Longspur

Abstract: The Lapland longspur (Calcarius lapponicus) is an arctic-breeding songbird that shows rapid behavioral changes during a short breeding season. Changes in plasma testosterone (T) in the spring are correlated with singing but not territorial aggression in males. Also, T treatment increases song but not aggression in this species. In contrast, in temperate-zone breeders, song and aggression are highly correlated, and both increase after T treatment. We asked whether regional or temporal differences in androgen-metabolizing enzymes in the longspur brain explain hormone-behavior patterns in this species. We measured the activities of aromatase, 5alpha-reductase and 5beta-reductase in free-living longspur males. Aromatase and 5alpha-reductase convert T into the active steroids 17beta-estradiol (E(2)) and 5alpha-dihydrotestosterone (5alpha-DHT), respectively. 5beta-Reductase deactivates T via conversion to 5beta-DHT, an inactive steroid. We examined seven brain regions at three stages in the breeding season. Overall, aromatase activity was high in the hypothalamus, hippocampus, and ventromedial telencephalon (containing nucleus taeniae, the avian homologue to the amygdala). 5beta-Reductase activity was high throughout the telencephalon. Activities of all three enzymes changed over time in a region-specific manner. In particular, aromatase activity in the rostral hypothalamus was decreased late in the breeding season, which may explain why T treatment at this time does not increase aggression. Changes in 5beta-reductase do not explain the effects of plasma T on aggressive behavior.

Abstract: The growth rate, general development, and the development of endothermy of two closely related passerines–the snow bunting (Plectrophenax nivalis) and the Lapland longspur (Calcarius lapponicus)–were studied near Barrow, Alaska. Although there is a 30% difference in adult weight of the two species, comparison of their daily weight curves and of the development of their plumage and behavior indicate essentially identical developmental rates. The rate and pattern of the development of endothermy support this conclusion. Both species are ectothermic at hatching, and both are essentially endothermic by the seventh day of life. The two species fledge at different ages, 7.4 days for the longspur and 13.1 days for the snow bunting. Fledging is thus shown to be a behavioral trait independent of development. The difference between the two species is correlated with different nesting ecologies: the longspur nests in open—cup nests, and the bunting nests in cavities. These results are compared with several other fri...

Abstract: -Breeding density, clutch size, hatching and fledging success, and survival of adult Lapland Longspurs (Calcarius lapponicus) were monitored over a 7-year period near the Naval Arctic Research Laboratory, Barrow, Alaska. Nesting begins as soon as the tundra starts to clear of snow and appears to be timed so that the young of the year reach independence before the end of adult insect emergence. Arthropod prey become abruptly scarce after the period of insect emergence and thus probability of success for late broods is low. Time of nesting is also discussed in relation to factors of predation and timing of molt. At least 42.9% of males and 45.4% of females survived the next season after 1 year of age. Maximum longevity observed for both sexes is 6 years. Mean clutch size for all years investigated was 5.06 eggs per clutch. Clutch size showed both yearly and seasonal variation. The data indicate that timing of nesting is the chief factor in the observed clutch size differences, further modified by habitat quality, second nesting attempts, and probably age of female. Over a 4-year period the longspur breeding population on a 17-ha study plot declined from 15 to 2 breeding females. Life-table analysis indicates that low fledgling success for 3 consecutive years apparently was the main cause of this decline. Overall mean egg success was 44.0%, but close to 60% in 4 years considered more "normal." The low egg success was due to 3 consecutive years of high predation, which may have been related to the disrupted lemming cycle of the Barrow region.-Museum of Vertebrate Zoology, University of California, Berkeley, California 94720. Present address of senior author: Patuxent Wildlife Research Center, Laurel, Maryland 20811. Accepted 9 December 1975. THE increase in fieldwork in the Arctic in the 1950's and 1960's has made it possible to examine various aspects of the demography of passerine birds there (Ricklefs 1969, 1973; Hussell 1972). Even so, information on density, clutch size, and hatching success of arctic birds is generally scarce, and only a few recent studies (e.g.Williamson 1968, Williamson and Emison 1971, Hussell 1972) had been carried out for more than one season. The demographic data presented here represent part of an investigation dealing with the role of the Lapland Longspur (Calcarius lapponicus) in the arctic coastal tundra ecosystem of northern Alaska. Data on clutch size, hatching and fledging success, and survival of adults, which span a seven-year period (1967-1973), are analyzed by life-table techniques. During the course of the study longspur breeding density decreased drastically at Barrow. The life-table analysis helps explain the observed decline. Some data pertinent to various aspects of this paper are also drawn from work on the Lapland Longspur by F. A. Pitelka during the period 1951-1969. Other parts of this study, dealing with diet, activity patterns, molt, and bioenergetics will be published elsewhere. Background information on coastal tundra as a habitat is available in Britton (1957) and Wiggins and Thomas (1962). The total ecological setting is compactly summarized by Bunnell et al. (1975).

