802 SHORT COMMUNICATIONS

The Condor962702-805 0 The CooperOrnithological Society 1994

ACTIVITY, SURVIVAL, INDEPENDENCE AND MIGRATION OF FLEDGLING GREAT SPOTTED CUCKOOS ’

MANUEL SOLER, Jo& JAVIER PALOMINO AND JUAN GABRIEL MARTINEZ Departamento de Biologia Animal y Ecologia, Facultad de Ciencias, Universidadde Granada, E-18071 Granada, Spain

JUANJosh SOLER Department of Zoology, Uppsala University, Villaviigen9, S-772 36 Uppsala, Sweden

Key words: Broodparasitism;Clamator glandarius; description of the study site is given in Soler (1990) Great SpottedCuckoo; magpie; parental care:Pica pica; and Soler et al. (in press). post-fledgingdependence. In all nests found, chicks were banded with num- bered aluminium rings (Spanish Institute for Nature Parental care of fledglingstends to last at least as long Conservation-ICONA). In 1991, a total of 19 Great as that of nestlings, and in some casestwice as long Spotted Cuckoo chicksreared in 13 parasitizedmagpie (Skutch 1976). The post-fledging dependence period nests were fitted with radiotransmitters. In 1992, 21 (hereafter called fledalina DeiiOd)is critical for iuvenile cuckoochicks and four magpiechicks were radio-tagged. survival (Royama 1$66rSullivan 1989) and the prob- In 1992, only one cuckoo chick in each nest was pro- ability of survival to independence appears to be an vided with a radiotransmitter and all were weighed adequate estimate of relative probabilities of survival with a 300 g Pesola spring balance one or two days to breeding in many bird species(Magrath 1991). before they left the nest. Other cuckoo chicks in these For avian brood parasites,very little is known about nestswere given a unique combination of color bands the behavior of foster parents in relation to their fledg- to enable individual recognition. To facilitate identi- ling parasites(see review in Payne 1977 and Rothstein fication, we attached a color tag (8 cm) of nylon coated 1990).Only one detailed studyexists (Woodward 1983) vinyl (Saflags)on each color ring. namely, on the fledging period of the Brown-headed One or two days before leaving the nest (when 15 Cowbird, Molothrus ater. Cowbirds are conspicuous days old), 44 chicks were fitted with radiotransmitters after they leave the nest (Woodward 1983) in contrast weighing approximately 4 g each (back-pack harness to other fledgling parasitessuch as EuropeanCuckoos, included), with a trailing 20 cm wire antenna (Biotrack. Cuculuscanorus, which hide in the vegetation and re- Dorset, UK). Transmitters had a range up to 1,000 m main immobile for long periods of time (Wyllie 1981). and a lifespan of 1O-l 2 weeks. The Great Spotted Cuckoo Clamator glandarius is This study was conducted throughout the breeding an obligate brood parasite which in Europe mainly seasonsof 1991 and 1992. A total of 111 and 166 parasitizesmagpies Pica pica (Cramp 1985). We have magpie nests was studied in 1991 and 1992, of which shown that Great Spotted Cuckoo fledglings often 58.6% and 66.9%, respectively,were parasitizedby the formed flocks (groupsize rangedfrom one to five), and Great Spotted Cuckoo. Nests were inspected at least that every group of cuckoo fledglingswas attended by once a week, and parasitized nests two, three or four a group of magpies (Soler et al., unpubl. manuscript). times a week. Cuckoo fledgling groups were frequently attended by Fledglings often remained well-hidden in the tree more magpiesthan those involved in nestling rearing, canopy. We therefore had at least one radio-tagged and the feedingrate of fledglingcuckoos increased with cuckoo chick in every group. We used the radio-track- the number of cuckoosper group and the number of ing method only to locate the trees occupied by the adult magpiesattending the group of fledglingcuckoos. radio-taggedchicks. Between 25 May and 8 August in We studied the behavior of fledgling Great Spotted both 1991 and 1992, systematic observations were Cuckoos. We paid special attention to the following made. Each group was located at least two or three aspects:(1) changesin the activity of fledglingcuckoos times per week and, when the fledglingswere present with age, (2) survival of fledglingcuckoos and magpies in an open and easily visible area, each fledgling was in parasitized nests,(3) post-fledglingdependence, and watched for 0.5-3 hr. (4) migration of fledgling and adult cuckoos. A total of 104 hr of effective observation was re- corded in 1991 and 164 hr in 1992. We observed pa- MATERIAL AND METHODS rental feedings and the behavior of young from a dis- Field work was carried out in Hoya de Guadix, south- tance of 20-100 m (mostly 40-50 m, and from the em Spain (37”10’N, 3’1 l’W), a cereal-producingpla- cover of a car wheneverpossible) with binoculars(10 x ). teau that is approximately 1,000 m a.s.1. A detailed The following data were recorded: individual, time of day, location, whether the fledgling was on the ground or perching in a tree, whether the bird was flying alone I Received 11 January1994. Accepted22 April 1994. or following one of the foster parents, and what the SHORT COMMUNICATIONS 803

