Fidelity to Territory, Nest Site and Mate, Survivorship, and Reproduction of Two Sympatric Forest-Falcons

j. RaptorRes. 35 (2):98-106 ¸ 2001 The Raptor ResearchFoundation, Inc.

FIDELITY TO TERRITORY, NEST SITE AND MATE, SURVIVORSHIP, AND REPRODUCTION OF TWO SYMPATRIC FOREST-FALCONS

RUSSELL THORSTROM ThePeregrine Fund, 566 WestFlying Hawk Lane, Boise,1D 83709 U.S.A.

CRISTOBALM. MORALESAND Jost D. RAMOS Tihal National Park, Per,n, Guatemala C.A.

ABSTRACT.--Fidelity,survivorship, and reproduction of Barred Forest-Falcons(Micrastur ruficollis) and Collared Forest-Falcons(M. semitorquatus)were studiedfrom 1988-96 at Tikal National Park, Guatemala. Forest-Falconsare year-round residents and nest in tree cavities.Barred Forest-Falconsand Collared Forest-Falconshad 100% fidelity to territories.Breeding pairs also had 100% mate fidelity,with pair bonds perennial and long-lasting.Only one territory switchin 98 territorial yearswas observed during the studyand that wasby a widowedmale to a neighboring territory with a widowedfemale. The rate of annual survivorshipof breedingadult Barred Forest-Falconsbanded in 1989was 95.3% (N = 7 males) and 92.3% (N = 7 females).Nineteen percent of femalesand malesthat bred produced >50% of the offspring. Forest-Falconsare longer lived and have a lower rate of a territory and mate switchingthan similar-sizedtemperate-zone raptors such as the European Sparrowhawk(Acdpiter nisus). The reproductive successof Barred Forest-Falconsduring this studysuggested that the factorsaffecting lifetime reproductivesuccess in temperate and tropical speciesdo not diffen KEYWORDS: Micrastur ruficollis; BarredForest-Falcon; Micrastur semitorquatus;Collared Forest-Falcon; fidelity;survivorship; reproduction.

Fidelidad territorial, sitiosde nido, parejas,sobrevivencia y reproduccionde dos especiessimpatricas de Micrastur

RESUMEN.--Lafidelidad, sobrevivenciay reproducci6n de Micrasturruficollis y Micrastursemitorquatus fueron estudiadasdesde 1988-96 en el Parque Nacional Tikal, Guatemala.Los halconesde bosqueson residentesanuales y anidan en cavidadesde firboles.Micrastur ruficollis y Micrastursemitorquatus fueron 100% fieles a susterritorios. Las parejasreproductivas tambien tuvieronel 100% de fidelidad, con lazos de pareja perennesy duraderos.Tan s61ohubo un cambio de territorio durante las observacionesdel afio 98. Este ocurri6 a partir de un macho viudo que se mud6 a un territorio vecino ocupado por una hembra viuda. La tasa anual de sobrevivenciade adultos reproductivosde Micrasturruficollis anillados en 1989 rue de 92.3% (N = 7 hembras).Diez y nueve por ciento de las hembrasy los machosen reproducci6nprodujeron > de 50% de los pichones.Los halconesde bosquetienen vidaslargas y una tasainferior de cambio de pareja y territorio que las especiesde similar tamafio de las zonastempladas como Accipiternisus. E1 •xito reproductivo de Micrasturruficollis durante este estudio sugiere que los factores que afectan la reproducci6n durante su vida no son diferentes entre las especiesde las zonas templadasy las tropicales. [Traducci6n de C6sar Mfirquez]

