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2002 POST-FLEDGING SURVIVAL AND DISPERSAL OF PEREGRINE DURING A RESTORATION PROJECT Sobre vivencia de volantones y dispersion de halcones peregrinos durante un proyecto de restauracion Larkin A. Powell University of Nebraska-Lincoln, [email protected]

Dan J. Calvert University of Dubuque

Irene M. Barry University of Dubuque

Lowell Washburn Iowa Department oj Natural Resources

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Powell, Larkin A.; Calvert, Dan J.; Barry, Irene M.; and Washburn, Lowell, "POST-FLEDGING SURVIVAL AND DISPERSAL OF PEREGRINE FALCONS DURING A RESTORATION PROJECT Sobre vivencia de volantones y dispersion de halcones peregrinos durante un proyecto de restauracion" (2002). Papers in Natural Resources. 426. http://digitalcommons.unl.edu/natrespapers/426

This Article is brought to you for free and open access by the Natural Resources, School of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Papers in Natural Resources by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. j RaptorRes. 36(3):176-182 ¸ 2002 The Raptor ResearchFoundation, Inc.

POST-FLEDGING SURVIVAL AND DISPERSAL OF PEREGRINE FALCONS DURING A RESTORATION PROJECT

LARKINA. POWELL,1 DAN J. CALVERT,AND IRENE M. BARRY EnvironmentalScience Department, University of Dubuque,2000 UniversityAvenue, Dubuque, IA 52001 U.S.A.

LOWELL WASHBURN Iowa Departmentof Natural Resources,1203 N. ShoreDrive, ClearLake, IA 50428 U.XA.

ABSTRACT.--Wemonitored 38juvenile PeregrineFalcons (Falcoperegrinus) up to 3 mo immediatelyafter their releasefrom a hack box during 1999-2000. The restorationsite was a cliff near Point Park in Dubuque, Iowa. Falconswere releasedin a staggeredmanner from mid-Juneuntil late July each summer.Older falconsremained at the site longer than at previousurban releasesand interactedwith the youngerfalcons. The four mortalities(11%) confirmed during the observationperiods were dis- coveredand reported by citizensnear the releasesite. We used radiotelemetry,observations of color- marked at the hack site, and recoveredmortalities to estimateweekly survival rates and dispersal patterns.We estimatedweekly survival rate to be 0.988 (SE = 0.01), and our weeklyresighting rate was high: 0.885 (SE = 0.03). Juvenileswere observedfor an averageof 4.3 wk in 1999 (SD = 2.5), but only 3.4 wk in 2000 (SD = 2.3). Accordingly,weekly fidelity rates were year-specific:0.903 (SE = 0.03) in 1999 and 0.795 (SE = 0.05) in 2000. No mortalitieswere attributed to Great-hornedOwl (Bubovirgi- nianus)predation, but substantialnumbers of owlswere seenin summer2000. The presenceof owlsin 2000 may have contributedto the dift•rence in fidelity rates and dispersalpatterns between years. KEYWORDS: PeregrineFalcon; Falco peregrinus; survival; dispersal; mark-recapture modeh population restcn'ation.

Sobrevivencia de volantonesy dispersi6nde halconesperegrinos durante un proyectode restauraci6n REsUMEN.--Monitoreamos38 halconesperegrinos (Falcoperegrinus)juveniles hasta 3 mesesinmediata- mente despu6sde su liberaci6n desde una "caja de suelta" durante 1999-2000. E1 sitio de restauraci6n eraun riscocerca la parquePunto del ,•guila en Dubuque,Iowa. Los halcones fueron liberados en forma escalonadadesde mediados de junio hasta finales de julio de cada verano. Los halcones mss adultospermanecieron pot milstiempo en los sitlosurbanos en los cualesinteractuaron con loshalcones mssj6venes. Las cuatro muertes(11%) confirmadasdurante los perlodosde observaci6nfueron des- cubiertasy reportadaspot ciudadanoscerca a los sitlosde liberaci6n. Utilizamosla telemetria y las observaciones de aves marcadas con colores en los sitios de liberaci6n. La recoleccion de animales muertosfue utilizada para estimarla tasade sobrevivenciasemanal y los patronesde dispersi6n.Esti- mamos la tasa de sobrevivenciasemanal en 0.988 (SE = 0.01), y una tasade avistamientossemanal alta: 0.885 (SE = 0.03). Los juveniles iheron observadosen un promedio de 4.3 pot semanaen 1999 (SD = 2.5), pero solo fue de 3.4 en el 2000 (SD = 2.3). En concordancia, las tasasde fidelidad semanal fueron especificaspara cada afio: 0.903 (SE = 0.03) en 1999 y 0.795 (SE = 0.05) en el 2000. No hubo mortalidadesatribuibles a la depredaci6n pot parte de Bubovirginianus. Sin embargo,un nfimero im- portante de bfihosfue observadoen el verano del 2000, lo que pudo haber contribuidoalas diferencias en las tasade fidelidad yen los patronesde dispersi6nentre aftos. [Traducci6n de C6sar Mfirquez]

