SHORT COMMUNICATIONS j RaptorRes. 39(1):55-60 ¸ 2005 The Raptor ResearchFoundation, Inc. SEASONALDIET OF THE APLOMADOFALCON (FALCOFEMORALIS) IN AN AGRtCULTURALARE• OF ARAUCAN•, SOUTHERN CHILE POCARDOA. FIGUEROAROJAS 1 AND EMA SOR•YACOMES STAPPUNG Estudiospara la Conservaci6ny Manejo de la Vida SilvestreConsultores, Blanco Encalada 350, Chilltin, Chile KEYWORDS: AplomadoFalcon; Falco femoralis; diet;agri- cania region, southern Chile. The landscape is com- cultural areas;,Chile. prised mainly of wheat and oat crops,scattered pasture and sedge-rush(Carex-Juncus spp.) marshes,small plan- The Aplomado Falcon (Falcofemoralis) is distributed tations of nonnativePinus spp. and Eucalyptusspp., and from southwesternUnited Statesto Tierra del Fuego Isla remnants of the native southern beech (Nothofagusspp.) forest. The climate is moist-temperatewith a Mediterra- Grande in southern Argentina and Chile. Aplomados in- nean influence (di Castriand Hajek 1976). Mean annual habit open areas such as savannas,desert grasslands,An- rainfall and temperatureare 1400 mm and 12øC,respec- dean and Patagonian steppes,and tree-lined pastures, tively. from coastalplains up to 4000 m in the Andes (Brown From August (austral winter) to December (austral and Areadon 1968, de la Pefia and Rumboll 1998). In spring-summer) 1997, we collected 65 pellets under the United States,the Aplomado Falcon is listed as en- trees and fence postsused as pluck sitesby at least one dangered (Shull 1986) due to the historical modification pair of AplomadoFalcons. We collected40 pelletsduring of its habitats and cumulative effects of DDT (Kiff et al. winter and 25 during spring-summer.A few prey remains 1980, Hector 1987). In contrast,the Chilean population were also collected beneath pluck sites during the may be increasing.Forest conversion to agricultural lands spring-summer period. Although pellets could be con- fused with those of the sympatricCinereous Harrier (Cir- have increasedhunting habitat and prey availabilityfor cus cinereus)or American Kestrel (Falcosparverius), we this species(Jaksic and Jim6nez 1986). Nonetheless,the only sawAplomado Falconsat the collectionsites during Aplomado Falcon is rare in southern Chile (Jaksicand our study.Perches identified as those of Cinereous Har- Jxm6nez1986) and it is protected legally (Repfiblica de riers and American Kestrelswere located awayfrom (1.0- Chile 1996, 1998). 1.5 km) knownAplomado Falcon pluck sites.In addition, The biology of the Aplomado Falcon is little known. Aplomado Falcons are aggressivetoward other raptors Breeding biology, survival, movements, and habitat use (Hector 2000, Brown et al. 2003). have recently been reported (P•rez et al. 1996, Montoya Avian preywere identified mainly on the basisof feath- et al. 1997). Studieson AplomadoFalcon summerdiet ers, using two complementary methods: microscopic have been conducted in northern Mexico (Hector 1981, analysisof feather structuressuch as nodes and barbules 1985), northern Chile (Jimfinez 1993), and southeastern (Reyes 1992), and a comparisonof feather coloration patternswith voucher specimensdeposited in the Zoolo Argentina (B6 1999). Some recent anecdotal descrip- ogy Department of the UniversidadAustral of Chile at tions of predation on crayfish (Combarusdiogenes; Clark Valdivia. We assumedthat speciesidentified in a pellet et al. 1989), SpottedTinamous (Nothura maculosa; Silveira representedonly