MIGRANT AND BREEDING PEREGRINE FALCONS IN NORTHWESTERN PERU

PETER K. SCHOONMAKER, MICHAEL P. WALLACE AND STANLEY A. TEMPLE

Peregrine Falcons (Falco peregrinus) have been sighted regularly throughout most of western South America from Colombia to Chile (Blake 1977) and have been found breeding in Ecuador (Jenny et al. 1981, Jenny et al. 1983), Chile (Johnson 1965), and Argentina (Ellis and Peres 1983). They are also suspected of breeding in southwestern Peru (Ellis and Glinski 1980), and this area has been included in the species' breeding range (Cade 1982). North American peregrines are known to winter in Central and South America as far south as Chile (Johnson 1965, Blake 1977). Parker et al. (1982) listed this species as a rare migrant in Peru from the coast to the central Andes. We present here the first evidence that Peregrine Falcons breed in the western foothills of the Peruvian Andes, and we summarize observations of migrating Peregrine Falcons at one point along the coast of northwestern Peru.

From June, 1980 to August, 1982, we watched migrating Peregrine Falcons in the Cerro Illescas, a peninsular range of rugged 400-m high desert hills in northwestern Peru (6°0'S, 81°0'W). Although the area's vegetation is sparse, consisting mainly of Prosopis juliflora, Acacia sp., Capparis angulata and C. ovalifolia, the cold coastal waters are rich in aquatic life and support large populations of sea and shore birds.

We also discovered and monitored three pairs of breeding Peregrine Falcons 200 km to the east, on cliffs rising 450 to 1,000 m from the 150-m scrub-desert floor near Olmos, Peru (5°59'S, 79°46'W). The vegetation and cli­mate of this area are markedly different from that of the coast. The highly dissected peaks are forested with 5-to 15-m tall trees, including Loxopterygium lusango, Cavanillesia platanifolia, Bursera graveolens and Bombax sp. (Tosi 1960:32-96). The scrub-desert floor vegetation shares several species with that of the coast, but is more lush owing to a mild rainy season from January to April.

During our two years in Peru, at least one observer was in the field on the coast every day, but not specifically looking for falcons. When a falcon was sighted, we watched it with binoculars. We guessed the sex on the basis of size for 62 of 90 peregrines, in most cases at fairly close range. Age was determined on the basis of plumage for 50 birds.

While it is generally accepted that North American peregrines winter in Central and South America, we present more specific data on timing of migration, and sex and age ratios for these birds. We considered the majority of peregrines that we saw along the coast to be migrants from North America, rather than migrant F. p. cassini or local residents, for the following reasons. We did not find any eyries or birds resident on cliffs in the Cerro Illescas region, despite our extensive search of cliffs. We saw falcons during distinct migration seasons, mostly flying southward from October through December, and northward from late January through April. Seventy of the 90 falcons were sighted in November, February, and March. Finally, all birds that we saw at close range (< 20 m) appeared pale, with little or no rufous wash on the breast, extensive white auricular areas, and a rather narrow malar stripe, all characteristics of the Arctic subspecies, F. p. tundrius (White 1968).

Of the 15 falcons that we saw during the 1980-1981 migration season, at least four were females and six were immatures. We made 75 sightings during the 1981-1982 season, owing to more effort on our part, and we identified 58 falcons to sex and 44 to age. The ratio of males to females was fairly even (28 ♂ 30 ♀) and remained so throughout the season, but adults (33) outnumbered immatures (11; Table 1). The ratio of adults to immatures in October and November (11:9) was significantly different from the ratio in February and March (21:2; x² = 14.53, P < 0.001). This suggests either that immature peregrines wintering in South America have lower survivorship than do adults, or that adults and immatures have different seasonal migration routes.

We visited three Peregrine Falcon eyries in the western foothills of the Andes, monthly to every few months, but remained to make observations only when we saw behavior that suggested breeding. We found a pair at Site A on 27 October 1980 when an adult male was seen chasing Andean Condors (Vultur gryphus) along a cliff face. This cliff site contained several ledges about 80 m up a craggy, 450-m high ridge. One ledge was heavily white-washed with excrement, suggesting long-term occupancy. We visited this cliff again on 28 August 1981 and saw a young male flying with two adults and, subsequently, feeding on the well-used ledge. This site produced this one male fledgling in late July-mid-August, 1981, and another fledgling in late May, 1984. We saw no conclusive evidence of breeding success in 1982 and made no observations in 1983.

