Frugivory in European Laurel: how extinct seed dispersers have been substituted

Capsule Extinction of ancient frugivores during the Quaternary has led to a depauperated seed disperser community for Laurus nobilis and a tight mutualism between the plant and the Blackbird Turdus merula.

Aims To describe a present-day frugivore assemblage of natural Laurel populations in southern Spain.

Methods Eight fruiting trees of different size were monitored with binoculars during 52 hours spread across one ripening season, and the identity and behaviour of foraging birds were recorded. Additional point counts were used to record the avifauna of the surroundings.

Results Despite a diverse frugivore community being present, Laurel fruits are almost exclusively (99%) consumed by Blackbird and rarely (1%) by Blackcap Sylvia atricapilla. Blackbirds concentrate at fruiting trees and individuals may remain there for several days. Birds usually forage in small groups and return at intervals of 12–14 minutes.

Conclusion The Blackbird population of the study area forages extensively on the energy-rich Laurel fruits, while the plants depend exclusively on this bird species for seed dispersal. Consequences of the depauperate frugivore community and the tight mutualism between Blackbirds and Laurels on plant recruitment and conservation are discussed.     

Endozoochorous dispersal of alien and native plants by two palearctic avian frugivores with special emphasis on invasive giant goldenrod <Emphasis Type="Italic">Solidago gigantea</Emphasis>

The role of frugivorous birds in dispersal of the seeds of fleshy-fruited plants is well understood, but other groups of birds like granivores and omnivores can also act as vectors, especially in the process of non-standard dispersal. In this study we examined the role of two widely distributed birds (the Eurasian Blackbird, Turdus merula, and the Black Redstart, Phoenicurus ochruros) in seed dispersal. We analyzed the content of 279 droppings of the Black Redstart collected between July and October and 85 droppings of the Eurasian Blackbird collected during January. In total we found 366 seeds, representing 11 plant taxa, in the faecal samples; 93% of the seeds belonged to fleshy-fruited species. The most numerous were two native taxa, Sambucus racemosa/nigra, in summer and autumn, Crataegus monogyna in winter, and one alien species Morus alba, which is dispersed in summer. We also found seeds of four dry-fruited species; the most interesting of which was the presence of anemochorous seeds of Solidago gigantea (a highly invasive alien species). The seeds were found only in droppings of the Eurasian Blackbird. Considering the obtained results the need for further studies on bird-plant interactions should be a priority.     

Modified dispersal‐related traits in disjunct populations of bird‐dispersed Frangula alnus (Rhamnaceae): a result of its Quaternary distribution shifts?

Many European tree species survived Pleistocene glaciations in Mediterranean refugia and rapidly recolonized temperate Europe afterwards. Inter‐ and postglacial migration processes are assumed to have catalized evolutionary optimizations of dispersal‐related traits, but up to now empirical evidence is lacking in vertebrate‐dispersed plants. We investigated if south Iberian glacial relict and central European “colonizer” populations of the bird‐dispersed tree Frangula alnus have experienced differentiations of dispersal‐related traits which increase the mobility of northern populations. A comparison of lifetime reproductive strategy, disperser guilds, ripening phenology, and fruit design revealed considerable differences. Compared to south Iberian conspecifics, central European plants were considerably smaller and experienced a highly accelerated generation turnover. In south Iberian populations seed dispersal was carried out almost completely by resident birds which occurred in constant abundances throughout the ripening season. In contrast, central European seeds were dispersed by migrants whose abundances changed considerably during the ripening season. Several bird species were involved in both study areas but rendered different importance for seed dispersal. The fruit ripening pattern was highly asynchronous throughout the ripening season in south Iberia, while central European trees showed a complex ripening sequence which resulted in a significant correlation between fruit abundance and changing disperser availability. Central European fruits were smaller and showed a considerably smaller seed load than south Iberian fruits, thus presumably being more attractive for their small‐sized main dispersers (Sylvia warblers). Chemical analyses revealed significant differences in contents of water, glucose, fructose, proteins, ash. and phenolic compounds. The extensive differentiation of dispersal‐related traits in F. alnus suggests that even weak selective pressures by frugivores may induce evolutionary adjustments of dispersal traits over large time scales. We suggest that the differences we observe today evolved during the species' distribution shifts in the Quaternary.     

