26 Distribution and Status of the Peregrine Falcon in South America

Home , List of birds of Chile, Strait of Magellan

PEREGRINE FALCON POPULATIONS: Their Management and Recovery, Edited by T.J. Cade, J.H. Enderson C.G. Thelander and C.M. White, The Peregrine Fund Inc., Soise, Idaho, 1988.

Distribution and Status 26 of the Peregrine Falcon in South America

J. Weldon McNutt, David H. Ellis, Cesar Peres Garat, Terry B. Roundy, W. Guillermo Vasina, and Clayton M. White

The breeding range of the Peregrine Falcon in South America has been typically illustrated to include the southern tip of South America and the Falkland Islands (Brown and Amadon 1968, Hickey 1969, Cade 1982), with scattered records for coastal and central Chile (Johnson 1965, 1967). Based on this supposed distribution and a few recent records for Peru (Ellis and Glinski 1980) and Ecuador (Jenny et al. 1981), Cade (1982) suggested that the population probably con- sisted of a few hundred pairs. The population and distribution of F. p. cassini is now known to be considerably greater than previously indicated. We summarize here the recent observations of the Peregrine Falcon in South America and provide a revised map of its breeding range. Recent fieldwork has revealed that Falco kreyenborgi, the "Pallid Falcon," (or previously, "Kleinschmidt's Falcon") is a color morph of F. p. cassini (Ellis et al. 1981, McNutt 1981, Ellis and Peres G. 1983, McNutt 1984), and it is included in our consideration of the South American Peregrine. HISTORICAL REVIEW In 1932, C. Hellmayr examined a few Peregrine specimens from central Chile and identified them as F. p. cassini. Since all were collected during the austral autumn or winter, he asserted that F. p. cassini was likely a "winter visitor" from the south. At the time of the Madison Conference in 1965, Johnson (1965) said that F. p. cassini was a "relatively common nesting species from the Strait of Magellan to Cape Horn in Chile and from southern Patagonia to Staten Island in Argentina." Because no other recent observations for central Chile were mentioned, this assertion was likely based on the statement by

237 238 McNutt, Ellis, Garat, Roundy, Vasina, and White

Olrog (1948) that F. p. cassini was "quite common in the northern part of Tierra del Fuego," and the fact that the majority of collected specimens at that time were from the Magellan region. In 1956 W. Partridge (then curator, Museo Argentine) told one of us (White) that he understood there were several pairs along the Santa Cruz River and in Rio Negro Province, Argentina. J. P. Myers (pers. comm. to White) reaffirmed the Santa Cruz information in 1966 when he noted "several" along the river while studying wading birds. The first data to indicate potential population size and density of Peregrines in South America were provided by Cawkell and Hamilton (1961) for the Falkland Islands, where 28-29 pairs were seen in a 1951-52 census of a portion of the archipelago. They mentioned that two (of more than 200 islands in the archipelago) had 10 eyries collectively. These two islands were both near "big colonies of petrels." Brown and Amadon (1968) described the range of R p. cassini as: "Breeds in Chile from Atacama south to Tierra del Fuego and the Falkland Islands," but their map includes virtually all of Argentine Patagonia and Tierra del Fuego and none of Chile north of the Straits of Magellan. Apparently the actual distribution was not clearly known in the 1960s, and this subspecies was largely ignored until recently. Apart from a trip in 1971 by F. Hughes to collection localities of F. p. cassini and a brief survey which revealed one eyrie in central Chile and one probable eyrie in southern Tierra del Fuego (Walker et al. 1973b), no systematic surveys have yet been undertaken to determine the distribution of the "normal" morph of the South American Peregrine. In contrast, the question raised by Streseman and Amadon (1963) about the correct identity of Falco kreyenborgi generated considerable interest and field activity, particularly in the latter part of the 1970s. Anderson and Ellis (1981) reviewed information on Falco kreyenborgi through 1980. Most data on breeding density and reproduction of Peregrines in South America are from studies on what is now known to be a pallid morph of the Peregrine Falcon, and pertain mainly to southern Patagonia and Tierra del Fuego. SOUTHERN CHILE AND ARGENTINA This region, including the Chilean province of Magallanes, and the Argentine provinces of Rio Negro, Chubut, Santa Cruz and Tierra del Fuego has especially attracted Peregrine surveyors because it was believed to be the home of the "Pallid Falcon," and because the region has been commonly cited as the primary range of F. p. cassini. We have studied breeding activities in this region since 1979, and have also relied on observations by C. Anderson and R. Stranek. Peregrines have been collected at many localities across Tierra del Fuego (Dabbene 1902, Reynolds 1934, Olrog 1948, Humphrey et al. Status in South America 239

