Male swarms at landmarks and scramble competition polygyny inPolistes gallicus (Hymenoptera: Vespidae)

At the end of summer, males of Polistes gallicusfly in swarms around vertical landmarks and land in clusters on their favorite perches, where they drag their legs and abdomen. Here males occasionally crowd around a perched female; they make no effort to defend an exclusive mating territory but instead attempt to copulate by displacing rivals from the female. In this work we describe this spatial-nuptial system, which entails site fidelity without territoriality, unisexual swarms, common patrol routes, collective sexual approaches, and scramble competition polygyny. Mating success is evaluated in relation to the familiarity with flight paths (routine patrollers versus newcomers), to the type of sexual approach (single males versus in- group males), and, in the laboratory, to the individual activity level.     

Fertility ofFusarium moniliforme from maize and sorghum related to fumonisin production in Italy

Forty-three strains ofFusarium moniliforme isolated from infected maize and sorghum plants in Italy were assayed for their ability to produce fertile crosses with A and F mating population tester strains, in relation to their ability to produce fumonisins on maize substrate. Most of the strains isolated from maize (ear and stalk rot and maize-based feed), producing fumonisin B₁ (FB₁) and B₂ (FB₂) (up to 4,100 and 855 mg/kg, respectively), belonged to the A mating population. All of the strains isolated from sorghum belonged to the F mating population and produced little or no FB₁ and FB₂. This is the first report of the occurrence of mating population F in Europe. Our data on strains from Italy are consistent with previous studies from the United States that found significant differences in sexual fertility and fumonisin production between strains from maize and sorghum.     

Zur biologischen Bedeutung des Estrildidengesanges

Zusammenfassung Viele Prachtfinken (Estrildidae) tragen außerhalb der Balz einen ungerichteten Gesang vor. Diese Gesangsform scheint primär mehr oder minder funktionslos und lediglich Ausdruck einer besonders ausgeglichenen Stimmungslage zu sein. Sekundär kann sie infolge großer intraspezifischer Modifikationsbreite ein persönliches Erkennen des 's gewährleisten und durch verschiedenartige Anpassungen (Gruppengesänge, Entwicklung des Zuhörens, Gesangshemmung in Partnernähe mit anschließendem Ablauf intensiver Paarbindungszeremonien) auch die Paar- und Gruppenbindung festigen. Mit dieser Zunahme der sozialen Funktionen wird der Gesang gleichzeitig von der Keimdrüsenreifung immer unabhängiger und ist bei drei der beobachteten Arten (Uraeginthus angolensis, Lagonosticta rhodopareia undAmadina erythrocephala) selbst bei völlig inaktiven Gonaden voll ausgebildet. Auf diese Weise kann er seine sozialen Aufgaben ganzjährig erfüllen.

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Summary Many species of Grass Finches (Estrildidae) sing not only during court-ship (display song) but also on numerous other occasions (solitary song). In general the solitary song does not seem to possess any significant biological function seeming rather to be just a sign of a very tranquil mood, not influenced by any other motivation. In some species, however, it has acquired several new, social functions: Due to its remarkably great individual variability the song of the may contribute to individual recognition within a pair or a breeding colony. It may also promote pair and flock cohesion. In connection with this, several behavioural adaptations have arisen such as singing in duos and trios or peering at the singer by other members of the flock.In theLagonosticta andUraeginthus species males and females possess a song. Solitary song, however, seems to be inhibited by the presence of other birds of the same species, especially the bird's own mate. For this reason the birds are forced to separate from each other for the utterance of solitary song. After having ceased singing they usually come together again and will go through their special greeting ceremonies — the stimulating and synchronizing properties of which are well known — with especially high intensity. Solitary song may thus contribute indirectly to cementing the pair bond.In all species in which solitary song possesses a marked social function it seems to have become more and more independent of gonadal development. Some species (e. g.Uraeginthus angolensis, Lagonosticta rhodopareia, Amadina erythrocephala) sing all the year round and even — as has been proved by histological examination — with completely inactive gonads (stage 1 of the testis cycle, followingBlanchard 1941). It is not clear yet whether song in these species is still sexual or partly social or autochthonous in motivation.The various social functions of solitary song clearly demonstrate thatAndrew's (1961) definition of song seems to be an unnecessarily restricted interpretation which should be abandoned.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