Bird Assemblage and Visitation Pattern at Fruiting Elmerrillia tsiampaca (Magnoliaceae) Trees in Papua New Guinea

Most tropical trees produce fleshy fruits that attract frugivores that disperse their seeds. Early demography and distribution for these tree species depend on the effects of frugivores and their behavior. Anthropogenic changes that affect frugivore communities could ultimately result in changes in tree distribution and population demography. We studied the frugivore assemblage at 38 fruiting Elmerrillia tsiampaca, a rain forest canopy tree species in Papua New Guinea. Elmerrillia tsiampaca is an important resource for frugivorous birds at our study site because it produces abundant lipid-rich fruits at a time of low fruit availability. We classified avian frugivores into functional disperser groups and quantified visitation rates and behavior at trees during 56 canopy and 35 ground observation periods. We tested predictions derived from other studies of plant–frugivore interactions with this little-studied frugivore assemblage in an undisturbed rain forest. Elmerrillia tsiampaca fruits were consumed by 26 bird species, but most seeds were removed by eight species. The most important visitors (Columbidae, Paradisaeidae and Rhyticeros plicatus) were of a larger size than predicted based on diaspore size. Columbidae efficiently exploited the structurally protected fruit, which was inconsistent with other studies in New Guinea where structurally protected fruits were predominantly consumed by Paradisaeidae. Birds vulnerable to predation foraged for short time periods, consistent with the hypothesis that predator avoidance enhances seed dispersal. We identified seven functional disperser groups, indicating there is little redundancy in disperser groups among the regular and frequent visitors to this tropical rain forest tree species.     

Are mismatches the norm? Timing of flowering,fruiting, dispersal and germination and their fitness effects in Frangula alnus (Rhamnaceae)

The close morphological and temporal links between phases of plant growth and reproduction call for integrated studies incorporating several reproductive phases from flowering to recruitment, and associated plant‐animal interactions. Phenological strategies, as well as plastic phenological response to climate change, incorporate complex interactions between developmental constraints, pollination and seed dispersal. Relationships between reproductive phenology and components of fitness were studied for two years in the north‐temperate, self‐incompatible, insect‐pollinated, and bird‐dispersed shrub Frangula alnus (Rhamnaceae). Fruit set, dispersal, germination and juvenile survival, as well as seed mass and juvenile size were measured in relation to flowering, fruiting and germination time. The results suggest that effects of flowering and fruiting time prevailed in subsequent phases, to some extent as far as to the juvenile phase, but effects of timing were complex and had partly opposing effects on different fitness components. Early flowers had higher fruit‐set and experiments indicated that synchronous peak flowering increased fruit‐set, but later flowers had higher seed mass. Peak fruiting was not associated with peak dispersal. Late fruits derived from late flowers promoted dispersal. Juvenile recruitment was enhanced by increasing seed size. We conclude that the phenology of flowering and fruiting in F. alnus comprises several features, each with different and sometimes counteracting effects on fitness components. From a general perspective, this result implies that we should not expect to find finely tuned matches in timing specifically between flowering and pollinators, and fruiting and seed dispersing birds.     

Trophic structure of a neotropical frugivore community: is there competition between birds and bats?

