J Raptor Res. 28(2):79-83 ¸ 1994 The Raptor ResearchFoundation, Inc.

BEHAVIOR OF COLONIAL COMMON (Falco tinnunculus) DURING THE POST-FLEDGING DEPENDENCE PERIOD IN SOUTHWESTERN SPAIN

JAVIERBUSTAMANTE EstacidnBioldgica de Do•ana, CSIC, Pabelldndel Per•, Avda. Matra Luisa s/n, 47073 Sevilla,Spain

ABST•½T.--Common (Falco tinnunculus)chicks from a small breeding colony in southwestern Spain fledgedan averageof 31 d after hatchingand remainedat the colony,depending on their parents for food,an averageof 16 more days.Fledglings perched close to and socializedwith their siblingsand unrelatedfledglings. Fledglings started to usehovering flights a mean of 9.7 d after fledging.Social play, in the form of chasesamong fledglings, manipulative play with objects,and the captureof insectsby the fledglingswere observedbefore fledglings became independent. KEY WORDS: fiedging;post-fiedging dependence period,' play; commonkestrel; Falco tinnunculus.

Comportamientodel cernlcalovulgar (Falcotinnunculus) durante el periodode emancipaci6nen suroeste de Espafia RESUMEN.--Enuna pequefiacolonia de cernlcalosvulgares (Falco tinnunculus) en el suroestede Espafia, los pollosvolaron por primera vez una media de 31 dias despuesde la eclosi6ny permanecieronen la coloniauna media de 16 dias m•tsdependiendo de sus padres.Los j6venestenlan un comportamiento socialy seposaban junto a sushermanos y junto a otrosj0venes no emparentados.Los j6venes empezaron a cernirseuna mediade 9.7 dias despu•sdel primer vuelo.Antes de que losj0venes se independizaran se observaronjuegos sociales, bajo la forma de persecucionesentre j6venes,juegos de manipulaci6nde objetosy capturasde insectos. [Traducci6n Autor]

The post-fledgingdependence period, defined as This studygives the estimatedduration of post- the periodafter the first flight during which young fledgingdependency in commonkestrels from a small continueto dependon their parentsfor food, colonyin southwesternSpain, and describesthe adult has receivedlittle attentionin raptors.The common and fledglingbehavior during this part of the breed- kestrel(Falco tinnunculus) is a well-studiedspecies, ing cycle. and its breedingcycle has been relativelywell doc- umented(e.g., Newton 1979, Cramp and Simmons STUDY AREA AND METHODS 1980, Cade 1982, Village 1990). However, infor- Observationswere carriedout in the springand summer mation about the duration of the post-fledgingde- of 1989 in a mixed colonyof commonkestrel and lesser pendenceperiod and behaviorof parentsand off- kestrel(Falco naumanni) in an abandonedsandstone quar- ry (37ø29'N, 5ø38'W) near Carmona,Seville, southwestern spring during this period is scarce.From casual Spain. Common kestrels (12-15 pairs started breeding) observations,it is estimatedthat the young remain nestedon ledgesand in holesof a cliff approximately20 near the nestfor at least2-3 wk after fledging(Vil- m high and 200 m long. The minimum distancebetween lage 1990). Tinbergen (1940) providedsome obser- neighboring nests was 6 m. The area surrounding the vationsof the behaviorof a wild brood during 20- quarry was a flat and open agricultural plain with small fieldsof cereals(wheat and barley), sunflowers,olive and 25 d of post-fledgingdependency. Komen and Myer fruit trees. (1989) describedthe behaviorof nine fledglingsheld We banded 22 common kestrel chicks from five nests in captivity and releasedat the time of fledging. when they were 19-30 d old with laminated plasticbands These fledglingscontinued to return for food for an with an alphanumeric code that could be read with a telescope.Brood sizesat the time of banding were three, averageof 42 d. Komenand Myer (1989) estimated four, four, five, and five chicks. One of the chicks had the durationof the post-fledgingdependence period alreadyfledged when bandedand it was not known from of a wild broodof three fledglingsto be 57 d. which nest it came. At least one other nest producedtwo