1970) and frequently observed north of the Strait of Magellan in Magallanes Province (Venegas and Jory 1979) and Chubut Province (J. P. Myers pers. comm.). Several specimens were collected in Rio Negro Province by the Kovac brothers, and some were said to be at breeding sites, but no records of actual eyrie locations appear in the literature. The seasonal and reproductive status of F. p. cassini in the putative core of its range remained unknown until the late 1970s. In northeastern Chubut Province an eyrie was located (Peres) in the 1978-79 breeding season. In November 1979, C. Anderson (pers. comm.) located two nest sites of normally-colored Peregrines in Magallanes Province. In the same season, Roundy filmed a pallid individual in central Chubut Province, and located eyries of normally- colored birds. He also visited the two eyries located earlier in the season by Anderson and obtained data on reproduction. In 1980, 15 other territories with all normal-colored adults, except one male, were found in two studies primarily concerned with locating and studying the "Pallid Falcon" (Ellis et al. 1981, McNutt unpubl. ms.), and a pallid juvenile was seen in a family group of normally-colored Pere- grines. In that breeding season, R. Stranek (pers. comm.) found a pair of normally-colored Peregrines at a cliff in the vicinity of Ushuaia, Tierra del Fuego. Their behavior suggested that they were nesting, but no eyrie was located. In 1981 three independent surveys looking for "Pallid Falcons" found at least 31 more territories in the southern tip of South America, including 16 sites in Magallanes and Tierra del Fuego (McNutt), 12 sites in Rio Negro, Chubut, and Santa Cruz provinces (Ellis), and 3 in Santa Cruz (Peres). In the 1982 season, reproductive data for 12 nests, including 6 that were previously unknown, were gathered in southern Argentina (Peres). In 1983 nine pairs were studied, and two of these were previously unknown (Table 1) (Peres). Peregrines are now known to nest in the Andean foothills, along the major rivers which cut through the Patagonian steppe, and along the coast south from southern Rio Negro Province. Surveys of these regions resulted in the location of 64 Peregrine nest sites between 1978-84 and far less than 20% of the range has been searched. Extensive, relatively inaccessible and uninhabited regions along the eastern and western slopes of the Andes and the extensive island archipelago extending over 1500 km south from Puerto Montt, Chile (latitude 42°S) have not been surveyed for Peregrines. Many of these islands and channels are lined by large cliffs suitable for nesting Peregrine Falcons. Large populations of petrels and other marine birds occur in the northern region of the island archipelago (Roundy, Walker et al. 1973b). Given the availability of suitable cliffs and the

Status in South America 241 potential for patches of high prey density, we speculate that there is very likely a large population of Peregrines typically associated with marine habitat on the Pacific side south of 42°S. In addition, some pairs likely occur inland on the western slopes of the Andes. This population could conceivably be as large as several hundred pairs. THE "PALLID FALCON" The "Pallid Falcon" is a color polymorph of F. p. cassini (Stresemann and Amadon 1963, Ellis and Peres 1983, McNutt 1984, Ellis 1985). Most populations of Peregrines show variation in plumage darkness, but the two discrete variants of F. p. cassini may be unique among the numerous races. Based on the morph mating frequencies and phenotype frequencies of offspring and assuming normal Mendelian segre- gation, the pallid morph appears to reflect an autosomal monogenic trait recessive to the normal plumage. Under this assumption the pallid phenotype would be expressed only in those falcons homozygous for the pallid gene. Further, any normal-colored falcon producing a pallid offspring would be heterozygous at the normal/pallid locus. If further data regarding the genetic mechanism of this plumage variation support the monogenic control hypothesis, the pallid morph of F, p. cassini could provide a unique opportunity among Peregrine Falcon populations to use a phenotypic marker to investigate gene flow among demes. At 38 eyries in 1981 in southern Chile and Argentina, 20 of the 76 adults were pallid (26.3%). At only three sites were both adults pallid. The remaining 14 pallid adults were paired with phenotypically normal Peregrines, representing 37% of the 38 pairs. Twenty offspring, 38% of the total produced, were pallid. A steep morpho-ratio cline where the pallid morph is most frequent in the region of the Strait of Magellan appears to correlate with gradients such as temperature and precipitation, suggesting a slight differential selection between the morphs (McNutt 1984). However, given the small population size, it could also be accounted for by random drift or by recent secondary contact between formerly allopatric gene distributions. In any case, the pallid morph of F. p. cassini may provide some interesting insights into evolutionary processes operating on the Peregrines in this region and, perhaps, on Peregrine populations worldwide. THE FALKLAND ISLANDS The Falkland Islands, lying approximately 400 km east of the eastern mouth of the Strait of Magellan (latitude 52°S, longitude 60°W), have rugged sea cliffs with large sea bird colonies. In 1979 a pair showed aggression toward an observer standing above a cliff on 242 McNutt, Ellis, Garat, Roundy, Vasina, and White