Summary Dietary overlap and competition between frugivorous birds and bats in the Neotropics have been presumed to be low, but comparative data have been lacking. We determined the diets of volant frugivores in an early successional patch of Costa Rican wet forest over a one month period. Ordination of the diet matrix by Reciprocal Averaging revealed that birds and bats tend to feed on different sets of fruits and that diets differed more among bat species than among bird species. However, there was overlap between Scarlet-rumped Tanagers and three Carollia bat species on fruits of several Piper species which comprised most of the diet of these bats. Day/night exclosure experiments on P. friedrichsthalli treetlets provided evidence that birds deplete the amount of ripe fruit available to bats. These results indicate that distantly related taxa may overlap in diet and compete for fruit, despite the apparent adaptation of animal-dispersed plant species for dispersal by particular animal taxa.     

Fruit fate,frugivory, and fruit characteristics: a study of the hawthorn,Crataegus monogyna (Rosaceae)

Summary The fate of fruits from a population of European hawthorn (Crataegus monogyna) in western Oregon, USA, was examined over a two-year period. Only one frugivore, the American robin (Turdus migratorius) foraged on the C. monogyna fruits, making this an unusually straightforward fruit-frugivore system. Dispersal efficiency was low, with an average 21% of seeds being dispersed (carried away from parent plants) each year; the most common fate of fruits was to simply fall. Robins dropped 20% of the fruits that they picked, and defecated/regurgitated 40% of the fruits (seeds) that they swallowed, beneath parent plants. One trait, gruit abundance, strongly affected the probability of bush visitation by robins, bushes with larger fruit displays being preferred. Both absolute dispersal success (number of seeds) and dispersal efficiency (proportion of seeds; success per propagule) were also found to be correlated most strongly with initial fruit abundance. Individual plant fecundity and fruit quality were found to vary little between years; as a result, dispersal efficiencies for individual plants were also annully consistent. Larger (older) plants produced more fruits and therefore had higher fitness. These results suggest that the optimal fruiting strategy for C. monogyna is therefore to get as big as possible as quickly as possible by delaying fruiting until later in life.     

Frugivory and seed dispersal by vertebrates in the Oriental (Indomalayan) Region

Current knowledge of frugivory and seed dispersal by vertebrates in the Oriental Region is summarized. Some degree of frugivory has been reported for many fish and reptile species, almost half the genera of non-marine mammals and more than 40% of bird genera in the region. Highly frugivorous species, for which fruit dominates the diet for at least part of the year, occur in at least two families of reptiles, 12 families of mammals and 17 families of birds. Predation on seeds in fleshy fruits is much less widespread taxonomically: the major seed predators are colobine monkeys and rodents among the mammals, and parrots, some pigeons, and finches among the birds. Most seeds in the Oriental Region, except near its northern margins, are dispersed by vertebrate families which are endemic to the region or to the Old World. Small fruits and large, soft fruits with many small seeds are consumed by a wide range of potential seed dispersal agents, including species which thrive in small forest fragments and degraded landscapes. Larger, bigger-seeded fruits are consumed by progressively fewer dispersers, and the largest depend on a few species of mammals and birds which are highly vulnerable to hunting, fragmentation and habitat loss.     

Directed vertebrate-mediated seed dispersal of a fleshy-fruited amaryllid in a heterogenous habitat

Most plants with fleshy fruits have seeds that are ingested by animals, but a less well-understood mode of seed dispersal involves fleshy fruits containing seeds that are discarded by frugivorous animals because they are too large or toxic to be ingested. We studied the seed dispersal biology of Haemanthus deformis, an amaryllid lily species found in a mosaic of bush clumps in a grassland matrix in South Africa. We asked whether seed dispersal is directed in and among bush clumps and whether germination and survival are greater for seeds dispersed to bush clumps than for those dispersed into grassland. Using camera trapping, we found that fruits are consumed mainly by birds and rodents. The pulp was removed from the seeds which were then discarded without ingestion. While many seeds were dispersed close to the parent plant, most (c. 78.5%) were dispersed further than 1 m away from the parent plant. Longer distance dispersal resulted mainly from birds flying off with fruits in their bill or from rodents engaging in scatter-hoarding behavior. Seedling survival was most successful within bush clumps as compared to grasslands and shade was identified as a primary requirement for seedling survival. Seeds from which the fruit pulp had been removed germinated faster than those in intact fruits. Haemanthus deformis deploys a system of directed seed dispersal, whereby both birds and rodents contribute to the dispersal of seeds within patchy bush clumps that are favorable for seedling survival.     

