Val Nolan Jr. died in March 2008 (see PDF of obituary in The Auk). Val was an eminent ornithologist, Professor of Law and Biology, and founder of a tradition of excellence in the study of birds at Indiana University where he trained 21 Ph.D. students. His specialties were the ecology and behavior of birds, principally passeriforms. His research interests included population biology, mating systems and parental behavior, natal dispersal and the development of site attachment in both migratory and nonmigratory passerines, dominance, and differential migration and the differential winter distribution that such migration produces. He worked almost entirely with free-living birds.
- 1957-58 Guggenheim Fellow (two projects: one legal and one biological)
- 1976 Fellow, American Ornithologists' Union
- 1976 & 1980 Acting Dean, School of Law, Indiana University
- 1982 Fellow, American Association of the Advancement of Science
- 1986 Brewster Memorial Award ('Most Meritorious Body of Work' on birds of western Hemisphere in last 10 years)
- 1987 IU Distinguished Alumni Service Award
- 1989 Indiana University Academy of Law Alumni Fellows
- 1989-90 Vice-President, American Ornithologists' Union
- 1996 Editor (with E.D. Ketterson), Current Ornithology (NY: Plenum Press)
- 1988 Editorial Board, Journal of Avian Biology
- 1998 Margaret M. Nice Award (with E.D. Ketterson), Wilson Ornithological Society
Nolan, V. Jr. 1978. Ecology and behavior of the prairie warbler Dendroica discolor. American Ornithologists' Union. Ornithological Monographs 26:1-595
Nolan, V. Jr., C.F. Thompson, and M. Carey. 1975. Abstract: Fidelity of indigo buntings Passerina cyanea to sites occupied in previous breeding seasons. Emu (Royal Australasian Ornithologists' Union) 74 (Suppl.):289
Nolan, V. Jr., and C.F. Thompson. 1975. Occurrence and significance of anomalous reproductive activities in two North American nonparasitic cuckoos Coccyzus spp. Ibis 117:496-503
Carey, M. and V. Nolan Jr. 1975. Polygyny in indigo buntings: a hypothesis tested. Science 190:1296-1297
Nolan, V. Jr. 1975. External differences in newly hatched yellow-billed and black-billed cuckoos (Coccyzus americanus and C. erythrophthalmus). Condor 77:341
Ketterson, E.D. and V. Nolan Jr. 1976. Geographic variation and its climatic correlates in the sex ratio of eastern-wintering dark-eyed juncos (Junco hyemalis). Ecology 57:679-693
Nolan, Jr. V. and C.F. Thompson. 1978. Egg volume as a predictor of hatchling weight in the brown-headed cowbird (Molothrus ater). Wilson Bulletin 90:353-358
Nolan Jr., V. 1978. Ecology and behavior of the prairie warbler Dendroica discolor. American Ornithologists' Union, Ornithological Monographs 26:1-595
Nolan Jr., V. and C.F. Thompson. 1978. Egg volume as a predictor of hatchling weight in the brown-headed cowbird (Molothrus ater). Wilson Bulletin 90:353-355
Ketterson, E.D. and V. Nolan Jr. 1978. Overnight weight loss in dark-eyed juncos (Junco hyemalis). Auk 95:755-758
Carey, M. and V. Nolan Jr. 1979. Population dynamics of the indigo bunting and the evolution of avian polygyny. Evolution 33:1180-1192
Ketterson, E.D. and V. Nolan Jr. 1979. Seasonal, annual, and geographic variation in sex ratio of wintering populations of dark-eyed juncos (Junco hyemalis). Auk 96:522-536
Ketterson, E.D. and V. Nolan Jr. 1982. The role of migration and winter mortality in the life history of a temperate-zone migrant, the dark-eyed junco, as determined from demographic analyses of winter populations. Auk 99:243-259