79 80 JAVIERBUSTAMANTE VOL. 28, NO. 2

fledglingsthat were not banded. Four chicks, each from tween fledglingswith radiotransmitters(• = 33 d, a different nest, were equipped with radiotransmitters N = 4) and thosewithout (• = 30.5 d; t = 1.46, df attachedwith a backpackharness (Beske 1978; weight with harness9 g, 4% of body mass). The eight chicks = 13, P = 0.17). Fledglingsbecame independent on without radiotransmitters from both of the nests with five average16 d after fledging(range 8-25 d, SD = 5.2, chicks,were marked with a 2.5 cm strip of coloredSAF- N = 20), and there were no differences between LAG piercedon the upper part of the wing (Young and fledglingswith radiotransmitters(• = 15.5 d, N = Kocherr1987), which allowedindividual recognition also 5) and thosewithout (• = 16.1 d; t = -0.21, P = in flight. Adult common kestrels were not marked, and they couldnot be identifiedonce they startedfeeding the 0.83). Neither fledgingdate (F -- 1.02, df = 1,18, P fledglingsout of the nest. = 0.31), fledging age (F = 0.085, df = 1,13, P = Observationswere performedby one observerfrom a 0.78), brood-size(F = 0.446, df--- 2,17, P = 0.65) variable point 130 m from the cliff, with 10x binoculars nor order within the brood (F = 1.683, df = 4,9, P and a 60-80 x field scope.The whole colonywas observed for approximately4-hr periods,between 0630-2000 GMT, = 0.24) had any significanteffect on the duration of every1-3 d (47 hr in 13 d). Observationsstarted 17 June, the post-fledgingdependence period. Fledglingsof when someof the chickswere startingto fledge,and ended the samebrood did not becomeindependent on the 14 July when all but fivebanded kestrels (one radiotagged) sameday and the maximum differencein indepen- had left the vicinity of the colony.Fledglings still at the dencedates within a broodaveraged 11.6 d (SD -- colonyon the last observationday spentmost of the time away from the cliff and were observedinfrequently. The 5.6, N = 5). Two banded chickswithout radiotrans- quarry was again visitedon 18, 22, and 27 July, for 30 mitterswere never observed at the colonyafter fledg- min each day, to checkif any fledglingswere presentor ing and probablydied before independence (9% mor- any radiotransmittersignal could be detected.No fledg- tality, N = 22). lingswere seenand no radiotransmitter signal was detected after 18 July. Fledgling Behavior. Commonkestrel fledglings Behavioralobservations were dictatedon a tape. Every returned infrequently to their nestsafter fledging 30 min the perchinglocation of everyfledgling on the cliff (only 4% of the observationswere at <2 m from the was recorded.Distances between each fledgling and its nest).They perchedon the ledgesand on top of the nest,nearest sibling, and nearestunrelated fledgling were cliff, alone (54% of observations)or in groups(46% estimatedlater on an enlargedphoto of the cliff with 0.5 m precision.I consideredthat fledglingswere perchedin of observations,N = 307). Groups ranged from 2- groupswhen distancebetween fledglings was <2 m. 5 fledglings(• = 3.6 fledglings,SD = 1.4, N = 76) The age of 15 of the chicksat the time of bandingwas and most of them, 84%, includedfledglings from estimatedfrom the equation:Age (d) = 8.14 + 0.17 x differentbroods. Of 20 markedfledglings observed, 8th primary length (mm), obtainedfrom growth data of commonkestrel chicksin central Spain (Veiga 1985). 19 were seenat leastonce in a group with unrelated Fledgingage was the first day a chickwas seenflying or fledglings.Fledglings perched closer to unrelated on a perch it had to reach flying. I consideredthe date of fledglingsthan to their nest(paired t-test for median independenceof a fledgling to be the mean betweenthe distances,t = 2.11, df = 14, P --- 0.049), or to their last day the fledglingwas seenat the colonyand the first siblings(t -- 2, df = 14, P = 0.06), althoughthe last day the fledglingwas no longerseen. Radio-tagged fledg- lingsshowed that not all fledglingspresent at the colony differencewas not significant.Median distanceto were observedon every 4-hr period, indicating that the the nearest sibling was not significantlydifferent duration of the post-fledgingdependence period of fledg- from median distanceto the nest (t = -0.99, df = lings without radiotransmitterscould have been under- 18, P = 0.34; Fig. 1). estimated.Fledglings with radiotransmitters,even if they were not seen, were consideredstill dependentif their Fledglingsfrequently begged for food,perched or signalscould be locatedat the colony.None of the fledg- in flight,from any adultkestrel coming to the colony. lingswith radiotransmitterswere observedor locatedby On at least six instancesthey beggedfor food un- telemetryafter leavingthe colonycliff for the first time. successfullyfrom lesserkestrels. I alsoobserved four I believeno radiotransmitterswere lost,but somefledg- juveniles eating insects4-13 d after fledging.Al- lingscould have died before independence. I found remains of at leastone unidentifiedfledgling eaten by a predator. though the capture was not witnessed,adults were neverobserved delivering to the fledglings. I observedfour fledglingsengaged in play behav- ior with objects16, 16, and 18 d after fledging.The RESULTS age of the fourth was unknown. On separate Commonkestrel chicks fledged at a mean age of occasionstwo fledglingsflew low over the cliff per- 31 d (range 27-36 d, SD = 2.8, N -- 15). There forming prey catchingand plucking movementson were no significantdifferences in fledging age be- smallroots hanging from the cliff. A similar behavior JUNE 1994 COMMONKESTREL POST-FLEDGING 81 was performedon a small twig, a stone,and an {a) airborne feather in quick successionby another fledgling. The fourth fledgling performed prey plucking movementson an objectcarried with its •40% [ talons. The most frequent play behavior were fast ß- N ß 271 flight chasesby two or more fledglings.Fledglings chasedeach other and dovetoward other fledglings perchedon the cliffs making them fly. The roles betweenchaser and chasedchanged frequently, sug- gestingsome kind of socialplay. Chasesamong fledg- lings-from the same and different broods--were observedon 15 occasions,5-13 d after fledging. 0%...... I ..... I I ,-•-I,,, I,, I I • Braking, a behaviorin which one individual nib- ½• 17 37 •7 77 07 1• 137 1•7 •7 107 •17 *• bles at the beak and lore area of another (Sherrod Dintnnae to neat (m) 1983), was observed in one instance between two (b) fledglingsservedhovering fromdifferentfor the broods.first timeFledglings a meanwereof 9.7ob- d afterAdultfledging Behavior. (SD =Adult6.5, common N= 10). kestrels were only .c_ N ß 176 seenat thecolony when delivering prey to the fledg-