The genusMicrastur is a little-knownNeotropical Paraguay and east through Brazil to the Guianas genus which includes six small- to medium-sized (Brown and Amadon 1989, del Hoyo et al. 1994). species.They have accipiter-like features and are Most information on this genuscomes from mu- characterizedby long tails, short wings, and slight seum notes and collections (Sclater 1918, Wetmore facial ruffs (Friedmann 1950, Wetmore 1965, Blake 1939, Friedmann 1948, Monroe 1968), or from an- 1977, Brown and Amadon 1989, del Hoyo et al. ecdotal notes and observations (Smith 1969, Mad- 1994). These features are adaptationsfor the trop- er 1979, Willis et al. 1983, Mays 1985). Even the ical foreststhat they inhabit from southern Texas two most widespread species of the genus, the (Lasley et al. 1994) south to northern Argentina, Barred Forest-Falcon (M. ruficollis)and Collared

98 JUNE2001 FIDELITYAND SURVIVORSHIP OF FOREST-FALCONS 99

Forest-Falcon (M. semitorquatus),are little-known. young present in the cavities.In some nests, eggs were Recently,howevex; new insightsinto the life histo- not visible becauseof the structure of the nest cavity In these caseswhile we could not alwaysverify presence of ries of these two cavity-nestingspecies have been a clutch, we did observe conclusive evidence of incuba- provided by intensivefield studiesin Guatemala tion behavior (e.g., the female was called off the nest by (Thorstrom et al. 1990, Thorstrom 1993). the male for feeding, followed by her return to the nest). Studieson mortality and population turnover of We assumednest-site occupancy as being equivalent to the percent use of yearsin which pairs made nesting at- tropical and subtropicalspecies could advanceour tempts (e.g., laid eggs or showedincubation behavior). understanding of the influence of ecologicalcon- All known alternative nest sites were checked and new ditions on these parametersmuch more quickly nest sites were searched for in known territories. than further work in northern latitudes (Newton Territoryfidelity was defined as occupancyand defense of a nesting area in consecutiveyears (Warkentin et al 1984). Understanding population dynamics in 1991, Rosenfield and Bielefeldt 1996). If the same tropical forestshelps determine how pressuresand marked bird was sighted or recaptured on the same nest- constraintsoperate in thesepoorly-known environ- ing area -->2yr after initial capture but was missingm ments and how they compareor contrastwith tem- someyears, we assumedthat it alsooccupied that nesung perate ecosystems.Using a group of colox:marked area in the interim years. This was based on our observations of marked birds on territories at the beginning individuals from the northernmost subspeciesof of the breeding seasonduring their nonbreeding years Barred Forest-Falcon(M. r. guerilla) and Collared Nest-sitefidelitywas the use of the same tree-hole dunng Forest-Falcon (M. s. naso), our objective was to the study. characterizeterritory and mate fidelity, survivor- Matefidelity was the establishmentof a pair bond and ship, and individual breeding performance as a production of eggs by the same individuals in ->2 consecutiveyears (Warkentin et al. 1991). Frequencyofnestzng comparisonto similar measuresin temperate rap- was defined as number of nesting attempts divided by tors. number of years the pair occupied the territory. Nestzng breahwas defined as a breeding lapse (-->1 yr of nonbreed- STUDY AREA AND METHODS ing) by the pair and then a breeding observationof the The studysite was in Tikal National Park (576 km2) in same pair on the same territory. Switchingmates or."d•- NE Guatemala (17ø13'N, 89ø36'W); it is centered around vorce" was inferred when either both members of a pair archeologicalruins in a 20 km2 area. Barred Forest-Fal- were found breeding with other partners (having pro- cons and Collared Forest-Falconsare year-round