Effect of road traffic on the breeding site-tenacity of male Willow Warblers (Phylloscopus trochilus)

Summary The breeding site-tenacity of colour-ringed male Willow Warblers (Phylloscopus trochilus) was studied in an homogenous area of 154 ha, which is crossed by a heavily travelled road (45 000 cars per day). Close to the road (<200 m) the dispersal of the males is much higher than for birds further away. There is also some evidence that most of the near-to-the-road males are yearlings. The differences indicate that adjacent to the road the habitat is less favourable for the Willow Warbler and can be considered as marginal.

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Zusammenfassung Untersucht wurde die Brutortstreue von individuell fabrberingter Männchen des Fitis (Phylloscopus trochilus) in einem 154 ha großen Gebiet, das von einer Autobahn mit regem Verkehr (45 000 Fahrzeuge pro Tag) durchschnitten wird. In der Nähe der Autobahn (<200 m) zeigten die Reviermännchen eine viel größere Dismigration als die Revierinhaber in größerem Abstand von der Verkehrstraße. Auch gab es Hinweise, daß in der Nähe der Autobahn überwiegend einjährige Männchen die Reviere besetzten. Für den Fitis kann man Habitate entlang der Autobahn als marginal betrachten.

     

Parental investment in nest defence by stonechats (Saxicola torquata)

Breeding stonechats (Saxicola torquata) made mixed sequences of two calls when a human intruder entered territories. ‘Whits’ are modulated notes with a small frequency range, and in laboratory tests caused nestlings to stop begging. ‘Chacks’ cover a wide range of frequencies, and in the field were combined with flights made so as to distract an intruder from the nest. On average male and female call-rates were similar, but varied greatly according to the intruder's distance from the nest, and at different stages of the nesting cycle. Rates increased rapidly after hatching, and this correlated most closely with the cumulative total of parents' visits to feed nestlings. This suggests that the level of defence may be adjusted to the value of the offspring to their parents. Call-rates declined about one week after fledging. A smaller peak by some pairs at the start of incubation was apparently related to probable poor condition after a previous breeding attempt, and after laying large clutches. Rates of Whits were higher at nests with larger broods, up to an asymptote, but rates of Chacks were independent of brood size. Birds suffering nest-predation showed lower call-rates before the event than equivalent successful birds, suggesting that the calls do reduce the risk of predation.     

Beobachtungen zur Lebensweise des Weidenlaubs?ngers (Phylloscopus collybita Vieill.)

Ohne Zusammenfassung     

Male-male pairs in Greylag Geese (Anser anser)

Summary For almost two decades a flock of 130 free-flying Greylag Geese (Anser anser) has been the focus of detailed ethological investigations at the Konrad Lorenz Institut in Grünau im Almtal, Austria. Gander pairs, i. e. male-male pairs, represent a prominent social unit in this flock and were the subject of a detailed behavioral investigation. Analysis of the composition and dynamics of the flock over a 15 year period indicated that the incidence of homosexual pairings closely paralleled the male bias of the sex ratio. The behavior of ganders in gander pairs was investigated and compared to that of gander and goose in heterosexual pairs. The behavior of the two males in a gander pair (1) was comparable in most aspects, (2) was similar to the behavior of the gander in heterosexual pairs, and (3) differed greatly from that of the heterosexually paired goose. Therefore, pseudo-female behavior in one partner cannot account for the formation of a pairbond between two males. As a unit, gander pairs were characterized by a higher frequency of offensive agonistic behavior compared to heterosexual pairs and spent significantly more time peripheral to, and away from the flock than did heterosexual pairs.

