Foraging behavior of migrant warblers in mixed‐species flocks in Venezuelan shade coffee: interspecific differences,tree species selection,and effects of drought

Shade coffee has been identified as an important habitat for Nearctic‐Neotropical migrants during the non‐breeding season, including species of conservation concern such as Cerulean Warblers (Setophaga cerulea). To better understand habitat features important for migrants in shade coffee, we studied the foraging behavior of migrants in mixed‐species flocks at six shade‐coffee farms in the Cordillera de Merida, Venezuela, in 2008–2009 and the El Niño drought year of 2009–2010. We examined interspecific differences in foraging behavior and tree species selection of three foliage‐gleaning migrants, Blackburnian (Setophaga fusca), Cerulean, and Tennessee (Oreothlypis peregrina) warblers, and aerial‐foraging American Redstarts (Setophaga ruticilla). For morphologically similar Blackburnian and Cerulean warblers, we also examined factors influencing foraging rates (attack and movement rates), capture of large prey, and maneuver/substrate type. We found that aerial‐foraging American Redstarts foraged lower, used more aerial maneuvers, showed no tree species selection, and were less likely to forage in flocks than foliage‐gleaners. Although foraging rates were similar for Blackburnian and Cerulean warblers, the three foliage‐gleaners differed in foraging height and use of maneuvers. Cerulean Warblers foraged lower than the other two species, whereas Blackburnian Warblers used the greatest proportion of woody gleans. All three foliage‐gleaners selected Inga spp. (a commonly planted shade tree in shade‐coffee farms) for foraging, and Blackburnian and Cerulean warblers captured a greater proportion of large prey in Inga spp. than in other tree species. During the drought year, Blackburnian and Cerulean warblers captured half as many large prey and used a greater proportion of woody‐gleans. We found that interactions among behavioral, floristic, and environmental drivers influenced the foraging behavior of migrants wintering in shade coffee. Our results support those of previous studies suggesting that migrants partition resources behaviorally during the non‐breeding season, that foliage‐gleaners may benefit from the presence of shade trees, especially Inga spp., in agroforestry systems, and that drought may influence the foraging behavior of foliage‐gleaning migrants, presumably due to reduced prey availability.     

Timing of events on the breeding grounds for five species of sympatric warblers

ABSTRACT On the breeding grounds, migratory birds have limited time to breed and molt before autumn migration. However, few studies of long‐distance migrants have examined the phenology of these events to determine what life‐history trade‐offs might result if these activities overlap. From 2000 to 2007, I used banding data to determine the timing of migration, breeding, and primary molt for Yellow Warblers (Dendroica petechia), Yellow‐rumped Warblers (D. coronata coronata), American Redstarts (Setophaga ruticilla), Ovenbirds (Seiurus aurocapilla), and Canada Warblers (Wilsonia canadensis) at a study site in Alberta, Canada. Hatching date did not differ among species (P= 0.63), with means ranging from 27 June to 3 July. All species began primary molt between 12 July and 18 July, near the expected fledging date of offspring, and therefore all species exhibited overlap between postfledging parental care and molt. The duration of primary molt ranged from 28 d for Canada Warblers to 69 d for Yellow‐rumped Warblers. Yellow Warblers, Yellow‐rumped Warblers, and American Redstarts began autumn migration having completed about 50% of their primary molt. However, Ovenbirds departed when 21% of molt was complete, and Canada Warblers departed 2 d after completing molt. For all five species of warblers, molt did not overlap with nest‐bound breeding activities. However, molt did overlap with both postfledging care and migration. This suggests that initiating migration as soon as possible is important, possibly because earlier arrival on the wintering grounds may improve access to high quality winter habitat. Overall, warblers may maximize individual fitness by combining life‐history events that result in overlapping portions of the breeding cycle, molt, and migration.     