TABLE 1. Survival and mass of Great Spotted Cuckoo fledglings.

1991 1992 Mass &) n % n % (i + SD)

Survived until independence 11 64.7 13 61.9 138 ? 8.31 Failed to survive 6 35.3 8 38.1 124 & 10.82 Depredated 5 29.4 5 23.8 130 * 4.27 Starved 1 5.9 3 14.3 115 & 13.32 Total 17 100.0 21 100.0 133 & 11.52

fledgling was fed by an adult magpie. The age of the fitted with radiotransmitters. Two of these chicks youngwas expressedas daysafter leaving the nest, with starved, four and six days, respectively, after leaving day 1 being the first day after leaving the nest. the nest. The other two were killed by predators four Relationships between behavioral parameters of and twelve days, respectively, after leaving the nest. groups of fledgling cuckoosand parametersof attend- Independenceand migration. Adult Great Spotted ing magpieswere analyzed by, first calculatingthe cor- Cuckoosleft the study area in mid-June in both years, relation coefficients(r) for eachgroup separately, which disappearing over a few days. The last adult cuckoo valueswere z-transformed (Sokal and Rohlf 1981), and was seen on 17 June 1991 and 18 June 1992. then, testing if they differed from 0 in a one-sample Post-fledgingdependence of Great Spotted Cuckoo t-test.When analysesinvolved fledglingsthey were made fledalinasranned from 25 to 59 davs (2 = 33.2, SD = in the same way, but we used only one fledgling per 11.63, n = 215).This large variation ‘is due to every group (the radio-taggedfledgling which is the one with fledgling cuckoo being fed until the moment in which greaternumber of observations),because the behavior all of them left the area. Thus, the sooner a cuckoo of fledglingsin each group is not independent. chick leaves the nest, the more prolongedis the period during which it is attended by magpies. In 1991. all the six arounsof fledglingsleft the breed- RESULTS ing area between 9 fuly and 8 August. In 1992 two Age-relatedchanges in cuckooactivity. During the first groupsdisappeared considerably sooner, between 5 and three davs out of the nest, Great Snotted Cuckoo fledn- 12 June. The other 11 groupsleft the area at about the lings perched quietly in the vicinity of the nest, w& same time as in 1991. When a fledgling group disap- hidden in the tree canopy, except when magpiescame peared from the home area, we looked for the radio- to the area with food. After these three days, fledging taggedbirds in a more extensive area (approximately cuckoosbecome more active, moving on their perches 5 km diameter), and if no birds were found the group and flying around more frequently. Later, the young was consideredto have migrated. Usually the fledglings chased the magpies actively while begging for food. left suddenly and directly. Only on one occasionwas Cuckoo groups were very sedentary, they usually oc- a group which had disappeared from the home area cupied the same area over the season. found again, at a distance of 2.3 km. This group re- The number of flights per hour did not increasewith mained at this second site for 5 days and then disap- age (mean r = -0.07, H,: r = 0, t = 0.3, P = 0.77), peared again. and the number of times that fledglings flew to the The last adult cuckoo was seen in the study area on ground did not increase as the fledglingsaged. Time 17 June in 1991 and on 18 June in 1992. Thus, it can spent on the ground did not vary with age either; con- be concluded that fledgling and adult cuckoosdo not trary to expectation, we found a slight decreasewith migrate together,adults leaving the breeding area about age (mean r = -0.18, H,: r = 0, t = 0.79, P = 0.49). two months earlier than the majority of the juveniles. Unexpectedly fledgling cuckoosdid not feed them- selves. In 268 hr of effective observation, we only oc- DISCUSSION casionallysaw a fledgling cuckoo peckingat objectson Age-related changesin activity. Davies (1976, 1978) the ground, but never saw self-feeding. showedthat parental reluctanceto feed the youngforc- F~edglingsurvival.Out ofa total of 38 fledglingcuck- es them to become more independent. This observa- oos fitted with radiotransmitters. 24 (63.2%) survived tion has been SuppOrted in most specieswhere fledgling to independenceand 14 (36.8%) died; either’from pre- behavior has been studied (Holheback 1974, Moreno dation (26.3%) or starvation(10.5%). Resultswere sim- 1984. Buitron 1988. Husbv and Slaasvold 1992). How- ilar in both study years (Table 1). Great Spotted Cuck- ever,‘it has been suggestedthat the-dependenceperiod oos that died after fledging weighed significantly less is determined by the young in some raptor species when ringed than those which survived to indepen- where the migratory departureof youngaffect the post- dence (Table 1, Mann-Whitney U-test, U = 13.5, P = fledging dependenceperiod (Bustamante and Hiraldo 0.004). Those which were starved did not weigh sig- 1990, Ferrer 1992). nificantly different from those which were preyed upon In Brown-headed Cowbird fledglings, activity was (Table 1, Mann-Whitney U-test, U = 5.5, P = 0.27). also found to increasewith age. It is likely that the host In three parasitized magpie nestswhere both cuckoo parentsforce the youngto feed themselvesby becoming and magpie chicks fledged, four magpie chicks were more reluctant and finally by refusing to provide food 804 SHORT COMMUNICATIONS

