The Condor9349-54 0 TheCooper Ornithological Society 1991 GROWTH AND DEVELOPMENT OF GREAT SPOTTED CUCKOOS AND THEIR MAGPIE HOST] M. SOLER AND J. J. SOLER Departamento de Biologia Animal, Ecologia y Gen&ica, Facultad de Ciencias, Universidadde Granada, Granada, Spain Abstract. The increasein body weight,and of tarsal,culmen, wing and tail lengthsin nestlingsof the Great SpottedCuckoo (Clamator glandarius) and of its host,the Magpie (Pica pica), was studiedin the “Hoya de Guadix” (southernSpain). The effectof parasitism on the growthof host nestlingswas also analyzed.Great SpottedCuckoo nestlings grew fasterthan Magpie nestlingsin unparasitizedand in parasitizednests. There is some evidence that the size of the host speciesdid not influence the growth rate of parasitenestlings. When more than one parasite chick was raised in the same nest, competition for food was strong and the younger nestling starved. Magpie chicks had a larger weight asymptote and reached 90% of the asymptotic value earlier in unparasitized nests than in parasitized ones. Key words: Great SpottedCuckoo; Clamator glandarius; Magpie; Pica pica;parasitism; nestlinggrowth. INTRODUCTION Cuckoo does not reject the host’s eggsor young Parasites are generally said to affect the fitness as does the European Cuckoo and therefore, par- oftheir hostsadversely. Two major kinds ofbrood asite young must compete with host chicks for parasites are know; those ejecting all other off- parental care. It is a general assumption that par- spring from the host nest (e.g., European Cuckoo, asites negatively affect the fitness of their hosts Cuculuscanorus) and those growing up together by affecting either the quantity or the quality of with the offspring of the host (e.g., Great Spotted their offspring. The main objective of this study Cuckoo, Clamator glandarius). While it is ob- was to test whether Great Spotted Cuckoo nest- viously detrimental for hosts to be parasitized lings depressedthe growth rate of Magpie host by a cuckoo ejecting their nestmates,the negative nestlings reared in parasitized nests. effects of being parasitized by a non-ejecting Very little information exists on the devel- cuckoo have less often been documented. Ad- opment of Great Spotted Cuckoo parasites, and aptation among cuckoosto sucha situation could the growth rate of host nestlings has only rarely be a rapid development, fast growth and superior been compared with growth rate of nestlings competitive ability (Payne 1977, Marvil and Cruz reared in unparasitized nests (Valverde 1971, 1989). Mundy and Cook 1977). The Great Spotted Cuckoo is an obligate brood STUDY AREA AND METHODS parasite whose palearctic populations are migra- tory, wintering in Africa south of the Sahara and The study was carried out in the “Hoya de Gua- breeding mainly in the Iberian Peninsula, being dix” (southern Spain), a cereal-producing plain numerous in the southern half (Cramp 1985). It at 900-1,100 m altitude (for details, see Soler is considered a specialist brood parasite mainly 1989, 1990) an area in which the Great Spotted parasitizing the Magpie (Pica pica) in Europe Cuckoo parasitism is very recent (Soler and Mol- (Cramp 1985, Soler 1990). ler 1990, Soler 1990). Great Spotted Cuckoo parasitism has a nega- The growth of Great Spotted Cuckoo and Mag- tive effect on Magpie reproduction; the breeding pie nestlings was studied in 17 nests (n = 26 successof the host in parasitized nests is very nestlings). Although 25 Magpie eggs hatched, low, only 19.2% of the nests fledged any host many chicks starved early during the nestling chicks (Soler 1990). The nestling Great Spotted period. The growth rate of Magpie nestlings was also determined in 10 unparasitized nests (n = 4 1 nestlings). During the last days of the nestling ’ Received 12 April 1990. Final acceptance25 Sep- period it is very difficult to measure Great Spot- tember 1990. ted Cuckoo chicks since they frequently escape 1491 GROWTH OF CUCKOOS AND THEIR MAGPIE HOST 5 1 Cuckoo, which parasitizeshosts larger than itself, the size of the host does not influence the growth rate of cuckoo nestlings. When more than one parasite chick exists in the same nest, the younger may starve because of competition with the older conspecific (Soler 1990). The growth rate of three parasite chicks that hatched on alternate days is shown in Figure 2 (data not included in Fig. 1). It is interesting to point out some aspects: 1) The only Magpie ,,,,,,1,,,,,,,,,,,,,,,,,,,,, chick that hatched, died on the next day. 2) The 9 14 19 24 29 3 8 last hatched parasite chick starved to death on DATE the fourth day without having grown. 