The influence of horn and body size on the reproductive behavior of the horned rainbow scarab beetlePhanaeus difformis (Coleoptera: scarabaeidae)

The reproductive behavior of horned rainbow scarab beetles,Phanaeus difformis, was studied to determine the influence of morphological traits on intersexual and intrasexual interactions.Phanaeus difformis is a sexually dimorphic dung beetle in which males possess much larger horns than females, and males can be grouped into major and minor male morph categories based on horn size. Male-female pairs cooperated in nest construction and provisioning. In the laboratory, males of both morphs assisted females and were equally successful at copulating. However, in the field larger individuals had a pairing advantage due to greater success in intrasexual competition. Some males used an alternative mating tactic which involved sneaking copulations with paired females. In most cases the sneak male was smaller than the paired male.     

Courtship inDrosophila sechellia: Its structure,functional aspects,and relationship to those of other members of theDrosophila melanogaster species subgroup

The courtship behavior of Drosophila sechelliais described. Male wing displays are mainly vibration and scissoring, with low levels of rowing. As courtship proceeds the proportion of courtship spent in male wing vibration and licking increases, whereas female movement decreases. The male courtship song of sechelliacontains pulse song but no sine song. This species also shows a distinctive copulation song associated with mounting and copulation. The main cuticular hydrocarbon in females is 7,11-heptacosadiene. The number of copulations increased when flies were placed in the presence of food. Visual and acoustic stimuli appear to be important for mating. A multidimensional comparison was used to compare members of the melanogaster species subgroup, based upon courtship behavior, song characteristics, and cuticular hydrocarbons. A multidimensional comparison of courtship sequences in sechellia, melanogaster, simulans,and mauritianashowed differences in variability between the two island species as compared to the two cosmopolitan species. The courtship song of D. orenais described: it shows both sine and pulse song; there is also a copulation song in this species.     

Lethal genes on the sex chromosomes concealed in a population of the mosquito Aedes aegypti L.

A population has been examined in which an overall parity between the sexes hides considerable between-family variation in sex ratio. A proportion of families show highly distorted sex ratios, with either an excess of females or an excess of males. Distorted sex ratios are invariably associated with mortality in the immature stages at a level appropriate to the action of recessive lethal genes. It has been shown that 26% of M-bearing (Y) chromosomes and at least 24% of m-bearing (X) chromosomes carry a recessive lethal gene.Two such genes have been investigated. l kills males and, in a cross between two heterozygotes, gives rise to a sex ratio close to 2:1 (excess families). k kills females and, in a cross between two heterozygotes, gives rise to a sex ratio close to 1:2 (excess families). Selection for excess or excess did not increase the level of sex ratio distortion.No crossing over occurs between k and the M/m locus whereas l shows 5–10% recombination with M/m. A test for allelism confirmed that l and k are not allelic. The penetrance of k is complete whereas l shows somewhat less than full penetrance. The penetrance of l has been improved by selection.The high frequency of lethals remained in the population during the two year period of study. There was evidence for heterosis preserving this frequency, the heterozygotes living longer and producing more progeny. However lethals were no longer to be found after four further years of laboratory culture.     

Assortative mating and the genetic correlation

Summary The effect of assortative mating on the genetic correlation between traits X and Y is considered. Assortation on trait X changes the magnitude of the genetic correlation but not its sign. There are two situations depending on the signs of the correlation between mates () and of the random mating genetic correlation (): 1) if sign () = sign (), then >, where is the genetic correlation at equilibrium after continued assortation, and 2) if sign () = sign (), then < . However, negative assortative mating is virtually powerless to alter the magnitude of the genetic correlation. The consequences of a mixed assortation model, e.g., high milk production females mated to fast growing males and lesser productive females mated to slower growing sires, were also studied. Mixed positive assortation always increases the genetic correlation, but negative assortation decreases it. The implications of assortative mating on correlated responses to selection and on the equilibrium covariances between relatives for pairs of traits are discussed.     

