BRENESIA 83-84: 89-90, 2015 Highest elevational record of the Long-billed Hummingbird (Phaethornis longirostris Delattre, 1843, Aves: Trochilidae) in Costa Rica Gerardo Avalos 1,2 1 The School for Field Studies, Center for Sustainable Development Studies, 100 Cummings Center Suite 534-G Beverly, Massachusetts 01915-6239, USA; avalos@ieldstudies.org 2 Escuela de Biología, Universidad de Costa Rica, 11501-2060 San Pedro, San José, Costa Rica, Tel: (506) 2511.4404, Fax: (506) 2511.4216; gerardo.avalos@ucr.ac.cr (Received: October 29, 2014. Accepted: May, 14 2015) KEY WORDS. Elevational shifts, Cerro de La Muerte, Phaethornis longirostris, Costa Rica. PALABRAS CLAVE. Cambios altitudinales, Cerro de la Muerte, Phaethornis longirostris, Costa Rica. The Long-billed Hermit (Phaethornis longiros- tris) has been the subject of classic studies on bird pollination and hummingbird-plant coevolution (e.g. Stiles 1975, 1980). It is a typical “trapliner”, in that it forages mostly in the understory along streams, forest edges, and secondary growth, fo- llowing a route of lowers and rarely returning to the same lower patch in one day (Skutch 1964). This species ranges from central Mexico, Cen- tral America, to northwestern Colombia, extre- mely western Venezuela, western Ecuador and Peru, and Amazonian Bolivia and Brazil (Stiles & Skutch 1989). The Long-billed Hermit is a cha- racteristic lowland rainforest species, and within Costa Rica it inhabits the humid lowlands of the Caribbean and South Paciic slope from sea level up to 1 200 masl (Garrigues & Dean 2007). In the Mexican state of Guerrero, the Long-billed Her- mit can thrive in dry pine-oak forests close to 1 700 masl (Almazán-Núñez et al. (2009). On 13 April 2012 at 08:30 h, I observed an individual of the Long-billed Hermit foraging on lowers of Giant Thistle Cirsium subcoriaceum (Asteraceae) at Cerro de la Muerte, Costa Rica (9 o 33´41´´N, 83 o 43´18´´ W; 2 900 masl, Caribbean side of the continental divide). This constitutes the highest elevational record of this species along its latitudinal range. Cerro de La Muerte is do- minated by oak forests and Paramo ecosystems. Temperatures range from 25°C-0°C, but may approach -5 o C before dawn and 28 o C at midday during the dry season (Wolf et al. 1976). The dry season lasts from November-April, and the wet season reaches a peak during September-October. Most hummingbird-pollinated plants show a blooming peak at the end of the dry season (Wolf et al. 1976). The area where this Long-billed Her- mit was observed is dominated by old growth oak forests and included a patch of C. subcoriaceum along the edge of a recently opened agricultural plot of about 300 m 2 delimited by shrubs of Fuch- sia paniculata (Onagraceae). This clearing allowed for sun penetration in an otherwise closed pri- mary oak forest, and favored the establishment of foraging territories of the resident hummingbird species Magniicent Hummingbird (Eugenes ful- gens) and Fiery-throated Hummingbird (Panterpe insignis), which mainly defended C. subcoriaceum lowers. The area was also visited intermittently by Volcano Hummingbirds (Selasphorus lammu- la). The weather conditions during the week in which the observation took place were typical of the highlands during the dry-to-wet season tran- sition (cold nights and cool days, sunny mornings and cloudy afternoons). The Long-billed Hermit approached the lowers of C. subcoriaceum and probed 4 inlores- cences within the same plant and was switching plants until it was chased by a male Magniicent Hummingbird. It did not return to the lower patch for the rest of the morning. This could have been an erratic individual that reached Cerro de La Muerte moving up, possibly following lower resources along mountain foo- thills. However, the observation is congruent with the more general trend of recent highland habitat use by lowland species, especially those that de- pend on transient resources such as lower nectar. Upward shifts in species ranges due to increased temperatures have been documented for tropical trees in Andean regions (e.g. Feely et al. 2011), and it is the likely scenario for current simulations re- garding bird elevational shifts (i.e. Thomas 2010). It is expected that mountain areas will serve as a Brenesia 83-84: 89-90, Marzo-Septiembre 2015. ISSN-0304-3711