Peregrine Falcons (Falcoperegrinus) once nested in urban areashave been successful,by using tops on ledgesof bluffs along Iowa rivers,but they were of tall buildingsas hack sitesto releasecaptive- exurpated in the 1950sand 1960s.Recovery efforts hatched juveniles. Becauseof efforts in Iowa and surrounding states, the Midwestern population • Gutrent address: School of Natural Resource Sciences, had grown to 67 territorial pairsby 1997,with 747 202 NRH, University of Nebraska, Lincoln, NE 68583- captive-producedjuveniles released (Tordoff and 0819 U.S.A.; e-mail address:[email protected] Redig 1997). As of 2002, PeregrineFalcons are still

176 SEPTEMBER 2002 PEREGRINE POST-FLEDGING SURVIVAl, 177

listed as an endangered speciesin Iowa. In 1998, the wing or tail with non-toxic paint. For individuals the Iowa Department of Natural Resources(DNR) marked on a single wing, we also marked the opposite side of the head, behind the eye, to allow observers to began a program of cliff- releases.During determine identity from any angle. the summer of 1999, the city of Dubuque, IA be- We monitored color-marked birds at the hack site fi'om came the site of Iowa's second cliff release. an observation point below the cliff, using a spotting Juvenilesare hacked in the absenceof their par- scopeand binoculars.Observations were taken daily,usu- ally at 0600-0830 H, 1100-1300 H, and 1800-2030 H ents. Therefore, humans feed the juveniles with During 1999, we radio-marked five individuals with leg- farm-raisedquail carcasses,and the hatchlingsin- mounted transmitters. Because the falcons were able to teract with their siblingsto le•u'n flying and hunt- remove the leg-mounted transmitters, we switched to ing skills, much as they would in the presence of backpackharnesses on four individualsduring 2000. We their parents (Shetrod et al. 1981). Great-horned determined the location of radio-marked birds by trian- gulating with at least two bearings,once each day follow- (Bubovirginianus) predation has been a key ing release; bearings were taken from six fixed points factor in the successof previous releases (Barclay surrounding the cliff site. We used Magellan GPS receiv- and Cade 1983, Redig and Tordoff 1988). Our pro- ers to determine the coordinatesof the fixed points, and ject was developedto monitor the survivaland dis- we used LOCATE II software to estimate the actual co- ordinates of each from the bearing data (Nams persal of juveniles from the hack site area in the 1990). We mapped the position of each bird using context of (1) a relativelylarge cliff releaseand (2) ArcView GIS software, version 3.2, and determined home concerns of owl predation. range using the Jennrich-Turner home range algorithm Natal dispersalis the movement from the hatch (Jennrich and Turner 1969) within ArcView as an exten- site to a breeding territory (Greenwood and sion (Hooge and Eichenlaub 1997). Compared to other home range estimators, the Jennrich-Turner method •s vey 1982), and previous studies have reported on especiallyuseful for determining confidence intervalsof Peregrine natal dispersal(e.g., Totdoff and home range size and deriving the axes of groups of lo- Redig 1997, Restaniand Mattox 2000). Although cation coordinates(Hooge and Eichenlaub 1997). natal dispersalis often used as an indicator of re- We calculatedthe proportion of fatalitiesin our sample based on documented deaths. We calculated 95% confi- cruitment success,the period immediately follow- dence intervals (CI) for each binomial sample propor- ing fiedgingmay be the mostcritical to the survival tion (Burieson 1980). To facilitatc comparisonswith oth- of juvenile Peregrine Falcons (Barclay and Cade er studies,we also calculatedan adjusted proportion of 1983). In this papre; we refer to this period as the fatalitiesby consideringbirds that disappearedfrom the "post-fiedgingperiod," and we use the dispersalof hack site within the first two weeks after release as dead the juveniles away from the hack site as the func- (three of our confirmed mortalitieshappened in the first week and one happened in the third week). The latter tional end of this period. method incorporates many biasesand assumptions,and Very little information has been published on we suggestis a "worst case" scenario. the survivaland movementsof juvenile Peregrine Just as we do not know what happened to birds that Falcons during the post-fiedgingperiod (but see disappearedduring the first 2 wk, surveysof mostwildhfe Perez and Zwank [1995] for Aplomado Falcons populations are unable to detect all in the m- tended population. To estimate the probability of surwv- [Falcofemoralis]). Our goal was to determine the ing a given time interval robustly, it is necessaryto use initial viability of the juvenile falcons released by methods which adjust for incomplete detectabiht¾ the Iowa DNR at the cliff hack site. To do this, we (Thompson et al. 1998). Therefbre, we summarized our monitored movements, determined habitat use, resighting data into weekly discrete time intervals for analysisin a Cormack-Jolly-Sebermark-recapture design and estimatedsurvival during the post-fiedgingpe- (Pollock et al. 1990). This method allows the estimation riod, prior to migration. of weekly survivalrates (the probability of survivingone week), as well as other parameters. METHODS We estimated demographic parameters using recovery We conducted this study during June-September of data from dead birds and resighting data from live birds 1999 and 2000 in Dubuque County, Iowa (42ø30'N, in the same estimatingmodel (Burnham et al. 1987) m 90ø38'W). We placed two hack boxes at the top of a 50- program MARK (White and Burnham 1999). In addition m, east-facing cliff, on the MississippiRiver, just below to the usual survival and resighting (the probability of Lock and Dam 11 (Fig. 1). Birds were releasedin a stag- being detected during a week given that the •s ' gered manner beginning on 22 June 1999 and 20 June alive) parameters, the incorporation of known deaths to 2000 (Fig. 2). the data set allowed the estimationof a fidelity parameter Prior to release,we banded eachjuvenile with a unique (t•, the probability of remaining at the site during a given color- and alpha-numerically-codedleg band, in addition week; Burnham et al. 1987). We consideredseveral po- to the National Bird Banding lab's (USGS-BRD) anod- tential models that varied by whether parameters were ized band. We also color-marked eachjuvenile on either year-specificor pooled acrossthe 2 yr (Table 1). Because 178 POWEIJ•ET AL. VOL. 36, No. 3

Figure 1. Rangesand locationsof radio-mm-ked,juvenile peregrine during 1999-2000 (A), immediately following releasefrom a hack site (/5) at Eagle Point Pm-kin Dubuque, IA along the MississippiRiver (B). Ellipsoidsindicate 95% of home range as determinedby the Jennrich-Turnermethod (Jennrichand Turner 1969); smallellipsoid is for 1999 and large ellipsoid is for 2000. SEPTEMBER2002 PEREGRINE POST-FLEDC.INt; SURVIVAL 179