Morphological aspects of the hypothalamic-hypophyseal system

Summary Enzyme-histochemical methods were used to study the metabolic activity of specialized ependyma of the ventrolateral walls and floor of the third ventricle in young male and female rats during the critical period of sexual differentiation of the hypothalamus (one week after birth). Histochemical tests were conducted for glutamic dehydrogenase, lactic dehydrogenase, glucose-6-phosphate dehydrogenase, glycerophosphate dehydrogenase and NADH₂-dehydrogenase. Enzyme activity was judged by cytospectrophotometry. All the data were treated statistically.It was found that the specialized ependyma of the ventrolateral wall and floor of the third ventricle (median eminence) in rats differed in their enzyme behaviour in males and females during the critical period of sexual differentiation of the hypothalamus. At the level of the arcuate nucleus ( ²-tanycytes) and the medial part of the median eminence ( ²-tanycytes) the ependyma was characterized by similar indices of metabolic activity in males and females in the decisive terms of the critical period (days 3, 5, and 7). On day 5 metabolic activity of these cells was reduced both in the males and in the females. Prominent sexual differences in the intensity of the enzyme reactions studied were noted in the ependyma of the lateral parts of the median eminence ( ¹-tanycytes) in the critical period. On day 5 metabolic activity of ¹-tanycytes was reduced in males and increased in females. It is suggested that these differences are caused by the receptor nature of ¹-tanycytes and suggest their implication in the mechanisms of sexual differentiation of the hypothalamus.     

The effect of variation in parameters of the male calling song of the katydid,Amblycorypha parvipennis (Orthoptera: Tettigoniidae), on female phonotaxis and phonoresponse

After being placed equidistant from playbacks of two computer-generated male calls, females of the katydidAmblycorypha parvipennis preferentially moved toward call phrases that were louder, longer, and leading (initiated without being overlapped by other call phrase endings). Because earlier tests with calling males had indicated that male mating success was related to these call parameters, we suggest that mating success is partly a result of female choice. Females also preferentially responded to the initial, rather than the latter, half of male phrases. Results of other tests suggested that females were responding to increased phonatome rate characteristic of the first half of the phrase. Males may compete to lead in order to prevent jamming of initial phrase information. Females also preferentially phonoresponded (ticked) in response to longer phrases. In earlier studies of male mating success and female phonotaxis using live males, male weight, sound level, and leading were intercorrelated; however, none of these parameters were correlated with phrase length. We suggest that females may respond to different call parameters under different environmental conditions.     

Reflections on Ernst Mayr's This is Biology

In this essay I argue that Ernst Mayr's idea that the emergence of evolutionary biology in Western thought was delayed by the pernicious influence of the false ideologies of Platonism, Christianity, and physicalism is ahistorical and anti-evolutionary, that similar ideas, especially his antipathy to physicalism, prejudice his account of the transformation of natural history and medical science into biology, that his organicist resolution of the perennial conflict between mechanism and vitalism is an unstable compound of semi-holism and semi-mechanism, that his conception of biology as the true bridge between the sciences and the humanities, ethics, and social theory is open to question (especially as to the adequacy of the theory of natural selection to account for every aspect of human nature), and that his depiction of science as the sovereign key to understanding everything known to exist or happen in this universe cannot be justified at the bar of reason.     

Sterol conjugates of two phenotypically different calli of Beta vulgaris

Steryl glycosides are the predominant form of sterol at 88% of the total sterol in non-betalain producing calli of Beta vulgaris. The total sterol decreases and sterol form shifts from steryl glycosides to 97% free sterol upon the transition of non-betalain to betalain producing calli. A substantial decrease in stigmasterol (24--ethylcholesta-5,22E-dien-3-ol) and sitosterol (24-ethylcholest-5-en-3-ol) levels is observed during this transition, and alters the ratio of ⁷:⁵ sterols. Spinasterol (24- ethyl-5-cholesta-7,22E-dien-3-ol) is the dominant sterol at 43% and 95% of the total sterol in non-betalain producing and betalain producing calli. The level of 22-dihydrospinasterol (24-ethyl-5-cholest-7-en-3-ol) is reduced in both calli to 3% from 25% in leaves. Lanosterol (4,4,14-trimethyl-cholesta-8(9),24-dien-3-ol) and cycloartenol (9,19-cyclopropyl-4,4,14-trimethyl-cholest-24-en-3-ol) were identified in betalain and nonbetalain producing callus respectively.     