(Woodward 1983). However, this was not the casewith fledglingdependence period in the Great SpottedCuck- Great Spotted Cuckoo fledglings,for which time spent oo? We suggestthe primary reason to be ecological in self-feeding did not increaseand time spent begging constraintsrelated to food availability. Cuckoosin gen- did not decrease;indeed, the provisioning rate of each eral have a specialized diet based on gregarioushairy fledgling cuckoo tended to increasewith age (Soler et caterpillars, which in our study area are not available al., unpubl. manuscript). after June (Soler et al., unpubl. data). At this time of According to Norton-Griffiths (1969), these changes the year and later, the only abundant prey are beetles have two components:the first is a motivational change and grasshoppers,which may not be easy to catch for leading to a reduction in the parents’ feeding behavior, juvenile cuckoos.Therefore, the best survival prospect and the second is dependent on how intensively and for fledglingsmay be to prolong feeding by the host in for how long the young demand food. Fledgling cuck- order to store the fat necessaryfor migration. Our ob- oos begged loudly and persistently throughout the servations suggestthat young cuckoosleave on migra- fledgling period; however, a similar behavior has been tion without having learned to forage by being totally found in the parasitic fledgling Brown-headed Cow- reliant on magpiefoster parents.In the EuropeanCuck- birds (Woodward 1983) even thoughtheir host stopped oo, the post-fledgling dependence period is consider- feeding them. The intensive beggingbehavior of fledg- ably shorter,probably becauseadequate prey are avail- ling magpiesfrom unparasitizedbroods elicited no re- able for juvenile European Cuckoos.This argument is action from their parents after days 5 l-55 (Husby and supportedby the fact that adult Great Spotted Cuckoos Slagsvold 1992). migrate in mid-June, whereasadult European Cuckoo Why did magpiesnot reduceparental care when they migration through Europe lasts from late June to Oc- were rearing cuckoos?This is discussedin detail by tober (Wyllie 1981). Soler et al. (unpubl. manuscript),in which three nonex- Adult Great Spotted Cuckoos migrate earlier than clusive hypotheses are proposed. (1) The fledgling juveniles. In the European Cuckoo it has also been cuckoo may be a supernormal releaser for parental recordedthat southwardautumn migrationsbegin ear- care. (2) Adult magpies attending fledgling cuckoosin lier in adultsthan in juveniles (Wyllie 1981). This means the groupswere displayingtheir ability as good parents that young cuckoo migrants are able to find their win- which might increasetheir possibilitiesto obtain a mate tering area without the help of conspecifics,suggesting and/or a territory. (3) Parental care provided by mag- a genetic basis to this behavior, as has been demon- pies other than the fosterparents could be an unselected strated in the BlackcapSylvia atricapilla (Berthold and consequenceof the fact that they are exposed to the Quermer 1981, Helbig 1991). beggingfledglings. We thank M. Martin-Vivaldi for field assistance. Fledging survival, independence and migration. The Constructive comments from T. R. Birkhead, S. Ulf- survival rate of Great Spotted Cuckoo chicks to in- strand, A. Zahavi and two anonymousreferees greatly dependence (63.2%) is high, considering that in un- improved the manuscript. We are specially indebted parasitized magpie nests an overall mortality rate of to A. P. Moller for suggestionsand valuable criticism 50% between the end of the nestling period and in- on an earlier version of the manuscript. Financial sup- dependencehas been recorded (Husby and Slagsvold port was given by the Commission of the European 1992). Survival rate has also been found to be very Communities (SCI*-CT92-0772) and DGICYT (PS90- high in the European Cuckoo, where 32 of 38 wing- 0227 researchproject). taggedyoung reached independence(Wyllie 1981). Martin (1987) stated that large and heavy nestlings LITERATURE CITED enjoy a higher probability juvenile survival. This as- sertion has been supported in some studies, but its BERTHOLD, P., ANDU. QUERMER. 1981. Genetic basis generalvalidity remains to be demonstrated(reviewed of migratory behaviour in Europeanwarblers. Sci- by Magrath [ 19911, but see Linden et al. [ 19921 for ence 212177-79. conflicting evidence). We have found a strongpositive BUITRON,D. 1988. Female and male specialization relationship between nestling weight and juvenile sur- in parental care and its consequencesin Black- vival. In unparasitized magpie nests, it has also been billed Magpies. Condor 90:29-39. found that smaller nestlingssuffer a higher rate of post- BUSTAMANTE,J., AND F. HIRALDO 1990. Factors in- fledgling mortality as compared to larger ones (Husby fluencingfamily rupture and parent-offspringcon- and Slaasvold 1992). flict in the Black Kite Milvus migrans. Ibis 132: The post-fledglingdependence period of Great Spot- 58-67. ted Cuckoo fledglingsis unusuallylong (in some cases Cm, S. [ED.]. 1985. The birds of the Western Pa- more than 50 days). This period lasts about 20 days learctic,Vol. IV. Oxford University Press,Oxford, for fledglingmagpies (Husby and Slagsvold1992). In the U. K. European Cuckoo it is as short as in non-parasitic DAVIES, N. B. 1976. Parental care and the transition species of the same size, young parasites remaining to independent feeding in the young Spotted Fly- dependent on the hosts after fledging for two to three catcher(Muscicapa striata). Behaviour59:280-295. weeks (Wyllie 1981). However, a long post-fledgling DAVIES,N. B. 1978. Parental meannessand offspring dependence period seems to be the rule in Clamator independence: an experiment with hand-reared species,given that it has been recorded that Striped Great Tits Parus major. Ibis 120:509-5 14. Cuckoo (Clamator levaillantii) fledglingswere fed by FERRER, M. 1992. Regulation of the period of post- their foster parents for at least 36 days after leaving fledgingdependence in the SpanishImperial Eagle the nest (Steyn 1973). Why is there such a long post- Aquila adalberti. Ibis 134:128-l 33. SHORT COMMUNICATIONS 805

