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ROSENFIELD,R. N., ANDJ. BIELEF’ELDT.1993. Cooper’s regation by habitat in American Kestrels (F&o Hawk (Accipiter cooperii). In A. Poole and E Gill sparverius) wintering in south-central Florida. [eds.], The birds of North America, No. 75. The Auk 105:3&46. Academy of Natural Sciences, Philadelphia, and SNYDER, N. E R., ANDJ. W. WILEY. 1976. Sexual size American Ornithologists’ Union, Washington, dimorphism in hawks and owls of North America. Omithol. Monogr. 20. DC. SPSS, INC. 1997. [email protected]: new statistics.SPSS, ROSENFIELD,R. N., ANDD. L. EVANS.1980. Migration Inc., Chicago. incidence and sequenceof age and sex classesof WOODREY,M. S., AND C. R. CHANDLER.1997. Age- the Sharp-shinnedHawk. Loon 52:66-69. related timing of migration: geographicand inter- SMALLWOOD,J. A. 1988. A mechanism of sexual seg- specific patterns.Wilson Bull. 109:52-67.
The Condor 101:678-681 0 The Cooper Ornithological Society 1999
FACULzTATIVE COMMUNAL BROOD REARING IN CALIFORNIA QUAIL’
DALE E LO?T AND SONKE N. A. MASTR& Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, CA 95616, e-mail: [email protected]
Abstract. We examined communal brooding in broods merging posthatch and being reared together. California Quail Callipepla culifomicu. Most broods Brown et al. (1998) report merged broods in Gambel’s are reared by their parents alone, but 23 of 195 (12%) Quail (Callipepla gambelii). broods combined and were reared communally by all Cooperative care in Acorn Woodpeckers(Meluner- their living parents. A 26% greater fledgling rate of pes formicivorus) (Koenig and Mumme 1987) and communally reared chicks was not statistically signif- Groove-billed Ani (Crotophuga sulcirostris) (Koford icant. Parents of communal broods lived significantly et al. 1990) increases the parents’ longevity, but de- longer (3.1 years) than parents of single broods (1.9 creasesthe annual per adult production of fledglings. years) and hatched significantly more young (36.3 vs. Posthatch aggregation of precocial young occurs in 15.7 young) during their lifetimes. Those that raised Common Eiders (Somateriu nwllissima), and in some their first surviving brood communally were signifi- predationregimens such aggregationcontributes to in- cantly (2.8 times) more likely to hatch a brood the creased ducking survivai
ness. Our goals are to describe communal brood rear- had died. Sixty-six of those banded as young of the ing behavior in California Quail and assessits potential year hatchedyoung and apparentlydied before the end direct and indirect fitness benefits. of our study Twelve apparentlydied without hatching young. This allowed us to determine each bird’s life- METHODS time reproductive output, and to compare the output California Quail are relatively small (160 g) granivo- of communal and non-communalparents. rous/herbivorousgallifotmes. Plumage is dimorphic Of all the birds we banded (n = 158), 102 remained and males are slightly larger than females. Their native in our study area. At the end of the study, 24 of these range extends over most of California and Baja Cali- were still alive and thus not included in our results.If fornia, Mexico below 1,500 m. Their natural annual these 24 were still alive becausethey were exception- mortality is about 70% year’ (Emlen 1940, Raitt and ally long-lived, our study sample would have been bi- Genelly 1964). In late summer, mated pairs and their ased against long-lived individuals. Of these 24, the adult-sized young coalesce into coveys (Johnsgard number of survivors per age group was: 15 months = 1973, Leopold 1977) that roost and forage as units 17 (9 males, 8 females), 27 months = 4 (2 males, 2 (Sumner 1935, Howard and Emlen 1942). Dispersal females), 39 months = 2 (1 male, 1 female), and 51 begins in the fall and continuesinto the beginning of months = 1 female. Because most of the survivors the breeding season.Most yearling males disperse to were quite young, we concludethat few were still alive a nearby area (Emlen 1939, Raitt and Genelly 1964). becausethey were exceptionally long-lived. Young females rarely disperseexcept as members of a The observer divided each day’s observation hours pair (Emlen 1939, Howard and Emlen 1942). In vir- into 15 min blocks. He started searchingfor a specific tually all populations, female mortality is higher, so individual at the start of the block. When he found that there are usually more males (Emlen 1940). In Feb- individual during the block, he recorded its behavior ruary or March, males begin to compete for accessto, during the remaining time. The observer worked and defend, females within the covey. From March through a list of all animals recently alive in a fixed through June, the mated