Ketterson, E.D. and V. Nolan Jr. 1983. The evolution of differential bird migration. Current Ornithology 1:357-402
Nolan, V. Jr. and E.D. Ketterson. 1983. An analysis of body mass, wing length, and visible fat deposits of dark-eyed juncos wintering at different latitudes. Wilson Bulletin 95:603-620
Ketterson, E.D. and V. Nolan Jr. 1983. Behavior of migratory dark-eyed juncos following release in the winter range during the breeding season. Journal of Field Ornithology 54:387-393
Ketterson, E.D. and V. Nolan Jr. 1983. Autumnal Zugunruhe and migratory fattening of dark-eyed juncos apparently suppressed by detention at the wintering site. Wilson Bulletin 95:629-635
Blank, J. and V. Nolan Jr. 1983. Offspring sex ratio in red-winged blackbirds is determined by maternal age. PNAS 80:6141-6145
Ketterson, E.D. and V. Nolan Jr. 1983. The evolution of differential bird migation. In Current Ornithology (R.F. Johnston ed.), 1:357-402. Plenum Press, New York
Ketterson, E.D. and V. Nolan Jr. 1985. Intraspecific variation in avian migration patterns. In: Migration: Mechanisms and Adaptive Significance (ed. M.A. Rankin), University Texas, Contrib. Marine Sci. Suppl. 27:553-579
Nolan, V. Jr., E.D. Ketterson and L. Wolf. 1986. Long-distance homing by non-migratory dark-eyed juncos. Condor 88:539-542
Ketterson, E.D. and V. Nolan, Jr. 1986. Effect of winter laparotomy on long-term survival of tree sparrows and dark-eyed juncos. J. Field Ornith. 57:239-240
Walton, R. and V. Nolan, Jr. 1986. Imperfect information and the persistence of pretenders: male prairie warblers contesting for territory. Amer. Nat. 128:427-432
Ketterson, E.D. and V. Nolan, Jr. 1987. Suppression of autumnal migratory unrest in dark-eyed juncos held during summer on, near, or far from their previous wintering sites. Auk 104:303-310
Ketterson, E.D. and V. Nolan, Jr. 1987. Spring and summer confinement of dark-eyed juncos at autumn migratory destination suppresses normal autumn behavior. Animal Behaviour 35:1744-1753
Rogers, C.M., E.D. Ketterson and V. Nolan, Jr. 1987. Predation risk and fasting capacity: do wintering bird maintain optimal body mass? Bull. Ecol. Soc. Amer.
Wolf, L., E.D. Ketterson, and V. Nolan Jr. 1988. Paternal influence on growth and survival of dark-eyed junco young. Animal Behaviour 36:1601-1618
Ketterson, E.D. and V. Nolan Jr. 1988. A possible role for experience in the regulation of the timing of bird migration. Proc. XIXth Int. Ornith. Congr. (Ottawa) Vol. II, pp. 2169-2179
Sniegowski, P., E.D. Ketterson, and V. Nolan Jr. 1988. Can experience alter the avian annual cycle? Results of migration experiments in indigo buntings. Ethology 79:333-341
Jackson, W.M., S. Rohwer and V. Nolan, Jr. 1989. Within-season breeding dispersal in prairie warblers and other passerines. Condor 91:233-241
Rogers, C.M., T. Theimer, V. Nolan Jr., and E.D. Ketterson. 1989. Does dominance determine how far dark-eyed juncos (Junco hyemalis) migrate into the winter range? Animal Behaviour 37:498-506
Murray, B.G., Jr. and V. Nolan, Jr. 1989. The evolution of clutch size: An equation for predicting clutch size. Evolution 43:1699-1705
Ketterson, E.D. and V. Nolan Jr. 1990. Site attachment and site fidelity in migratory birds: experimental evidence from the field and analogies from neurobiology. In: Bird Migration, E. Gwinner (ed.). Springer Verlag, p. 117-129