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Zusammenfassung Das Sozialgefüge einer Schar Graugänse ist weitaus komplizierter, als es das monogame Fortpflanzungssystem erwarten ließe (Collias &Jahn 1959,Fischer 1965,Kalas 1979,Rutschke 1982). Ganterpaare, die häufig über Jahre hinweg bestehen bleiben, sind für tiersoziologische Untersuchungen interessant, weil ihre Funktion nicht im Rahmen der Fortpflanzung gesehen werden kann. Welche Bedingung begünstigen die Bildung von Ganterpaaren, und welche Verhaltensmechanismen tragen zum Entstehen und zur Aufrechterhaltung dieser Verbindung bei? Die Zusammensetzung der Grünauer Graugansschar 1973–1988 zeigt, daß die Anzahl der Ganterpaare von einem Überschuß von Männchen in der Schar abhängt. Das Verhalten von 6 Ganterpaaren wurde untersucht und mit dem von heterosexuellen Paaren verglichen. Innerhalb eines Ganterpaares entsprachen sich die Partner in der Häufigkeit von agonistischem sowie sozial-bindendem Verhalten. Homo- und heterosexuell verpaarte Ganter zeigten sich im Verhalten vergleichbar. Der Ganter eines Ganterpaares unterschied sich jedoch in der Häufigkeit aller untersuchten Verhaltensweisen von dem der heterosexuell verpaarten Gans. Folgende Schlußfolgerungen und Hypothesen bieten sich an: (1) Pseudo-weibliches Verhalten bei einem der Ganter scheint nicht die Bildung von Ganterpaaren erklären zu können. Beide Ganter verhalten sich rein männlich und behandeln den Partner so, als ob dieser ein Weibchen wäre. (2) Ein Mangel an gegengeschlechtlichen Schargenossen fördert die Bildung von homosexuellen Paaren und aufzuchtsbekannte Vögel werden dabei vorgezogen. (3) Ein Zusammenschluß mit einem gleichgeschlechtlichen Artgenossen sollte, verglichen mit der Möglichkeit alleine zu bleiben, eine überlegene Strategie darstellen, da unverpaarte Gänse geringeren Zugang zu Futterquellen haben und eher Raubtieren zum Opfer fallen. (4) Homosexuelle Paare könnten als ein Puffersystem für Ganter angesehen werden, vor allem zu Zeiten in denen das Geschlechtsverhältnis in Richtung der Männchen verschoben ist. (5) Aggression des Ganters richtet sich generell gegen andere männliche Schargenossen. Die Bildung von Ganterpaaren, also besonders aggressiven Paaren, könnte daher dazu beitragen, Ganter aus der Schar zu vertreiben und ein Übermaß von Männchen in der Schar zu verhindern. (6) Da wir zeigen konnten, daß sich homosexuelle Paare oft am Rande der Schar aufhalten und dabei häufig sichern, könnte solchen Paaren eine Art Wächterfunktion zukommen. (7) Andererseits ist es durchaus möglich, daß Ganterpaare bloß ein Epiphenomen einer Graugansschar mit einem Überschuß an Männchen darstellen.

     

Der Berglaubvogel [Phylloscopus bonelli bonelli (Vieill.)] und seine Verbreitung in Bayern

Ohne Zusammenfassung     

Maternal energetic investment in a monogamous mouse

Concurrent gestation and lactation is costly and rodent females may manage their reproductive effort by adjusting the length of the inter-litter latency. In this study, we attempted to build a model of this phenomenon as a function of maternal condition and energetic investment (measured as the litter size and weight) in the mound-building mouse, Mus spicilegus. We analysed the distributions of two successive inter-litter latencies using linear models. These distributions revealed a high inter-individual variability in latencies (22–38 d). Our results showed that none of the parameters reflecting female investment could explain this variability. The only link revealed by our analyses was a significant positive correlation between two successive inter-litter latencies. These results suggested that other parameters were involved in the regulation of inter-litter latencies. We propose that paternal care, which has a direct effect on inter-litter latency, may play a major role by allowing females to save energy or through differential allocation. In addition, genetic characteristics of the females and the prenatal environment of the female should also be considered.     

Reaktionen von Zilpzalp und Fitis (Phylloscopus collybita, Ph. trochilus) auf verschiedene Gesangsformen des Zilpzalps

Zusammenfassung 1. Die mitteleuropäische, die spanische und die kanarische Gesangsform des Zilpzalps sind voneinander klar verschieden.2. Die Zilpzalp- von Teneriffa (kanarische Inseln) und aus Mitteleuropa reagieren auf ihre vom Tonband vorgespielten Gesänge wechselseitig wie verschiedener Arten, d. h., nur einzelne werden angelockt.3. Zilpzalp- aus Mitteleuropa verhalten sich gegenüber der spanischen Gesangsform des Zilpzalps wie gegenüber artfremdem Gesang. Spanische Zilpzalp- werden von Gesangsformen des Zilpzalps aus Mitteleuropa und den kanarischen Inseln zu einem hohen Prozentsatz angelockt (86,6 und 66,6%).4. Die Zilpzalp-Populationen in Mitteleuropa, Spanien und auf den kanarischen Inseln befinden sich vermutlich auf verschieden weit fortgeschrittenen Stufen der Artaufspaltung.5. Interspezifische Kontrastbetonung ist wahrscheinlich nicht die Ursache für die großen Unterschiede zwischen dem Gesang des Fitis und des mitteleuropäischen Zilpzalps.