ß'o 16 Table 1. Alternate models and model selection data from recoveriesand resightingsof juvenile Peregrine Fal- •D •2 cons following release from a hack site in Dubuque, IA, f'• 10 summers 1999-2000. Each model resulted in estimates of o •_ 8 survival (S, probability of surviving the week), resighting o rate (p, probability of live birds being detected), recovery rate (r, probability of dead animals being reported), and fidelity rate (•, probabilityof remaining at the hack site during the week). Falcons were grouped in two cohort groups by year of release; models varied by either esti- f- 14 o 2000 [• NewTotalreleasesobserved_J mating two year-specificparameters (g) or one pooled •.• 12 parameter (.) acrossyears. Models were ranked by AIC values (see text), and the AAICc column shows the dif- O 8 ference between the best model (row l) and the alter- nate models' (rows 2-8) AIC values. E " 2 Z N AIC PAgAM- MODEL •IC c WEIGHTa ETERS Weeks {S(.) p(.) r(.) q•(g)/ 0.00 0.2786 5 Figure 2. Numbers of juvenile Peregrine Falcons re- {S(.) p(.) r(.) q•(.)} 1.29 0.1464 4 leased and total numbers observed at the hack site dur- {S(g) p(.) r(.) •(g)} 1.91 0.1074 6 ing 1999-2000 at Eagle Point Park in Dubuque, IA. {S(.) p(g) r(.) •(g)} 2.16 0.0947 6 {S(.) p(.) r(g) •(.)} 2.79 0.0690 5 {S(g) p(.) r(.) •(.)} 3.16 0.0573 5 of small cohort sizes, we used a corrected Akaike Infor- {S(.) p(g) r(.) •(.)} 3.33 0.0528 5 mation Criterion (AICc) to select the best estimating {S(g) p(g) r(g) •(g)} 6.31 0.0117 8 model (Burnham and Anderson 1998). We extrapolated (•m•wk= •wkm, • .....a• = •wk52) our weeklyestimates to • AIC Weight is the weight of evidencein favor of the given model obtain 10-wk (post-fledgingperiod) and annual survival being from the set of models considered.AIC Weight is a fimc- estimatesfor comparisonwith other studies.We used the tion of the model's AAIC½value, comparedto the other models' delta method for approximating variancesfor these ex- AAIC½ values (Burnham and Anderson 1998). In our data set, trapolated survival estimates(Weir 1990). the bes• model is twice •s likely (0.2786 compared to 0.1464) as the second-best model to be the best model.

RESULTS We released 38 juvenile Peregrine Falcons;21 in immediately around the hack site to dissuade 1999 and 17 in 2000 (Fig. 1). During 1999,we ob- mammal scavengers,and severalraccoons (Procyon served Great-horned only once near the hack lotor) and a red (Vulpesvulpes) were seen near site, but we observed them at least eight times in the hack site. The death in 2000 resulted from an 2000. electrocution on a power pole; severalfalcons were Survival. We documented four deaths (10.5%, seen using the utility pole as a roost prior to the 95% CI = + 10%) during the two post-fledgingpe- mortality. No detected fatality appeared to be the riods (1999 and 2000); by incorporating six other result of Great- predation. The mean birds that disappeared before 2 wk the adjusted distance of the four deaths from the hack site was (worst-casescenario) mortality estimatewas 26.0% 676 m (SD = 411). (95% CI = ___14%).Three of 21 juveniles(14.3%, Weeklysurvival (g = 0.988,SE = 0.01)did not 95% CI = ___11%)were known to have died in differ between years, and our weekly resighting 1999, and 1 of 17 (7.1%, 95% CI = ---7%) was probability (p) was also constantbetween years (p found dead in 2000. The fatalities in 1999 consist- = 0.885, SE = 0.03; Table 1). Extrapolating the ed of (1) hypothermia from becoming trapped in weekly survival to the entire post-fiedgingperiod a livestockwatering tank, (2) overcome by fumes resultedin a 10-wksurvival rate of g = 0.886 (SE after entering a garbagedumpster recentlytreated = 0.07, or a 0.114 mortality rate estimate for the with chlorine tablets, and (3) an assumed mammal same 10-wkperiod); assumingconstant survivalfor predation. In the latter case,skeletal remains were the first year would result in an annual survivales- found with skull intact. We used electric fencing timateof g = 0.534 (SE = 0.84). 180 PO%rELLET AL. VoI,. 36, No. 3