lings.Both male and female adults fed the fledglings •o •,o% duringthe post-fledgingdependence period. Of 22 N preydeliveries in whichthe sex of theadult was • 10% recorded,nine were performedby malesand 13 by o females.Twice a male was seentransferring the prey

tothe female before she fed the fledglings. No aerial o%2 17 37 57 77 97 117 137157177 197 217 }252 preytransfers tofledglings wereobserved, andall (½) Distance to sibling (rs) prey transferstook place on cliff perchesor on the ground.After all chickshad fledged, 85.3% of the 40% prey transferstook place on perchesdifferent from thenest (N = 34).All prey delivered were birds and • ao% smallmammals. The average prey delivery rate by N - 299 adult commonkestrels at the colonywas 0.9 prey/ 0 20% hr. Correctingfor the number of fledglingspresent, each fledglingreceived an averageof 1.1 prey/d. ._o After young fledged, adults frequently transferred •-•10% prey to groupsof fledglingsfrom morethan onenest. Adults did not seem to select the fledgling in the 0% groupto which they transferredthe prey. As adults <2 17 ;37 57 77 07 117 1;37 157 177 107 217 250 were not marked, it was not clear if adults were Distance to unrelatedfledgling (m) feedingonly their offspringor occasionallyfeeding other fledglings. Aggression.I neverobserved aggressive behavior among commonkestrel fledglings.Most of the ag- Figure 1. Frequencydistribution of the observationsof gressivebehavior observed was allospecific.A lesser perchedcommon kestrel fledglingsin relation to distance to their nest (a), distanceto the nearest sibling (b), and kestrel adult female took 0.5 hr to expel a common distanceto the nearestunrelated fledgling (c), during the kestrelfledgling from her nestthat had accidentally post-fledgingdependence period. Data on all fledglings landed there. An adult common kestrel attacked a were pooled.The valuesare givenin 5 m intervals,except lesserkestrel female who had previouslyattacked a the first interval, <2 m, and the last interval, >252 m. commonkestrel fledgling. An adult male common Arrows indicate the medians. Distances were measured kestreldove four times toward a fledglingwho was every 30 min with 0.5 m precision. 82 JAwEP,BUSTAMANTE VOL. 28, NO. 2 beggingin a fluttering flight after him and forced Lawrence and Gay 1991, Varland and Loughin the fledglingto perch on the cliff. 1992). Although Newton (1979) contendedthat most DISGUSSION fledglingraptors perch apart from their siblings, Gommon kestrel chicksfledged in southwestern commonkestrel fledglings perched close to eachoth- Spain at an average age of 31 d, similar to that er, were never aggressivetoward other fledglings, reportedby otherauthors in (27-32 d; Gramp and engagedin socialbehavior (beaking) and social andSimmons 1980) andin (34 d; Steyn1982). play(chases) with theirsiblings and with otherfledg- The average duration of the post-fledgingdepen- lings.Siblings of otherspecies of falconsalso socialize denceperiod I observed,16 d, was shorterthan those during the post-fledgingdependence period. Allo- reportedboth in Europe (20-25 d, Tinbergen 1940; preeningand beakinghave also been observed (Sher- 1 mo, Cramp and Simmons 1980; 30 d, Masman rod 1983, Lett and Bird 1987, Varland et al. 1991, 1980 in Komen and Myer 1989), and in Africa (1 Varland and Loughin 1992). mo, Steyn 1982; 41.5 d, Komen and Myer 1989). Fledglings from different broods intermingled I do not think that the kestrel groupsI during the post-fledgingdependence period because