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Reactions of the Chiffchaff and Willow-Warbler to different song forms of the Chiffchaff

Summary 1. The song forms of the Chiffchaff in Central Europe, in Spain and on the Canary Islands are clearly distinct from each other.2. Chiffchaff males of Tenerife (Canary Islands) and Central Europe react to the playback of each other songs in the same way, as to songs of other species, i. e. only a few males being attracted.3. Chiffchaff males of Central Europe behave in the same way to the Spanish song form of the Chiffchaff as to songs of another species. A high % of Spanish Chiffchaff males are attracted to song forms of the Chiffchaff of Central Europe (86,6) and of the Canary Islands (66,6).4. Chiffchaff populations in Central Europe, Spain and on the Canary Islands should stay split as they are different evolutionary stages.5. Interspecific contrast reinforcement is probably not the cause of the differences between the song of the Willow Warbler and the song of the Chiffchaff of Central Europe.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Breeding ecology of an Old World high-altitude warbler, Phylloscopus affinis

Reproduction of Tickell’s Leaf Warblers Phylloscopus affinis was studied in an alpine valley (29°27′N, 91°40′E, 3,980–5,600 m) in the Lhasa mountains, Tibet, at the upper elevational limit of the species’ breeding range. This species is a summer breeder, and is the only breeding Phylloscopus species in the valley. It nested in all types of shrubby vegetation across the altitudinal range of the valley. Most nests were placed close to the ground (<1 m) in low thorn bushes. Egg-laying dates fell between late May and early July, most within the first 3 weeks after the commencement of breeding. Mean clutch size was 4.0 (3–5) and mean brood size at fledging 3.4 (2–5). Incubation was by the females and lasted 13–14 days, and both parents cared for the young for 14–17 days. Nestlings ready to leave the nest were 13% heavier than the adults. Overall, 76% of nesting attempts produced at least one fledged young. Some aspects of the breeding biology of this high-altitude warbler were compared with those of lower-altitude Phylloscopus species.     

CuckooCuclus canorus parasitism onAcrocephalus Warblers in Southern Moravia in The Czech Republic

Summary The Reed Warbler,Acrocephalus scirpaceus, in the Lednice area, Southern Moravia in the Czech Republic, was parasitized by the Cuckoo,Cuculus canorus, at a rate of at least 18.0 %. The Cuckoo eggs showed poor mimesis with the Reed Warbler eggs, but showed a greater resemblance to the eggs of other species breeding in the area, including the Great Reed Warbler,A. arundinaceus. This latter species was also parasitized, but we did not find enough nests to obtain a reliable estimate for the rate of parasitism. The parasitized Reed Warblers rejected the Cuckoo eggs at a high rate (42.1 %) and therefore both the hatching success and the breeding success of the Cuckoo was considerably lower than shown by comparable results from Britain. On the background of these results (poor mimesis of the Cuckoo eggs and a high rejection rate by the hosts) the question of the degree of specialization versus generalism in the Cuckoo's host preference is discussed.

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Zusammenfassung Teichrohrsänger im Gebiet von Lednice (Südmähren, Tschechei) waren mindestens zu 18 % vom Kuckuck parasitiert. Die Kuckuckseier glichen jenen der Teichrohrsänger nur wenig, waren jedoch den Eiern anderer im Gebiet brütender Arten einschließlich des Drosselrohrsängers ähnlicher. Drosselrohrsänger waren auch parasitiert; wir fanden jedoch nicht genug Nester, um eine Parasitierungsrate ermitteln zu können. 42,1 % der Kuckuckseier wurden vom Teichrohrsänger nicht angenommen; daher waren Schlüpf- und Ausfliegerate des Kuckucks merklich geringer als in vergleichbaren Ergebnissen aus Großbritannien. Vor dem Hintergrund unserer Ergebnisse — geringe Angleichung der Kuckuckseier und hohe Ablehnungsrate durch die Wirtsart — wird die Frage von Spezialisierung und Generalismus in der Wirtswahl des Kuckucks diskutiert.