one individual. Small mammalswere et al. 1997), and lizards (Liolaemuslineomaculatus; Trejo identified and quantified on the basisof skulls or denti- et al. 2003) have also been published. Piracy also has tion following Pearson (1995). Insects were identified been documentedas an important foraging method for and quantified by head capsulesor elytra following Pefia obtaining mammal prey from other raptors (Brown et al. (1986). We identified prey items to the finest possible 2003). However, seasonal differences in diet have not taxonomic category.Biomass contribution wasestimated been described.Here, we report the seasonaldiet of following Marti (1987). Massesfor small mammal and Aplomado Falconsand correlateit with prey abundance avian prey followed Figueroa and Corales (1999). Insect in the Araucanian agriculturalarea in southern Chile. masseswere based on the authors' unpublished data. We assumedthat unidentified prey masseswere similar to the STUDY AREA AND METHODS mean massof the most closelyrelated identified taxon. Concurrent to the collection of pellets, we evaluated Our study area was the Tricauco Farm (200 ha), 6 km south of Traigufincity (38ø14'S,72ø38'W) in the Arau- bird and small mammal prey abundancein the field. We estimated bird abundance using parallel, fixed-band (2000 m long, 100 m wide) line transects(Bibby et al. I Email address: [email protected] 1993) placed 400 m apart in the hunting areasof falcons. 55 56 SHORT COMMUNICATIONS VOL. 39, NO. 1 Table 1. Diet of the Aplomado Falcon (Falcofemoralis) determined from pellets in an agriculturalarea of the Ar- aucaniaregion, southern Chile. WINTER SPRING-SUMMER ANNUAL PERCENT PERCENT PERCENT MASSa FREQUEN- PERCENT FREQUEN- PERCENT FREQUEN- PERCENT PREYSPECIES (g) DIETb CY BIOMASS CY BIOMASS CY BIOMASS Mammals 42.5 15.9 2.4 0.7 27.8 9.7 Rodentia Abrothrix olivaceus 23 O 12.3 4.6 0 0 7.9 2.7 Oligoryzomyslongicaudatus 26 G (F) 6.9 2.9 0 0 4.3 1.7 Mus domesticus 21 O 6.9 2.3 0 0 4.3 1.4 Unidentified rodents 23 16.4 6.1 2.4 0.7 11.3 3.9 Birds 57.5 84.1 88.1 99.2 68.7 90.2 Columbiformes Columbaaraucana 300 F (G) 2.7 13.3 4.7 19.2 3.5 15.7 Zenaida auriculata 137 G 13.7 30.4 14.4 26.3 13.9 28.7 Passeriformes Turdusfalcklandii 90 F (I) 17.8 26.0 23.8 28.8 20.0 27.1 Anthus correndera 22 I 0 0 4.7 1.4 1.7 0.6 Sicalis luteiventris 16 G 12.3 3.2 23.8 5.1 16.5 4.0 Zonotrichiacapensis 22 G (I) 1.4 0.5 0 0 0.9 0.3 Sturnellaloyca 96 I (G) 4.1 6.4 12.0 15.3 7.0 10.0 Unidentified Passeriformes 49 5.5 4.3 4.7 3.1 5.2 3.8 Insects orders: 0 0 9.5 T c 3.5 T ½ Odonata 1.0 0 0 2.4 T c 0.9 T c Coleoptera 0.5 0 0 7.1 T c 2.6 T c Total prey items 73 42 115 Total biomass 4508 3130 7638 Total pellets 40 25 65 Massestimates from Figueroa and Corales (1999), except for A. correnderaand Z. capensis(unpubl. data). Determinedfrom Murfia (1996) for smallmammals and Estadesand Temple (1999) for birds;F = frugivores,G = granivores,! = msectivores,O = omnivores.Secondary diet is given in parentheses. T = trace; values less than 1%. Eight line transectswere establishedduring winter and estimate GMW. Differencesamong GMW were analyzed three during spring-summer.The abundance of small using t-tests (Fowler and Cohen 1986). To determine mammalswas evaluated by trapping transects(Call 1986) whether falcons took vertebrate prey selectivelyor op- using medium Sherman live traps (10-15 m apart) portunistically,we compared frequency distribution of