Reservoir water levels do not influence daily mass gain of warblers at a riparian stopover site

ABSTRACT Hydroelectric dam operations that lead to fluctuations in the water levels of reservoirs can influence the amount of riparian habitat available for migrating songbirds and may impact the use and quality of remaining habitat. Our objective was to determine if use of riparian habitats and mass gain by five warbler species at the Columbia River‐Revelstoke Migration Monitoring Station in British Columbia, Canada, were influenced by water levels in the surrounding Arrow Lakes Reservoir. We analyzed fall migration data collected from 1998 to 2006. Capture rates of American Redstarts (Setophaga ruticilla), Common Yellowthroats (Geothlypis trichas), Orange‐crowned Warblers (Vermivora celata), Wilson's Warblers (Wilsonia pusilla), and Yellow Warblers (Dendroica petechia) varied between years and weeks of the migration period, but were not affected by annual or weekly variation in water levels. Annual variation in capture rates was driven by hatch‐year birds (>80% of individuals captured were juveniles) and could reflect conditions on the breeding grounds that influence productivity. We found that mass gain by the five species of warblers varied between 0.32% and 0.98% of lean body mass/hour. Mass gain did not vary between years or across weeks of the migration period and was not influenced by annual or weekly variation in reservoir water levels. Although the amount of available riparian habitat was reduced when reservoir water levels were high, we found no evidence that this loss of habitat influenced either the number of warblers or the mass gain of warblers using the riparian habitat that remained. Body mass at the time of first capture varied between years and across weeks for all five species. For American Redstarts and Orange‐crowned Warblers, body mass declined as average weekly water levels increased, a pattern that could arise if water levels influenced either their settlement decisions or length of stay.     

Extreme genetic similarity does not predict non‐breeding distribution of two closely related warblers

Detailed knowledge of migratory connectivity can facilitate effective conservation of Neotropical migrants by helping biologists understand where and when populations may be most limited. We studied the migratory behavior and non‐breeding distribution of two closely related species of conservation concern, the Golden‐winged Warbler (Vermivora chrysoptera) and Blue‐winged Warbler (Vermivora cyanoptera). Although both species have undergone dynamic range shifts and population changes attributed to habitat loss and social interactions promoting competition and hybridization, full life‐cycle conservation planning has been limited by a lack of information about their non‐breeding ecology. Because recent work has demonstrated that the two species are nearly identical genetically, we predicted that individuals from a single breeding population would have similar migratory timing and overwintering locations. In 2015, we placed light‐level geolocators on 25 males of both species and hybrids in an area of breeding sympatry at the Fort Drum Military Installation in Jefferson and Lewis counties, New York. Despite extreme genetic similarity, non‐breeding locations and duration of migration differed among genotypes. Golden‐winged Warblers (N = 2) overwintered > 1900 km southeast of the nearest Blue‐winged Warbler (N = 3) and spent nearly twice as many days in migration; hybrids (N = 2) had intermediate wintering distributions and migratory timing. Spring migration departure dates were staggered based on distance from the breeding area, and all birds arrived at the breeding site within 8 days of each other. Our results show that Golden‐winged Warblers and Blue‐winged Warblers in our study area retain species‐specific non‐breeding locations despite extreme genetic similarity, and suggest that non‐breeding locations and migratory timing vary along a genetic gradient. If the migratory period is limiting for these species, our results also suggest that Golden‐winged Warblers in our study population may be more vulnerable to population decline than Blue‐winged Warblers because they spend almost twice as many days migrating.     

Crosswise migration by Yellow Warblers,Nearctic‐Neotropical passerine migrants

Yellow Warblers (Setophaga petechia) are abundant breeding birds in North America, but their migratory and non‐breeding biology remain poorly understood. Studies where genetic and isotopic techniques were used identified parallel migration systems and longitudinal segregation among eastern‐ and western‐breeding populations of Yellow Warblers in North America, but these techniques have low spatial resolution. During the 2015 breeding season, we tagged male Yellow Warblers breeding in Maine (N = 10) and Wisconsin (N = 10) with light‐level geolocators to elucidate fine‐scale migratory connectivity within the eastern haplotype of this species and determine fall migration timing, routes, and wintering locations. We recovered seven of 20 geolocators (35%), including four in Maine and three in Wisconsin. The mean duration of fall migration was 49 d with departure from breeding areas in late August and early September and arrival in wintering areas in mid‐October. Most individuals crossed the Gulf of Mexico to Central America before completing the final eastward leg of their migration to northern South America. Yellow Warblers breeding in Maine wintered in north‐central Colombia, west of those breeding in Wisconsin that wintered in Venezuela and the border region between Brazil, Colombia, and Venezuela. Our results provide an example of crosswise migration, where the more easterly breeding population wintered farther west than the more westerly breeding population (and vice versa), a seldom‐documented phenomenon in birds. Our results confirm earlier work demonstrating that the eastern haplotype of northern Yellow Warblers winters in northern South America, and provide novel information about migratory strategies, timing, and wintering locations of birds from two different populations.     