males’ aggressionkeeps the order, starting each day with the individual that fol- pairs temporally isolated in their extensively overlap- lowed the previous day’s last individual. This distrib- ping home ranges (Sumner 1935, Raitt 1960). uted repeatedobservations on each individual over the The female incubatescontinuously except for short daylight hours, assuringthat sampling of each individ- feeding breaks. The male perches nearby while she ual recorded for several hundred minutes represented incubates, preventing unmated males from approach- the entire day. ing her, and probably serving as a sentinel against We recorded behavioral interactions and reproduc- predators. Both parents accompany the highly preco- tive outcomesby dictating the observationsinto a tape cial young. The male spends most of his time acting recorder and later transcribing them for analysis. We as a sentinel with no opportunity to feed. Parents are sampled behavioral events via focal animal sampling, usually aggressive toward other families, attacking and sampled states on an all events basis (Altmann both parents and young chicks (Howard and Emlen 1974). Communal broods were defined as the chicks 1942). from more than one nest combined, with at least one We observed free ranging California Quail at the parent of each nuclear brood accompanyingthe com- University of California Sierra Foothills Field Station, bined brood. Values are reported as means + SD. For 18 km northeast of Marysville, California. Our sub- inferential statistical tests we used Minitab software jects occupied a well defined drainage of 140 ha of (Ryan and Joiner 1994). brushy grasslandgrazed by cattle. This drainage was not hunted during those years, but was hunted prior to RESULTS them, and individuals from nearby hunted areas im- In all, 23 of 195 broods (12%) were combined with migrated during our study. During our study years one or more other broods, creating 11 communal (1983 through 1988), the mean number of individuals broodsfrom 1983 through 1988. One communalbrood was 112 (range 61-159). We observed the quail from was very large, consistingof seven adults (four males a 5-m tower at the foot of the drainagebowl and other and three females) and 41 chicks. Two communal vantage points using 10X binoculars and a 20-60X groups were formed when each of two widowed fe- spotting scope. The distance from observer to subject males combined her brood with a pair’s brood. We saw ranged from l-300 m, and the modal distance was each nuclear brood after it hatched and before it be- about 100 m. came part of a communal brood. All communalbroods During November, December, and January of each were formed of broods from neighboring nests. We study year, we trapped as many individuals as we have precise data on the distance between nine of the could in funnel traps baited with seed. Each trapped pairs of nests from which communal broods formed. individual was marked with a unique combination of This distance(10.7 + 4.0 m) was less than the distance colored leg bands and classified as young of the year between the next most proximate 18 pairs of nests, or adult by its plumage (Leopold 1977). Because the none of which formed communal broods (97.7 + 47.8 observation tower was placed at the bottom of the m) (Mann-Whitney test, W = 45, P < 0.001). Eleven drainage bowl and the area was grazed, observers communal broods were observed from 1983 through could read leg bands and identify individuals. We 1988. searchedadjoining areasbut, like Emlen (1939). never We documented chick survival to 14 weeks in 6 located a bird that had mated and nested in our area. communal broods and 17 non-communal broods Therefore, when an adult disappearedwe assumedit reared in 1987 and 1988. In communal broods, 77% 680 SHORT COMMUNICATIONS survived, whereas in non-communalbroods 61% sur- Quail. Combining broods posthatching avoids pre- vived. This difference is not statistically significant hatch costs such as egg destructionor inadequatein- (Fisher exact test, P = 0.30). cubation of a large combined clutch. Ten adults that participated in communal broods at We do not know whether the parents or the chicks least once disappearedand almostcertainly died before initiate brood merging. The parents would increase the end of our study, as did 56 adults that participated their lifetime reproductive successby initiating brood only in non-comm;nal broods. The 10 communal par- merging. If the- quail chicks initiate brood merging, ents lived significantly longer: 3.1 2 1.O vs. 1.9 5 0.8 thev would increase their inclusive fitness bv extend- years (Mann-Whitney, W = 1695, P < ,001). Com- ing’ their parents’ reproductive careers gi&g each munal parents hatched more chicks: 36.3 f 11.7 vs. chick more siblings at no cost to themselves.Because 15.7 ? 