Breeding site fidelity in willow ptarmigan: the influence of previous reproductive success and familiarity with partner and territory

Summary Breeding site fidelity is high in willow ptarmigan: only 9% of males and 31% of females switched territories between years. Unpaired males were more likely to switch territories than paired males. For paired males, survival of their previous partner and reproductive success in year x did not influence probability of switching in year x+1. A female was more likely to switch territories if her previous partner disappeared. If her partner returned, she had a higher probability of switching if she did not produce chicks the previous year. Most hens moved to the territories of older males, although hens paired with unfamiliar older males did not have higher reproductive success than those paired with yearlings. Individuals that paired with their previous partner laid earlier and produced heavier chicks than those paired with unfamiliar partners. Excluding birds paired with familiar partners, survival and reproductive success in year x+1 was similar for males and females that did or did not switch territories. Males had a higher probability of producing chicks after switching than before, but females were more likely to lose their clutch after switching. For both sexes, birds that switched territories were as successful as the birds that replaced them on their former territories. We conclude that high site fidelity in willow ptarmigan is maintained because of the benefits of pairing with a familiar partner.     

Habitat selection and polygyny in breeding Corn Buntings Miliaria calandra

Unlike many other polygynous passerine species, female Corn Buntings Miliaria calandra apparently do not suffer costs by pairing polygynously, yet it is unclear whether this is because polygynous males hold the highest quality territories or because pairing with polygynous males is unimportant in determining female reproductive success. Male Corn Buntings on North Uist, Scotland, consistently defended territories which contained nesting habitat, and females often foraged outside male territories when provisioning nestlings. Females showed strong preferences for nesting in uncultivated land, and 80% of nests were under Hogweed Heracleum sphondylium, possibly because this provided cover against predation and the weather. When provisioning nestlings, females showed strong preferences for foraging in cereal crops, probably because this habitat provided better food resources and/or better cover from predators. Males were unpaired or paired with one to three females per breeding season, but variation in territory size or vegetation composition did not explain differences in the number of females paired with individual males. We suggest that when females neither gain benefits nor suffer costs by breeding polygynously, and males do not differ greatly in the areas of habitat selected, polygyny can arise through random female settlement within the nesting habitat.     

Habitat selection and reproductive success of Ortolan Buntings Emberiza hortulana on farmland in central Sweden – the importance of habitat heterogeneity

Many granivorous birds have shown severe population declines in Europe during recent decades. The aim of the present study was to analyse habitat preferences and reproductive success of one such species, the Ortolan Bunting Emberiza hortulana, in different farmland habitats in south‐central Sweden. Four seemingly different land‐use types were preferred: permanent set‐asides, short rotation coppice, and grazed and unmanaged semi‐natural pastures. Territories and random sites differed considerably in the proportion of these preferred land‐use types; 39% of territories had > 70% preferred habitat (at the 100‐m scale) compared to 5% of random sites. In contrast, 22% of territories and 65% of random sites had no preferred habitats. All the preferred habitats had heterogeneous ground vegetation characterized by patches with bare ground, or at least sparse ground vegetation, intermixed with patches with taller vegetation. Ortolan Buntings also preferred a heterogeneous habitat structure with occurrence of field islets, shrubby edges, barns and electric wires, which could act as song posts or suitable nest‐sites, in 88% of territories. At a larger (1‐km square) scale, territories occupied by pairs aggregated strongly in areas with high proportions of preferred habitats. The number of territories with single males correlated positively with the number of pairs, which suggests that conspecific attraction may influence territory distribution. No measured habitat factors were related to reproductive success. However, due to habitat preferences and the higher proportion of paired males in one habitat type (set‐aside), the production of young (fledglings/ha) is expected to be higher in set‐asides, as well as in short‐rotation coppices and semi‐natural pastures. Thus, these habitats are important for the conservation of the Ortolan Bunting. Large areas with habitat structures such as field islets are especially important because the Ortolan Bunting breeds in aggregations in these areas.     