Bleaker Island and was thought likely to have a nest nearby (R. Stranek pers. comm.). Stranek also related that a resident ornithologist knew of at least two eyries on New Island in 1979. Vasina (1975) described the Falkland Islands as the region of highest density of F. p. cassini, probably on the basis of a 1951-52 census by Cawkell and Hamilton (1961). Apart from the Anglo-Argentine conflict over the possession of the islands in April-May 1982, very little has changed with respect to human population size or activity in the past 50 years. Because of limited human activities, the geographic isolation, and the extent of favorable nesting habitat throughout the archipelago, we estimate that the Peregrine population in the Falkland Islands is probably between 50-120 pairs but could be as high as 200 pairs. The pallid morph is not known to occur there. CENTRAL AND NORTHERN CHILE AND ARGENTINA Most data from northern central Argentina are from Cordoba Province. W. Vasina and R. Stranek have surveyed the area to some extent, and for several years only one and possibly two eyries were known (Table 2). Several locations were checked in 1980 by C. White, J. Albuquerque and R. Brimm and, while adults were seen at two locations, only one nest was found. Vasina has found most of the 20 eyries now known (Table 2). At least one is in a stone quarry in southern Buenos Aires Province. The success of one pair that attempted to nest on a cathedral in the city of Cordoba is unknown (Vasina and Stranek 1984). The only records from northern Argentina are from two areas within 10 km of each other in Salta Province, where two adults and nesting ledges were present in 1984 (White and Boyce). These were areas where river valleys bisected outlying foothills along the eastern Andean slope. Numerous valleys of a similar ecological configuration occur in northern Argentina and southern Bolivia, and other pairs can be expected. In Salta Province, C. Olrog (pers. comm.) saw many Peregrines that he did not consider to be North American wintering migrants, but he found no eyries. No systematic survey for Peregrines has been done in Chile north of Magallanes Province. In 1972, Walker et al. (1973b) checked two sites W. Millie located in 1966 (Johnson 1967) on coastal Chile and found them unoccupied. They did, however, locate another coastal site which had three young approximately 12 days old. W. Vasina found nine sites on the coast south of Coquimbo between 1969-74. Roundy surveyed a small coastal region of central Chile in Coquimbo Province in 1975 not far from the sites found by Millie; he found three nest sites from which young had recently fledged (Table 2). In April 1982, McNutt met a falconer in Santiago who reportedly knew of about 15 Peregrine eyrie locations in central Chile from which he typically