Wolf, L., E.D. Ketterson, and V. Nolan Jr. 1990. Behavioral response of female dark-eyed juncos to the experimental removal of their mates: implications for the evolution of male parental care. Animal Behaviour 39:125-134
Nolan, V. Jr. and E.D. Ketterson. 1990. Effect of long days on molt and autumn migratory state of site-faithful juncos held at their winter sites. Wilson Bull. 102:469-479
Nolan, V. Jr. and E.D. Ketterson. 1990. Timing of autumn migration and its relation to winter distribution in dark-eyed juncos. Ecology 71:1267-1278
Cristol, D.A., Nolan, V., Jr., and E.D. Ketterson. 1990. Effect of prior residence on dominance status of dark-eyed juncos (Junco hyemalis). Animal Behaviour 38:580-586
Ketterson, E.D., V. Nolan, Jr., L. Wolf, and A. Goldsmith. 1990. Effect of sex, stage of reproduction, season, and mate removal on prolactin in dark-eyed juncos (Junco hyemalis). Condor 92:922-930
Nolan, V. Jr. and E.D. Ketterson. 1991. Experiments on winter-site fidelity in young dark-eyed juncos. Ethology 87:123-133
Wolf, L., Ketterson, E.D., and V. Nolan, Jr. 1991. Female condition and delayed benefits to males that provide parental care: a removal study. Auk 108:371-380
Ketterson, E.D., V. Nolan, Jr., C. Ziegenfus, D.P. Cullen and M. Cawthorn. 1991. Non-breeding season attributes of male dark-eyed juncos that acquired breeding territories in their first year. Proc. XXth Inter. Ornith. Congress (Christchurch) 1229-1239
Ketterson, E.D., L. Wolf, C. Ziegenfus, A.M. Dufty, G. Ball and T. Johnsen. 1991. Testosterone and avian life histories: the effect of experimentally elevated testosterone on corticosterone, body mass, and annual survivorship of male dark-eyed juncos. Hormones and Behavior 25:489-503
Nolan, V. Jr., E.D. Ketterson, C. Ziegenfus, D.P. Cullen and C.R. Chandler. 1992. Testosterone and avian life histories: the effect of experimentally elevated testosterone on molt and survival in male dark-eyed juncos. Condor 694:364-370
Ketterson, E.D. and V. Nolan Jr. 1992. Hormones and life histories: an integrative approach. American Naturalist 140:S33-S62
Ketterson, E.D., V. Nolan Jr., L. Wolf and C. Ziegenfus. 1992. Testosterone and avian life histories: the effect of experimentally elevated testosterone on behavior and fitness of the dark-eyed junco. American Naturalist 140:980-999
Rogers, C.M., N. Nolan Jr. and E.D. Ketterson. 1993. Geographic variation in winterfat of dark-eyed juncos: displacement to a common environment. Ecology.
Rogers, C.M., M. Ramenofsky, E.D. Ketterson, V. Nolan Jr. and J.C. Wingfield. 1993. Plasma corticosterone, adrenal mass, winter weather and season in natural populations of dark-eyed juncos (Junco hyemalis hyemalis). Auk 110:279-285
Rogers, C.M., V. Nolan Jr. and E.D. Ketterson. 1994. Winter fattening in dark-eyed juncos: environmental effects, plasticity and interaction with post-breeding migration.
Chandler, C.R., E.D. Ketterson, V. Nolan, Jr., and C. Ziegenfus. 1994. Effects of testosterone on spatial activity in free-ranging male dark-eyed juncos, Junco hyemalis. Animal Behaviour 47:1445-1455
Ketterson, E.D. and V. Nolan, Jr. 1994. Male parental behavior in birds. Ann. Rev. Ecol. Syst. 25:601-628
Ketterson, E.D. and V. Nolan, Jr. 1994. Hormones and life histories. In.: Behavioral mechanisms in evolutionary ecology (ed. L.A. Real) pp. 327-353. Univ. Chicago Press, Chicago.