placed in unaltered pasture and marshes.Three 10-trap prey in pelletsversus prey abundancein the field using transectswere establishedin pasture during winter and Spearman's rank correlation as recommended by Jaksic three in pasture and two in marshesduring spring-sum- (1979) for a comparisonbetween prey consumptionand mer, and these were sampled for 5 nights. Thus, total availability.Because of the smallsample size for each sea- effort was 351 trap-nights (nonfunctional trapswere dis- son, we combined resultsof the winter and spring-sum- counted). mer diet for correlations. Seasonal changes between proportions in different prey taxa in diet were evaluatedwith chi-squaretests us- RESULTS ing contingencytables (Fowler and Cohen 1986). Only Whole pellets averaged27.3 + 1.3 mm length X 13.3 vertebrate prey were included for analysis;contribution of insects was insignificant. Geometric mean weight of _+ 0.5 mm width and had a mean dry weight of 0.9 + prey (Marti 1987) wascalculated as follows: GMW = an- 0.08 g (i _+SE, N = 36). In total, we identified 115 prey tilog (:•nJogwi/En,),where ni was the numberof individ- items in the pellets including sevenbird species,three uals of the ith speciesand w•was the mean weight. Only rodent species,and three insectorders (Table 1). Byboth prey items identified to specieslevel were included to number and biomass,birds were the most common prey MARCH 2005 SHORT COMMUNICATIONS 57 Table 2. Relativebird abundanceestimated by the line-transectmethod during 1997 in an agriculturalfield in Tricauco,Araucania region, southern Chile. Valuesare pooled resultsof the winter and spring-summer surveys. PERCENT INDMDUALS SPECIES (%) Eared Dove ( Zenaida auriculata) 2.7 Black-facedIbis (Theristicusmelanopis) 1.8 California Quail (Callipeplacalifornica) 2.1 Southern Lapwing (Vanelluschilensis) 20.0 Austral Parakeet (Enicognathusferrugineus) 3.0 Dark-faced Ground-Tyrant ( Muscisaxicolamacloviana) 2.0 House Wren (Troglodytesaedon) 3.3 Austral Thrush (Turdusfalcklandii) 11.5 Correndera Pipit (Anthuscorrendera) 4.2 Grassland Yellow-Finch ( Sicalis luteiventris) 22.5 Rufous-collaredSparrow (Zonotrichiacapensis) 7.6 Yellow-wingedBlackbird ( Agelaiusthilius) 3.2 Long-tailed Meadowlark ( Sturnellaloyca) 4.1 Common Diuca-Finch (Diuca diuca) 4.3 Black-chinned Siskin (Carduelisbarbata) 3.0 Other birds a 4.7 Total individuals 1782 Includesall bird speciesthat individuallyaccounted for lessthan 1% in abundance. of the Aplomado Falcon (Table 1). Passerineswere the prising 33 species.The most numerous specieswere the group of birds most frequentlyfound in pellets,with Aus- GrasslandYellow-Finch, Southern Lapwing (Vanellusch•- tral Thrushes (Turdusfalcklandii) and GrasslandYellow- lensis),Austral Thrush and Rufous-collaredSparrow (Zon- Finches (Sicalisluteiventris) being the mostcommon prey otrichiacapensis; Table 2). More birds were observed dur- species(Table 1). By biomass,the Austral Thrush and ing winter (993 birds/km9) than spring-summer(482 Eared Dove (Zenaidaauriculata) were the mostimportant birds/km9). We captured 43 rodents comprisingseven avian prey both during winter and spring-summer.Ro- species.By number, the most abundant specieswere the dents were an important part of the winter and overall olivaceusfield mouse, long-tailed rice rat (Oligoryzomys diet with olivaceusfield mice (Abrothrixolivaceus) being longicaudatus),and house mouse (Mus domesticus;Fig.