The human genes for the α and γ subunits of the mast cell receptor for immunoglobulin E are located on human chromosome band 1823

The receptor with high affinity for immunoglobulin E (FcERI) is a key molecule in triggering the allergic reaction. It is tetrameric complex of one subunit, one subunit, and two disulfide-linked subunits. This receptor is present exclusively on mast cells and basophils. Molecules identical to the subunit of FcRI also form cell surface complex with other Fc receptors such as mouse FcRIIa in macrophages and most probably with human FcRIII (CD16) in natural killer (NK) cells. Here we show by in situ hybridization that the human genes for the (FCER1A) and subunits (FCER1 G) of FcERI and the gene for FcRIII (FCGR3, CD16) are located on human chromosome band 1823.     

A new enzymatic route to the synthesis of 12-ketoursodeoxycholic acid

Summary Cholic acid (3,7,12-trihydroxy-5-cholanoic acid) was completely and selectively transformed into 12-ketoursodeoxycholic acid (3,7-dihydroxy-12-oxo-5-cholanoic acid) by means of two consecutive enzymatic steps catalyzed, the first, by 7- and 12-hydroxysteroid dehydrogenase and, the second, by 7-hydroxysteroid dehydrogenase. Coenzyme regeneration was carried out with -ketoglutarate-glutamate dehydrogenase and glucose-glucose dehydrogenase, respectively.     

Acoustic communication in the trilling field cricket,Gryllus rubens (Orthoptera: Gryllidae)

Male field crickets produce calling songs that are used for attracting conspecific females for mating. Acoustic communication was studied in the trilling field cricket, Gryllus rubens.A trilled calling song consists of a continuous train of sound pulses, each of which was repeated at a stereotyped rate. Singing males were recorded at different temperatures. The pulse period of the calling song decreased with increasing temperature; there was less effect of temperature on pulse duration. Female phonotaxis was studied on a noncompensating, spherical treadmill. In two-stimulus (choice) playback experiments, females preferred the conspecific trilled song over the chirped calling song of a sympatric species, Gryllus fultoni.This preference persisted even when the song of G. fultoniwas 6 dB louder. Females also discriminated between synthetic trills having different pulse periods; females chose trills with the conspecific pulse period over trills having lower and higher pulse periods.     

Lebenslange Stabilit?t des Gesangs handaufgezogener Gartenbauml?ufer (Certhia brachydactyla)

Zusammenfassung Vier handaufgezogene Gartenbaumläufer- sangen ihre ein bis zwei Strophentypen nach ihrem Geburtsjahr zeitlebens (bis zum 3. bis 5. Kalenderjahr) weitgehend stabil (Abb. 2, 3). Ein fünftes hatte drei Strophentypen von zwei Vorsängern erlernt und zwei Strophentypen selbst entwickelt (Abb. 4). Es sang zwei der erlernten Strophentypen nach seinem Geburtsjahr erstmalig im dritten bzw. vierten Kalenderjahr. Seine beiden selbst entwickelten Strophentypen traten im vierten Kalenderjahr zum ersten Mal in seinem Repertoire auf (Tab.). Sogar im vierten Kalenderjahr kann zu Beginn des Jahres eine plastische Phase auftreten, in der ein im Geburtsjahr erlernter Strophentyp variabel gesungen wird (Abb. 5). Keines der fünf lernte nach der sensiblen Lernphase im Geburtsjahr neue Strophentypen von anderen , obwohl dazu Gelegenheit gewesen wäre.