Dispersal. We observedfirst-year juveniles at our and measured 1861 m southwest-to-northeast and hack site from 22 June-12 Septemberin 1999 and 512 m northwest-to-southeast; in 2000 the home from 20 June-9 August 2000 (Fig. 2). No juveniles range ellipsoid was 682 ha, and measured 4839 m from 1999 were observed in 2000, and no juveniles east-to-west and 1795 m north-to-south. In both from either year were observedat the site in sum- years,the ellipsoid coveredEagle Point Park, Mis- ruer 2001. sissippiRivet', islands on the river, and some urban Individual juvenile falcons were observed for a area. At least 50% of the area was coveredby the mean of 4.3 wk (SD = 2.5) during 1999, and for a forested Park (Fig. 1). mean of 3.4 wk (SD = 2.3) during 2000 (F•,,•a= DISCUSSION 2.82, P = 0.10). Weekly fidelity (•) the probability of not dispersingfrom the hack site during the We did not design this study to measure the ef- week) was lower in 2000 (1999: • = 0.903, SE = fects of Great-horned Owls on juvenile Peregrine 0.03; 2000: • = 0.795, SE = 0.05; Table 1). Falcons. However, the increased presence of owls Habitat Use. We observed color-marked birds at the hack site in 2000 suggestsrationale for the most often at the hack boxes. However, the juve- observed changesin peregrine behavior. In 2000, niles also used the cliff face for roosting, feeding, when more owlswere seen,peregrine juveniles had and social interactions. In addition, we observed lower site fidelity, shorter mean observation peri- juveniles in trees surrounding the hack site. In ods, increaseddaily distancefrom the hack site, 1999, 23 of the 28 (82%) "non-hack site" obser- and greater use of more secluded perch sites vations were from the cliff face; 5 of the 28 (18%) (trees). However, survival did not seem to be af- were from trees. In 2000, only 31 of 72 (43%) fected by the presence of the owls. Availability of "non-hack site" observations were from the cliff quail at the hack site may have attracted the owls, face; 41 of the 72 (57%) were from the trees (X2 while also satisfyingthe owls' dietary needs (thus, = 5.56, df = 1, P = 0.018). reducing predation pressure on the falcons). At In 1999,we obtained17 setsof useablebearings the least, our study provides evidence that pere- from radio-marked birds before the leg-mounted grine restoration projects can be carried out suc- radios fell off the birds. The birds were observed cessfully in the presence of Great-horned Owls p•cking at the leather/cotton thread attachments, (but see Craig et al. 1988, Redig and Tordoff and were soon able to dislodge the transmitters; 1988). otherwise, all behaviors of radio-marked birds were The Iowa Department of Natural Resourcescon- normal. In 2000, we obtained 40 sets of useable sidered this release to be successful for several rea- bearings; apparent signal bounce from the cliff sons, including high post-fiedgingsite fidelity and walls prevented program LOCATE II from deter- survival.Juveniles from previousurban releasesin m•ning a precise location estimatefor other setsof Iowa have left the hack site much earlier (ca. 2 wk) bearings. Birds remained closer to the cliff and than the juvenilesii•om Dubuque'snatural cliff site hack site during 1999 than in 2000. The mean dis- (P. Schlarbaum pers. comm.). The longer time tance of radio-marked birds from the hack site was spent at the hack site during the post-fiedgingsea- 268 m (SD : 296.2) during 1999; in 2000, the son could provide for higher survivalto the migra- mean distance was 619 m (SD = 871, t = 2.26, df tory period. Juveniles remained at hack sites in = 53, P = 0.03; Fig. 1). In 1999, the minimum Canadafor a mean of 22.9-27.7 d (Fyfe 1988) and d•stance from the hack site was 72 m and the max- from 4-7 wk in Sweden (Lindberg 1988), com- imum was 1342 m; in 2000, the minimum was 52 pared to our observationsof 4.3 wk (30 d) in 1999 m and the maximum was 5329 m. The number of and 3.4 wk (24 d) in 2000. Fyfe (1988) also re- useful setsof bearings per bird ranged P?om1-8 ported that birds remained longer at the site of in 1999, and from 4-22 in 2000; the backpack har- multiple releases,similar to ours. nesses in 2000 provided more useful data, al- Radio-markedjuveniles in this studyhad a much though one fell off prematurely. more limited range than juveniles or adults in oth- Movements of young peregrines were more of- er studies.For comparison,Enderson and Kirven ten in an east-to-west direction ("inland" from the (1983) reported long (ml kin) daily movements river), than in a north-to-south direction (along for an adult male. Jenkins and Benn (1998) re- the river). The home range ellipsoid,representing ported mean flights of 10.3-21.9 km for adult 95% of their daily use,for birds in 1999 was75 ha, males and females,with a mean home range of 123 SEPTEMBER 2002 PEREGRINE POST-FLEDGING SURVIVAL 181 km2. Perez