Intra‐ and interspecific interactions between aphidophagous ladybirds: the role of prey in predator coexistence

Cannibalism (CANN) and intraguild predation (IGP) may provide energy and nutrients to individuals and eliminate potential competitors. These negative competitive interactions could also affect the coexistence of predatory species. The co‐occurrence of aphidophagous ladybird species in crops creates opportunities for CANN and IGP, especially when aphids become scarce. The Lotka–Volterra model predicts the coexistence of two species if intraspecific competition is stronger than interspecific interference interactions. Cycloneda sanguinea L. and Eriopis connexa (Germar) (both Coleoptera: Coccinellidae) coexist in sweet pepper crops in La Plata (Argentina) consuming mainly Myzus persicae (Sulzer) (Hemiptera: Aphididae). The present study used laboratory experiments to estimate levels of CANN and IGP by adults and larvae on eggs, and by adults on larvae, in both the presence and absence of prey (i.e., M. persicae), to explain the effect of prey on coexistence of these two predators. Levels of CANN by C. sanguinea and E. connexa were high in the absence of aphids, and decreased when prey was present. Intraguild predation was bidirectional and asymmetric. Adults and larvae of E. connexa were more voracious IG predators of C. sanguinea than vice versa, the former being the stronger IG predator and interference competitor. Eriopis connexa always won when larvae of the same instar were compared, whereas the larger larva always won when larvae were of different instars, regardless of species. In the presence of prey, CANN by both species decreased, but IGP by E. connexa on C. sanguinea remained high, suggesting that E. connexa could displace C. sanguinea via interspecific interference competition. Other factors potentially affecting the coexistence of C. sanguinea and E. connexa in sweet pepper crops are discussed.     

Foraging Behavior and Coexistence of Two Sunbird Species in a Kenyan Woodland

We investigated the mechanism of coexistence of the rare Amani Sunbird (Hedydipna pallidigastra) and the widespread Collared Sunbird (H. collaris), within Brachystegia woodland in the Arabuko‐Sokoke Forest, Kenya. We compared how prey abundance and search strategies affect resource exploitation by the two species. We used foraging theory to direct our measures of feeding activities as influenced by sunbird species, tree species and foraging height. We evaluated invertebrate abundance among tree species at different heights within trees. The Collared Sunbird primarily used the understory, and the Amani Sunbird primarily used the upper‐canopy. Overall, the rate of prey attacks per flight of the Amani Sunbird was 2.8 times greater than that of the Collared Sunbird. The Amani Sunbird, however, used increased search and attack rates in the understory compared with the mid‐ and upper‐canopies, but the Collared Sunbird foraged similarly throughout all strata. We hypothesize that the increased foraging rate of the Amani in the understory reflects increased foraging costs due to interference from the Collared Sunbird in that stratum. Furthermore, the Collared Sunbird exploits rich patches by moving frequently from place to place. The Amani Sunbird forages slowly, with reduced travel rates, and with a greater number of prey captures within a patch. Arthropod density did not differ among the vegetative strata, but was higher in Brachystegia spiciformis and Hymenaea verrucosa than in six other tree species. We hypothesize that the Amani Sunbird appears dependent upon continued tall B. spiciformis trees within the canopy of the Arabuko‐Sokoke Forest.     

Seasonal diet and prey selection of black‐backed jackals on a small‐livestock farm in South Africa

The extent to which black‐backed jackals (Canis mesomelas) selectively consume domestic sheep (Ovis aries) compared to wild prey is unknown. Using faecal analysis and prey surveys, we determined the seasonal diet and prey selection of jackals on a small‐livestock farm in South Africa. Sheep comprised 25–48% of the biomass consumed by jackals across seasons, and consumption peaked during the lambing seasons, indicating sheep often were the main food resource for jackals. Another main food resource was wild ungulates <50 kg, primarily springbok (Antidorcas marsupialis) and steenbok (Raphicerus campestris), which comprised 8–47% of the biomass consumed. Other important food items were mammals 1–3 kg (4–16%), which included hares (Lepus spp.) and springhares (Pedetes capensis), and small rodents (10–14%). Compared to the biomass available, jackals selectively consumed mammals 1–3 kg over sheep across all seasons, whereas wild ungulates <50 kg were selectively consumed over sheep in most seasons. Our results showed that jackals selectively consumed different food items throughout the year and that wild prey were consistently selected over sheep.     

