Species and Their Hybrids with Implications for Conservation

j RaptorRes. 39(4):386-393 ¸ 2005 The Raptor Research Foundation, Inc.

MORPHOMETRIC ANALYSIS OF LARGE FALCO SPECIES AND THEIR HYBRIDS WITH IMPLICATIONS FOR CONSERVATION

CHRIS P. EASTHAM 1 NationalAvian ResearchCentre, The Falcon Facility, Penllynin Farm, CollegeRoad, Carmarthen,Wales SA33 5EH UnitedKingdom

MIKE K. NICHOLLS 2 EcologyResearch Group, Canterbury Christ Church University College, Canterbury, Kent, CT1 1QU UnitedKingdom

ABSTP•ACT.---Morphometricexamination of severallarge falcon speciesand their hybridswas conducted to ascertainwhether phenotypewas an accurateindicator of hybrid parentage.Six externalbody measurementswere recorded from 167 Gyrfalcons(Falco rusticolus), Saker (E chefrug),Peregrine (E peregrinus), and New ZealandFalcons (E novaezeelandiae)and from 100 F1, F2, and backcrosshybrids of thesespecies. PrincipalComponent Analysis separated pure speciesand alsoindicated clusters for F1 peregrineX saker, gyr X peregrine,and gyr X sakerhybrids. Gyr X peregrinehybrids were distinguishablefrom their parent species,but it wasimpossible to discriminateaccurately between a complex(F1, F2, and backcross)of gyr X saker hybridsand betweenthese and the parent species.Escaped or releasedfalconry hybridsare perceivedas a significantthreat to the conservationof wild falconpopulations. Under currentlegislation, gyrsand their hybridsare CITESAppendix I species,and sakersare AppendixII species.We suggestthat phenotypiccharacteristics are not reliable for identificationof suchhybrids for legal purposes.Further- more, analysisof measurementsalso identified a "paternal effect," wherebyF• hybrids,irrespective of gender,were phenotypicallymore similarto their paternal than their maternalprogenitors. KEYWOaDS: PeregrineFalcon; Falco peregrinus; Gyrfalcon; Falco rusticolus; SakerFalcon; Falco cherrug; New ZealandFalcon; Falco novaezeelandiae; Falcon hybrids, movphometric,, p•incipal component analysis; PCA; CITES.

AN•LISIS MORFOM•TRICO DE LAS ESPECIES DE FALCO DE TAMA•O GRANDE Y DE SUS HIBRIDOS, E IMPLICACIONESPARA LA CONSERVACION RESUMEN.--Seanaliz6 la morfologia de variasespecies de halconesy de sushibridos para averiguarsi el fenotipo es un indicadorpreciso de la paternidadde los hibridos.Se registraronseis medidas cor- poralespara un totalde 167individuos pertenecientes alas especies Falco rusticolus, E cherrug; E peregrinus y E novaezeelandiae,y para un total de 100 hibridos F1, F2 y retrocrucesde estasespecies. Un an51isis de componentesprincipales separ6 alas especiespuras e identific6 grupos formadospor hibridos F1 E pereg•inusX E cherrug,E rusticolusX E peregrinusy E rusticolusX E cherrug.Los hibridosE rusticolusX E pereg•inusse diferenciaronde las especiesparentales, pero fue imposibledistinguir claramente entre un complejo (F1, F2, retrocruces)de hibridosF. rusticolusX E cherrug,y entre este complejoy las especiesparentales. Los halconeshibridos de cetreria que escapano son liberadosse consideranuna amenazapara la conservaci6nde las poblacionessilvestres. Bajo la actual legislaci6n,E rusticolusy sus hlbridosestrin registradas en el Ap6ndiceI de CITES y E cherrugen el Ap6ndiceII. Consideramosque las caracteristicasfenotipicas no son confiablespara la identificaci6nde estoshibridos con prop6sitos legales.Adem•s, el anrlisis morfom6trico identific6 "efectospaternos," en donde los hibridos F1, in- dependientementede su sexo,fueron fenotipicamentemils similaresa susprogenitores paternos que a los maternos. [Traducci6n del equipo editorial]