and Zwank (1995) found dispersal the release for this study. The city of flights of 2-16 km for juvenile Aplomado Falcons Dubuque and Eagle Point Park provided the location for the release. Several members of the Dubuque Audubon in Texas. The farthest distance we recorded a fal- Societyworked asvolunteer feedersand monitors dunng con from the hack site wasjust over 5 km, and the 1999. J. Monat, J. Robertson, and D. Reding provided combined home range for our group of falcons in field assistance during 2000. This undergraduate re- 2000 wasjust 472 ha. The continuedpresence of search was sponsoredby a grant from Region 3 of the U.S. Fish and Wildlife Service, as well as Student Re- food at the hack site, in addition to forest habitat search Grants, a Faculty/Student Research Grant concentrated near the MississippiRiver probably the McElroy Trust and Maytag Foundation of the Iowa contributed to this observation. College Foundation, and the School of Natural Resource Approximately90% of all juvenilessurvived the Sciencesat the Universityof' Nebraska-Lincoln. 10-wkpost-fiedging period, and the sourcesof mor- LITERATURE CITED talitywere similar to thosereported by Barclayand Gade (1983). Our observedmortality of 10.5%was BARCI,AY,J.H., AND T.J. CADE. 1983. Restoration of the very similar to the 10-wkmortality rate of 11.4% Peregrine Falcon in the eastern .Pages estimated using the mark-recapture model. The 3-40 in S. Temple [ED.], Bird conservation. Vol 1 survival of these juveniles was high compared to Univ. of Wisconsin Press, Madison, WI U.S.A. other estimates. Burnham et al. (1988) estimated BURLESON,D.R. 1980. Elementary statistics.Winthrop that 81% of hackedyoung survivedthree weeksin Publishers,Cambridge, MA U.S.A. BURNItAM, K.P. AND D.R. ANDERSON. 1998. Model selec- the Rocky Mountain region during 1976-85; our tion and inference: a practical information-theorenc survival over 3 wk would be 96.4%. Barclay and approach. Springer-Verlag,New York, NY U.S.A. Gade (1983) used estimatesfrom other raptor spe- , D.R. ANDERSON, G.C. WHITE, C. BROWN1E, AND cies to arrive at an approximationof 75% survival K.H. POLLOCK.1987. Designand analysismethods for during the pre-dispersalperiod--the same as our fish survivalexperiments based on release-recapture worst-casescenario estimate. Totdoff and Redig Am. Fish. Soc.Monogr. No. 5. (1997) usedresightings of PeregrineFalcons to es- BURNHAM, W.A., W. HEINRICH, C. SANDFORT,E. LEVINE, timate a minimum first-year survival estimate of D. O'BRIEN,AND D. KONKEL.1988. Recoveryeffort for 23%, although many survivorswere probably not the Peregrine Falcon in the . Pages resighted. Our extrapolated first-yearsurvival rate 565-574 in TJ. Cade,J.H. Enderson,C.G. Thelander, of 53% could potentiallybe loweredby migratory and C.M. White [EDs.], Peregrine Falcon populations. mortalities. However, the period we monitored their management and recovery., Inc., Boise, ID U.S.A. may be the most hazardousfor juveniles without CRAIG,G.R., D.D. BERGER,^NDJ.H. ENDERSON.1988. Per- parental protection (Barclay and Gade 1983); all egrine managementin Colorado. Pages575-586 zn of our documented fatalities occurred during the TJ. Cade, J.H. Enderson, C.G. Thelander, and C M first 1-3 wk following fiedging. Thus, annual sur- White [EDS.], Peregrine Falcon populations: their vival could actually be higher than 53% for the management and recovery.The Peregrine Fund, Inc., birds we monitored. For comparison, Totdoff and Boise, ID U.S.A. Redig (1997) reported a survivalrate of 86% for ENDERSON,J.H. ANDM.N. KIRVEN.1983. Flightsof nesting adults in the Midwest; they also determined that Peregrine Falcons recorded by telemetry. RaptorRes hacked juveniles survived at better rates than wild 17:33-37. juveniles in the Midwest. FWE, R.W. 1988. The Canadian Peregrine Falcon recov- Juvenile survivalrates are critical, becausea low ery program, 1967-1985. Pages599-610 in T.J. Cade, J.H. Enderson, C.G. Thelander, and C.M. White proportion of available individuals are recruited [EDs.], Peregrine Falcon populations: their manage- into the breeding population (Totdoff and Redig ment and recovery. The Peregrine Fund, Inc., Boise, 1997, Restaniand Mattox 2000). With 38juveniles ID USA. released in one location and high survival rates, GREENWOOD,PJ. ANDP.H. HARVEY.1982. The natal and the cliffs near Dubuque, IA on the MississippiRiver breeding dispersalof birds. Ann. Rev.Ecol. Syst.13:1- have high potential to a breeding pair in the 21. near future. HOOGE, P.N. AND B. EICHENLAUB.1997. Animal move- merit extension to ArcView (Vet. 1.1). Biolog- AGIiNOWLEDGMENTS ical Science Center, U.S. Geological Survey,Anchor- We are grateful to the Iowa Department of Natural Re- age, AK U.S.A. sourcesand the Iowa FalconersAssociation for providing JENKINS,A.R. ^ND G.A. BENN.1998. Home range sizeand 182 POWELL ET AL. VOL. 36, NO. 3

