| 1. |
- Alatalo, Rauno V, et al.
(författare)
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Can Female Preference Explain Sexual Dichromatism In The Pied Flycatcher, Ficedula-Hypoleuca
- 1990
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Ingår i: Animal Behaviour. - 0003-3472 .- 1095-8282. ; 39, s. 244-252
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Tidskriftsartikel (refereegranskat)abstract
- How important female choice is for the evolution of male secondary sexual characteristics is controversial. Two field and one laboratory experiment, using the pied flycatcher, were performed to test the female choice aspect of sexual selection. In addition, non-manipulative data from 5 years are presented. The observational data suggest a slight preference for dark males by females but in field experiments in which males had territories at random sites (i.e. they did not choose a territory) or the colour of concurrently arriving males was altered, there was no preference for darker ones. Similarly, oestradiol-treated females did not prefer black or brown males in the laboratory. Thus, there is little support for the idea that female choice has been an important mechanism in the evolution of sexual dichromatism in the pied flycatcher.
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| 2. |
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| 3. |
- Almgren, Jonas, et al.
(författare)
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SICStus Prolog library manual, version 2.1 #8
- 1993. - 1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This Manual corresponds to SICStus Prolog release 2.1. #8 The Prolog library comprises a number of packages which are thought to be useful in a number of applications. Note that the predicates in the Prolog library are built-in predicates. One has to explicity load each package to get access to its predicates. To load a library package Package, you will normally enter a query. I ?- use_module(library(Package)). Library packages may be compiled and consulted as well as loaded.
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| 4. |
- Axelsson, Björn, et al.
(författare)
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Managing by International Travelling
- 1992
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Ingår i: Managing Networks in International Business. - : Gordon & Breach, Philadelphia. ; , s. 93-109
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 5. |
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| 6. |
- Björklund, Mats, et al.
(författare)
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Mate Guarding In The Great Tit - A Reply
- 1994
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Ingår i: Animal Behaviour. - : Elsevier BV. - 0003-3472 .- 1095-8282. ; 47:5, s. 1230-1231
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Tidskriftsartikel (refereegranskat)
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| 7. |
- Staffas, Louise, et al.
(författare)
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Further characterization of hormonal regulation of glutathione transferase in rat liver and adrenal glands. Sex differences and demonstration that growth hormone regulates the hepatic levels
- 1992
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Ingår i: Biochemical Journal. - : Portland Press. - 0264-6021 .- 1470-8728. ; 286 ( Pt 1), s. 65-72
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Tidskriftsartikel (refereegranskat)abstract
- Immunoblot experiments and reverse-phase h.p.l.c. were used to study the levels of glutathione transferase subunits 1, 2, 3, 4, 6, 7 and 8 in the liver and adrenal of intact and hypophysectomized male and female Sprague-Dawley rats. A sexual dimorphism in the levels of several of these isoenzymes and in their responses to hypophysectomy was demonstrated. In the liver of sham-operated females and males there are differences in glutathione transferase activities and isoenzyme pattern. H.p.l.c. analysis showed higher levels of subunits 1, 3 and 4 in male rats compared with females. In contrast with the pronounced sex differences in sham-operated rats, the isoenzyme patterns of hypophysectomized males and females were very similar. In the adrenal glands, however, a sexual dimorphism became apparent only after hypophysectomy, when the level of subunit 4 was increased 14-fold in the female, whereas the corresponding increase in the male rat was only 2.7-fold. The hepatic pattern of glutathione transferase subunits could be altered by continuous infusion of growth hormone to both sham-operated and hypophysectomized rats of both sexes. This treatment feminized the isoenzyme pattern in sham-operated males and a similar effect was obtained upon treating hypophysectomized rats with thyroxine, cortisone acetate and a continuous infusion of growth hormone.
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| 8. |
- Sundberg, Jan
(författare)
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Absence Of Mate Guarding In The Yellowhammer (Emberiza-Citrinella)
- 1992
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Ingår i: Ethology. - 0179-1613 .- 1439-0310. ; 92:3, s. 242-256
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Tidskriftsartikel (refereegranskat)abstract
- The mate guarding behaviour of male yellowhammer (Emberiza citrinella) was studied with special reference to the effects of age, body size (tarsus length) and coloration of males. Measurements of intra-pair distance do at the most provide evidence for relatively lax mate guarding. On the other hand, patterns of male song activity and inter-male aggression were more in agreement with the predictions of the mate guarding hypothesis. The reasons for the comparatively low mate guarding intensity in the yellowhammer may be that males do not need to guard their mates intensely. Age differences were found in song and aggressive activity, older males singing and fighting the most. Size had no effect on guarding behaviour. Coloration was correlated with inter-male aggressiveness and conflict initiation propensity. Less colourful males fought the most in the pre-fertile period of their mates, whereas colourful and old males fought the most during the fertile period. This suggests that coloration may be an indicator of individual fighting and guarding ability.
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| 9. |
- Sundberg, Jan, et al.
(författare)
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Male Coloration As An Indicator Of Parental Quality In The Yellowhammer, Emberiza-Citrinella
- 1994
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Ingår i: Animal Behaviour. - : Elsevier BV. - 0003-3472 .- 1095-8282. ; 48:4, s. 885-892
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Tidskriftsartikel (refereegranskat)abstract
- In monogamous species the amount and quality of male parental care may be essential for females since fitness depends on number and quality of offspring. Degree of male ornamentation may be used by females as an indicator of paternal effort and thus may be an important factor in mate choice situations. This was tested by observing feeding rates of yellowhammers, a species showing considerable colour variation. Male and female feeding rates were inter-correlated and were both negatively correlated with male coloration. Relative male feeding rate was not correlated with male colour. In spite of a low feeding rate by more highly coloured older males, no effect was found on nestling condition, indicating compensation by high quality food or bigger load per nest visit. Nevertheless, coloration was positively related to the number of fledged young for old males and so may indicate parental quality. These results suggest that older and generally more colourful males may be more experienced and of higher quality and so may be preferred by females.
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| 10. |
- Sundberg, Jan
(författare)
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Paternity Guarding In The Yellowhammer Emberiza-Citrinella - A Detention Experiment
- 1994
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Ingår i: Journal of Avian Biology. - : JSTOR. - 0908-8857 .- 1600-048X. ; 25:2, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- The importance of male presence on their territories for maintaining paternity in their mates' offspring was investigated in the Yellowhammer. Males were experimentally detained for one hour before and during their mate's fertile period. When males were detained, their territories received an increased number of intrusions and intruding males. Also the duration of intrusions increased compared with when they were present on their territories. No difference was found in intrusion patterns between the prefertile and the fertile period. No intrusions were observed during the post-fertile period. The rate of intrusion was not related to number of neighbouring males although young males suffered from a higher intrusion rate when the number of young neighbouring males increased. Old males with much yellow were subject to more intrusions than other males, predominantly by other older males, indicating a cost of wearing colourful plumage. In spite of the low intensity, or absence, of mate guarding found in a previous study of the Yellowhammer, results indicate that male presence on their territories may reduce the potential for extra-pair fertilizations.
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