244 McNutt, Ellis, Garat, Roundy, Vasina, and White collected six young each year for falconry. The sites were not verified, but video tapes were seen of at least three, one of which was obviously coastal. In addition, he possessed six Peregrines from the 1981-82 season as well as four in adult plumage said to be 2-4 years old. G. F. Edmunds (pers. comm.) found a nest inland on the Andean foothills about 300 km south of Santiago in the 1960s, and F. Jaksic (pers. comm.) found one in the same situation near Santiago in the 1980s. Vast areas of central Chile should be searched, particularly regions of suitable cliffs along the western foothills of the Andes and the coast. Based on the limited data now available on the presence of nesting Peregrines in the coastal desert regions to the north and in the mesic coastal regions of central and southern Chile, we project that more than 100 pairs occupy central and northern coastal Chile and perhaps 200 pairs nest in the western Andean foothills. PERU AND ECUADOR Reports of Peregrines in Peru (Morrison 1939, Gochfeld 1977) and Ecuador (Albuquerque 1978) in the past were assumed to be of migrants from breeding areas in southern Chile and Argentina. A record of Peregrines nesting in the Andes north of Quito, Ecuador in 1979 GennV et al. 1981) very near the equator greatly expanded the known nesting range in South America. That eyrie has been monitored since (Hilgert Chapter 72). Peregrines may occur in many of the high dry valleys in Ecuador, where some have been seen (S. Temple pers. comm.). Several sites are known in Peru. In March 1979, Ellis and Glinski (1980) located a probable nest site near Tacna in southern Peru. Although no young were seen, a pair of adults attended the cliff, and the adult female was observed for an extended period in a small cave with much excrement on the floor. Molted feathers and prey remains indicated that the falcons were resident. The following year a single adult was observed on a cliff in northwestern Peru approximately 100 km from the coast (Risebrough et al. unpubl. ms.). In 1980 a pair was reported at this same site but produced no offspring. Two other pairs bred further inland in northern Peru in 1981-82 (Schoonmaker et al. 1985) (Table 3). Although pairs of Peregrine Falcons have been observed in coastal situations in Peru (C. Thelander pers. comm., M. Wallace pers. comm.), no evidence of breeding has been obtained. Nest records for Peru (Ellis and Glinski 1980, Schoonmaker et al. 1985) are all for the western Andean foothills. Perhaps 50-100 pairs nest in similar habitat from southern Ecuador into Chile. The Peregrine eyrie in central Ecuador and observations of pairs in interior Peru (Morrison 1939, Gochfeld 1977) suggest an extensive if not dense population in mid-elevation valleys of the northern Andes.

246 McNutt, Ellis, Garat, Roundy, Vasina, and White

DISCUSSION Breeding Seasons and Distribution. — Peregrines near the equator in Ecuador nest at various times of the year from June to December and seemingly have no precise reproductive season (Hilgert Chapter 72). The three pairs in northern Peru produced young in a breeding season extending from April to September. The Peregrines in Chile, Argentina and the Falkland Islands typically nest from Sep- tember to January. These data are suggestive of a possible gradient in reproductive seasonality among South American Peregrines. More complete surveys are required to determine latitudinal variation throughout the Peregrine's range in South America. Although nesting records from northern South American countries are scarce, Peregrines identified as F. p. cassini have been recorded for various locations in Chile (Hellmayr 1932), Argentina (Olrog 1948, Vasina 1975), Uruguay (Escalante 1961), Peru (Morrison 1939, Gochfeld 1977, Risebrough et al. unpubl. ms.) and Ecuador (Albu- querque 1978). Most of these sightings, however, have been ascribed to migrants from Fuegia because observations were made during the austral fall and winter. These birds may have been residents because recent evidence for a wide range of nesting dates in Ecuador and Peru decreases the likelihood that a particular falcon can be designated as migrant or resident and because the migratory patterns of South American Peregrines are unknown. In view of recent evidence of breeding Peregrines in South America from Ecuador to Tierra del Fuego, we believe it possible that most Peregrine sightings, excluding North American migrants in central and northwestern South America (e.g., Morrison 1939, Gochfefd 1977), represent resident birds. Vast areas of South America have not been searched for breeding Peregrines. The few territories outside Argentina and Chile may be a part of an extensive breeding distribution in northwestern South America. Peregrines may even occur in Colombia and western Bolivia because they nest in adjacent parts of Ecuador, Peru and northern Argentina. We cannot speculate on resident Peregrines in the mesic zones from the eastern slopes of the Andes to the Atlantic Ocean. No breeding birds have been found in Brazil where Peregrines were studied for several years (H. Sick pers. comm., Risebrough et al. unpubl ms.), and it is difficult to believe that breeding residents could have been overlooked. Nonetheless, it is curious that the bold granitic monoliths near Rio de Janeiro, Brazil, where North American migrants occur October-March, are devoid of resident Peregrines. Reproduction and Pesticides. — We have reproductive data for 134 pair-years representing 104 breeding territories in three broad geographic regions of South America (Tables 1, 2, 3). Unfortunately, the Status in South America 247 data were not gathered uniformly from area to area. Prior to 1975 only the number of downy young is available, not the number of young fledged. Pre-1977 data and, to a lesser extent, data from the year an eyrie was found are biased in favor of successful eyries which are easier to locate. Despite such biases, reproduction was apparently very good for two of the three regions. Ratcliffe (1980) proposed a value of 1.0 young fledged per pair as representing the minimum required to maintain a population, and Newton (1979) proposed the value of 2.0 young fledged per successful pair as representing a healthy rate of reproduction. A high proportion (74%) of the pairs successfully fledged young. Reproduction was also high on the basis of all pairs (1.7 young per pair) and for successful pairs (2.4 young per pair) (Table 4). Lower values were found in Peru and Ecuador but only 13 reproductive attempts were seen. These may reflect the reduced reproductive output commonly found in tropical nesting species and races (Newton 1979). Concordant with the high reproductive values, pesticide levels were low in two eggs and tissue samples from migrants, and eggshell thickness remained high (Ellis 1985), Jenny et al. (1983) reported extremely low pesticide levels for two Ecuadoran eggs. Eggshells from nine sites in southern Argentina (Ellis 1985) averaged only 2% thinner than the pre-DDT average for California. Pesticides in three eggs from Patagonia were about half the level normally associated with a decline in reproductive performance. Residues in body tissues were recently examined in a small sample of North American migrants and a single resident adult female from Chubut Province, Argentina (Springer et al. unpubl. ms.). Migrant birds contained elevated DDE levels, perhaps from shorebird prey, while the resident adult had low levels. Walker et al. (1973b) also reported low levels in biopsies from two adults taken in central Chile in 1972. The difference in residue amounts in migrants in South America and residents may be unreliable because of small sample size. If the samples analyzed to date reflect an existing difference, perhaps South American falcons eat prey with lower residue levels compared to