     

Der sibirische Zilpzalp (Phylloscopus collybita tristis): Gesang und Reaktion einer mitteleurop?ischen Population im Freilandversuch

Zusammenfassung Der Gesang des sibirischen ZilpzalpsPhylloscopus collybita tristis unterscheidet sich markant von jenem der beiden mittel- und ost-europäischen SubspeziesPh. c. collybita undPh. c. abietinus. Unterschiede betreffen Qualität und Quantität des Element-Repertoires, Syntax, Rhythmus innerhalb der Strophen und Frequenzumfang der Strophe.Tristis verfügt über den reicheren und vielfältigeren Gesang. Das wird als apomorphes Merkmal betrachtet. Eine mitteleuropäischecollybita-Population reagiert auftristis-Gesang im Feld-Experiment fast nicht. Nur solche Kunst-Strophen aus natürlichen Elementen vontristis werden vergleichsweise gut beantwortet, die Elementen entsprechen, über die auch mitteleuropäischecollybita verfügen. Die sibirische Gesangsform ist auf über 4000 km W-O-Erstreckung offensichtlich nahezu konstant. Der westliche Arealteil vonc. tristis, oft alsc. fulvescens bezeichnet (Ural bis Jenissei-Tal, 2000 km W-O) kann nicht als Hybrid-Population angesehen werden (abietinus xtristis), da sich in diesem Gebiet keine Merkmale desabietinus-Gesanges nachweisen lassen.

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Territorial song of the siberian chiffchaff (Phylloscopus collybita tristis) and playback experiments within a central european population (Ph. c. collybita)

Summary Territorial songs of Siberian ChiffchaffsPhylloscopus collybita tristis distinctly differ from songs of the Central and East European subspeziesPh. c. collybita andPh. c. abietinus (which do not differ from each other). Differences betweentristis andcollybita/abietinus concern quality and quantity of the notes within the song verses, syntax, rhythm within the song verses, and frequency range of the song verses.Tristis disposes of richer and more manifold song which is said to be an apomorphic character.Ph. c. collybita from Central Europe (Mainz area) using much more limited numbers of differing notes, displays nearly no territorial response totristis song in the field experiments. Only those artificial verses consisting of notes which are used also byc. collybita, were reacted on. The Siberian form of chiffchaff song is apparently more or less constant to about 4000 km in W-E extension. The Western part of thetristis range, often calledc. fulvescens (Ural to Yenisei river, 2000 km W-E), is not to be considered a hybrid population ofabietinus andtristis proper, for no characteristics ofabietinus song are taceable in thefulvescens area.

     

Parental investment of male two-spotted goby, Gobiusculus flavescens (Fabricius)

The trade-off between parental care and feeding was studied in the male two-spotted goby (Gobiusculus flavescens F.). Two temperatures, 8.5 degrees C and 13.0 degrees C, were used, with five replicates at each temperature, in order to determine whether temperature influenced parental behaviour. In each replicate, two males and four females were introduced to an aquarium, where the males chose between two nests and courted the females. In each replicate, one male spawned. After spawning, the males guarded the eggs until hatching. The guarding males' behaviour was recorded with a video camera twice a day (15 min each time), once before and once after they were fed. The male's condition (c-factor) was calculated at the start of the experiment and after egg hatching. The eggs were spawned in an artificial nest (half of a PVC tube), and attached to the nest in a single layer. The areas with eggs (representing brood size) were marked after spawning and the fry counted after hatching (which was used to calculate area hatched). Numbers of prey eaten (plankton) and number of aggressive encounters between the guarding male and the other fishes were recorded. Time spent in the nest and time used on fertilisation, fanning and cleaning were estimated and related to egg age, brood size, hatching success, temperature and food availability (no food or food).The results showed that feeding (expected to influence future reproduction) decreased and parental expenditure (current reproduction) increased, as the eggs developed (became closer to independence). Parental expenditure was significantly higher at 13.0 degrees C than at 8.5 degrees C, presumably due to higher oxygen demands by the eggs, and a greater risk of egg-infections. The c-factor of the males guarding eggs decreased over time, in contrast to the non-guarding males' c-factor. Guarding males' aggressiveness decreased as the eggs got older, but increased just before hatching. A possible explanation for this could be the decreasing intrusion by the non-guarding male and females caused by high aggressive behaviour by the guarding male early in the brood cycle. The exploitation of the nest (percentage of total nest area covered by eggs) seemed to determine the amount of parental expenditure and loss of condition, while brood size (area of eggs) had no effect.     

Habitat associations of Wood Warblers Phylloscopus sibilatrix breeding in Welsh oakwoods

Capsule Territory locations, density and the change in numbers over 20 years were associated with characteristics of the canopy, understorey structure and field-layer vegetation cover.