Stage‐dependent responses to emergent habitat heterogeneity: consequences for a predatory insect population in a coffee agroecosystem

Interactions among members of biological communities can create spatial patterns that effectively generate habitat heterogeneity for other members in the community, and this heterogeneity might be crucial for their persistence. For example, stage‐dependent vulnerability of a predatory lady beetle to aggression of the ant, Azteca instabilis, creates two habitat types that are utilized differently by the immature and adult life stages of the beetle. Due to a mutualistic association between A. instabilis and the hemipteran Coccus viridis – which is A. orbigera main prey in the area – only plants around ant nests have high C. viridis populations. Here, we report on a series of surveys at three different scales aimed at detecting how the presence and clustered distribution of ant nests affect the distribution of the different life stages of this predatory lady beetle in a coffee farm in Chiapas, Mexico. Both beetle adults and larvae were more abundant in areas with ant nests, but adults were restricted to the peripheries of highest ant activity and outside the reach of coffee bushes containing the highest densities of lady beetle larvae. The abundance of adult beetles located around trees with ants increased with the size of the ant nest clusters but the relationship is not significant for larvae. Thus, we suggest that A. orbigera undergoes an ontogenetic niche shift, not through shifting prey species, but through stage‐specific vulnerability differences against a competitor that renders areas of abundant prey populations inaccessible for adults but not for larvae. Together with evidence presented elsewhere, this study shows how an important predator is not only dependent on the existence of two qualitatively distinct habitat types, but also on the spatial distribution of these habitats. We suggest that this dependency arises due to the different responses that the predator's life stages have to this emergent spatial pattern.     

Coevolution of competing Callosobruchus species does not stabilize coexistence

Interspecific resource competition is expected to select for divergence in resource use, weakening interspecific relative to intraspecific competition, thus promoting stable coexistence. More broadly, because interspecific competition reduces fitness, any mechanism of interspecific competition should generate selection favoring traits that weaken interspecific competition. However, species also can adapt to competition by increasing their competitive ability, potentially destabilizing coexistence. We reared two species of bean beetles, the specialist Callosobruchus maculatus and the generalist C. chinensis, in allopatry and sympatry on a mixture of adzuki beans and lentils, and assayed mutual invasibility after four, eight, and twelve generations of evolution. Contrary to the expectation that coevolution of competitors will weaken interspecific competition, the rate of mutual invasibility did not differ between sympatry and allopatry. Rather, the invasion rate of C. chinensis, but not C. maculatus, increased with duration of evolution, as C. chinensis adapted to lentils without experiencing reduced adaptation to adzuki beans, and regardless of the presence or absence of C. maculatus. Our results highlight that evolutionary responses to interspecific competition promote stable coexistence only under specific conditions that can be difficult to produce in practice.     

Experimental evolution of competing bean beetle species reveals long‐term reversals of short‐term evolution,but no consistent character displacement

Interspecific competition for shared resources should select for evolutionary divergence in resource use between competing species, termed character displacement. Many purported examples of character displacement exist, but few completely rule out alternative explanations. We reared genetically diverse populations of two species of bean beetles, Callosobruchus maculatus and Callosobruchus chinensis, in allopatry and sympatry on a mixture of adzuki beans and lentils, and assayed oviposition preference and other phenotypic traits after four, eight, and twelve generations of (co)evolution. C. maculatus specializes on adzuki beans; the generalist C. chinensis uses both beans. C. chinensis growing in allopatry emerged equally from both bean species. In sympatry, the two species competing strongly and coexisted via strong realized resource partitioning, with C. chinensis emerging almost exclusively from lentils and C. maculatus emerging almost exclusively from adzuki beans. However, oviposition preferences, larval survival traits, and larval development rates in both beetle species did not vary consistently between allopatric versus sympatric treatments. Rather, traits evolved in treatment‐independent fashion, with several traits exhibiting reversals in their evolutionary trajectories. For example, C. chinensis initially evolved a slower egg‐to‐adult development rate on adzuki beans in both allopatry and sympatry, then subsequently evolved back toward the faster ancestral development rate. Lack of character displacement is consistent with a previous similar experiment in bean beetles and may reflect lack of evolutionary trade‐offs in resource use. However, evolutionary reversals were unexpected and remain unexplained. Together with other empirical and theoretical work, our results illustrate the stringency of the conditions for character displacement.     