Review of the vertebrate-mediated dispersal of the Date Palm,Phoenix dactylifera

As a major agricultural crop in the semi-arid and arid zone of North Africa and the Middle East, drupes (“fruits”) of the Date Palm Phoenix dactylifera form with their high carbohydrate content of the flesh and oils in the seed a major part of the diet of resident and migratory bird species and fruit bats. This paper reviews the range of known instances of drupe predation by volant and non-volant vertebrate vectors. While documented dispersal distances range from tens of metres to about 50 km, the efficacy of that dispersal has not been assessed in any of the papers under review. While volant animals, primarily birds, make up the greatest number of dispersal vectors and also account for the greatest number of seeds dispersed, long distance dispersal of a larger quantity of seeds per dispersal event seems to rely on terrestrial animals, primarily canids, but also bears and flightless birds, such as the Emu (Dromaius novaehollandiae).     

Assessing breeding success in common woodland birds using a novel method

Capsule Repeated counts of fledged broods can provide a useful estimate of breeding success for most common woodland birds.

Aims To assess the efficacy of comparing fledged-brood survey data with territory mapping using simple mark–recapture analysis techniques to provide an estimate of breeding success for common woodland birds that does not involve finding nests.

Methods Three observers undertook territory mapping surveys of adults, followed by counts of fledged broods four times a week during May–July 2007 in two 15 ha woods each, both in southern England. Using known fledging to maturity periods, these counts were used to calculate daily detection probabilities for broods of ubiquitous species. These enabled fledged brood territory occupancy probabilities (i.e. brood to territory ratios) to be estimated that take account of the possibility that broods were present but missed by surveys.

Results Of the 19 species found in all six woods, mean daily detection probability estimates for fledged broods of 17 species ranged from 0.17 to 0.50 with significant variation between woods for 12 species, but within region/observer for four species. The mean probability of detecting a brood at least once was over 75% using four visits per week and over 50% using two visits. Only for Great Spotted Woodpeckers Dendrocopos major and Garden Warblers Sylvia borin was the fledging period too short and the daily detection probability too low to provide a reasonable estimate of the territory occupancy probability.

Conclusion Daily detection probabilities for fledged broods of most common woodland birds were sufficiently high to enable useable estimates of fledged-brood territory occupancy probabilities to be made based on a survey programme involving two or three visits per week between late May and the end June. The method used may have application as a means of providing a relatively easily derived productivity index for woodland bird monitoring programmes or for research studies.     

南京中山植物园鸟类对香樟 果实（种子）的取食

香樟(Cinnamomum camphora)是亚热带地区广泛分布的常绿阔叶树种,其果实数量多、果期长,可为鸟类提供大量食物资源。2018年11月至2019年2月,借助Safari 10×26变焦双筒望远镜,采用焦点扫描法对南京中山植物园内访问香樟果实(种子)的鸟类行为进行观察,详细记录鸟类的种类、取食基质、取食次数、取食时间、取食数量和取食方式等信息。研究期间有效记录达48d,累计记录到27种鸟类1021次取食香樟果实(种子)行为,存在2种取食基质(地面和树上)和3种取食方式(整吞果实、啄食果肉和取食种子)。T检验显示,不同鸟类对香樟果实(种子)的取食次数存在显著差异(t=3.096,df=26,P 0.01);不同月份间鸟类对香樟香樟果实(种子)的平均访问只数、平均取食次数、平均取食时间和取食数量均存在极显著差异(P0.001)。白头鹎(Pycnonotussinensis)、乌鸫(Turdusmendarinus)和灰喜鹊(Cyanopicacyanus)是访问次数及取食量最多的3种鸟类。单因素方差分析(One-way ANOVA)表明,上述这3种鸟类的取食数量存在极显著差异(F3, 598=25.219,P 0.001)。按照时间统计,11月份访问的鸟类种类和数量最多,1月份鸟类的取食次数、时间和数量最多。鸟类的形态特征(体重、体长和嘴峰长)与取食数量呈显著正相关,其中,体重和体长对取食数量的影响比嘴峰长的影响更显著,但嘴峰长影响鸟类对果实的取食方式。在鸟类常活动和停歇的树木下方地面往往散落着较多表面洁净、无果肉包裹的香樟种子,且园内人工林和自然更新林地可见许多香樟幼苗,表明鸟类对香樟具有潜在传播作用。     