Nolan, V. Jr., and E.D. Ketterson. 1996. Current Ornithology, Vol. 13, 320 pp. + index. Plenum Press, New York
Johnsen, T.S., Hengeveld, J.D., BLank, J.L., Yasukawa, K., and Nolan V., Jr. 1996. Epaulet brightness and physical condition in female red-winged blackbirds. Auk 113:356-632
Ketterson, E.D., V. Nolan, Jr., M.J. Cawthorn, P.G. Parker, and C. Ziegenfus. 1996. Phenotypic engineering: using hormones to explore the mechanistic and functional bases of phenotypic variation in nature. Ibis 138:1-17
Chandler, C.R., E.D. Ketterson, and V. Nolan, Jr. 1997. Effects of testosterone on use of space by male dark-eyed juncos when their mates are fertile. Animal Behaviour 54:543-549
Enstrom, D.E., E.D. Ketterson, and V. Nolan, Jr. 1997. Testosterone and mate choice in the dark-eyed junco. Animal Behaviour 54:1135-1146
Klukowski, L., M.J. Cawthorn, E.D. Ketterson, and V. Nolan, Jr. 1997. Effects of experimentally elevated testosterone on plasma corticosterone and corticosteroid binding globulin in dark-eyed juncos (Junco hyemalis). General and Comparative Endocrinology 108:141-151
Titus, R.C., E.D. Ketterson, and V. Nolan, Jr. 1997. High testosterone prior to song crystallization inhibits singing behavior in captive yearling dark-eyed juncos (Junco hyemalis). Hormones and Behavior 32:133-140
Titus, R.C., C.R. Chandler, E.D. Ketterson, and V. Nolan, Jr. 1997. Song rates of dark-eyed juncos do not increase when females are fertile. Behavioral Ecology and Sociobiology 41:165-169
Ketterson, E.D., P.G. Parker, S.A. Raouf, V. Nolan Jr., C. Ziegenfus, and C.R. Chandler. 1997. The relative impact of extra-pair fertilizations on variation in male and female reproductive success in dark-eyed juncos (Junco hyemalis). Pp. 81-10. In Avian Reproductive Tactics: Male and Female perspectives (P.G. Parker, and N.T. Burley, eds.). Ornithological Monographs, No. 49. Allen Press, Lawrence, KS
Raouf, S.A., P.G. Parker, E.D. Ketterson, V. Nolan, Jr., and C. Ziegenfus. 1997. Testosterone affects reproductive success by influencing extra-pair fertilizations in male dark-eyed juncos (Aves: Junco hyemalis). Proceedings Royal Society, Series B., London 264:1-5
Nolan, V. Jr., E.D. Ketterson and C.F. Thompson (eds.). 1997. Current Ornithology, vol 14. Plenum Press, New York
Kast, T.L. E.D. Ketterson, and V. Nolan, Jr. 1998. Variation in ejaculate quality in the dark-eyed junco, according to season, stage of reproduction, and testosterone treatment. Auk 115:684-693
Cawthorn, M.J., D.L. Morris, E.D. Ketterson, and V. Nolan, Jr. 1998. Influence of experimentally elevated testosterone on nest defence in dark-eyed juncos. Animal Behaviour, 56:617-621
Nolan, V. Jr., Ketterson, E. D., and C. F. Thompson (eds.). 1999. Current Ornithology Vol. 15. Plenum, New York.
Nolan, V., Jr., E. D. Ketterson, and C. A. Buerkle. 1999. Prairie Warbler (Dendroica discolor). In The Birds of North America, No. 455 (A. Poole and F. Gill, eds.). The Birds of North American, Inc., Philadelphia, PA.
Lipar, J. L., E. D. Ketterson, V. Nolan Jr., and J. M. Casto. 1999. Egg yolk layers vary in the concentration of steroid hormones in two avian species. General and Comparative Endocrinology, 115:220-227.
Ketterson, E. D., and V. Nolan Jr. 1999. Exaptation, adaptation, and constraints; a hormonal perspective. American Naturalist, in press.
Hill, J. A., D. E. Enstrom, E. D. Ketterson, V. Nolan Jr., and C. Ziegenfus. 1999. Mate choice based on static vs. dynamic secondary sexual traits in the dark-eyed junco. Behavioral Ecology 10(1):91-96.
Lipar, J. L., E. D. Ketterson, and V. Nolan Jr. 1999. Intra-clutch variation in testosterone content of eggs of red-winged blackbirds. Auk 116:231-235.