Patch exploitation by non‐aggressive parasitoids under intra‐ and interspecific competition

The behavioral strategies evolved by insect parasitoids to optimize their foraging efforts have been the subject of many theoretical and empirical studies. However, the effects competition may have on these strategies, especially for species that do not engage in antagonistic behaviors, have received little attention. The objective of this study was to evaluate the effects of intraspecific and interspecific competition on patch exploitation strategies by two non‐aggressive species, Trichogramma pintoi Voegelé and Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae), both generalist egg parasitoids. We analyzed the patch residence times of females, their patch‐leaving mechanisms, and the sex allocation of their progeny while foraging either alone, with an intraspecific competitor, or with an interspecific competitor. To some extent, each species responded differently to the presence of a competitor in the patch. Trichogramma pintoi females did not change their patch‐leaving mechanisms in response to competition and behaved as if under an exploitative competition regime, whereas T. minutum females did change their patch‐leaving mechanisms in response to competition and remained longer in the host patch than expected. Antennal rejection, and not oviposition, was the proximate behavioral mechanism underlying patch‐leaving decisions by both species. Neither species adjusted the sex allocation of their progeny in response to competition. These results indicate that the effects of competition differ even among closely related parasitoid species.     

Stable isotope ratios in winter‐grown feathers of Great Reed Warblers Acrocephalus arundinaceus,Clamorous Reed Warblers A. stentoreus and their hybrids in a sympatric breeding population in Kazakhstan

Analyses of the stable isotope composition of feathers can provide significant insight into the spatial structure of bird migration. We collected feathers from Great Reed Warblers Acrocephalus arundinaceus, Clamorous Reed Warblers A. stentoreus and a small sample of their hybrids in a sympatric breeding population in Kazakhstan to assess natural variation in stable isotope signatures and delineate wintering sites. The Great Reed Warbler is a long‐distance migrant that overwinters in sub‐Saharan Africa, whereas the Clamorous Reed Warbler performs a short‐distance migration to the Indian sub‐continent. Carbon (δ¹³C), nitrogen (δ¹⁵N) and deuterium (δD) isotope signatures were obtained from winter‐grown feathers of adult birds. There were highly significant differences in δD and less significant differences in δ¹³C between Great and Clamorous Reed Warblers. Thus, our results show that the stable isotope technique, and in particular the deuterium (δD) signal, resolves continental variation in winter distribution between these closely related Acrocephalus species with sympatric natal origin. The isotope signatures of hybrid Great × Clamorous Reed Warblers clustered with those of the Great Reed Warblers. Hence, a parsimonious suggestion is that the hybrids undergo moult in Afrotropical wintering grounds, as do the Great Reed Warblers. The observed δD values fell within the range of expected values based on available precipitation data collected at precipitation stations across the wintering continents of each species. However, the power to predict the winter origin of birds in our study system using these data was weak as the expected values ranged widely at this broad continental scale.     

Strong influences of a dominant,ground‐nesting ant on recruitment,and establishment of ant colonies and communities

Many factors drive the organization of communities including environmental factors, dispersal abilities, and competition. In particular, ant communities have high levels of interspecific competition and dominance that may affect community assembly processes. We used a combination of surveys and nest supplementation experiments to examine effects of a dominant ground‐nesting ant (Pheidole synanthropica) on (1) arboreal twig‐nesting, (2) ground‐foraging, and (3) coffee‐foraging ant communities in coffee agroecosystems. We surveyed these communities in high‐ and low‐density areas of P. synanthropica over 2 years. To test for effects on twig ant recruitment, we placed artificial nesting resources on coffee plants in areas with and without P. synanthropica. The first sampling period revealed differences in ant species composition on the ground, in coffee plants, and artificial nests between high‐ and low‐density sites of P. synanthropica. High‐density sites also had significantly lower recruitment of twig ants and had species‐specific effects on twig ant species. Prior to the second survey period, abundance of P. synanthropica declined in the high‐density sites, such that P. synanthropica densities no longer differed. Subsequent sampling revealed no difference in total recruitment of twig ants to artificial nests between treatments. Likewise, surveys of ground and coffee ants no longer showed significant differences in community composition. The results from the first experimental period, followed by survey results after the decline in P. synanthropica densities suggest that dominant ants can drive community assembly via both recruitment and establishment of colonies within the community.     