resi- duced eggstogether in a previousyear) or one partner dentsand secondary-cavitynesters at Tikal NationalPark. was found with a different mate the following year and This park is a lowland, dry, semi-deciduous,tropical for- its original partner was subsequentlytrapped in a later estwith an elevationfrom 200-350 m. Rainsusually begin year (Warkentin et al. 1991). Natal dispersalwas the d•s- •n May and decrease by December. Monthly mean pre- persalof youngbetween hatch site and first breeding s•te cipitation ranged from a low of 1.0 mm in April to a high Breedingdispersal was defined as movement of adults of 303 mm during September,with an annual mean rain- among nesting areasacross years (Greenwood 1980). fall of 1309 mm (1989-95, Tikal National Park unpubl. Lifetimereproductive success (LRS) wasdefined as the total number of young produced by individuals dunng data). Mean monthly temperaturesranged from a low of 15øCin January to a high of 35øCin May, from 1989-95 their lives (Newton 1989). Reproductivesuccess during the (Tikal National Park). studyperiod (RSSP) was defined as the total number of Schulze and Whitacre (1999) have described several young produced by individualsduring the studyperiod. All trapped birds and nestlings were banded w•th foresttypes that occuralong the topographicaldrainages, unique combinations of two to four aluminum colored soil types,and moisturegradients within the park. Two extremes of this forest type continuum are upland or leg bands. Statisticaltests were performed with Systat© high-groundforests (tall, semi-evergreenforests on well- (SPSSInc., Chicago, Illinois, U.S.A.), except a few ch•- drained shallow soils) and bajo forests (low in stature, square testswhich were done by hand. open canopy with dense understory, and occurring in RESULTS low-lyingsites of deep clay-richsoils, subject to seasonal flooding and drought). Thirty-nine adult Barred Forest-Falconsand six We studieda population of Barred Forest-Falconsdur- adult Collared Forest-Falconswere trapped (Thor- ing the 1988-96 breeding seasonsand Collared Forest- Falconswere studied during the 1988-93 breeding sea- strom 1996) through the breeding seasonbegin- sons. We searched the forest and visited occupied ning in 1989. We alsomarked 57 nestlingBarred territories daily from March through July to determine Forest-Falconsand five nestling Collared Forest- the nesting activityof potential breeding pairs. Courting Falconswith unique band combinations. pairs were followed aurally and visuallyuntil a nest was confirmed. The nestingdensity for the Barred Forest-Falcon A nestingattempt was defined as any nestthat contained washighly saturatedin the upland and transitional at least one egg. When possible,nest contents were forestsof the park. In a 6 km2 area centered in checked by climbing nest trees and observing eggs or and around the main archeological ruins of the 100 THORSTROMET AL. VOL. 35, NO. 2 park, there were six Barred Forest-Falconbreeding study for breeding Barred Forest-Falconsbanded territories(1 pair/km2). in 1989 was 6.1 yr q- 1.5 for males (N = 7) and 5.0 Fidelity to Territory, Nest Site, and Mate. Nest- yr q- 2.8 for females (N = 7). Clearly,these birds ing activitybegan in March for Gollared Forest-Fal- may have been on the same territories from before cons and in April for Barred Forest-Falcons.We the time our studybegan, and some may have re- documented 70 Barred Forest-Falcon and nine mained after it ended.The longestbreeding span GollaredForest-Falcon nesting attempts. Males and by a pair of Barred Forest-Falconswas at one spe- femalesof both specieswere highly faithful to their cific nest sitewhere they bred successfullysix years breeding territories. The one exception, a male, out of seven. switched to a neighboring territory during the Reproduction During the Study Period. For 27 1992 breeding seasonwhen his mate