Schoech, S. J., E. D. Ketterson, and V. Nolan Jr. 1999. Exogenous testosterone and the adrenocortical response in the dark-eyed junco, (Junco hyemalis). Auk 116:64-72.
Lynn, S. E., A. M. Houtman, W. W. Weathers, E. D. Ketterson and V. Nolan Jr. 2000. Testosterone increases activity but not daily energy expenditure in captive male dark-eyed juncos (Junco hyemalis). Animal Behavior 60: 581-587.
Hudman, S. O., E. D. Ketterson, and V. Nolan Jr. 2000. Effects of time of sampling on oocyst detection and effects of age and experimentally elevated testosterone on prevalence of coccidia in male dark-eyed juncos. Auk 117:1048-1051.
Smulders, T. V., J. M. Casto, V. Nolan Jr., E. D. Ketterson, and T. J. DeVoogd. 2000. Effects of captivity and testosterone on the volumes of four brain regions in the dark-eyed junco (Junco hyemalis). J. Neurobiology 43:244-253.
Ketterson, E. D., Nolan, V. Jr., Casto, J. M., Buerkle, C. A., Clotfelter, E., Grindstaff, J. L., Jones, K. J., Lipar, J. L., McNabb, F. M. A., Neudorf, D. L., Parker-Renga, I., Schoech, S. J., and E. Snajdr. 2001. Testosterone, phenotype, and fitness: a research program in evolutionary behavioral endocrinology. Pp. 19-40 in A. Dawson and C. M. Chaturvedi (eds.), Avian Endocrinology. Narosa Publishing House, New Delhi, India.
Casto, J. M., Nolan, V. Jr., and E. D. Ketterson. 2001. Steroid hormones and immune function: experimental studies in wild and captive dark-eyed juncos (Junco hyemalis). American Naturalist 157: 408-420.
Clotfelter, E. D., Nolan, V. Jr., Ketterson, E. D. 2001. The effects of experimentally elevated testosterone and food deprivation on food consumption and prey size preferences in male dark-eyed juncos (Junco hyemalis, Emberizidae: Passeriformes). Ethology 107: 439-449.
Grindstaff, J.L., C. A. Buerkle, J. M. Casto, V. Nolan, Jr., and E. D. Ketterson. 2001. Offspring sex ratio is unrelated to male attractiveness in dark-eyed juncos (Junco hyemalis). Behavioral Ecology and Sociobiology 50: 312-316.
Nolan, V. Jr. and C. F. Thompson (eds.). 2001. Current Ornithology Vol. 16. Plenum, New York.
Nolan, V. Jr., Ketterson, E.D., Cristol, D.A., Rogers, C.M., Clotfelter, E.D., Titus, R., Schoech, S.J., and E. Snajdr. . 2002. Dark-eyed Junco (Junco hyemalis). In The Birds of North America, No. 716. (A. Poole and F. Gill, eds), 44p. The Birds of North America, Inc., Philadelphia, PA.
D. L. Neudorf, Ziolkowski, D.J., Jr., V. Nolan Jr., and E. D. Ketterson. 2002. Movement by female dark-eyed juncos during the fertile peiod suggest that males visit females for extra-pair copulations. Ethology. 108:1-15.
Clotfelter, E.D., Schubert, K.A., Nolan, V. Jr., and E.D. Ketterson 2003. Mouth colour signals thermal stress in nestling dark-eyed juncos (Junco hyemalis). Ethology 109:171-182.
Wolf, W.L., Casto, J.M., Nolan, V. Jr., and E. D. Ketterson. 2004. Female ornamentation and male mate choice in dark-eyed juncos. Animal Behaviour 67 (1): 93-102.
Clotfelter, E.D., O’Neal, D.M., Gaudioso, J.M, Casto, JM, Parker-Renga, I.M., Snajdr, E.A., Duffy, D.L., Nolan, V. Jr., and E.D. Ketterson. 2004. Consequences of elevating plasma testosterone in females of a socially monogamous songbird: evidence of constraints on male evolution? Hormones and Behavior 46:171-178.