HELBIG,A. J. 1991. Inheritance of migratory direc- ROYAMA,T. 1966. Factors governing feeding rate, tion in a bird species:a cross-breedingexperiment food requirementsand brood size ofnestling Great with SE- and SW-migrating Blackcaps(Sylvia atri- Tit Parus major. Ibis 108:313-347. capilla). Behav. Ecol. Sociobiol. 289-12. SKUTCH,A. F. 1976. Parent birds and their young. HOLLEBACK,M. 1974. Behavioral interactions and Univ. Texas Press, Austin, TX. the dispersalof the family in Black-cappedChick- SOKAL,R. R., ANDF. J. ROHLF. 1981. Biometry. 2nd adees. Wilson Bull. 86:466-468. edn. W. H. Freeman, New York. HUSBY,M., ANDT. SLAGSVOLD.1992. Post-fledgling SOLER,M. 1990. Relationship between the Great behaviour and survival in male and female mag- Spotted Cuckoo, Clatnator glandarius. and its pies Pica pica. Omis Stand. 23:483490. corvid hosts in a recently colonized area. Omis L~N&N, M., L. GUSTAFSSON,AND T. P;~RT. 1992. Se- Stand. 21:212-223. lection on fledgingmass in the Collared Flycatcher SOLER,M., AND J. J. SOLER. 199 1. Growth and de- and the Great Tit. Ecology 73:336-343. velopment of the Great Spotted Cuckoosand their MAGRATH,R. D. 1991. Nestling weight and juvenile magpie host. Condor 93:49-54. survival in the blackbird, Turdus me&a. J. Anim. SOLER,M., J. J. SOLER,AND J. G. MARTINEZ. In press. Ecol. 60:335-35 1. Sympatry and coevolution between the Great MARTIN, T. E. 1987. Food as a limit on breeding Spotted Cuckoo (Clamator glandarius) and its birds: a life-history perspective.Annu. Rev. Ecol. magpie (Pica pica) host. In S. I. Rothstein [ed.], Syst. 18:453+87. Evolution and ecology of brood parasitism. MORENO,J. 1984. Parental care of fledged young, STEYN,P. 1973. Some notes on the breeding biology division of labor, and the development of foraging of the Striped Cuckoo. Ostrich 44: 163-169. techniques in the Northern Wheatear (Oenanthe SULLIVAN,K. A. 1989. Predation and starvation:age- oenanthe L.). Auk 101~741-752. specific mortality in juvenile juncos (Bunco phae- NORTON-GRIFFITHS,M. 1969. The organization,con- notus). J. Anim. Ecol. 58:275-286. trol and development of parental feeding in the WOODWARD,P. W. 1983. Behavioralecology of fledg- Oystercatcher (Huematopus ostrulegus). Behav- lina Brown-headed Cowbirds and their hosts. iour 34:55-l 14. Condor 85:151-163. PAYNE,R. B. 1977. The ecologyof brood parasitism WYLLIE, J. 1981. The cuckoo. B. Y. Batsford, Lon- in birds. Ann. Rev. Ecol. Syst. 8:1-28. don. Ro-~Hs-~~~N,S. I. 1990. A model system for coevo- lution: avian brood parasitism. Ann. Rev. Ecol. Syst. 21:48 l-508.