One of the first domestichybrid falconswas pro- • Presentaddress: Klumpstugevfgen 1, 61892Kolmarden, duced in 1971 from a female Saker Falcon (Falco Sweden. cherrug)and male Peregrine Falcon (E peregrinus; 2 Correspondingauthor's address:LEAP, Universityof Morris and Stevens1971, Morris 1972). Since then, Greenwich at Medway, Chatham Maritime, Kent ME4 falconersand raptor breedershave produced many 4TB, United Kingdom. Email: [email protected] different hybrids from members of the Falconifor-

386 DECEMBER 2005 MORPHOMETRICS OF FALCON HYBPdr>S 387

Table 1. Identity of hybrid falcons used in the analysis.

HYBRID IDENTITY a SAMPLES SIZES 1VIALE PARENT FEMALE PARENT

Fls Gyr X Peregrine 6 c•, 7 9 Gyr Peregrine Gyr X Saker 7 c•, 5 9 Gyr Saker Peregrinex Saker 3 c•, 13 9 Peregrine Saker Peregrinex Gyr 1 c• Peregrine Gyr Peregrine x New Zealand 1 c• Peregrine New Zealand Gyr/Saker X Peregrine 1 c•, 1 9 Gyr X SakerF2 hybrid Peregrine F2s Gyr X Saker 4 c•, 5 9 Gyr X SakerF1 hybrid Gyr X SakerF1 hybrid Backcrosses•lst generation Gyr X Gyr/Saker 3 c•, 1 9 Gyr Gyr X SakerF1 hybrid Saker X Gyr/Saker 3 c•, 3 9 Saker Gyr X SakerF1 hybrid Gyr/Saker X Saker 14 c•, 17 9 Gyr X Saker F1 hybrid Saker Gyr/Peregrine x Peregrine 2 c• Gyr X Peregrine F1 hybrid Peregrine Backcrosses•2nd generation Gyr (3/8)b/Saker 1 c• Gyr X SakerF1 hybrid Gyr/Saker X Saker (backcrosshybrid) Gyr (5/8)b/Saker 1 c•, 1 9 Gyr Gyr/Saker X Saker (backcrosshybrid) • When naming hybrids,the paternal speciesis cited first. For example,a crossbetween a male gyr and female sakeris a gyr X saker (or gyr/saker) hybrid, whereasa male saker crossedwith a female gyr is a saker X gyr (saker/gyr) hybrid. b Thesenumbers represent a simpleway to showthe proportionof genesfrom the parentspecies, assuming that a F1 hybridinherits % of the genesfrom both the male and female parent species.For example,a gyr (•/s)/saker,produced by backcrossinga gyr X saker F1 hybridwith a gyr/sakerbackcross hybrid, has •/sgyrfalcon and % sakergenes. mes (Boydand Boyd 1975, Cade and Weaver1976, ropean, and Arabian falconry markets (Fox and Bunnell 1986, Weaver and Cade 1991), including Sherrod 1999b) has prompted conservationcon- intergeneric hybrids (e.g., Harris's Hawks [Para- cerns. Escapeddomestic hybrids may be merely a buteounicinctus] X Cooper's Hawk [Acdpitercoope- curiosity (Forseman 1999), a nuisance for bird nz] and Harris's Hawk X FerruginousHawk [Buteo watchers (Gantlett and Millington 1992), or a regalis];Fox and Sherrod 1999a) for falconry pur- threat to the integrity of wild populations.Indeed, poses. falcon pairs made up of an escapedhybrid and a Many F1 hybrids are fully viable (Heidenreich wild, pure individual have been documented sev- 1997), in their turn producingF9 hybridsor back- eral times (e.g., Kleinst/uber and Seeber 2000, crosses(B1 and B9 representing 1st and 2nd gen- Lindberg 2000). A further conservationissue pre- eration backcrosses)to one or other parent spe- sumablyconcerns illegal-trade in falcons,whereby cies. Indeed, hybrids from within the subgenus protected falcon speciesmay be "laundered" as Hierofalco,the "desert falcon" group (Heidenreich domestichybrids. In this study,we examine the re- 1997), exhibit full fertility, presumablyover indef- lationship between falcon speciesand their hy- inite generations.Less closely-related pairs of spe- brids, particularly the accuracyof using morpho- cies, suchas gyr (E rusticolus)and peregrine, pro- metric characters for identification, and discussthe duce hybrids with reduced fertility, manifest as conservationissues concerning falcon hybrids. deformed spermatozoa,completely sterile females METHODS (Heidenreich and Kuspert 1992), or unviable em- bryos (Rosenkranz1995). We investigatedfour large falcon species,namely Per- egrine, Gyr, Saker, and New Zealand falcons (E novaezee- This extended viability of some falcon hybrids landiae)and severalof their hybrid typesused for falcon- coupled with increasing demand over the last 10 ry. Hybrid falcons were all bred in captivity and, yr for domesticfalcons from North American, Eu- therefore, their parentagewas known. Six external body 388 EASTHAM AND NICHOLLS VOL. 39, NO. 4