8.6 (independenttc4 = 5.30, P < ,001) in more the fitness gain must be assignedto those that initiate breeding seasons:2.3 5 0.7 vs. 1.5 ? 0.7 (Mann-Whit- brood merging, it will be important to identify the ini- ney, W =1724.5, P < 0.01). tiators. Eight adults raised their first surviving brood com- The greater survival of communalmales may be due munally; of these, seven (87.5%) also hatched a brood in part to their increased foraging compared to non- the following year. Fifty-eight raised their first surviv- communal males, which is likely to reduce the weight ing brood as a nuclear family; of these, only 18 (31%) 1oss typical of brood-rearing males (Sumner 1935, also hatched a brood the following year. This differ- Riatt 1960). We have not identified a mechanism to ence is highly significant (Fisher exact test, P = increase female survival, but both sexes may benefit 0.004). Thus, the longer lives and increased lifetime from reduced predation via dilution (Calvert et al. reproductionof communal parents was apparentlyre- 1979) or increasedpredator detection (Kenward 1978). lated to participation in communal brood rearing early Given its advantages,it is somewhat surprisingthat in their reproductivecareer. communalbrood rearing is not more frequent. Because One reason for increased longevity is suggestedby only neighboring broods merge, merging may depend comparing the time budgets of five communal brood on adults developing mutual tolerance of their neigh- males and nine non-communalbrood males which we bors during mating and incubation, and/or be con- had observed for more than 15 hr each. Each male’s strainedby the limited mobility and small home range data was summarizedas a single data point in each of of young chicks. Because females seldom disperse, three categories:percent time (1) vigilant, (2) feeding, merged broods might be related through their mothers. and (3) resting. The communal brood males suent less time‘vigilant G2.6 ? 4.8% vs. 73.0 f 5.7%) ind more J. Calkins, N. Davies, J. Eadie, S. Emlen, J. Hagelin, time feeding (36.2 2 5.5% vs. 14.5 2 2.6%) and rest- W. Koenig, M. West, and two anonymous reviewers ing (21.2 2 4.2% vs. 13.4 2 4.2%). All these differ- read an earlier draft of this manuscriptand their com- ences are statisticallysignificant (independentt,,, two- ments greatly improved the present version. We are tailed P < 0.01). grateful to the staff of the University of California Si- erra Nevada Foothills Field Station. The study was DISCUSSION supported by federal funds administered through the Twelve percent of California Quail broods were raised Agricultural ResearchStation as Hatch project 3915. communally. Parents that raised their first surviving brood communally lived longer and hatched more LITERATURE CITED young. The correlation of communal brooding in Cal- ifornia Quail with greater longevity and more broods ALTMAN, J. 1974. Observational study of behavior: does not by itself demonstratecausality. If there were sampling methods. Behaviour 49:227-267. a fixed probability of rearing a brood communally in ARMSTRONG,A. J., AND J. JURITZ.1996. Prediction of any given year, adults that lived longer would be more cooperativebreeding by terrestrial bird speciesin likely to have raised a brood communally. But if com- South Africa. Ostrich 67:1-8. munal brood rearing did not affect longevity, com- BROWN,D. E., J. C. HAGELIN,M. TAYLOR,AND J. GAL- munal rearing would be as likely to follow single fam- LOWAY.1998. Gambel’s Quail (Callipepla gam- ily brood rearing as to precede it. In fact, parentsthat belii). In A. Poole and E Gill [eds.], The birds of reared their first surviving brood communally were North America, No. 321. The Birds of North more likely to hatch additional broods. This supports America, Inc., Philadelphia. the notion that communal brood rearing extends an CALVERT,W. H., L. E. HEDRICK,AND L. I? BROWER. individual’s reproductivecareer. 1979. Mortality of the monarch butterfly, Danaus Communal nesting and brood rearing also was re- plexippus: avian predation at five over-wintering lated to increasedlongevity of parental Groove-billed sites in Mexico. Science 182:1272-1275. Anis (Koford et al. 1990) and Acorn Woodpeckers CRAIG,J. L., AND I. G. JAMIESON.1990. Pukeko: dif- (Koenig and Mumme 1987), but in these altricial spe- ferent approachesand some different answers,p. cies communal groups fledged fewer young adult-’ 387-414. In F?B. Stacey and W. D. Koenig [eds.], year’. Pukeko (Porphyria porphyn’o) young are pre- Cooperative breeding in birds. Cambridge Univ. cocial with respect to locomotion, although they must Press, Cambridge. be fed for several weeks. Communal groups nest in a EADIE,J. McA., AND B. E. LYON. 1998. Cooperation, single nest and, again, per capita productiondecreases conflict and creching behavior in Goldeneye as group size increases (Craig and Jamieson 1990). Ducks. Am. Nat. 151:397-408. There was no evidence of sucha trade-off in California EMLEN,J. T, JR. 1939. Seasonalmovements of a low- SHORT COMMUNICATIONS 681