The Condor96305-809 0 The CooperOmithologkxl Society 1994

A TECHNIQUE FOR MEASURING PRECOCIAL CHICKS FROM PHOTOGRAPHS’

BRUCE E. LYONS Division of Life Sciences, University of Toronto, Scarborough Campus, Scarborough, Ontario, MI C IA4 Canada

Key words: American Coot; Fulica americana;body ulation (Perrins 1965) indicating that these measures size; distance; growth rate; nidifusous chicks: photog- can be important indices of fitness.In nidicolousbirds, raphy. measuresof nestling body size can be obtained simply by visiting nests. However, obtaining growth data for Measures of the body size and growth rate of chicks the nidifugous young of precocial birds is often far are central to many avian studies (Ricklefs 1983). In more difficult. Here I describe a technique for esti- some species,growth rate or body size at fledging is mating the size of objects in photographs and show correlated with subsequentrecruitment into the pop- how this technique can be used to obtain size and growth measuresfor chicks, especially the swimming chicks of aquatic speciesthat can be approachedwith I Received 13 July 1993. Accepted 3 February 1994. floatingblinds (Nuechterlein 1982). I then demonstrate * Present address:Kananaskis Field Stations. Uni- the accuracyand utility of this method usingdata col- versity of Calgary,2500 University Dr. N.W., Calgary, lected from both captive and free-ranging American Alberta, T2N lN4, Canada. Coot (Fulica americana) chicks.