White-winged Diuca Finch nesting on Quelccaya Ice Cap, Peru

Wilson Journal of Ornithology, The, Sept, 2008 by Douglas R. Hardy, Spencer P. Hardy

DISCUSSION

Although indirect, all evidence indicates that Quelccaya glacier nests were built and used by White-winged Diuca Finch. Little information exists on nesting habits of this species from anywhere in the Andes although Johnson (1967: 368) reported that in the Parinacota area of Chile, a White-winged Diuca Finch nest was found "on the ground beneath some loose stones on a hillside." In lieu of breeding-season observations of White-winged Diuca Finches at Quelccaya, our deduction is based upon their local presence, feathers, and the species known association with glaciers.

Small groups of White-winged Diuca Finches of unknown age class were frequently observed among rocky moraine surfaces and bogs in the area. This species is known to not typically retreat northward or to lower elevations during winter (Johnson 1967, 1972). On one occasion in June 2007, while we were investigating an apparent roosting site within a crack of the glacier, a flock of ~20 White-winged Diuca Finches began gathering late in the afternoon at the glacier margin, both on and off the glacier (Fig. 1). The birds acted disturbed by our presence in contrast to their behavior during diurnal feeding.

Several feathers observed in proximity to the nests were White-winged Diuca Finch wing or tail feathers. In addition, two nearly-entire wings (chord = 105 mm) of Whitewinged Diuca Finch were found on the ice at a 2007 nest site. No feathers were found from other passerine species (e.g., ground tyrants [Muscisaxiola spp.]) observed in close proximity to the glacier.

White-winged Diuca Finch is the only species to be repeatedly associated in the ornithological literature with Western Hemisphere glaciers. Niethammer (1953) observed an estimated 100 White-winged Diuca Finches gathering for the night inside a glacier crevasse at Chacaltaya (5,200 m) Bolivia in midsummer. He also collected one male specimen on 20 December in breeding condition with enlarged testes (6 x 4 mm vs. ~3 mm for another specimen collected in late August). A second association between White-winged Diuca Finch and glaciers was in the mid-1960s when P. R. Parker of the Chacaltaya Astrophysical Observatory found a nest "in an ice cave" at 5,300 m, leading Johnson (1967:368) to postulate the species "quite possibly nests at a higher altitude than any other passerine form." Subsequently, several sources mention that White-winged Diuca Finch has been recorded roosting in glacier fissures (Meyer de Schauensee 1970), glacier crevasses (Ridgely and Tudor 1989) or glacier cracks (Fjeldsa and Krabbe 1990).

Relatively little is known about the timing of White-winged Diuca Finch nesting in Pert1 or elsewhere. Johnson (1967) suggested this species nested after the summer rains in the Parinacota region (Chile-Bolivia) where White-winged Diuca Finches were present all year. Immature White-winged Diuca Finches in Bolivia were noted by Fjeldsa and Krabbe (1990) during July and August (La Paz), and August (Cochabamba). These findings are consistent with the Quelccaya situation, where climatic conditions present multiple difficulties for breeding birds, especially snow and low temperature (cf. Hendricks and Norment 1992, Martin and Wiebe 2004).