observedcontinued together somewhereelse after nestswere close and fledglingsdid notavoid perching leavingthe colony.Siblings would havedisappeared closeto fledglingsfrom other broods.Groups of on the sameday, but they did not. It is still possible fledglingswere not causedby fledglingstrying to that I underestimatedthe post-fledgingdependence stay closeto their own nests,where it could be ex- period of the fledglingswithout radiotransmitters, pectedthat parents came with prey, or byfledglings becauseon averageonly 66% of the dependentfledg- trying to maintain a closegroup with their siblings lings were observedon each 4-hr period. Also, the at somepoint on the cliff, wherethey could be easily death of somefledglings before independence could found and fed by their parents. have remained unnoticed, but the mean duration of Adults providedprey to fledglingsthat were usu- the post-fledgingperiod of the five fledglingswith ally in groupsand did not seemto be able to select radiotransmitterswas not significantlydifferent from who finally obtainedthe prey. They neverbehaved that of the fledglingswithout. This supportsthe idea aggressivelytoward fledglings and never chased that I did not underestimatethe durationof the post- fledglingsfrom otherbroods away from the vicinity fledging dependenceperiod. of their nests, in contrast to what has been observed Somespecies of raptorshave shorter post-fledging in the coloniallesser kestrel (Bustamante and Negro dependenceperiods in populationsbreeding at high- in press).Also fledglingswere not selectiveto whom er latitudes(Bustamante 1993, unpubl. data). The they directedtheir begging.All this suggeststhat high variability amongindividuals in the duration adultscould have accidentally provided food to fledg- of the post-fledgingdependence period, small sample lings that were not their own. Even lesserkestrels, sizesin all studies,and this latitudinal effectprob- which seemto be able to recognizetheir offspring ably explain the high variability among estimates after fledgingand behaveaggressively toward un- from differentauthors. Also, the shortpost-fledging relatedjuveniles near their nests,have beenrecorded dependenceperiod I observedcould be related to the accidentallyfeeding fledglings from othernests (Bus- conditions(possibly, high abundanceof prey) that tamanteand Negro in press)and adoptingunrelated permit that commonkestrels nest coloniallyin this nestlings(Don•tzar et al. 1991, J.L. Tella pers. area. comm.). My observationsalso confirm that the nestis rare- The capacityto recognizeits own offspringafter ly usedby commonkestrels after fledging(Tinber- fledgingcould be lessdeveloped in the commonkes- gen 1940), and that fledglingsplay with objectsdur- trel than in the . The common kestrel ingthe post-fledging period (Komen and Myer 1989), is generallyterritorial and a solitarynester. Breeding possiblyas a way to developand train their hunting colonies, like the one I studied, are uncommon skills. Also, the first prey caught were insectsas (Cramp and Simmons 1980, Village 1990). It is observedby Komen and Myer (1989), and this has probably not necessaryfor commonkestrels to dis- beenobserved in many other speciesof raptors(e.g., criminate betweentheir offspring and unrelatedju- Baker-Gabb 1978, Mueller et al. 1981, Sherrod1983, venilesduring the post-fledgingdependence period Oliphant and Tessaro 1985, Varland et al. 1991, under normal circumstances, and hence the lack of JUNE 1994 COMMON KESTRELPOST-FLEDGING 83