Abstract: -I compared the reproductive anatomy of the polygynandrous Smith's Longspur (Calcarius pictus) with two other polygynandrous passerines (Dunnock [Prunella modularis] and Alpine Accentor [P. collaris]) and with a wide range of socially monogamous species. All three polygynandrous species were found to have enlarged testes and cloacal protuberances (i.e. the site of sperm storage) compared to species with other mating systems. Testes lengths in polygynandrous species averaged 44% longer and cloacal protuberances 213% greater in volume than expected for the body sizes of these species. Testes mass in Smith's Longspurs comprised 4.2% of adult body mass or more than twice (2.0%) that found in the congeneric and monogamous Lapland Longspur (C. lapponicus). Smith's Longspurs also had larger cloacal protuberances, larger seminal glomera and higher sperm stores, suggesting a greater overall rate of sperm production than in Lapland Longspurs. In contrast, females of polygynandrous species did not show any consistent differences in the pattern of sperm storage due to increased sperm production by males, although this needs to be evaluated more thoroughly. The enlarged male reproductive organs of Smith's Longspurs and other polygynandrous species appear to have evolved as a consequence of sperm competition, whereby large sperm reserves function to insure paternity through diluting or displacing the ejaculates of rival males. Received 26 December 1991, accepted 25 November 1992. SPERM COMPETITION results whenever females mate with more than one male during the span of a single breeding attempt (Parker 1970). Although multimale mating may be advantageous to females in some situations (e.g. Smith 1988, M0ller 1988a), it can also reduce a partner's paternity (e.g. Gibbs et al. 1990). To counter female infidelity and increase the probability of paternity, males have evolved several elaborate counter measures. For example, males in some species continually guard and defend their mates from the advances of other males during the period when eggs are fertilizable (Beecher and Beecher 1979, Birkhead 1979). If extrapair copulations occur, then pair males may reduce their subsequent parental investment to avoid wasting energy or resources on raising another male's offspring (Trivers 1972, Burke et al. 1989). Sometimes female infidelity cannot be prevented because of ecological constraints, but males may nonetheless increase paternity confidence through frequent copulations that dilute or displace rival ejaculates (McKinney et al. 1984, Birkhead et al. 1987). Indeed, inter' Present address. specific comparisons of primates (Harcourt et al. 1981, Harvey and Harcourt 1984), birds (Cartar 1985, M0ller 1991) and mammals (Kenagy and Trombulak 1986, Brownell and Ralls 1986) have shown that nonmonogamous animals have relatively larger testes than monogamous species. Since larger testes produce more and larger ejaculates (M0ller 1988b), an increase in testes size has been interpreted as an adaptation to sperm competition (Harcourt et al. 1981, M0ller 1988b, 1991). Smith's Longspurs (Calcarius pictus) are unusual among passerine birds in that females regularly pair and copulate with more than one male for a single clutch of eggs at the same time that males pair and copulate with several females (Briskie 1992). In a color-banded population near Churchill, Manitoba, 76.2% of 21 females observed mated with two males, 9.5% with three males, and only 14.3% with a single male (Briskie 1992, 1993). Of 27 males observed in the same population, 63.0% mated with two females, 7.4% with three females, and 29.6% with a single female. This combination of polyandry and polygyny is termed polygynandry and has been reported in only two other passerines to date (Dunnock, Prunella modularis [Davies 1985]