Seed‐swallowing Toucans are Less Effective Dispersers of Guettarda viburnoides (Rubiaceae) than Pulp‐feeding Jays

For many tropical plants, birds are the most important seed dispersers. Not all birds, however, will provide equally effective dispersal services. Behavioral differences, during and after feeding, can result in different establishment probabilities of new individuals. During 3 yr, we examined species‐specific quantitative and qualitative aspects of Guettarda viburnoides seed dispersal by avian frugivores, focusing on how these aspects modify seed dispersal effectiveness. Fruits of G. viburnoides were consumed by ten species of birds, two of which, Cyanocorax cyanomelas and Pteroglossus castanotis, removed 80 percent of the fruits. These two species differ in qualitative aspects of seed dispersal. First, they select for fruits of different sizes; C. cyanomelas feeds on larger fruits than P. castanotis, which results in the former dispersing larger endocarps than the latter. Second, they differ in their fruit handling treatment; C. cyanomelas are pulp consumers, whereas P. castanotis swallow the fruit whole, and are thus traditionally considered ‘legitimate’ dispersers. The probability of seedling emergence, the temporal pattern of emergence, the number of emerged seedlings per endocarp, and the probability of post‐dispersal seed predation differs between endocarps dispersed by C. cyanomelas and P. castanotis; endocarps dispersed by the former have higher emergence probabilities, higher number of seedlings, faster emergence times, and lower predation probabilities than those dispersed by the latter. Finally, these birds differ in their landscape patterns of endocarp deposition; C. cyanomelas disperses endocarps to habitats with higher recruitment probabilities. Ultimately, the pulp consumer C. cyanomelas is a more effective disperser of G. viburnoides than P. castanotis.     

Fruit size in wild olives: implications for avian seed dispersal

1. The response of frugivorous birds to an enlargement of fruit size, and the consequences for both birds and plants, are analysed for the interaction between avian seed dispersers and olives ( Olea europaea) .
2. The enlargement of fruit size promotes a shift in frugivorous birds' feeding behaviour, from swallowing fruits whole to pecking pieces of pulp. The relative frequency of olive consumption using each feeding behaviour was assessed by combining field data on frequency of appearance of olive pulp and seeds with data from laboratory trials.
3. Sardinian Warblers ( Sylvia melanocephala ) and European Robins ( Erithacus rubecula ) were mainly peckers both on cultivated and wild olives. Blackcaps ( Sylvia atricapilla ) consumed wild olives mainly by swallowing but consumed cultivated olives (larger than the wild ones) primarily by pecking. Song Thrushes ( Turdus philomelos ) were primarily swallowers of both types of fruits.
4. Laboratory trials with Song Thrushes, Blackcaps and European Robins showed that: (a) all were able to peck fruits; (b) fruit size determined a shift from swallowing to pecking, as pecking frequency increased with the enlargement of the fruit size; (c) all the species had an increased fruit handling failure rate when trying to swallow increasingly large fruits; and (d) from the birds' perspective, small shifts in fruit size may have important consequences on fruit profitability.
5. Pecking on olives turns the mutualistic fruit–frugivore interaction into a fruit-pulp predator interaction, thus arising a conflict between the plant and frugivorous birds.
6. This study shows that heavy dependence on fruit is not always simply related to seed dispersal. The same frugivorous bird species can act as a seed disperser or a pulp predator for the same plant species. The threshold between these roles is highly influenced by the ratio gape size/fruit size.     