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Lifelong stability of the song of handraised short-toed tree creepers (Certhia brachydactyla)

Summary Four handraised of short-toed tree creepers sung their one or two song types rather unchanged throughout life up to 3. to 5. year after hatching (fig. 2, 3). A fifth copied three song types from two live tutors and developed two song types alone (fig. 4). It sung two of its acquired song types in its third or fourth calendar year, respectively, for the first time after its year of birth. Both song types which it developed by itself appeared in its fourth calendar year. A plastic phase may occur even as late as the beginning of the fourth calendar year, when a song type learned in the first year, is sung again in a variable way (fig. 5). None of the five copied new song types from other after the song learning phase during their year of birth, although they had a chance to do so.

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Prof. Dr. Konrad Lorenz zum 80. Geburtstag     

Ortstreue, Altersaufbau und Mortalit?t einer Population des Baumpiepers(Anthus t. trivialis)

Zusammenfassung 1. Von den in einer intensiv untersuchten Population des Baumpiepers in Nordbelgien beringten Nestlingen kehrten 24 junge und 3 junge zurück. 12 von 17 farbberingten Jungvögeln stammten dabei aus Erstbruten.2. 6 und die beiden waren Heimatansiedler, 1 Fremdansiedler, 6 geburtsortstreu und 2 Geburtsorts-Rücksiedler.3. Die mittlere Entfernung des Revieres vom Geburtsnest betrug bei den geburtsortstreuen 184±118 m, bei den anderen 818±368 m.4. Alte zeigen größere Umsiedlungsentfernungen als alte .5. Einjährige haben in der Population einen sehr hohen Anteil.6. 79 % der und 50 % der kehrten wieder in die Population zurück.7. Die Population umfaßte durchschnittlich 42 Brutpaare. Der Anteil an ledigen Altvögeln betrug 7 %. Die Siedlungsdichte erreichte einen Wert von 3,6 Brutpaaren pro 10 ha (ohne Gewässer).8. Angaben zu Paartreue, Paarauflösung, Bigynie und Paarbildung werden mitgeteilt.9. Aus den Rückkehrzahlen errechnet sich eine durchschnittliche Mortalität der jungen von etwa 65 %, eine Lebenserwartung von einem Jahr und ein Durchschnittsalter von 1,5 Jahren.10. 2,5 % der gelegten Eier bzw. 4,6 % der ausgeflogenen Jungvögel erbrachten brutreife Rückkehrer.11. Für alte errechnet sich eine Mortalität von 47,5 %, für alte von 66,7 % und eine Lebenserwartung von 1,6 bzw. 1,0 Jahren.12. Zum Erhalt der Population müssen jährlich etwa 46 % der ausgeflogenen Jungvögel bis zum nächsten Jahr überleben.13. Die untersuchte Population ist durchschnittlich aus 4,6 % geburtsortstreuen Jungvögeln, 41,3 % fremden Jungvögeln, 37,4 % ortstreuen Altvögeln und 16,7 % unbekannter Altvögel zusammengesetzt.

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Site-tenacity, age structure and mortality in a population of the tree pipit(Anthus t. trivialis) in northern Belgium

Summary 1. 24 first year and 3 first year , ringed as nestlings, returned in next years. 12 of 17 colour-ringed birds came from first broods.2. 6 and the 2 were Heimatansiedler, 1 Fremdansiedler, 6 geburtsortstreu and 2 Geburtsorts-Rücksiedler.3. The mean distances between the first territory and the birth nest of the geburtsortstreue and of the other were 818±368 m and 184±118 m respectively.4. Adult showed greater settling distances than adult .5. The percentage of first year was very high.6. 79 % and 50 % returned to their breeding population in next years.7. The mean density of the population was 42 pairs or 3,6 pro 10 ha. Unpaired adults amounted 7 %.8. Data on pair formation, mate-faithfulness and bigyny are treated.9. Calculation of mortality from the data of returned birds yielded a mortality of young of 65 %, a life expectancy of one year and a mean life time of 1,5 years.10. Sexual mature individuals derived from 2,5 % of all eggs laid and from 4,6 % of all youngs fledged.11. The computed mortality of adult is 47,5 % and of adult 66,7 %. The life expectancy is 1,6 and 1,0 years for adult and respectively.12. Allowing for the annual losses of adults a survival rate of first year birds of about 46 % is necessary.13. The mean annual composition of the population should be: 4,6 % geburtsortstreue juveniles, 41,3 % non-autochthonous juveniles, 37,4 % ortstreue adults and 16,7 % unknown adults.