Table 2. Principal Component Analysis(PCA) of six anatomical measurementsfrom juvenile male Gyrfalcon,Saker, Peregrine, and New Zealand falcon speciesand hybridsof thosespecies. Eigenvalues and eigenvectors(based on the correlation matrix).

PRINCIPAl. COMPONENT

1 2 3 4

Eigenvalue 3.0328 1.3691 0.7459 0.6833 Percent of variability 0.5055 0.2282 0.1243 0.1139 Cumulated Percent 0.5055 0.7336 0.8580 0.9718

CHARACTERS EIGENVECTORS

Wing chord 0.4990 - 0.2324 0.1490 - 0.3852 Wing width 0.5552 -0.0321 -0.0688 -0.1697 Tail length 0.5195 0.2308 -0.2347 -0.1471 Tail step 0.0247 0.6402 0.7536 -0.1395 Tarsuslength 0.3536 0.3591 -0.1598 0.7769 D•git three length 0.2170 - 0.5940 0.5697 0.4221

measurementswere collected from live juvenile Gyrfal- and females, as this measurementwas reported by Wyllie cons (N = 7 males and 6 females), Saker (N = 34 males and Newton (1994) and Eastham (2000) to be the most and 40 females), Peregrine (N = 17 males and 24 fe- reliable indicator of overall body size. males), and New Zealand falcons (N = 25 males and 14 females), and their varioushybrids (Table 1). Apart from RESULTS European Peregrine Falcon subspecies,the majority of which were E peregrinusperegrinus, no other differentia- Males. Principal Component (PC) 1 (Table 2, tion was made between subspecies or geographic Fig. 1) accountedfor the majority (50.5%) of var- morphs. All birds were kept at the National Avian Re- iation. Because all eigenvectorsfor PC1 showed search Center's Falcon Facility in Carmarthen, Wales, U.K. The majority of F9 and backcross1 and 2 hybrids positiveand nearly equal values,we concludedthis were between gyrs and sakers.This is becausehybrids component represents overall body size (Wiley between members of the subgenusHierofalco remain fer- 1981). Male gyrs and F1 and F2 gyr/saker hybrids tile for an indefinite number of generations,whereas hy- had the largest body size, whilst male peregrines brids between more out-crossedfalcon species, such as and New Zealand Falcons were the smallest. peregrinesand sakers,have a reduced fertility. Some of the hybrids included are produced in very low numbers PC 2 (Table 2, Fig. 1) accountedfor 22.8% of (e.g., Peregrine Falcon X New Zealand Falcon), and pub- the variation, as indicated by a contrast in eigen- hshed data on these are rare. Therefore, we included vectors between the positivelyweighted tail step, them in the analysis. tail and tarsuslength, the negativelyweighted digit One of us (C. Eastham) took six measurements, namely wing chord length and width, tail length, tail step (the three length, and wing chord length and width difference between the outermost tail feather [rectrix 6] (Table 2). This component summarizesvariation and the tip of the center tail feather [rectrix 1] on the related to body shape. Tail step and digit three same side), tarsus length, and third digit length from length showedthe strongestpositive and negative each bird. Measurement protocols followed standard weightings, respectively. With a low negative methodsdescribed by Baldwinet al. (1931), Fox (1977), Biggset al. (1978), Kemp (1987), and Fox et al. (1997). weighting, wing width was of limited use in further Feather characters were measured to the nearest 1 mm analysisof PC 2. New Zealand Falconshad the rel- and non-feather charactersto the nearest 0.1 mm using ativelylongest tail step (indicatinga more rounded a pair of digital calipers,a steel ruler, and tape measure. tail), tail and tarsuslength, and shortestdigit three Inclusion of single individuals, for example, a male Per- egrine Falcon X New Zealand Falcon, allowed us to em- and wing chord, whilst peregrines,the single per- ploy Principal Component Analysis(PCA) on XLSTAT- egrine x New Zealandhybrid and gyr/sakerx per- Pro (Fahmy 1998) statisticalsoftware as a suitablemethod egrine hybrid had the relativelylongest digit three for data analysis.Male and female data were analyzed and wing chord length and shortesttail step and separatelyto eliminate background variation due to re- versed sexual size dimorphism (Brown and Amadon tail and tarsuslength. F1 gyr X peregrinesand sa- 1968, Cade 1982), or other sex-linked or sex-limited char- kers showed a wide variation in PC 2 values, with acters. We used wing chord length to distinguishmales an individual saker having the highestPC 2 value. DECEMBER 2005 MORPHOMETRICS OF FALCON Hy•mr)s 389