density Valley Quail population.J. Wildl. Manage. MENDENHALL,V. M. 1979. Brooding of young duck- 3:118-130. lings by female Eiders Somateria mollissima. Or- EMLEN, J. T, JR. 1940. Sex and age ratios in survival nis Stand. 10:94-99. of the California Quail. J. Wildl. Manage. 4:92- MUNRO,J., AND J. BEDARD.1977. Gull predation and 99. creching behaviour in the Common Eider. J. HOWARD,W. E., AND J. T EMLENJR. 1942. Intercovey Anim. icol. 46:799-810. social relationships in the Valley Quail. Wilson NASTASE,A. J. 1983. Behavioral ecology of the Can- Bull. 54:162-170. ada Goose Branta canadensis canadensis. Ph.D. JOHNSGARD,F? A. 1973. Grouse and quails of North diss., Univ. Pittsburgh,Pittsburgh, PA. America. Univ. Nebraska Press, Lincoln, NE. Rra?~, R. J., JR. 1960. Breeding behavior in a popu- KENWARD,R. E. 1978. Hawks and doves: factors af- lation of California Ouail. Condor 62:284-292. fecting successand selection in goshawk attacks RAITT, R. J., AND R. D. &NELLY. 1964. Dynamics of on wood-pigeons. J. Anim. Ecol. 47:449-460. a population of California Quail. J. Wildl. Man- KOENIG,W. D., AND R. L. MUMME. 1987. Population age. 28:127-141. ecology of the cooperatively breeding Acorn RYAN, B. E., AND B. L. JOINER.1994. Minitab hand- Woodpecker.Princeton Univ. Press,Princeton, NJ. book. 3rd ed. Duxbury Press, Belmont, CA. KOFORD,R. R., B. S. BOWEN,AND S. L. VEHRENCAMP. SHERWOOD,G. A. 1967. Behavior of family groups of 1990. Groove-billed Anis: joint-nesting in a trop- CanadaGeese, p 340-355. In Trans. 32nd N. Am. ical cuckoo, p. 333-355. In F? B. Stacey and W. Wildl. Nat. ResourceConf., Wildl. Manage. Inst., D. Koenig [eds.], Cooperative breeding in birds. Washington,DC. Cambridge Univ. Press, Cambridge. STACY,l? B., AND W. D. KOENIG.1990. Cooperative LEOPOLD,A. S. 1977. The California Quail. Univ. Cal- breeding in birds: long term studies of kcology ifornia Press, Berkeley, CA. and behavior. Cambridge Univ. Press,Cambridge. MENDENHALL,V. M. 1975. Growth and mortality fac- SUMNER,E. L., JR. 1935. i life history study of ;he tors of Eider ducklings (Somateria m. mollissima) California Quail, with recommendations for its in north-east Scotland. Ph.D. diss., Univ. Aber- conservation and management.Calif. Fish Game deen, Aberdeen, Scotland. 21:167-253, 275-342.
The Condor 101:681-686 0 The CooperOrnithological Society 1999
INCUBATION BEHAVIOR OF LONG-TAILED TITS: WHY DO MALES PROVISION INCUBATING FEMALES?’
B. J. HATCHWELL,M. K. FOWLLE,D. J. Ross AND A. E RUSSELL Department of Animal and Plant Sciences, University of Sheffield, ShefJield SIO 2TN, U.K., e-mail: [email protected]
Abstract. The incubation period of Long-tailed of either males or females influenced the length of the Tits Aegithalos caudatus is highly variable, ranging incubation period. from 14 to 21 days. Females alone incubate the eggs, Key words: Aegithalos caudatus, courtship feed- but males provide females with some food during the incubation period, although females must also forage ing, incubation, Long-tailed Tit. for themselves. Our aim was to investigate whether male provisioning of incubatingfemales influencedfe- Male birds often provide food for females during the male incubation behavior and the length of the incu- breeding season,behavior known as courtshipfeeding. bation period. Provisioning rates varied between Provisioning may occur during pairing or egg-laying, males, and female nest attentivenesswas negatively but it also is frequent during the incubation period related to short-term variation in the rate at which their (Ricklefs 1974). The traditional interpretationof court- partner fed them. However, the provisioning rate of ship feeding is that it serves a pair-bonding function, individual males also varied significantlythrough time, helping to cement the relationship between breeding and there was no significant effect of male care on partners (Lack 1940, Kluijver 1950). A second hy- female incubationacross the whole incubationperiod. pothesis proposes that courtship feeding provides in- There was no evidence that variation in the behavior formation to females about male quality, in particular, his ability to feed nestlings (Nisbet 1973, 1977). Fe- male fitness may depend on the extent of paternalcare ’ ’ Received 27 October 1998. Accepted 15 April (Lyon et al. 1987, Yasukawa et al. 1990, Davies and 1999. Hatchwell 1992), so such information, and male ad-