3) The FIGURE 2. Weightincrease in threeparasitic chicks second parasite chick lived for 13 days, but it (dot. star and asterisk)and one host chick (triangle). was a runt and died on its 14th day. 4) The first bnly one cuckoofledged (f) and the otherthree nest- lingsdied (d). Datesare from May 9th & onwards.All parasite chick to hatch had a nestling period lon- weightswere obtainedin the evening,between 19:30 ger than usual and it left the nest with a weight and 20:30 hours. less than normal (see Fig. 1). In spite of this, it is not rare to find more than one parasite chick is kept at least until day 16; we have found that surviving per nest (Soler 1990); so it is possible in the majority of chicks it remained throughout that in this nest there are some problems with the nestling period, and even after fledging (83%, food availability or with the ability of the indi- n = 12). In most birds this tooth is usually lost vidual or pair to rear their offspring. a few days after hatching (O’Connor 1985). How- ever, in some corvids as in the Jackdaw (Soler GENERAL GROWTH PATTERN and Soler 1990) and Magpie (pers. obs.), it is The values for the various body measurements conserved during the entire nestling period. per day are illustrated in Fig. 3. The development At hatching, the lower mandible is longer than of Great Spotted Cuckoo chicks has been de- the upper mandible. Between days 11 and 12, scribed in two different papers (Valverde 197 1, they reach the same length and after 13 days the Mundy and Cook 1977) but data do not exist latter is longer than the former. After hatching, about the growth rate of the different parameters, the buccal cavity darkens, becoming red with only about the primary feather and tail lengths more conspicuouspapillae, but from day 7 or 8, in one nestling (Valverde 197 1). both lose color intensity and become less con- Dorsal skin darkens between days 3 and 6. spicuous. The eyes begin to open on the fourth Quills develop on day 4 or 5. The feathers of the day and on the ninth they are completely open tail break the vanes between days 8 and 9, and in practically all the nestlings. they appear in the majority of the quills between At hatching, tarsi are pink, but begin to darken days 12 and 13, being well feathered by day 15 about day 4. This is the measured parameter that or 16. See also Valverde (197 1) and Mundy and changedmost quickly, mainly until day 16. From Cook (1977). Wings and tail grow quickly, main- then on, it grows slowly (Fig. 3). Fledglings leave ly after the feathers emerge (Fig. 3). At fledging, the nest with tarsal length very similar to that of wing length was 54% and 56% of that of the adult adults (92% of the male and 97% of the female) male and female length, respectively (data from (Cramp 1985). Cramp 1985). The tail remains lessdeveloped at fledging, representing only 37% of the adult male EFFECT OF PARASITISM ON THE GROWTH length and 40% of the adult female length (data RATE OF HOST CHICKS from Cramp 1985). Magpie chicks had a larger asymptote in unpar- At hatching, the bill is pale pink and begins to asitized than in parasitized nests (Fig. 4) and darken about day 5. The culmen length grows reached90% ofthe asymptotic value (&, = 18.59) slowly (Fig. 3) and at fledging (between day 19 earlier than nestlings from parasitized nests (tgo and the end of the nestling period), it represents = 20.02). Considering only data after nestlings 80% of the adult male length and 81% of the reaching 90% of the asymptote, Magpie fledg- adult female length (data from Cramp 1985). Ac- lings weighed more in unparasitized (X = 167.4 cording to Valverde (197 l), the hatching tooth + 1.8, n = 50) than in parasitized nests (X = 52 M. SOLER AND J. J. SOLER WING LENGTH @ml PRIMARY 6 LENGTH (mml . 90- 120 - . ..( . p.S 60- 8. 60- . *.‘ 8 : .6. e*. 4 ’ 40- 30- */ *f5 .ev ’ .,~I~’ I / I I,, I I I, I I I I,, I I I, I I I I I I f I, I I, I, I I I,, I I I I, I I I I 5 l0 15 20 5 10 15 20 (m4 TAIL LENGTH . C-mm1 RECTRIX LENGTH . 90 . 90 . I 1 ..*; 60 -I DAY IN NESTLING PERIOD DAY IN NESTLING PERIOD FIGURE 3. Mean size for body measurementsof Great Spotted Cuckoo nestlingsas a function of age. Point = one individual, closed circle = two individuals, star = three individuals, open circle = four individuals. 149.7 f 3.8, IZ = 26, t = 4.3, P -C 0.001). This However, in Yellow Warbler (Dendroica pete- supposesan important handicap in future sur- chia) and Red-winged Blackbird (Agelaius vival because it has been demonstrated that phoeniceus),growth rates do not differ signifi- heavier Magpie chicks have a higher probability cantly with or without cowbirds (Weatherhead of survival (Eden 1985). 1989). In our study the growth rate constant is The growth rate of Magpie nestlings in un- significantly smaller for nestlings raised in un- parasitized nests is slower than that cited by parasitized (K = 0.24) than in parasitized nests Ricklefs (1968, K = 0.332) probably becauserunts (K = 0.27, ANCOVA, F = 10.03, P < 0.01).