McGlothlin, J., Neudorf, D.L., Casto, J.M., Nolan, V. Jr., and E.D. Ketterson. 2004. Elevated testosterone reduces choosiness in female dark-eyed juncos (Junco hyemalis): evidence for a hormonal constraint on sexual selection? Proceedings Royal Society, London B 271:1377-1384.
McGlothlin, J. W., P. G. Parker, V. Nolan Jr., and E. D. Ketterson. 2005. Correlational selection leads to genetic integration of body size and an attractive plumage trait in dark-eyed juncos. Evolution 59:658-671.
Ketterson, E.D., V. Nolan Jr., and M. Sandell. 2005. Testosterone in females: mediator of adaptive traits, constraint on the evolution of sexual dimorphism, or both? American Naturalist 166: S85-S98.
Reed, W.L, Clark, M.E., Parker, P.G., Raouf, S.A., Arguedas, N., Monk, D.S, Snajdr, E., Nolan, V. Jr., and E.D. Ketterson. 2006. Physiological effects on demography: A long-term experimental study of testosterone's effects on fitness. American Naturalist, tentatively accepted.
Clotfelter, E.D., Pedersen, A.B., Cranford, J.A., Ram, N., Snajdr, E.A., Nolan Jr., V. and E.D. Ketterson. 2007. Acorn mast drives long- term dynamics of rodent and songbird populations. Oecologia 154:493-503.
Clotfelter, E.D., Chandler, C.R., Nolan, V. Jr., and E.D. Ketterson. 2007. The influence of exogenous testosterone on the dynamics of nestling provisioning in dark-eyed juncos. Ethology 113:18-25.
Murray, BG and V. Nolan Jr. 2007. A more informative method for analyzing reproductive success. Journal of Field Ornithology 78: 401-406.
Selected Abstracts
ABSTRACT : Migratory Dark-eyed Juncos in eastern North America migrate southward in autumn and tend to segregate in the winter range according to sex and age. North to south, the most abundant classes are young males, adult males, young females, and adult females. Because adults tend to dominate young at winter feeding sites, this distribution appears at first to conflict with the view that dominance interactions are responsible for differential avian migrations and that dominant interactions are responsible for differential avian migration and that dominant individuals remain nearest the breeding range. However, if young juncos establish winter residency at earlier dates than adults, a prior residence effect might make them dominant. This hypothesis requires that young arrive at wintering sites earlier than adults and that residents of all classes arrive earlier than their transient counterparts. We tested these predictions by comparing first-capture dates of juncos at Bloomington, Indiana, which is north of the latitudinal midline of the junco's winter range. During 13 autumns, individuals were classed as local residents or as transients and were sexed and aged. Contrary to predictions, residents were not caught earlier than transients. Further, adults were caught earlier, not later, than young among transients and probably also among residents. Thus, settlement of the winter range does not proceed from north to south, and dominance established through prior residence cannot account for the concentration of 1st-yr males in the northern part of the winter range. The fact that some sex-age classes tend to winter south of others predicts that at a northern capture site the classes that migrate farthest should be commoner among transients than among residents. This expectation was fulfilled. In addition, the median capture dates of the sex-age classes were arranged approximately according to the north-to-south order of their distribution, indicating that classes with the farthest to travel passed through (transients) or settled (residents) earliest in autumn. We conclude that comparison of autumn migration schedules of transient and resident passerine birds at a single location can yield considerable information about the dynamics of settlement of the entire winter range, including possible information about differences in destination of subsets of transients.