Gyr/ Peregrines• Sakers New Zealand

Falcons -.,

Gyrfalcons

o 0 I I I I o

0_ Peregrin

-3 Peregrine/Sakers[ F1 & F2Gyr/ Sakers -4 -3 -2 -1 0 1 2 3 PrincipalComponent 1 Gyrfalcon mSaker )KPeregrine -New Zealand falcon AGyr /Peregrine +Gyr /Saker -F1 ßGyr /Saker -F2 Peregrine/ Saker ß Peregrine/ New Zealand OGyr x Gyr/ Saker [] Gyr/ Saker x Saker OSaker x Gyr / Saker ;;Gyr (5/8) / Saker OGyr / Saker x Peregrine

Figure 1. Principal component scoresfrom morphometric comparison of various male falcon speciesand their hybrids.

PC 3 and 4 (Table 2) accountedfor only 12.4% positivelyweighted tail step,tail and tarsuslength, and 11.3% of the residualvariation, respectively. the negatively weighted digit three length, and Tail step and digit three length had a high positive wing chord length and width (Table 3). Positively weighting in PC 3, and in PC 4, there was a con- weighted tail step and negativelyweighted digit trast between positivelyweighted tarsusand digit three and wing chord length had the highest ei- three length and negativelyweighted wing chord genvectorsfor this PC. New Zealand Falcons had length. As PC I and 2 together accountedfor the the longest tail step and the shortestdigit three majority (73%) of variation, we did not consider and wing chord length, whilstF1 gyr X peregrines PC 3 and 4 further. and peregrineshad the shortesttail length and the Females. The PCA for juvenile female falcons longest digit three and wing chord length. PC 3 showeda similar pattern of variation as that seen and PC 4 (Table 3) accounted for 18.4% and in juvenile males. Again PC 1 (Table 3, Fig. 2) ac- 11.4% of the variation, respectively.As for males, countedfor the largestproportion (44.7%) of var- we did not consider these principal components iation and asindicated by mostlypositive and near- further. ly equal values represents, as with males, overall size (Wiley 1981). Gyrs and the various gyr/saker DISCUSSION F1, F2 and backcrosseshad the largestsize, whilst Peregrine and New Zealand falconswere the small- Using PCA we found that the four falcon species, est. irrespective of sex, were clearly separated into PC 2 (Table 3, Fig. 2) accountedfor a further groups: New Zealand Falcons with a small size, 21.8% of the variation, and we concluded that this, long rounded tails and tarsi, and short wings;per- again like males,was related to shape.This wasin- egrines, also with a small size, long digit three dicated by a contrast in eigenvectorsbetween the lengths, and long narrow wings;sakers with a large 390 EASTHAM AND NICHOLLS VOL. 39, NO. 4

Table 3. Principal Component Analysis (PCA) of six anatomical measurementsfrom juvenile female Gyrfalcon, Saker,Peregrine, and New Zealand falcon speciesand hybridsof those species.Eigenvalues and eigenvectors(based on the correlation matrix).