Social organization and spawning in the Atlantic sharpnose puffer,Canthigaster rostrata (Tetraodontidae)

Synopsis Social organization and spawning in the sharpnose pufferCanthigaster rostrataere studied on a reef in the San Blas Islands, Panama. Sexes were dimorphic. In mixed coral and rubble habitat, females defended territories against other females and small males. From one to six female territories were included within the territories of certain large males. These haremic males visited their females and patrolled their territories throughout the day. Smaller, non-haremic males occupied territories or home ranges within or adjacent to those of haremic males or were wanderers. Spawning between a haremic male and a territorial female occurred within the female's territory. The female prepared an algal nest into which demersal eggs were deposited. There was no parental care. Eggs were spherical, translucent, and measured approximately 0.66 mm in diameter. Larvae were about 1.4 mm TL and closely resembled those of other species ofCanthigaster.     

Territoriality in Lake Eyre Dragons Ctenophorus maculosus: are Males ‘Superterritorial’?

The Australian Lake Eyre dragon, Ctenophorus maculosus, lives on dry salt lakes in the Australian interior. An unusual characteristic of this habitat is that windblown insects are the major food resource, which makes it impossible for males to defend site-related resources. Male territory size is not correlated to male size; thus, males do not seem to defend trophic territories in relation to their own energy demands. Instead, males with higher densities of lookout sites have larger territories, and males with larger territories have more mates. In consequence, males primarily seem to guard sexual resources on territories that are not economically defensible from a trophic point of view; males appear to conform to the concept of ‘superterritoriality’ (sensu Stamps 1983).     

Conflicting Territory Use in Males and Females of a Monogamous Ungulate,the Kirk's Dikdik

In monogamous mammals it is often unclear why males do not defend larger territories to attract more than one female. I investigated the territoriality of the monogamous Kirk's dikdik, Madoqua kirki, a dwarf antelope, in which food resources increase with territory size and some males defend enough resources for more than one female. Yet, all males are paired monogamously. When males were removed from small territories, their female partners spent more time outside of their territories than females in large ones. When females were removed, their male partners almost never left. Pairs in small territories spent more time together than pairs in large ones. Paired males left mostly together with their females, apparently not on their own initiative. Presumably because females in small territories left more often, their males spent more time outside in the female's company than males in large territories. I argue that males in smaller territories can keep better track of their females and that they can effectively reduce their females' time outside. Male intrusion pressure was unrelated to territory size, but it increased in the presence of unguarded females. If large territories decrease the ability to mate guard, and if unguarded females attract competing males, then defending large territories may be uneconomical, even it they could attract more than one female. On the other hand, territories must be large enough to satisfy the requirements of a single female.     

Home‐range size and habitat use of European Nightjars Caprimulgus europaeus nesting in a complex plantation‐forest landscape

In Europe, the consequences of commercial plantation management for birds of conservation concern are poorly understood. The European Nightjar Caprimulgus europaeus is a species of conservation concern across Europe due to population depletion through habitat loss. Pine plantation‐forest is now a key Nightjar nesting habitat, particularly in northwestern Europe, and increased understanding of foraging habitat selection is required. We radiotracked 31 Nightjars in an extensive (185‐km²) complex conifer plantation landscape in 2009 and 2010. Home‐range 95% kernels for females, paired males and unpaired males were an order of magnitude larger than song territories of paired males, emphasizing the importance of habitats beyond the song territory. Nightjars travelled a mean maximum distance of 747 m from the territory centre each night. Home‐range placement relative to landscape composition was examined by compositional analysis. Pre‐closure canopy forest (aged 5–10 years) was selected at all scales (MCP, 95% and 50% kernels), with newly planted forest (aged 0–4 years) also selected within 50% kernels. For telemetry fixes relative to habitat composition within 2 km of their territory centre, individuals again selected pre‐closure and newly planted forest, and also grazed grass heath. Open ungrazed habitat was not selected, with implications for open habitat planning for biodiversity conservation within public‐owned forests. Despite the Nightjars’ selection for younger growth, moth biomass was greater in older forest stands, suggesting that foraging site selection reflects ease of prey capture rather than prey abundance. Within large plantation‐forest landscapes, a variety of growth stages is important for this species and our results suggest that grazing of open habitats within and adjacent to forest will additionally benefit the European Nightjar.     