disappeared Barred Forest-Falconpairs, 19 of 27 females and early in the breeding period. That male mated with 21 of 27 malesraised 54 and 64 youngto fledging a neighboring female that had also lost its mate age during this study,respectively (Fig. 1). Of those early in the breeding season.This male fledged adults that attempted to breed, 30% (8/27) of the five young at its original territory (1989-91) and six young on his new territory (1992-94), includ- femalesand 22% (6/27) of the malesproduced no ing two fledglings during the year of territory young. Nineteen percent (the percent of the switching. breeders that produced more than half of the For Barred Forest-Falcons,the frequencyof nest- fledglings) of the females and males produced ing (yearsof nesting attemptsdivided by the years 58% (N= 44 young) and 54% (N= 49) of the a pair wason territory) for 16 territorial pairs (85 fledglings,respectively. Of the 70% of femalesthat territorial years) was 74.1 ___20% (-SD, range = raised young to fledging, the number fledged var- 40-100%). We calculatednesting frequency sepa- ied from 1-14 per femalefor the sevenstudy years. rately for each territory; pairs nested on average Recruitment. The overall annual productivity 73.2 + 21% (range = 50-100%, N-- 16 pairs). from 1988-95 was 1.1 (76 fledged young/70 nest- This wassimilar to the 80 q- 20% nestingfrequency ing attempts) and 0.9 (8 fledged young/9 nesting for two breeding pairs of Collared Forest-Falcons attempts) for Barred and Collared Forest-Falcons, (eight territorial years;range = 60-100%). respectively.Of 57 young Barred Forest-Falcons Of 70 nestingattempts by BarredForest-Falcons, banded from 1989-95, only one young female, 53% (N = 37) were successfuland 47% (N = 33) banded as a nestlingin 1995,was subsequently ob- failed. Barred Forest-Falconpairs that were suc- served as a breeder; she occupied a nest site as a cessfultended to remain at the same nesting site first-yearbird in 1996 and successfullyfledged two while pairs that failed tended to switchto another young. This natal dispersalwas 4 km SE. No band- sitewithin the samenesting territory (X21= 8.0, P ed young Collared Forest-Falconswere observed < 0.01). Of 40 consecutivetwo-year nesting at- entering or acquiring territories within the study tempts,42.5% (N = 17) of the breedingpairs of area. Barred Forest-Falcons were successful and reused Barred Forest-FalconSurvivorship and Mortality. the previousyear's nest site, 12.5% (N = 5) were The annual rate of survivorshipof breedingadults successfulbut changednest sitesfrom the previous banded in 1989 was high in the sevenstudy years; year the following year, 15% (N = 6) were unsuc- the rate for males was 95.3% (N = 7) and for fe- cessfulbut reusedthe previousyear's nest site,and 30% (N = 12) were unsuccessfuland changednest maleswas 92.3% (N = 7). Given the high territory sitesfrom the previousyear. One pair that failed fidelity and, if we assumeadults that disappeared in 1989 reused the same site from 1990-94 and from breeding territories died, then in sevenyears successfullyfledged young in all five years.Preda- two males (4.7% mortality) and three females non on eggs, nestling and females accounted for (7.7% mortality) disappeared.The annual turn- 91% (N = 30) of the 33 failed nests. over (change of breeding birds on territories) of During this study, seven Barred Forest-Falcon males and females banded since 1989 did not dif- males had residence periods of -->4yr (five were fer statistically(X21 = 0.5, P > 0.10). Althoughthe residents for all sevenyears) and five females had data on adult mortality were limited, many individ- been presentfor ->5 yr (four were presentfor sev- uals of unknown age were still alive and on the en years). Average residence period in the 7-yr same territory for sevenconsecutive years. JUNE 2001 FIDEI,ITYAND SURVIVORSHIP OF FOREST-FALCONS 101

