there on 28 January 1970. The species was present at Monteverde during four consecutive winter seasons: 1968-69, 1969-70, 1970-71, and 1971-72. The range in elevation of my sightings was from 1390 to 1540 m along the transition between Lower Montane Wet and Lower Montane Rain Forest zones in the vicinity of Monteverde. With the exception of two or three birds in isolated broad-leaf pasture trees, all individuals were found in edge situations, in or close by Guatemalan cypress plantings. Most Monteverde sightings were of fall-plumaged birds in which extensive yellow on the underparts and dark auriculars were used as primary field marks for their identification. A few spring birds were in plumages intermediate between those of winter and summer. Most Townsend's Warblers occurred in loose associations with other wintering migrants, usually with Blackthroated Green and Wilson's (Wilsonia pusilla) Warblers.