Use of farmland by Ortolan Buntings (Emberiza hortulana) nesting on a burned forest area

Summary Most passerines have all-purpose territories in which both breeding and feeding take place. However, Ortolan Buntings (Emberiza hortulana) in Norway seem to depend on foraging areas outside nesting territories. We used radio transmitters to study patterns of farmland use by Ortolan Buntings nesting on a burned forest area. Territories on the forest burn were located closer to farmland than expected by chance. Males were absent from territories on average 27 % of the time and used foraging areas up to 2.7 km away from their territories. Males had to fly over an average of 1.4 territories of other males to reach those foraging areas. The distance between territory and closest area of farmland (range 40–460 m) did not affect the proportion of time absent from territories, or other measures of farmland use. However, there was a trend that duration of absences increased with territory-farmland distance among mated males, and duration of absences were shorter during the nestling period than before. Thus, it seems that minimizing travel costs may be a behavioural strategy. Even so, males with territories close to farmland were not more often paired than males further away from farmland. These findings indicate that the spatial distribution of one habitat (farmland) affects territory establishment and foraging behaviour of Ortolan Buntings nesting in another habitat (a forest burn).

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Nutzung von Ackerland durch Ortolane (Emberiza hortulana) einer benachbarten Brandfl?che

Zusammenfassung Bei den meisten Singv?geln ist das Revier sowohl Brut- als auch Nahrungsraum. Bei Ortolanen (Emberiza hortulana) in Norwegen, die auf Brandflachen brüten, scheint dies aber anders zu sein. Radiotelemetrische Untersuchen zeigten, dass sie von Nahrungsgründen au?erhalb der Brutterritorien abh?ngig sind. Die Nester auf den Brandflachen h?uften sich am Rand zum benachbarten Ackerland. M?nnchen waren durchschnittlich 27 % der Zeit vom Brutrevier abwesend und gingen his zu 2,7 km vom Brutplatz entfernt auf Nahrungssuche, wozu sie durchschnittlich 1,4 Reviere anderer M?nnchen überfliegen mussten. Der Abstand zwischen Brutrevier und n?chstem Nahrungsplatz (zwischen 40 und 460 m) hatte keinen Einfluss auf den Zeitanteil au?erhalb des Brutreviers. Die Dauer der Abwesenheit stieg jedoch bei verpaarten M?nnchen mit der Entfernung zwischen Brutrevier und Ackerland und sie war kürzer w?hrend der Nestlingsphase. Dies wird als Verhaltensstrategie zur Minimierung der Flugkosten interpretiert. M?nnchen mit Revieren n?her am Ackerland waren nicht h?ufiger verpaart als mehr entfernte Revierinhaber. Diese Untersuchungen zeigen, dass beim Ortolan die r?umliche Verteilung eines Habitats (hier Ackerland) einen Einfluss auf die Etablierung von Brutrevieren und das Nahrungssuchverhalten in einem anderen Lebensraum (hier Brandfl?chen) hat.