Vertebrate Fruit Removal and Ant Seed Dispersal in the Neotropical Ginger Renealmia alpinia (Zingiberaceae)*

Plants frequently display fruit characteristics that support multiple seed‐dispersal syndromes. These ambiguous characteristics may reflect the fact that seed dispersal is usually a complex process involving multiple dispersers. This is the case for the Neotropical ginger Renealmia alpinia (Zingiberaceae). It was originally suggested that the aromatic fruits of R. alpinia located at the base of the plant are adapted for terrestrial mammal seed dispersal. However, the dark‐purple coloration of the fruits and bright orange aril surrounding the seeds suggest that birds may play a role in R. alpinia seed dispersal. At La Selva Biological Station, Costa Rica, we used camera traps to record vertebrate visits to infructescences of R. alpinia. Most visitors were toucans and aracaris (Ramphastidae). However fruits were also removed by terrestrial mammals (coatis and armadillos). In addition to vertebrate fruit removal, some of the fruits dehisce and the seeds that fall on the ground are dispersed by ants. Fruitfall traps showed that 77 percent of fruits are removed by vertebrates. However, 15 percent of fruits fall to the base of parent plants to be potentially dispersed by ants. Experiments using a laboratory ant colony showed that ants are effective seed dispersers of R. alpinia. Ant seed manipulation increased germination success and reduced time to germination. In conclusion, primary seed dispersal in the Neotropical ginger R. alpinia is mostly performed by birds, additionally ants are effective dispersers at short distances. Seed dispersal in R. alpinia is a complex process involving a diverse array of dispersal agents.     

BIRD-DISPERSAL OF PHYTOLACCA AMERICANA L. AND THE INFLUENCE OF FRUIT REMOVAL ON SUBSEQUENT FRUIT DEVELOPMENT

Characteristics of fruits, seeds, and ripening of Phytolacca americana were studied in New Jersey, USA to assess their importance in the dispersal strategy of this species. Removal by birds was directly related to the percent of ripe fruits available on a raceme. Fruit removal from a raceme resulted in lower fruit pulp and seed weights for fruits developing on the same raceme, but these differences probably do not influence probability for dispersal by birds. We demonstrate that characteristics of the fruit pulp may decrease seed availability for the primary seed predator, Peromyscus leucopus, and increase the time fruits are available for dispersal. We speculate on the significance of the sequential fruiting in Phytolacca and the relationship to availability of dispersal agents and high-lipid fruits. Sequential ripening and protection from predation result in seed dispersal from late August to early December.     

High-quality seed dispersal by fruit-eating fishes in Amazonian floodplain habitats

Seed dispersal is a critical stage in the life history of plants. It determines the initial pattern of juvenile distribution, and can influence community dynamics and the evolutionary trajectories of individual species. Vertebrate frugivores are the primary vector of seed dispersal in tropical forests; however, most studies of seed dispersal focus on birds, bats and monkeys. Nevertheless, South America harbors at least 200 species of frugivorous fishes, which move into temporarily flooded habitats during lengthy flood seasons and consume fruits that fall into the water; and yet, we know remarkably little about the quality of seed dispersal they effect. We investigated the seed dispersal activities of two species of large-bodied, commercially important fishes (Colossoma macropomum and Piaractus brachypomus, Characidae) over 3 years in Pacaya-Samiria National Reserve (Peru). We assessed the diet of these fishes during the flood season, conducted germination trials with seeds collected from digestive tracts, and quantified fruit availability. In the laboratory, we fed fruits to captive Colossoma, quantified the proportion of seeds defecated by adult and juvenile fish, and used these seeds in additional germination experiments. Our results indicate that Colossoma and Piaractus disperse large quantities of seeds from up to 35% of the trees and lianas that fruit during the flood season. Additionally, these seeds can germinate after floodwaters recede. Overexploitation has reduced the abundance of our focal fish species, as well as changed the age structure of populations. Moreover, older fish are more effective seed dispersers than smaller, juvenile fish. Overfishing, therefore, likely selects for the poorest seed dispersers, thus disrupting an ancient interaction between seeds and their dispersal agents. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The Fecundity,Seed, and Seedling Ecology of the Edible Palm Euterpe edulis in Southeastern Brazil1