PRINCIPAL COMPONENT

i 2 3 4

Elgenvalue 2.6826 1.3071 1.1023 0.6864 Percentof variability 0.4471 0.2179 0.1837 0.1144 Cumulatedpercent 0.4471 0.6649 0.8487 0.9631

CHARACTERS EIGENVECTORS

W•ng chord 0.4717 -0.3853 -0.1963 0.4118 W•ng width 0.5765 - 0.1767 - 0.0356 - 0.0129 Tail length 0.5737 0.1670 - 0.0642 - 0.1107 Tail step 0.0866 0.6865 0.1871 0.6869 Tarsuslength 0.3077 0.2169 0.6899 -0.4484 D•git three length - 0.1177 - 0.5236 0.6672 0.3809 size, long rounded tails, and short digits; and gyrs homogameticsex (male in birds; Mittwoch 1977) with the largest size. and only one third by the heterogameticsex (Fal- Using these external body measurements,we coner 1967). Therefore, falcon sires (the homo- alsofound it possibleto identify three main hybrid gameticsex) will contribute more sex-linkedalleles groups: a complex of F1, F2 and backcrossgyr/ to their hybrid offspring than will (heterogametic) sakers;F1 gyr X peregrines and F1 peregrine X dams. sakers.Further, it was possibleto separate gyr X International trade in endangered species,such peregrines from their parent species,but impossi- assome falcons, can be a profitableenterprise and, ble to separate completely the F1, F2, and back- if unregulated, can threaten their conservation. crossgyr/sakers hybrid-complexfrom pure sakers Regulation of the trade in such endangeredspe- or particularly,from pure gyrs. cies is by international agreements, such as the Overall, we found that the hybrids were gener- Convention on International Trade in Endangered ally of intermediatephenotype between their par- Speciesof Wild Fauna and Flora (CITES). Accord- ents. However,beyond this it appearsthat the pa- ing to their degree of endangerment in the wild, ternal progenitor influences the phenotype to a all speciesare classedin one of three CITES ap- greater extent than maternal. For example, for pendices.Special conditions apply to the most en- both males and females,the clustersrepresenting dangered, known asAppendix I species(i.e., those F1 gyr X peregrine hybrids, hybrids whose male threatened with extinction and whose survival parentswere gyrs,were spatiallycloser to the gyr could be impaired by trade), which allowsrestrict- clustersthan to the peregrine clusters (Fig. 1, 2). ed trade in captive and domesticbred individuals. Thus, both male and female gyr x peregrine hy- Appendix II includes species considered less brids have a morphologycloser to that of gyrsthan threatened. The saker is an Appendix II species, to peregrines. Further, that the single female per- and although trade is regulated, this is lessexact- egrine x gyr, whose sire was a peregrine, was spa- ing than for Appendix I species.Despite relatively tially closer to the peregrine cluster than the gyr healthy world populations and for reasonswhich cluster,adds further weight to this proposedgen- are largelypolitical (White and Kiff 1998), gyrsand erality.Similarly, the male and female F1 gyr X sa- peregrines and their hybrids are included in Ap- kers, both with gyrsas male parent, appear more pendix I. gyr-like than saker-likein morphology.Except for The resultswe present here showthat it can be male F1 peregrine X sakersthis "paternal effect" difficult to discriminate falcon speciesaccurately seems true for all speciescombinations. We ex- from their hybrids,especially hybrids of Appendix plain this by consideringthat two thirds of the sex I gyrs and Appendix II sakers.Similarly, plumage linked genes in a population are carried by the variation, especiallyin juvenile falcons,is difficult DECEMBER 2005 MORPHOMETRICS OF FALCON HYBm•)S 391

3.5 NewZealand falcons• T

2.5 F1 & F2 Gyr / Sakers

1.5

o 0.5 ......