     

Home‐ranges,population densities,vocal behavior,and post‐fledging movements of Cipo Canasteros (Asthenes luizae,Furnariidae), a rock‐specialist endemic of the highlands of eastern Brazil

Cipo Canasteros (Asthenes luizae, Furnariidae) have a fragmented and limited range restricted to the campos rupestres (rupestrian grasslands) habitat in the Brazilian highlands of the Espinhaço Range, and little is known about their behavior, ecology, and population biology. From March 2009 to November 2010, we monitored birds (24 banded and 22 radio‐tracked) at two study sites at Serra do Cipó in the state of Minas Gerais, Brazil, to estimate their home‐range sizes and population density, and describe their habitat use, natal dispersal behavior, and vocal behavior. We found an average density of 8.7 paired adults/km² in our study areas or 22.9 paired adults/km² when considering only used habitats. The sex ratio was male‐biased (males/total adults = 0.68), adults exhibited high site fidelity, home‐ranges averaged 4.0 ha (fixed kernel 95%) or 3.5 ha (95% minimum convex polygon) in size, and both sexes defended territories year‐round. We recorded four main types of songs, including two uttered more often during the breeding season. We monitored the natal dispersal of two males and one female who moved maximum distances of 1238 m, 780 m, and 1056 m, respectively, from natal areas. Our results confirm that Cipo Canasteros are restricted to the rocky‐outcrop habitat of the campos rupestres. In part due to their habitat specialization, Cipo Canasteros are considered Near Threatened, but other factors contributing to their demographic fragility include the small number, and probably low survival, of females and low reproductive success due to predation and brood parasitism by cowbirds. Given these threats, along with their specialized habitat and restricted range, the future conservation of Cipo Canasteros will likely depend on the extent to which their campos rupestres habitat can be conserved.     

Mating system of the lefteye flounder,Engyprosopon grandisquama

Underwater observations were conducted on the reproductive behavior and mating system of the lefteye flounder,Engyprosopon grandisquama, off Nagashima, southwest of Kyushu Island, Japan. Two types of males were found: large males, which defended territories against other large males, and small males, which did likewise but only against smaller males. Large males established territories which encompassed or ovelapped the home ranges of 1 or 2 cohabitant females. Territories of the small males, in which a smaller female often maintained a home range, overlapped those of large males. Pair spawning occurred around sunset. Mating of large males with cohabitant females was observed 36 times and that of a small male with a smaller female once. Pair formation was assorted by body size, paired males being larger than females in most cases. Thus, inE. grandisquama, gigamous large males were common, small males occurring within the former's erritorial boundaries mating with smaller females.     

Nightingales Luscinia megarhynchos in scrub habitats in the southern fens of East Anglia, England: associations with soil type and vegetation structure

The southeast corner of the East Anglian Fens supports a large concentration of Nightingale Luscinia megarhynchos territories. A total of 382 territories were located in extensive surveys in 1999 and 2000, probably representing over 5% of the English population. Transect counts revealed that the Fenland population is restricted in distribution and is associated with localized thickets of scrub. The highest densities are found on humus‐rich soils, suggesting that soil type, in addition to habitat availability, may have a strong influence on the Nightingale's distribution in this region. This paper provides the first assessment of habitat requirements of the Nightingale in scrub, which now forms a principal habitat for the species in England. Detailed studies of the attributes of over 100 Nightingale territories revealed subtle differences in the vegetation structure of these thickets when compared with paired, unoccupied, but apparently similar thickets. The Nightingale territories tended to have a higher proportion of bare ground or short vegetation in the field layer under the canopy, whereas paired sites were more likely to have low field layer vegetation beneath the canopy. The bare ground within the thickets is a feature of shading beneath very dense foliage cover. Within Nightingale territories, low field layer volume and shrub twig volume at the thicket edges was higher than in unoccupied thickets. The differences detected in vegetation structure suggest that a dense and continuous canopy forming a shell over bare ground but with dense low foliage at thicket edges provides the ideal vegetation structure for Nightingales in scrub habitats. Our study suggests that Nightingales occupy scrub of a very specific structure, and specific stage in vegetation succession. This structure probably provides an optimal combination of foraging habitat, microclimate and cover from predators. It is suggested that humus‐rich soils may be preferred because they may support a particularly rich source of invertebrate food, but this remains to be tested empirically.     

Aggressive behaviour in subadult and adult black redstarts: status-signalling strategy?