Aims To identify habitat characteristics associated with territory locations and density of Wood Warblers Phylloscopus sibilatrix in Welsh oakwoods in 2009–2011, and the change in abundance between 1982–1984 and 2003–2004.

Methods In 2009–2011, habitat characteristics were compared between 106 territories and 226 unoccupied points in 19 woods. Mean wood-scale habitat values were related to density in 27 woodland blocks. The change in Wood Warbler numbers between 1982–1984 and 2003–2004 was related to initial habitat quality in the 1980s and the change in habitat characteristics between the two time periods.

Results The location of territories in 2009–2011 was positively associated with canopy height, and with intermediate values of slope steepness, field-layer vegetation cover, canopy cover, the proportion of Oak Quercus in the tree community and subcanopy cover. Density was positively associated with slope, subcanopy cover at 0.5–2 m height and a landscape dominated by coniferous plantation and moorland; and with intermediate values of the proportion of oaks in the tree community. Wood Warblers declined by 24.4% in the two Welsh regions between 1982–1984 and 2003–2004, and trends were positively associated with the initial cover of Bramble and, in Gwynedd only, canopy cover.

Conclusions Wood Warblers were associated with a number of structural habitat variables, which could be related to the past management of the study woods. Management should be targeted at restoring habitat quality for Wood Warblers through the introduction of a moderate grazing regime.     

Male extraterritorial forays, age and paternity in the socially monogamous reed bunting (Emberiza schoeniclus)

Genetic studies have shown that extra-pair paternity is widespread among socially monogamous bird species. Yet, the role of males and females and their behavior leading to this mixed reproductive strategy is poorly understood. Here, we analyze paternity in relation to male age and mating behavior in the socially monogamous reed bunting (Emberiza schoeniclus). We report a positive relation between male extraterritorial forays and success in obtaining extra-pair fertilizations. Extraterritorial forays tended to increase in frequency with male age and older males sired a larger number of extra-pair offspring than young males. Identified extra-pair sires were old in nine out of ten cases. The likelihood of being cuckolded was not affected by male age. Although based on correlative data, our results highlight age-dependent explorative male behavior as a key determinant for the understanding of extra-pair mating in the reed bunting. We do, however, emphasize the need for further studies to reveal the role of females in extra-pair copulations and fertilizations.     

Enhanced vigilance in monogamous pairs of the lizard, Tiliqua rugosa

The Australian sleepy lizard, Tiliqua rugosa, forms monogamouspairs for up to 8 weeks each spring before mating. We observedthat males had food in their mouths significantly less oftenwhen they were in pain than when they were alone. Females hadfood in the mouth independent of the presence or absence ofmales. Among females that had been feeding, indicated by foodin the mouth, we observed them feeding, as we approached, lessoften when they were in pairs than when they were alone. Amongfemales in pairs with food in their mouths, we observed themfeeding less often when their male partners were not feedingthan when their partners were feeding. This suggests that femalesare alerted to approaching danger earlier when they are in apair, and alerted earlier in a pair when their male partneris not feeding. Enhanced vigilance may be one function of pairingbehavior.     

Geographical variation in reproductive investment in Canada Geese (Branta canadensis) in Sweden

Summary Clutch volume, egg volume and clutch size were studied in four populations of introduced Canada Geese in Sweden along an 850 km latitudinal gradient. These recently established populations were not assumed to be adapted to their breeding habitats. Clutch volume as well as egg volume differed significantly between some of the populations. Clutch volume was significantly higher in a population which had its breeding area within spring feeding areas, compared to a population which migrated 350 km between the last major foraging area and the breeding area. Thus, we found some support for the energy reserve hypothesis, which predicts that the body reserves of the female determine her energy investment in the clutch. Egg size differed on a geographic basis, and one population had significantly smaller eggs than two of the others. Clutch size did not vary significantly between the populations. A significant year effect on clutch volume and clutch size was found.