-0.5 ../

-1.5

Peregrines -2.5 Gyr / Peregrines -3.5 -2.5 -1.5 -0.5 0.5 1.5 2.5 3 5 PrincipalComponent 1

ß Gyrfalcon ß Saker • Peregnne - New Zealand falcon ,&Gyr/ Peregrine +Gyr / Saker - F1 ß Gyr/ Saker - F2 X Peregnne/ Saker • Peregnne/ Gyr O Gyr x Gyr / Saker ß Gyr/ Peregnnex Peregnne [] Gyr / Saker x Saker O Saker x Gyr/ Saker •-' Gyr (5/8) / Saker -- Gyr (3/8) / Saker •:,•Gyr / Saker x Peregrine

Figure 2. Principal component scoresfrom morphometric comparisonof variousfemale falcon speciesand their hybrids. to assessobjectively and make comparisons be- thing that will corrupt them. Thus, if the species tween species and their hybrids. These observa- concept for birds is much looser than conservation tions may provide fuel for two separatearguments. law dictates,then perhaps it is the legislation and Ornithologists are increasingly aware of the not the speciesconcept that must be challenged. widespread genomic compatibility and potential For example, the so-called"Altai falcon" (Falcoal- for hybridization amongst what appear to be very taicusMenzbier), whose phenotype seemsto share dissimilar species (Grant and Grant 1992), such characterswith both gyrsand sakers,is believed by that hybridization between avian speciesis consid- some to be the result of introgressivehybridization ered more common than originally thought (Gill between gyrs and sakers, rendering all these as 1998). Mayr and Short (1970) estimatedthat up to allospecieswithin a single superspecies(Pfander 10% of North American bird speciesregularly hy- 1987, Ellis 1995a, 1995b). This being so, then to bridize; it's so common that hybrids are even in- discriminatebetween Appendix I gyrsand Appen- cluded in birdwatchers'field guides (Sibley 2000). dix II sakersmay be irrelevant, and artificiallypro- The presenceof natural hybridsis not believed to duced crossesbetween these two may be of no evo- be a threat to the integrity of a species, even lutionary threat should they escapeto the wild. If, though they may challenge the biological species however, the Altai Falcon is merely a large, dark concept of taxonomists(Brookes 1999). Amongst race of the saker (Eastham and Nicholls 2002), and free-living, wild birds of prey such hybridization is any resemblanceto gyrsis merely superficial,then increasinglydocumented at the subspecific(Fefe- escaped hybrids between these speciescould po- lov 2001), specific (Hamer et al. 1994), and even tentially compromise wild populations, and the in- to the intergeneric levels (Corso and Gildi 1998, tegrity of gyrs and sakersmust be recognized and Yosef et al. 2001). CITES regulations enforced. Introgressivehybridization may therefore be a A different view of the role of natural hybridiza- processby which speciesevolve, rather than some- tion acceptsthat avian speciesare dynamicentities, 392 EASTHAMAND NICHOLLS VOL. 39, NO. 4 which in certain circumstances,freely exchange allied species.Ph.D. thesis,University of Kent at Can- geneswith other such entities. Despite these inter- terbury, Canterbury, Kent, England. actions, the integrity of the whole is a fragile one, --AND M.K. N•CHOLLS.2002. Morphological classi- and to short circuit gene flow via artificial hybrids fication of the so-called"Altai Falcon." Pages211-219 in R. Yosef,M.L. Miller, D. Pepler lEDS.], Raptors•n is a danger to this integrity. CITES protocolsare the new millennium. Int. Birding and Res. Centre, the responseto perceivedconservation status, and Eilat, Israel. therefore, it should be mandatory to discriminate ELLre,D.H. 1995a. The Altai falcon: origin, morphology, between speciesas we know them. Accurate iden- and distribution. Pages143-168 in Middle EastFalcon tification to assistin controlling the trade in fal- ResearchGroup [EDS.],Proceedings of the Specialist consis paramount,and we haveshown that criteria Workshop. Abu Dhabi, United Arab Emirates. other than phenotypic characteristics(e.g., DNA