In some birds, yearling males (subadults) are less brightly coloured than the adult ones. To explain this phenomenon known as delayed plumage maturation (DPM), several hypotheses have recently been proposed. The aim of this paper was to test predictions of status signal hypothesis (SSH). This hypothesis claims that the adults less frequently attack dull coloured subadult males, and consequently DPM facilitates survival of subadults during the first breeding season. The experiments were performed in two habitats in the Prague suburbs: a housing estate and garden city. Subadult and adult males of the black redstart (Phoenicurus ochruros) were exposed to stuffed dummies of both age categories. Contrary to predictions of SSH, brown (subadult like) coloration of the dummy had no suppressive effect on defensive behaviour of the resident males. On the other hand, subadult males were more active in vocal territorial defence such as singing and producing snarl and whistle sounds during the experiments. The defenders of smaller territories generally behaved more aggressively than defenders of large territories in habitat of garden city, and especially adult males responded more aggressively against dummies in this habitat. In a housing estate, a habitat of evenly distributed resources (i.e. vertical surfaces), the birds tended to observe the dummy prior to attack it directly.     

On the song resumption, polyterritorial behaviour and their population context in the Sedge Warbler Acrocephalus schoenobaenus

Mating tactics in species with facultative polygyny seem to be very flexible and to depend on local environmental conditions. We analysed the habitat and population contexts of territorial behaviour, associated with polygyny, in a population of Sedge Warblers Acrocephalus schoenobaenus inhabiting natural wetlands. Nearly one-third of all breeding males (46 individuals) resumed song after completing their mating with the first female, in order to attract another one. Resuming males were usually the earliest arrivals. There was a continuity in the territorial behaviour between resuming song on first territory and polyterritorial behaviour. Fifty-nine percent of resuming males set up second territories, clearly separated from the first. The second territory was usually located close to the primary female activity area. The quality of the first and second territories were correlated, with second territories being significantly inferior. However, their quality was not significantly different from the territories of non-breeding males. The quality of the second territories was also negatively related to the distance from the first territories. Polyterritorialism was influenced by population numbers: the higher the number of territorial males, the lower the number of second territories settled and the lower their average quality. Although the polygyny frequency in the studied population was very low, polyterritorial males were significantly more likely to be polygynous. We concluded that polygyny frequency can be significantly influenced by population numbers, which might be one of the main factors responsible for the variability in the mating system in this species.     

Effects of habitat use on food acquisition and food caching during a nonbreeding season in a winter-breeding,food-storing passerine

ABSTRACT

Capsule: Wintering male Bull-headed Shrikes Lanius buchepalus preferred vegetable fields with perch sites to search for and detect terrestrial prey, and males occupying territories with large areas of vegetable fields acquired more prey and cached more food.

Aims: To better understand effects of habitat use on food acquisition and food caching of the Bull-headed Shrike, we investigated relationships between habitat quality (measured through foraging-site selection and foraging success) and food caching during the non-breeding season.

Methods: We monitored 66 territorial male shrikes during the non-breeding season from 2014 to 2016, and collected data on foraging-site selection, foraging success, and food caching.

Results: Our field observations showed that male shrikes preferred to forage over vegetable fields and that males occupying territories incorporating large areas of that habitat were able to acquire more food items and store more food caches in their territories during the nonbreeding season.

Conclusion: We suggest that for male Bull-headed Shrikes, a winter-breeding food-storing passerine, the quality of habitat in the nonbreeding season has the potential to affect their subsequent fitness.     