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Mit Unterstützung des Nat. Fonds v. Wetenschappelijk Onderzcek, Brüssel.     

On the role of the invariant glutamine at position 54 in the human choriogonadotropin β subunit

The twelve Cys and eight of the non-Cys residues are invariant in the glycoprotein hormone subunits from a variety of mammalian species. -Gin-54 of human lutropin (hLH) and choriogonadotropin (hCG) is one of these invariant amino acid residues. A single AG mutation in the LH gene of a patient presenting with hypogonadism resulted in the replacement of Gin-54 with Arg [1]. The authors also reported that an expressed mutant of hLH, with Arg replacing Gin-54, associated with the subunit, but there was no demonstrable binding of the mutant hormone to receptor. We have replaced Gin-54 in hCG with Glu and with Lys using site-directed mutagenesis. The expression plasmids pRSV-hCG (wild-type and mutants) were transiently transfected into CHO cells containing a stably integrated gene for bovine , and the media were analyzed for holoproteins, which were characterizedin vitro using competitive binding and steroidogenic assays with MA-10 cells. hCG(Glu-54) bound to almost as well as hCG wild-type, and the resulting heterodimer competed with [¹²⁵l]hCG binding to the LH/CG receptor and stimulated progesterone production to the same extent as the wild-type control. However, the apparent potencies, as judged by ED₅₀s, were less than those of the wild-type control, the effect being more pronounced in binding than in steroidogenesis. In contrast, hCG(Lys-54) associated very poorly with . Our results suggest that while Gin-54 in hCG participates in receptor binding, its major function appears to involve binding. Such dual functionality leads to interesting models for holoprotein formation and receptor binding.     

Paarungssystem und Fortpflanzungsstrategie der Beutelmeise (Remiz p. pendulinus)

Zusammenfassung Paarungssystem und Fortpflanzungsstrategie der Beutelmeise wurde in 10 Jahren in Süddeutschland und Österreich untersucht. Der Saisonablauf für und wird in einem Schema zusammengefaßt. Die Brutpflege übernimmt i. allg. nur ein Altvogel (bei ca. 60 % aller Brutnester , bei 10 % ). Unklar ist, wie die Abstimmung erfolgt, welcher Altvogel das Gelege betreut. Offenbar herrscht eine Konfliktsituation zwischen den Geschlechtern, die sich in zahlreichen Gelegeaufgaben niederschlägt (ca. 30 % aller Brutnester). Die Verhaltensweisen betreuen bzw. verlassen sind für und nicht gleichmäßig über die Brutsaison verteilt. Die Mediane für die Betreuung durch das und die Aufgabe der Nester liegen dicht beieinander, betreuen die Nester erst wesentlich später. In Illmitz/Österreich nahm die Gelegegröße mit fortschreitender Jahreszeit ab. Die Gelegegröße der aufgegebenen Gelege war kleiner als die zeitgleich zu erwartende Gelegegröße der betreuten Gelege. Wenn das abwandert, komplettiert es das Gelege offensichtlich nicht; damit wird für das zurückbleibende erfolgreiche Brutpflege möglich. Beide Geschlechter verfolgen unterschiedliche Strategien, um einen möglichst guten Fortpflanzungserfolg zu erreichen. Beim besteht die ganze Brutsaison hindurch Bereitschaft, mehrere Nester zu bauen und möglichst viele zu haben. Gegen Ende der Brutsaison, wenn nur noch wenige brutbereite verfügbar sind, übernehmen die u. U. selbst die Brutbetreuung. betreuen zu Beginn der Brutsaison komplette Gelege selbst. Bei rund 30 % der ist aber schon zu Beginn der Brutsaison die Bereitschaft vorhanden, das Gelege mit unvollständiger Gelegegröße nicht selbst zu betreuen und die Verantwortung hierfür dem zu überlassen. Zum Geschlechterkonflikt kommt es, wenn beide Strategien hinsichtlich Abwandern kollidieren; er läßt sich mit Hilfe der Spieltheorie erklären. Wegen der großen Wanderungen während der Brutperiode haben die Angaben zum Verpaarungsstatus der einzelnen Vögel Minimalcharakter. Mindestens 25 % aller und 12 % aller waren polygam. Daß während der ganzen Brutsaison keine Partner haben, ist nachgewiesen. Der Bruterfolg polygamer war signifikant größer als der von mit nur einem Brutnest. Polygame hatten größere Flügel als die übrigen; auch deutet sich an, daß alte erfolgreicher sind als junge. Eine Polygynierate von bis zu 60 % dürfte realistisch sein; die Polyandrierate dürfte bei ca. 30 % liegen. Polyandrisches Verhalten ist aber nicht immer mit einer Steigerung der Reproduktionsrate verbunden. Besonders zu Beginn der Brutsaison bedeutet die Abwanderung des mit hoher Wahrscheinlichkeit die Aufgabe des Nestes, da die in dieser Phase die Brutbetreuung in der Regel nicht übernehmen. Einzelne waren in der Lage, nacheinander zwei Bruten alleine großzuziehen.