ß 1995b. What is Falcoaltaicus Menzbier? J. Raptor markers) must be employedto identify individuals Res. 29:15-25. and species.This is imperative if CITES is to re- FAHMY, T. 1998. XLSTAT-PRO statistical software. Paris, Franceß main an effective means of regulating legitimate FALCONER,D.S. 1967. Introductionto quantitativegenet- trade and protectingspecies in the wild. ics. Oliver and Boyd, London, England. ACKNOWLEDGMENTS FEFELOV,I.V. 2001. Comparative breeding ecology and hybridization of eastern and westernMarsh Harriers Thanks to His Highness Sheikh Khalifa bin Zayed AI Circusspilonotus and C. aeruginosusin the Baikalregion Nahyan and His HighnessSheikh Hamdan bin ZayedA1 of eastern Siberia. Ibis 143:587-592. Nahyan for sponsoringthis research.Thanks also to M. A1 Bowardi,managing director of the EnvironmentalRe- FOaSEMAN,R. 1999. The raptors of Europe and the Mid- searchand Wildlife DevelopmentAgency (ERWDA), Drs. dle East: a handbook for field identification. T. and Nick Fox, Director of the ERWDA Falcon Programme, A.D. Poyser,Ltd., London, England. Robert Kenward, and Juan Negro and Violeta Munoz for Fox, N.C. 1977. The biologyof the New ZealandFalcon comments on this manuscript. (Falconovaezeelandiae; Gmelin 1788). Ph.D. disserta- tion, Universityof Canterbury,New Zealand. LITERATURE CITED , C.P. EASTHAM,AND H.J. MACDONALD.1997. The BALDWIN, S.P., H.C. OBERttOLSER,AND L.G. WOOLLY. 1931. ERWDA handbook of falcon protocols.Environmen- Measurements of birds. Sci. Publ. Clevel. Mus. Nat. Hist. tal Researchand Wildlife Agency,Abu Dhabi, United 2:1-65. Arab Emirates. BIGGS, H.C., R. BIGGS,AND A.C. KEMP. 1978. Measure- --AND S. SHERROD. 1999a. The use of exotic and ments of raptors.Pages 77-82 in A.C. Kemp [ED.], hybrid raptors in falconry. Information arisingfrom Proceedingsof a Symposiumon African Predatory the International Committee on Hybrids.Internation- Birds.Northern TransvaalOrnithological Society, Pre- al Wildlife ConsultantsLtd., Carmarthen,Wales, Eng- toria, South Africa. land. BOYD,L.L. AND N. BOYD.1975. Hybrid falcons. Hawk --AND S. SHEPmOD.1999b. Cited in "Scale produc- Chalk 14:53-54. tion and use of hybridsin falconry."Falco 13, Middle BaoOI•ES, M. 1999. Live and let live. New Scientist2193: East Falcon Research Group, International Wildlife 32-36. ConsultantsLtd., Carmarthen, Wales, England. BaOWN,L. AND D. AMADON.1968. Eagles,hawks and fal- GANTLETY, S. AND R. MILLINGTONß 1992. Identification of cons of the world. Vol. 2. The Wellfleet Press, Secau- large fhlcons.Birding World5:101-106. cus, NJ U.S.A. G•LL,F.B. 1998. Hybridization in birds. Auk 115:281-283. BUNNELL,S. 1986. Hybrid falcon overview--1985. Hawk GP,ANT, P.R. ANDB.R. GP,ANT. 1992. Hybridization of bird Chalk 25:43-47. species.Science 256:193-197. BURTON,J.F. 1995. Birds and climate change.Christopher HAMER, T.E., E.D. FORSMAN,A.D. FUCHS, AND M.L. WAL- Helm Publishers,London, England. TEAS.1994. Hybridization between Barred and Spot- CADE, T:J. 1982. Falcons of the world. William Collins ted owls. Auk 111:487-492. Sons and Co. Ltd., London, England. HEIDENREICH,M. 1997.Birds of prey:medicine and man- --ANDJ.D. WEAVER.1976. Gyrfalcon X peregrinehy- agement. BlackwellScientific Ltd., Oxford, England. brids produced by artificial insemination.J. NorthAm. --AND H. KUSPERT.1992. Metodos de la reproduc- Falconers Assoc. 15:42-47. cion en cautividad de las diferentesespecies de hal- CoP,so, A. ANDR. GILDL 1998. Hybrids of Black Kite and cones.E1 problema de los hibridos y la cooperacion Common Buzzard in Italy in 1996. Dutch Birding20: entre criadoresy autoridades.Proc. Cong• Nac. Cria. 226-233. Aves Cetre•a 1:15-17. EASTHAM,C.P. 2000. Morphological studiesof taxonomy HOELLEa, T. AND P. WEGNEa. 2001. Der Wanderfalke ist of the Saker (Falco cherrug: Gray 1833) and closely in Gefahr! Die zweite Hybridfalken-Wildbrut in DECEMBER 2005 MORPHOMETRICS OF FALCON HYBRIDS 393