TABLE 4. Summary of reproductive performance of Peregrine Falcons in South America, 1967-85.

Total known sites 104 No. pair-years of productivity data 134 No. successful nesting attempts (%) 99(74) Total young 236 Mean young, all pair-years 1.7 Mean young per successful pair 2.4 248 McNutt, Ellis, Garat, Roundy, Vasina, and

FIGURE 1. Probable breeding distribution of Peregrine Falcons in South America. Status in South America 249

North American Peregrines. Reproductive performance of Peregrines in South America supports this possibility. CONCLUSIONS Peregrines breed in South America where there are suitable nesting cliffs, an abundance of potential prey, especially Columbiforrn.es, and relatively open habitat. They are inexplicably absent from coastal Brazil. We predict that resident Peregrines will be found in drier or more elevated regions of Colombia, southern Venezuela, and northern Brazil. Peregrines are now known to breed in Ecuador, Peru, central and southern Chile and central and southern Argentina. On the basis of known densities and available habitat, we doubt that there are fewer than 1000 pairs of Peregrines in South America. In Figure 1, the known breeding distribution plus conservative range extrapolations, based on habitat, are presented. The South American Peregrine population appears healthy and is considerably larger than previously supposed. ACKNOWLEDGEMENTS For their contributions of unpublished observations and discussions about Peregrines breeding in South America we gratefully acknowledge J. Albuquerque, C. Anderson, G. Hoy, F. Jaksic, J. Jehl, J. Myers, the late W. Partridge, C. Olrog, R. Sierra, R. Stranek, S. Temple, C. Thelander, and M. Wallace. Support for travel was provided by a fellowship to JWM from the Thomas J. Watson Foundation and grants to DHE from the National Geographic Society, the U. S. Air Force, and the USFWS (Patuxent Wildlife Research Center). Support while writing this manuscript was provided by a Graduate Fellowship to JWM from the University of California at Davis.

Editors' Note: Clifford Anderson and Tom Maechtle, assisted by Guillermo Vasina, located 14 active Peregrine nest sites in southern Argentina from 17 November-22 December 1986 (Chapter 27). A minimum of 32 young (2.3 per site) was produced. The researchers banded 22 individuals (13 nestlings, 9 adults). Pallid-form F. p. cassini were present at three of the sites. In these cases, pallid adult females were paired with nonpallid adult males. All young produced at these locations were the nonpallid form. Li:eraiure Cited

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