7 [] Male J ½ 6

m 5 4

I I I I I r I r I I I I I I I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Number of fledglings Figure 1. Number of fledglingsproduced by 27 pairsof Barred Forest-Falconsat Tikal NationalPark, Guatemala, 1989-95.

DISCUSSION all caseswere due to pairs taking a break from Barred and Collared Forest-Falconsare year- breeding between nestingseven though the mated round residents in Tikal National Park. Territories pairs were present on their breeding territories. of Barred Forest-Falconswere more aggressively European Sparrowhawk occupancy of nesting defended from conspecifics than were those of territories occurred when females remained in Collared Forest-Falcons. Intruders into defined ter- good habitatsrich in food but frequently changed ritories were unbanded, nonpaired forest-falcons nesting territories after failed nesting attempts searchingfor territorial vacancies,but no intruders (Newton 1986). For Eurasian Kestrels,year-round were observedacquiring a territorial positionfrom resident males tended to ternate with the same fe- residents. male whereas migratory males did not (Village Our resultsshowed that the breeding strategyof 1990). The 100% mate fidelity of forest-falconsis these two cavity nesting forest-falconsfollows pat- contrary to observed pair fidelity of resident Eu- terns thought to be characteristicof tropical birds ropean Sparrowhawks(Newton 1979) and migra- (Skutch 1985): long-livedindividuals, long repro- tory Eurasian Kestrels (Village 1990), which expe- ductive cycleswith pairs not necessarilybreeding rienced high levels of mate switches and everyyear, sedentary,long residencyperiods, and re-pairings.For forest-falconsthe only mate chang- high survivorship. es that occurred were replacements of females Fidelity. Pair bonds of forest-falconsappear to be known to have been killed and several males that strong and perennial, as we observed in Barred disappeared.In contrastto sparrowhawksand kes- Forest-Falcons.We believe that pair bonds are trels, forest-falconsremained on the same territory strong and even longer lasting in Collared Forest- and reused the same nest after failing in that site Falconsbecause of their larger size and presumed the previousyear or changed nest siteswithin the greater longevity. same territory. Barred Forest-Falconpairs had higher territory On severaloccasions forest-falcon pairs returned and mate fidelity (100%) than EuropeanSparrow- to a nest site they had used two or three years ear- hawks(Accipiter nisus)(Newton and Marquiss1976) lier. In general, pairs that reused the same nest site and Eurasian Kestrels (Falco tinnunculus;Village raised more young than pairs that switched nest 1990) (Table 1). Nest-sitevacancy in known terri- sites. We speculated that pairs at nest sites that toriesduring the studyyears was 27%, and nearly were successfuland used continuouslywere occu- 102 THOmSTP.OM •;T At•. VOI. 35, No. 2 JUNE 2001 FIDELITYAND SURVIVORSHIP OF FOREST-FALCONS 103 pying optimal nesting cavities.Another possibility filled by resident birds that may not have otherwise was that no or few alternative potential nest sites attempted to breed that year. This explained the (cavities) existed within the forest-falcons' territo- recruitment of new unbanded individuals into ter- ries. ritorial vacancies but not the territorial switch of We did not know how much pair compatibility one male to a neighboring widowedfemale. In an- and experience affected breeding success,but other removal experiment on a passerine, Marra some pairs that failed continued breeding in con- and Holmes (1996) suggestedthat males respond secutiveyears while others did not. Original resi- to female availabilityand not to habitat vacancies. dent pairs that did not breed were observed to- This may explain the switchby this male to a neigh- gether and engaged in nest inspection during the boring territory where a breeding female wasavail- early breeding seasonbut did not lay eggs.Lack of able. successfulbreeding, either through nonlaying or European Sparrowhawkshad averageperiods of failure, did not causepairs to divorce and move to residence on territories of only 1.4 and 1.5 yr for new territories. Pair experience appears to be an males and females, respectively (Newton 1986). important component of successfulnesting in For Eurasian Kestrels the average period of resi- hole-nestingkestrels (Village 1990) and many oth- dence was 1.6 yr for both sexes(Village 1990; Table er speciesof raptors (Newton 1979, 1986). 