Deutschlandzeigt die Brisanzder Hybridfalkenzucht. tical calculation manual. Oxford University Prcss,Ox- Greifvb•elu. Falknerei2000:64-66. ford, England. KEMP,A.C. 1987. Taxonomyand systematics.Pages 251- PFANDER,P.V. 1987. Once again concerning the Altay Gyr- 259 in B.A. Giron Pendleton, B.A. Millsap, K.W. Cline, falcon. Selevinia 2:38-42. and D.M. Bird [EDS.], Raptor management tech- ROSENKRANZ,D. 1995. Cited in M. Heidenreich. 1997. niques manual. National Wildlife Federation Scientif- Birds of prey: medicine and management. Blackwell ic and Technical Series No. 10. Scientific Ltd., Oxtbrd, England. KEEINST•UBER,G. ANDHJ. SEEBER.2000. Die erfolgreiche S•BLEY,C. 2000. The North American bird guide. Chris- topher Helm, London, England. Brut eines Gerfalke-X-Wanderfalke-Hybriden (Falco WE^VER,J.D. AND T.J. CADE.1991. Falcon propagation. rusticolusX Falco peregrinus)in freier Wildbahn-Re- The Peregrine Fund, Inc., Boise, ID U.S.A. port, MaBnahmen, SchluBfolgerungen.Poplations6- WHITE, C.M. ANDL.F. KIFF.1998. Languageuse and m•s- kol. Greifvogel-u. Eulenarten4:323-332 applied, selective "science;" their roles in swaying LINDBERG,P. 2000. Hybridfalk hSckarigen. Vc•rFdgelviirld public opinion and policy as shown with two North 8:28-29. Americanraptors. Pages 547-560 in R.D. Chancellor, MAY•, E. 1963. Animal speciesand evolution. Belknap B.-U. Meyburg, andJJ. Ferrero lEDs.], Holarctic birds Press of Harvard University Press, Cambridge, MA of prey. ADENEX-WWGBP,Badajoz, Spain. U.S.A. Wn.EY, E.O. 1981. Phylogenetics:the theory and practice --AND L.L. SHORT.1970. Speciestaxa of North of phylogenetic systems.Wiley/Interscience, Hobo- American birds. No. 9 Publ. Nuttal Ornithol. Club. ken, NJ U.S.A. M•TTWOCH,U. 1977. Genetics of sex differentiation. Ac- WYLLIE, I. AND I. NEWTON. 1994. Latitudinal variation •n ademic Press,Burlington, MA U.S.A. the body-sizeof Sparrowhawks(Accipiter nisus) within Britain. Ibis 136:434-440. MORRIS,J. 1972. Peregrine/Saker breeding. Cap. Breed. YOSEF,R., AJ. HELmG, AND W.S. CLAPre.2001. An intra- Diurn. Birdsof Prey1:14-15. generic Accipiterhybrid from Eilat, Israel. Sandgrouse --AND R. STEVENS.1971. Successfulcross-breeding 23:141-144. of Peregrine tiercel and a Saker falcon. Cap. Breed. Diurn. Birdsof Prey,1:5-7. Received 13 April 2004; accepted 24 March 2005 PENNYGUIGK,C.J. 1989. Bird flight performance: a prac- Former AssociateEditor: Juan Jos• Negro