The role of territory settlement,individual quality,and nesting initiation on productivity of Bell's vireos Vireo bellii bellii

Variation in habitat quality among territories within a heterogeneous patch should influence reproductive success of territory owners. Further, territory settlement order following an ideal despotic distribution (IDD) should predict the fitness of occupants if territory selection is adaptive. We recorded settlement order and monitored nests in territories occupied by individually marked Bell's vireos Vireo bellii bellii across a range of shrubland habitats in central Missouri, USA. We used an information theoretic approach to evaluate multiple hypotheses regarding the relationship between territory settlement order and seasonal territory productivity (productivity), which we define as the number of young fledged from all nest attempts in a territory. Territory settlement order and arrival date were not analogous and later arriving males displaced early settlers in 13 of 49 territories. Settlement order and lay date together were the best predictors of a territory's productivity; productivity decreased 2.08 young from earliest to latest settlement rank and lay date. Males that defended the same territory in successive years occupied territories with earlier settlement dates, but we found little evidence that age or prior ownership influenced productivity. Territory selection by male Bell's vireos was adaptive because males preferred to settle in territories that had high seasonal offspring production, but even though settlement rank was linked to territory quality, high productivity was only realized on high quality territory when also linked to early nest initiation date. While settlement rank was related to territory quality, obtaining a high quality territory had to be combined with early nest initiation to maximize productivity. We found support for the IDD hypothesis because the highest quality territories, (i.e. most productive), were settled earlier. Research that identifies high quality habitat by linking individual fitness with habitat characteristics may elucidate the importance of habitat quality, individual experience and temporal factors to productivity of Bell's vireos.     

Territoriality and Survivorship of the Sierra Madre Sparrow in La Cima,México

We studied the life-history of the Sierra Madre sparrow (Xenospiza baileyi) in a subalpine grassland-agriculture mosaic south of Mexico City. From March to early September 1999 we captured and color-banded 53 adults with mist-nets and mapped the breeding territories of 21 males. We again mapped territories in the same spot in April and May 2000. The number of breeding territories was found to be the same in the two consecutive years and interannual survivorship was found to be relatively high. Breeding territories were restricted to the bunchgrass-covered areas. We used the density of territories and the amount of remaining habitat to estimate a total population size of 5,380–6,150 adults for this species. Using this and other recent data, we recommend raising the Sierra Madre sparrow to the status of critically endangered using BirdLife International criteria.     

Using remote sensing image texture to study habitat use patterns: a case study using the polymorphic white-throated sparrow (Zonotrichia albicollis)

Aim Ecological factors that vary along spatial scales can greatly influence the outcome of evolution. However, often it is difficult for researchers to identify significant ecological variables that might be associated with the geographical distribution of phenotypes and genotypes in nature. In this paper, we use remote sensing image texture analyses to investigate breeding territories of the white‐throated sparrow (Zonotrichia albicollis), a polymorphic passerine species that has been shown to segregate spatially according to morph. Our aim was to examine how an integrative measure of landscape feature, such as image texture, could be used to distinguish subtle differences in habitat use and, presumably, habitat selection. Location A population of white‐throated sparrows located 1.5 miles east of the Cranberry Lake Biological Station in the Adirondack Mountains of St Lawrence County, New York, was used in this study; the study site itself was approximately 1 km². Methods We analysed 27 territories (16 white males; 11 tan males) to determine if image texture can be used to distinguish differences in vegetation and structure in territories of the two colour morphs. First (variance)‐ and second (homogeneity)‐order image texture measurements with three different window sizes were derived using the green, red, and near infrared bands of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. Texture was then placed into t‐tests to determine statistical differences between the territories of the two male morphs. Results Significant differences between the territories of the two morphs were found in both variance and homogeneity texture measures in the red and green ASTER bands in all three window sizes. There were no differences with any near infrared texture measures. Main conclusions Examination of first‐ and second‐order statistical measures indicated that the territories of tan males have significantly more spectral variance than the territories of white males, while white males’ territories are significantly more homogeneous. These findings are consistent with the previous finding of the morphs settling in ‘high’ and ‘low’ neighbour density habitats that differ with respect to the amount of useable area on their borders. Previous study has also suggested that white and tan male territories differ according to overall landscape structure, not vegetation composition. Therefore, we suggest that red and green spectra may be more useful when examining differences in territory structure and possibly territory quality of similar edge‐type species. Our results suggest that image texture is a useful tool for ecological and evolutionary modelling of the distributions of phenotypes/genotypes across landscapes.     