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Zusammenfassung An vier Populationen in Schweden eingeführter Kanadagänse wurden einem Gradienten geographischer Breite folgend Volumina von Gelege und Eiern sowie Gelegegröße untersucht. Es ist nicht anzunehmen, daß diese erst seit kurzer Zeit ansässig gewordenen Populationen an ihre Bruthabitate angepaßt sind. Sowohl im Gelege- wie im Eivolumen zeigten sich signifikante Unterschiede zwischen einigen Populationen. In einer Population, deren Brutgebiet innerhalb der Weideflächen liegt, die die Vögel im Frühjahr aufsuchen, war das Gelegevolumen signifikant höher als in einer Population, die vom letzten bedeutenden Weidegebiet bis zu ihrem Brutgebiet ca. 350 km gezogen war. Die Energiereserve-Hypothese, die besagt, daß die Körperreserven des Weibchens seine Investition an Energie in das Gelege bestimmen, findet somit in unseren Ergebnissen etwas Unterstützung. Die Eigröße variierte von Brutgebiet zu Brutgebiet mit der geographischen Lage; eine Population wies signifikant kleinere Eier auf als zwei der übrigen. Nicht signifikant variierte die Gelegegröße zwischen den Populationen. Gefunden wurde ein signifikanter Effekt der jeweiligen lokalen Bedingungen auf Gelegevolumen und -größe.

     

Interactions in family pairs and parental care in captive steppe lemming (Lagurus lagurus)

Partner interactions and parental activities in pair-bonded male and female steppe lemmings (L. lagurus) were estimated under laboratory conditions. Interactions between adults in family pairs were found to be neutral or peaceful with rare agonistic contacts. Compared to other rodent species living in family groups, the frequency and duration of partner grooming in adults were found to be low, indicating relatively weak pair bonding in steppe lemmings. At the same time, males spend much more time with pups in the nest than females, but they are inferior to the latter in grooming (licking) and nest material delivery. Parental behavior of L. lagurus is discussed in comparison with that of other species of the subfamily Microtinae.     

Cuckoldry and recapture probability of adult males are not related in the socially monogamous coal tit ( Parus ater)

Despite substantial research effort, the benefits of female extra-pair matings in socially monogamous bird species remain elusive. The good genes hypothesis assumes that females engage in extra-pair copulations with males of superior genetic quality compared to their respective social mate. Therefore, a negative association between the degree of cuckoldry and male survival is predicted, if genetic quality is phenotypically reflected by high viability. Furthermore, genetic sires of extra-pair offspring (EPO) should survive better than the social fathers they cuckolded. We tested these predictions in a nestbox population of the coal tit (Parus ater), a socially monogamous passerine with low breeding dispersal and high rates of extra-pair paternity (EPP). Based on 257 genotyped first broods of two consecutive years, we found no relationship between the incidence of EPP or the proportion of EPO within a given brood and male or female recapture probabilities. Furthermore, recapture rates did not differ between social and genetic fathers of EPO or males that did or did not appear as extra-pair sires in other broods. Our results were not affected by differential (short-range) breeding dispersal with respect to EPP or by other potentially confounding variables. Hence, they are not in accordance with the good genes as viability genes hypothesis.Communicated by F. Bairlein     

Parental food conditions affect sex-specific embryo mortality in the yellow-legged gull (Larus michahellis)

Different mortality of males and females during early post-hatching development in sexually size-dimorphic bird species is usually attributed to different nutritional requirements of the sexes, because mortality is mostly biassed toward the larger sex. We investigated whether sex-specific embryo mortality in the yellow-legged gull (Larus michahellis), a size-dimorphic seabird, depends on parental condition. To test this, we experimentally modified parental nutritional conditions by supplementary feeding of yellow-legged gulls during egg formation, to evaluate sex-biassed environmental sensitivity of gull embryos. We found that eggs were larger in supplemented clutches, but egg size did not affect embryo survival. Survival of male gull embryos was more related to parental food conditions than was survival of female embryos. Survival of male embryos in supplemented clutches was greater than in unsupplemented clutches whereas survival of female embryos was similar in both groups. Because size at hatching was similar in both sexes our results suggest that male phenotype disadvantage is not exclusively linked to the energy demands of size-dimorphic development at the embryo stage.     

Factors affecting female parental investment in the monogamous goby, Valenciennea longipinnis

Female Valenciennea longipinnis construct a conspicuous rubble mound on a burrow after spawning while the paired male tends eggs in the burrow until hatching occurs. The mound has a function of promoting water-exchange in the burrow through hydrodynamic effects, contributing to prevention of the male egg-desertion by reducing his parental costs. Although higher mounds are more effective in water exchange, they cost females much work after spawning. In this study, I investigated effects of six ecological and environmental factors on the mound height, i.e., female parental investment. Multiple regression analysis indicated that only female body size could explain the female parental investment: larger females tended to construct higher mounds. The size-assortative mound building suggests that the females strive to construct mounds as high as they can irrespective of the other ecological and environmental factors. Because current strength and oozing of underground water fluctuated even in a day, females may be obliged to construct high mounds on the basis of the worst condition.