adult discrimination of offspring and lack of ag- fledglingNew Zealand (Falco novaeseelandiae). gressiontoward unrelated fledglingsI observedin Notornis 38:173-182. this colony. LETT, D.W. AND D.M. BIRD. 1987. Postfledgingbe- haviorof Americankestrels in southwesternQuebec ACKNOWLEDGMENTS Wilson Bull. 99:77-82. I am grateful to Dr. F. Hiraldo for his guidance,to J. MUELLER, H.C., N.S. MUELLER AND P.G. PARKER. 1981. Komen, D.M. Bird, D.E. Varland, and J.J. Negro, for Observationof a broodof sharp-shinedhawks in On- helpful commentson a previousdraft, and to S. Nadeau tario, with comments on the functions of sexual di- for correctionsof the English text. This work is part of a morphism. Wilson Bull. 93:85-92. doctoral dissertation at the Universidad Aut6noma de Ma- drid. Funds were provided by project PB87-0405 DGI- NEWTON,I. 1979. Populationecology of raptors.T. & CYT, and fellowshipsfrom the MEC and CSIC. A.D. Poyser, Berkhamsted,U.K. OLIPHANT, L.W. AND S.V. TESSARO. 1985. Growth rates LITERATURE CITED and foodconsumption of hand-raisedmerlins. J. Raptor BAKER-GABB,D.J. 1978. Aspectsof the biologyof the Res. 19:79-84. Australasian harrier Circus aeruginousapproximans. SHERROD,S.K. 1983. Behaviorof fledglingperegrines M.S. thesis,Massey Univ., Palmerstron,New Zealand. The Peregrine Fund, Inc., Ithaca, NY U.S.A. BESKE,A.E. 1978. Harrier radio-taggingtechniques and STEYN,P. 1982. Birds of prey of southernAfrica. David localand migratory movementsof radio-taggedjuvenile Philip, Gape Town, South Africa. harriers. M.S. thesis, Univ. Wisconsin, Stevens Point, TINBERGEN,L. 1940. Beobachtungentiber die Arbeit- WI U.S.A. steilungdes Turmfalken (Falcotinnunculus) w//hrend BUSTAMANTE,J. 1993. The post-fledgingdependence der Fortpfianzungszeit.Ardea 29:63-98. period of the black-shoulderedkite (Elanus caeruleus). VARLAND, D.E. AND T.M. LOUGHIN. 1992. Social hunt- J. Raptor Res. 27:185-190. ing in broodsof 2 and 5 Americankestrels after fledg- -- AND J.J. NEGRO. In press. The post-fledging ing. J. Raptor Res. 26:74-80. dependenceperiod of the lesserkestrel Falco naurnanni. --, E.E. KL•S AND T.M. LOUGHIN. 1991. De- J. Raptor Res. velopmentof foragingbehavior in the Americankestrel. CADE, T.J. 1982. The falconsof the world. Collins, J. Raptor Res. 25:9-17. London, U.K. VEIGA,J.P. 1985. Crecimientode los pollosde Falco CRAMP, S. AND K.E.L. SIMMONS. 1980. Handbook of tinnunculusen el centrode Espafia,aspectos energ6ticos the birds of Europe the and North Africa. y eco16gicos.Ardeola 32:187-201. Vol II. Oxford Univ. Press, Oxford, U.K. VILLAGE,A. 1990. The kestrel.T. & A.D. Poyser,Lon- DONAZAR,J.A., J. J. NEGROAND F. HIRALDO. 1991. A don, U.K. note on the adoption of alien young by lesserkestrels YOUNG,L.S. ANDM.N. KOCHERT.1987. Marking tech- b•zlco naurnanm. Ardea 79:443-444. niques. Pages 125-156 in B.A. Giron Pendleton, B.A. KOMEN,J. AND E. MYER. 1989. Observationson post- Millsap, K.W. Cline and D.M. Bird, [lEDs.I, Raptor fledgingdependence of kestrels(Falco tinnunculus rup- management techniques manual. Nat. Wildl. Fed., •colus)in an urban environment.J. RaptorRes. 23:94- Washington, DC U.S.A. 98. LAWRENCE,S.B. AND C.G. GAY. 1991. Behaviour of Received20 September1993; accepted8 March 1994