Territory configuration moderates the frequency of extra‐group mating in superb fairy‐wrens

The frequency of extra‐pair paternity (EPP) in socially monogamous birds varies substantially between and within species, but ecological drivers of this variation remain poorly understood. Habitat configuration could influence EPP by moderating access to extra‐pair mates, because species occupying territories in a clustered ‘honeycomb’ configuration have a larger pool of potential extra‐group mates in their immediate neighbourhood than those living in linearly arranged territories (e.g. along narrow strips of riparian or fragmented habitat). We exploited variation in the spatial arrangement of territories due to anthropogenic modification of habitat of the cooperatively breeding superb fairy‐wren Malurus cyaneus to test whether habitat configuration influenced the frequency of EPP. In this species, most paternity is obtained by males outside the social group [extra‐group paternity (EGP)]. We found that the frequency of EGP among groups living in linear strips of roadside vegetation (41% of 44 offspring) was lower than it was for groups living in clustered territories within continuous habitat (59% of 70 offspring). Differences in group size and pair relatedness did not explain differences in EGP associated with territory configuration, although the frequency of EGP was negatively correlated with pair relatedness. Our finding suggests that territory configuration can influence rates of EGP and that anthropogenic habitat fragmentation has the potential to limit access to extra‐pair mates, affecting mating systems and ultimately fitness.     

Floater interference reflects territory quality in the Spanish Imperial Eagle Aquila adalberti: a test of a density‐dependent mechanism

We report on an 11‐year study of floater interference in a population of Spanish Imperial Eagles Aquila adalberti. We analysed changes over the years in the productivity of 15 territories to test predictions of two hypotheses of density‐dependent productivity in relation to the presence of floaters (birds without territories). According to the ‘interference' hypothesis, the frequency of intrusion by floaters increases with density, resulting in a decrease in productivity. Thus, in a high‐density population a negative relationship between floater intrusions and productivity of the territory is expected. In contrast, under the ‘habitat heterogeneity' hypothesis, as density increases a higher proportion of individuals is forced to occupy lower quality habitats. Support of this hypothesis requires that floaters detect differences in quality among territories and preferentially visit the better quality territories. Consequently, a positive relationship between floater intrusions and productivity is expected. Results showed that floaters tended to visit their natal area at the beginning of the breeding season. Among floater Eagles, males made significantly more intrusions per day than did females, but females stayed in the natal population for longer each year than males. Floater intrusions and productivity were highly positively correlated, supporting the ‘habitat heterogeneity' hypothesis; individuals were apparently able to assess the quality of a territory and, at the frequencies observed, their interference with the breeding pair had no obvious negative effect on productivity.     

Habitat choice in adult longfin damselfish: territory characteristics and relocation times

Habitat selection by coral reef fish during initial settlement has been shown to depend on various biotic and abiotic characteristics. However, relatively little is known of the factors influencing habitat choice by adults during post-settlement processes such as relocation or migration. In this study, we first characterised the habitat of longfin damselfish (Stegastes diencaeus Jordan and Rutter) territories to quantify territory variability. Characteristics such as percentage cover of rock, sand, live coral and distance from sand were highly variable, while territory area, turf and macro algae cover were relatively uniform across territories.We then assessed the importance of specific habitat characteristics by experimentally removing damselfish and measuring recolonisation times in relation to these characteristics. The presence of nest sites markedly increased the speed of territory recolonisation after experimental removals. Other variable territory characteristics such as substrate type, rugosity and the presence of cleaning stations did not affect recolonisation speed. In general, males recolonised territories faster than females, and males were more likely to recolonise territories previously owned by males with an active nest site. Thus, intraspecific competition for high-quality nest sites may generate sex differences in territory relocation and highly stable sex-specific patterns of adult distribution.