© 1990 by the Ecological Society of America
© 1990 by the Ecological Society of America
ABSTRACT : Male Dark-eyed Juncos (Junco hyemalis) that breed in Virginia begin their prebasic molt after breeding has ended, usually in August. Almost all males caught in late October have completed the molt. In 1989, we obtained anecdotal evidence that males whose testosterone (T) we maintained at artificially elevated levels beyond the end of the breeding season postponed or suppressed prebasic molt. To test the effect of T experimentally, in spring 1990 we implanted some males (T-males) with testosterone and others (C-males) with empty implants, and we released both groups to breed. We caught some members of both treatment groups in October and removed their implants. The T-males had delayed their prebasic molt, while the C-males were molting on schedule. Other implanted T- and C-males were not caught; these carried their implants into winter. Next spring we examined surviving males whose implants we had removed in October as well as males whose T- and C- implants had not been removed. T-males whose implants we had removed had molted completely, despite their delayed start, whereas T-males whose implants we had not removed had not molted. Still-implanted C-males had molted. We compared the minimum over-winter survival (i.e., return rates in spring) of the treatment groups. T- and C- males whose implants we had removed in October returned at the same rate, but among males whose implants we had not removed, significantly fewer T-males than C-males returned. The transition between reproduction and molt of male juncos apparently can be blocked by preventing the normal seasonal decline in T. This suggests a physiological basis for a possible trade-off between time allocated to reproduction and time allocated to molt. Our results indicate that males could maintain high T and prolong breeding, possibly into October, and still molt completely with no adverse effects. We consider why such a modification of schedule has not occurred. However, postponement of molt beyond some date in autumn, possibly late October, suppresses it altogether, as indicated by the failure to molt of the returning T-males whose implants we did not remove. This treatment group apparently suffered higher overwinter mortality, and we consider possible reasons.
© 1992 The Cooper Ornithological Society
© 1992 The Cooper Ornithological Society
ABSTRACT : Epaulets of female Red-winged Blackbirds (Agelaius phoeniceus) vary in brightness from brown to bright red-orange. We test predictions of the hypothesis that condition at the time of molt determines female epaulet brightness and that females in superior condition produce brighter epaulets. We compared each female's epaulet with a series of color photographs ranked from 1 (dull brown) to 12 (bright red-orange) and considered females to have increased in brightness between years if their color increased by at least two ranks. More first-year females than older females increased in brightness, more older females increased in brightness after a year of superabundant food (an emergence of periodical cicadas, Magicicada spp.) than after other years. In each case, we expected an improvement in condition. We estimated female condition and regressed condition index on day of the breeding season. During the breeding season, females that later increased in brightness previously reported correlation between age and epaulet brightness, but age does not explain the relationship between change in brightness and either reproductive effort or the emergence of cicadas. We conclude that the most likely explanation for our results is that condition, at least in part, determines epaulet brightness in female Red-winged Blackbirds and that superior signaling hypothesis and mate-choice hypotheses for the evolution of variable plumage. The best explanation for the evolution of variable plumage among female Red-winged Blackbirds is that brightness signals status in female-female aggressive encounters.
ABSTRACT : Testosterone is an important determinant of spatial activity in male birds. Using radio-telemetry, male dark-eyed juncos, Junco hyemalis, were followed during the period when their mates were fertile to investigate the relationship between testosterone and behaviours (territoriality, consorting with female) through which males might guard paternity. Males with experimentally elevated testosterone levels (T-males) and control males (C-males) did not differ significantly in their use of space during this period. T-males and C-males occupied similar home ranges, used similar-sized core areas (areas enclosing 95% of all activity), spent similar amounts of time close to their mates, and experienced similar intrusion rates onto their territories. Experimentally elevating testosterone above control levels did not detectably affect the spatial activity of male juncos during the female fertile period, although earlier studies have shown that its effects are pronounced during other stages of the nesting cycle.
© 1997 The Association for the Study of Animal Behaviour
© 1997 The Association for the Study of Animal Behaviour
ABSTRACT : Frequency of singing by birds may vary with reproductive stage in ways that reflect variation in the functions of song in intersexual and intrasexual communication. In dark-eyed juncos (Junco hyemalis) high-amplitude song is produced only by males. To investigate the function of this song, we tested whether fertility of females affected singling by their mates or by neighboring males. Using focal observations, song censuses, and radiotracking data, we determined whether song production varied between and among periods when females were fertile and non-fertile. Our findings show that males do not increase song production when their mates are fertile, nor do they increase song production when neighboring females are fertile. These results suggest that male juncos do not signal their intent to defend territories (or mates) more when females are fertile and that they do not use song to advertise to specific potential participants in extra-pair fertilizations.
© Springer-Verlag 1997
© Springer-Verlag 1997