1). Tropical forest-falconshad a much longer res- Some pairs had breeding breaks of two or three idence period on territory than these two temper- years (nonbreeding periods) and then they re- ate species,suggesting that constraintssuch as presumed breeding again, paired with the same mate dation, competition for territories, and food as in previous nesting attempts. There was no syn- resourcesoperate differently in these two environ- chrony within the studypopulation in the breeding ments. breaks and no correlation between the outcome of Reproduction During the Study Period and Re- prior nests and the tendency to take a breeding cruitment into the Breeding Population. Barred break. We do not know why there was a lack of Forest-Falconsvaried greatly in the number of annual breeding by severalterritorial pairs but sug- young they produced to fledging. During this gest that this probably relates to some breeding study, forest-falcons with long and continuous mechanism peculiar to tropical environments breeding produced more fledglingsbecause more where birds have long life spans and low produc- breeding attempts increased the number of suc- tivity. cessful efforts and fledglings. Of those that at- Residence Periods. In 1989, of the seven breed- tempted to breed, 22% of males and 30% of fe- ing Barred Forest-Falconpairs banded, five males males produced no young during this 7-yr study and four females were still alive and resident in (Table 1, Fig. 1). Although the samplesize of RSSP their original territoriesin 1996. Unfortunately,we by forest-falconswas small, it was probably repre- were not able to follow this study population lon- sentative for this speciesat Tikal and also similar ger, but we suspectthat severalof these forest-fab to observationsof LRS in temperate raptors.In the cons could still be alive and maintaining territories cavity-nestingEastern Screech-Owl (Otus asio), 14% beyond 10 yr. In contrast,the longestresident pe- of the breeders produced no young (Gehlbach riod for a pair of European Sparrowhawksstaying 1989), and for European Sparrowhawks,with data together was 4 yr (Newton 1986). All forest-falcons on 142 females, Newton (1086) found that 16% of except for one male spent their studyperiod lives those that attempted to breed produced no young on territories where they were originally found. during their lives.In Sweden,20% of 92 male Mer- Pairsthat failed during one seasonstayed on the lins (Falcocolumbarius) produced no young during same territory and usually nested again but typi- their lifetime (Wiklund 1006). cally at a different nest site. Our results showed In studies on LRS, Newton (1989) concluded that territory turnover was extremely low for these proportions of nonreproductive birds tended to be forest-dwellingraptors. In only one of the 70 large in those long-lived specieswhich bred only Barred Forest-Falconnesting attempts did birds in certain years and also in short-lived passetines change territories or mates after a failed breeding with high predation of nest contents. Barred For- attempt. Newton and Marquiss (1991) showedin a est-Falconshave both high predation of nest con- removal experiment on both sexes of sparrow- tents and a long life spanwith breeding only in cer- hawksthat nearly 50% of territorial vacancieswere tain years (Thorstrom et al. 2000). Nonbreeding 104 THORSTROM ET AL. VOL. 35, NO. 2 years among establishedbreeders are frequent in true for European Sparrowhawks(Newton 1986). speciessubject to annual fluctuationsin conditions We also had a shorter mean resident period for and in long-lived speciessubject to more stable female Barred Forest-Falcons (5.0 yr) than for conditions (Newton 1989). These and other factors males (6.1 yr), and this difference was caused by may be operating in the tropical environment of predation during the nesting season.In contrast, Barred Forest-Falcons. in Merlins predation on nests during incubation In comparisonto LRS studiesof European Spar- was the principal factor limiting lifetime reproduc- rowhawks,where 20% of femalesproduced 50% of tive successof males (Wiklund 1996). all fledged young (Newton 1986) and Eastern In our study, two adult female deaths resulted Screech-Owlswhere 21% of femalesproduced 50% from predation during the incubation and nestling of offspring, 19% of breeding forest-falconspro- stages.Male mortality was never documented, but duced 54-58% of all young reared to fledgingage severalmales disappearedfrom the territories they in this 7-yrstudy period. This similarityof the LRS had previously occupied for severalyears. We sus- values in the studies in Newton (1989) and the pect that these males may have died (perhaps of RSSPvalue for Barred Forest-Falconssuggest that old age) or were preyed upon, creating territorial the environmental factors affecting LRS in tem- vacanciesrather than