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Mating system and strategy of reproduction in Penduline TitRemiz p. pendulinus

Summary From 1978 to 1987, 477 nests of the Penduline Tit were checked in Bavaria and Austria. Adult birds were marked individually with colour rings.In northern Bavaria, the major part of Penduline Tits started building nests in April and May (median date: May 10). As early as end of May a large number was leaving the breeding grounds. The population in the riverine forests of the river March/Austria basically followed the same cycle. On the other hand, birds breeding at Lake Neusiedl/Austria arrived as late as the beginning of June (median date for start of nestbuilding: June 23). A generally valid seasonal pattern for both sexes see fig. 1, 2. Penduline Tits exhibit uniparental care. Most of the nests (about 60 %) were attended by females, about 10 % by male and about 30 % were deserted, because neither the female nor the male decided to incubate (tab. 1).Early in the year, clutches were reared by the female or abandoned; preferably at the end of the breeding season males incubated. A significant relation between clutch size and season could be found at Illmitz/Austria. If average clutch size for female, male or no care are compared with the average clutch size of the respective five-day periods in which the medians of the three categories were found, a significantly smaller clutch size was apparent in abandoned nests. Due to extensive migratory behaviour during the breeding season, a calender effect of clutch size was not calculated for the Upper Main/Bavaria. However, clutch size in nests incubated by females exceeded the size of the abandoned ones. The incubation of smaller clutches by males in the same area is hard to explain. Insufficient data and/or the lack of potential mates as a consequence of early migration may account for it. If a female decides to abandon a nest she evidently leave the clutch incomplete, as if to give the male a commission to care for the young. Thereby, females economize on their reserves in order to be able to produce additional clutches with other males.To achieve optimal reproductive success both sexes follow different strategies. Males: During the whole breeding season males are able to construct a large number of nests to attract as many females as possible. At the end of the breeding season, when only few females are available, some of the males care for their broods themselves. Females: At the beginning of the breeding season, most females are ready to incubate complete clutches. But already at this time, approximately 30 % of the females desert incomplete clutches so as trying to give commission for brood care to the male.The battle of the sexes arises, if both sexes abandon the clutch. This conflict may probably be explained by the game theory. Due to the migrations during breeding season, an exact documentation of the mating status of individual birds was limited. Polygamy occured at least in 25 % of the males and 12 % of the females (tab. 4). A number of unpaired males was also evident during the whole breeding season. Polygynous males reached higher breeding success (tab. 8), and were larger (wing-length) as compared to the other males. Older males may be more successful than younger. According to the number of males leaving nests, the rate of polygyny might be up to 60 % and, due to the number of clutches abandoned by females, approx. 30 % of them are polyandrous. However, polyandrous behaviour was not linked to an increased reproduction rate. Especially at the beginning of the breeding season, most of the nests deserted by females were completely abandoned. Some females were able to raise two broods in one season.