habitat requirements of Peregrine Falcons on the [EDS.], Peregrine Falcon populations: their manage- Cape Peninsula,South Africa. J. RaptorRes. 32:90-97. ment and recovery.The Peregrine Fund, Inc., Boise, JENNRICH,R.I. ^ND EB. TU•tNEP,.1969. Measurementof ID U.S.A. non-circularhome range.J. Theor:Biol. 22:227-237. RESTANI,M. ANDW.G. M^TTOX. 2000. Natal dispersalof LINDBERG,P. 1988. Reintroducing the Peregrine Falcon Peregrine Falconsin .Auk ]17:500-504. in Sweden.Pages 619-628 in T.J. Cade,J.H. Enderson, SHEPROD,S.K., W.R. HEINRICH,W.A. BUt4NHAM,J.H. CAp,- C.G. Thelander, and C.M. White [EDs.], Peregrine CLAY,AND T.J. CADE.1981. Hacking: a method for re- Falcon populations:their managementand recovery. leasingPeregrine Falcons and other birds of prey.The The Peregrine Fund, Inc., Boise, ID, U.S.A. Peregrine Fund, Inc., Fort Collins, CO U.S.A. NAMS,V.O. 1990. Locate II user's guide. Pacer software: THOMPSON, W.L., G.C. WHITE, AND C. GOwAN. 1998. Mon- Truro, Nova Scotia, . itoring vertebrate populations.Academic Press,San PEREZ,C:]. AND PJ. ZWANK.1995. Dispersaland habitat Diego, CA U.S.A. TORDOVF,H.B. ANDP.T. R•DIG. 1997. MidwestPeregrine selectionof releasedAplomado Falcons.J. RaptorRes. 29:64. Falcon demography,1982-1995. J. RaptorRes. 31:339- 346. POLLOCK,K.H., J.D. NICHOLS, C. B•tOWNIE,AND J.E. WEIR, B.S. 1990. Genetic data analysis.Sinauer Assoc., HINES. 1990. Statistical inference for capture-recap- Inc., Sunderland, MA U.S.A. ture experiments.Wildl. Monogr. 107. WHITE, G.C. AND K.P. BURNHAM.1999. Program MARK: R•DIG, P.T. AND H.B. TO•tDOVV.]988. Peregrine Falcon survival estimation from populationsof marked ani- reintroduction in the upper MississippiValley and mals. Bird Study46 Supplement:120-138. western Great Lakes region. Pages 559-564 in TJ. Cade,J.H. Enderson, C.G. Thelander, and C.M. White Received13 November 2001; accepted19 May 2002