havingdispersed to other ter- perate and tropical speciesdo not differ. Newton ritories outside the studyarea. Recruitment of new (1989) suggestedthat chance events,and not en- breeders occurred only on nesting territories that vironmental conditions and phenotype, were re- lost a breeder. With the one exception of a single sponsiblefor most of the variation in LRS between male switchingto a neighboring territory, no band- individuals. ed birds were observed to change territories due Survivorshipand Mortality. Snowand Lill (1974) to nest failure. reported that Neotropical passerinesare long-lived Breeding populationsof Barred and, most likely, compared to their temperate zone counterparts, Collared Forest-Falconsappear to be stablein Tikal but in a comparative study between temperate and National Park. Breeding territories may be difficult tropical birds, Karr et al. (1990) found no support to acquire, and once there is a vacancya forest- for this long-standing view. However, we found a falcon will take over the territory and remain there very high survival rate for Barred Forest-Falcons until it dies. Competition for breeding territories during the studyperiod (99-95% annually)which probably inhibits birds from switchingor searching gave support to the idea that tropical forest rap- for new areas. The seven years of this study were tors, at least, are long-lived. In North America, inadequate to follow the life spansof a cohort of Sharp-shinned Hawks (Accipiterstriatus), a compa- forest-falcons. Several individuals were still alive rable-sized raptor to Barred Forest-Falcons,rarely and on territories after sevenyears, and we do not live beyond5 yr with only 19% survivingmore than know how long studypairs had been on territory 3 yr (Palmer 1988). Among other temperate-zone nor their ageswhen they first acquired their terri- raptors, Village (1990) estimateda survivalrate of tories. Ten years or more might sufficefor a long- 66% per annum for adult Eurasian Kestrels,and term study of the Barred Forest-Falconbut be in- Newton (1986) estimated 67-71% for European sufficient for the larger Collared Forest-Falcon.We Sparrowhawks(Table 1). Becauseforest-falcons are suggestthat future studiesof Barred Forest-Falcons long-lived, we expect that once a territorial posi- and Collared Forest-Falconsshould examine pop- uon is acquired, most individualsremain sedentary ulations throughout their geographicdistribution on that site until their death. If a bird moves, it and make comparisonswith this study.These stud- may miss out in trying to obtain a territory and ies should concentrate on demographic parame- future breeding opportunities. In such a scenario, ters. selectionfor sedentarybehavior, 100% territory and mate fidelity, high frequencyof nesting,a long ACKNOWLEDGMENTS period of residence, and high survivorshipresult This studywas part of a multi-year researcheffbrt con- in maximizing lifetime reproductive success. ducted by The Peregrine Fund, in cooperationwith the In Eurasian Kestrels, Village (1990) reported Instituto Nacional de Antropologia y Historia (IDAEH), Gentro de Estudios Gonservationistas (GEGON), Guate- that females seemed to have a lower survival rate mala, and GonsejoNacional de Areas Protegidas (GON- than males based on a lower persistence in the AP), Guatemala. We would like to thank the staff of Tikal breeding population, whereas the opposite was National Park, Guatemala. A special thanks to W. Burn- JUNE 2001 FIDEI,ITYAND SURVIVORSHIPOF FOREST-FALCONS 105 ham and J.P.Jenny of The Peregrine Fund for their as- ford [EDS.], Proceedingsof the second symposiumon sistanceand supportßWe thank J. Wiley, D. Whitacre, L. African predatory birdsßNatal Bird Club, Durban, Kiff, T. Cade, I. Newton, R. Bierregaard, D. Varland, and South At?ica. one anonymous reviewer for helpful suggestionsand ß1986. The SparrowhawkßT. & A.D. Poyser,Calton commentson earlier drafts of the manuscript.For assist- U.K. ing in the field we thank A. Manzanero Quixch•tn, C. Solano Mateo, J. Maria Castillo, A. Morales Gutierrez, E ß 1989. Lifetime reproduction in birdsßAcademic Gutierrez Ramirez, V.M. Moro Mendez, H. de JesfisGi- Press, London, U.K. rtn Manzanero, and O. Annibal Aguirre. --AND M. MARQUISS.1976. Occupancyand success of nesting territories in the European Sparrowhawk. LITERATURE CITED RaptorRes. 10:65-71. B•d•, E.R. 1977. Manual of neDtropical birds. Vol. 1. --AND ---. 1991. Removal experiments and the Spheniscidae(penguins) to Laridae (gulls and allies). limitation of breeding density in Sparrowhawks.J Univ. Chicago Press,Chicago, IL U.S.A. Anim. Ecol. 60:535-544. BROWN,L.H. AND D. 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