Euterpe edulis flowers at the beginning of the wet season and fruits over an extended period during the end of the wet season and the dry season. Reproductive plants produced an average of ca 1500 fruits within a season. Five species of birds belonging to the family Turdidae were observed to feed on and disperse the fruits. Most seeds fell directly to the ground, where there was some subsequent local dispersal by water. The dispersion of seeds was highly clumped with most seeds being found in close proximity to adult plants; the distance of dispersal could be described by a negative power curve. Germination was higher on wetter soils. The probability of seedlings advancing to the next size class within a year was inversely related to the density of seedlings, and occurred optimally at ca 4 m from adult plants. The latter observation indicates that the survival and growth of seedlings are suppressed in the immediate vicinity of conspecific adults.     

Seed dispersal effectiveness by understory birds on Dendropanax arboreus in a fragmented landscape

This study analyzes dispersal effectiveness of understory birds that feed on fruits of the tropical tree Dendropanax arboreus in a fragmented forest at Los Tuxtlas, east-central Mexico. The quantity and quality components of effectiveness were estimated in three different sites: continuous forest, 40 ha forest fragment, and 3 ha forest fragment. The quantity component was estimated through relative abundance, frequency of visits to fruits, and number of seeds in fecal samples. The quality component was estimated by analyzing germination of seeds defecated by birds and seed deposition patterns by birds. Seed deposition patterns were estimated by comparing the number of seeds found in fecal samples and the number of reproductive adults of D. arboreus in each site. Results showed that dispersal effectiveness of birds varied among sites. Turdus grayi was the most effective disperser in continuous forest, while Hylocichla mustelina was the most effective one in 40 and 3 ha forest fragments. These birds are contributing to the gene flow between fragments and continuous forest because they are able to use forest or riparian remnants, living fences, and isolated trees.     

Directed dispersal of mistletoe (Plicosepalus acaciae) by Yellow-vented Bulbuls (Pycnonotus xanthopygos)

We studied avian dispersal of seeds from the hemiparasitic mistletoe Plicosepalus acaciae (Loranthaceae) to its tree hosts Acacia raddiana and A. tortilis in the Syrian–African Rift (Arava) valley, Israel. The Yellow-vented Bulbul (Pycnonotus xanthopygos) was the sole avian visitor observed feeding on mistletoe fruits. Bulbuls consumed mistletoe fruits whenever they were available, but the fruits only constituted a significant portion of the diet (71% of foraging attempts) when they were most abundant. These birds are potentially good dispersal vectors of P. acaciae because they swallowed the fruit whole and defecated viable seeds that were covered in a viscid pulp, which allowed the seeds to adhere to substrates when voided. In addition, bulbuls spent a large proportion (66–93%) of total observation time perched in Acacia trees, allowing for directed dispersal. Ephemeral river valleys (wadis) with high mistletoe infection were adjacent to those containing no infections, demonstrating that mistletoe dispersal is common within, but not among wadis. This is consistent with the flight behaviour in bulbuls, which do not typically move among wadis. We combined data on bulbul movements between Acacia trees with transit times of mistletoe seeds to create a hypothetical seed shadow as a function of distance from the parent mistletoe plant. Because they are directed dispersers, the movement patterns of bulbuls may explain the current distribution of P. acaciae in the Arava valley.