Site B, about 60 km south of site A, was found on 2 July 1981. This site consisted of several caves 30 m up a 600-m, east-facing cliff. The main cave was divided into two compartments, and was heavily coated with excrement. A female nestling was in this cave on the day the site was discovered, and had fledged by 18 July. This site produced the one female fledgling in mid-July, 1981, and a male fledgling in early July, 1982; it was not inspected in 1983 or 1984.

Site C, about 15 km south of site B, was discovered on 8 December 1981. The site was halfway up a 500-m high, west-facing cliff. The occupants frequented a ledge at the back of a narrow gorge and were considerably harder to watch than the other two pairs because of the inaccessibility of the site. We saw behavior that suggested nestling care in May, 1982, and then saw a single immature flying above the eyrie in June. We did not visit this site after August, 1982.

During our observations of these breeding pairs, we saw Peregrine Falcons either chase or capture Scarlet-backed Woodpeckers (Veniliornis callonotus), Tropical Gnat­catchers (Polioptila plumbea), White-winged and Eared doves (Zenaida asiatica and Z. auriculata), and Pacific Parrotlets (Forpus coelestis).

All three pairs of Peregrine Falcons were most evident at the nest sites between the months of April and September, and they produced young between late May and mid-August. These dates are intermediate between the October-to-February breeding period reported for one site in Ecuador (Jenny et al. 1981, Jenny et al. 1983) and the September-to-December period reported for nine sites in Patagonia (Ellis and Peres 1983).

In summary, our observations, when considered with those of other investigators, suggest that the Peregrine Falcon's breeding range extends from Ecuador to Chile and Argentina, throughout the western foothills of the Andes, and possibly into the central and eastern Andes as well. Our observations also document the migration of North American Peregrines at one point along the coast of western South America.

We made these observations while studying Andean Condors, with support from a U.S. Fish and Wildlife Service contract (FWS 14-16-0009-78-923) to the University of Wisconsin. We thank L. Hecht, III, and W. Torres Arce for their assistance in the field; G. del Solar for his hospitality and logistical support; and F. P. Ward for his helpful comments and suggestions on an earlier draft of this paper.

LITERATURE CITED

• BLAKE, E. M. 1977. Manual of neotropical birds. Vol. I. Univ. of Chicago Press, Chicago.
• CADE, T.J. 1982. Falcons of the World. Collins,London.
• ELLIS, D. H., AND R. L. GLINSKI. 1980. Some unusual records for the Peregrine and Pallid falcons in South America. Condor 82:350-351.
• ELLis, D. H., AND C. PERES GARAT. 1983. The Pallid Falcon Falco kreyenborgi is a color phase of the Austral Peregrine Falcon (Falco peregrinus cassini). Auk 100:269-271.
• JENNY, J. P., W. A. BURNHAM, T. DE VRIES, N. HILGERT, AND F. ORTIZ. 1983. Analysis of Peregrine Falcon eggs in Ecuador. Condor 85:502.
• JENNY, J.P., F. ORTIZ, AND M. D. ARNOLD. 1981. First nesting record for the Peregrine Falcon for Ecuador. Condor 83:387.
• JOHNSON, A. W. 1965. The birds of Chile and adjacent regions of Argentina, Bolivia, and Peru. Vol. 2. Platt Establecimientos Graficos, Buenos Aires.
• PARKER, T. A., III, S. A. PARKER, AND M.A. PLENGE. 1982. An annotated checklist of Peruvian birds. Buteo Books, Vermillion, SD.
• TOSR, J. A. 1960. Zonas de vida natural en el Peru. Boletin Tecnico No. 5. Instituto Interamericano de Ciencias Agricolas de la OEA Zona Andina, Lima, Peru.
• WHITE, C. M. 1968. Diagnosis and relationships of the North American tundra-inhabiting Peregrine Falcons. Auk 85:179-191.

Department of Wildlife Ecology, University of Wisconsin, Madison, Wisconsin 53076. Present address offirst au­thor: Department of Organismic and Evolutionary Biolo­gy, Harvard University, Cambridge, Massachusetts 02138. Received 8 August 1984. Final acceptance 22 April 1985.