Overlapping trophic niches among co‐occurring amphipods from a cryptic species complex

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Malaria infections reinforce competitive asymmetry between two Ficedula flycatchers in a recent contact zone

Parasites may influence the outcome of interspecific competition between closely related host species through lower parasite virulence in the host with which they share the longer evolutionary history. We tested this idea by comparing the prevalence of avian malaria (Haemosporidia) lineages and their association with survival in pied and collared flycatchers (Ficedula hypoleuca and F. albicollis) breeding in a recent contact zone on the Swedish island of Öland. A nested PCR protocol amplifying haemosporidian fragments of mtDNA was used to screen the presence of malaria lineages in 1048 blood samples collected during 6 years. Competitively inferior pied flycatchers had a higher prevalence of blood parasites, including the lineages that were shared between the two flycatcher species. Multistate mark–recapture models revealed a lower survival of infected versus uninfected female pied flycatchers, while no such effects were detected in male pied flycatchers or in collared flycatchers of either sex. Our results show that a comparatively new host, the collared flycatcher, appears to be less susceptible to a local northern European malarial lineage where the collared flycatchers have recently expanded their distribution. Pied flycatchers experience strong reproductive interference from collared flycatchers, and the additional impact of species‐specific blood parasite effects adds to this competitive exclusion. These results support the idea that parasites can strongly influence the outcome of interspecific competition between closely related host species, but that the invading species need not necessarily be more susceptible to local parasites.     

Investigating variability and behaviour of Colletotrichum gloeosporioides strains from lesions of coffee blister spot

Coffee blister spot has been associated with species from the Colletotrichum genus, but there is no information on the variability of isolates present on leaf lesions. This study evaluated a population of Colletotrichum gloeosporioides strains from blister spot lesions in Coffea arabica. Colletotrichum spp. isolates were collected from blister spot lesions on leaves of coffee trees from Catuaí and Topázio cultivars (Coffea arabica). Monosporic cultures were obtained from colonies with sporulation. A pathogenicity test was carried out by inoculation of pathogens on the leaves of young coffee plants. C. gloeosporioides strains were characterized by morphologial, cytological and physiological analyses. The molecular analysis was carried out using Inter‐Retrotransposon Amplified Polymorphism (IRAP) markers. C. gloeosporioides strains showed no pathogenicity on coffee plants and presented a wide variability in all traits evaluated. The presence of sexual strains, formation of CATs (conidial anastomosis tubes) among conidial strains and high mycelial compatibility among strains observed suggest the occurrence of sexual and asexual recombination. The role of these C. gloeosporioides strains on the lesions of coffee plant leaves is unclear.     

Disentangling mite predator‐prey relationships by multiplex PCR

Gut content analysis using molecular techniques can help elucidate predator‐prey relationships in situations in which other methodologies are not feasible, such as in the case of trophic interactions between minute species such as mites. We designed species‐specific primers for a mite community occurring in Spanish citrus orchards comprising two herbivores, the Tetranychidae Tetranychus urticae and Panonychus citri, and six predatory mites belonging to the Phytoseiidae family; these predatory mites are considered to be these herbivores’ main biological control agents. These primers were successfully multiplexed in a single PCR to test the range of predators feeding on each of the two prey species. We estimated prey DNA detectability success over time (DS₅₀), which depended on the predator‐prey combination and ranged from 0.2 to 18 h. These values were further used to weight prey detection in field samples to disentangle the predatory role played by the most abundant predators (i.e. Euseius stipulatus and Phytoseiulus persimilis). The corrected predation value for E. stipulatus was significantly higher than for P. persimilis. However, because this 1.5‐fold difference was less than that observed regarding their sevenfold difference in abundance, we conclude that P. persimilis is the most effective predator in the system; it preyed on tetranychids almost five times more frequently than E. stipulatus did. The present results demonstrate that molecular tools are appropriate to unravel predator‐prey interactions in tiny species such as mites, which include important agricultural pests and their predators.     

Growth and Chloroplast Replacement of the Benthic Mixotrophic Ciliate Mesodinium coatsi

While the ecophysiology of planktonic Mesodinium rubrum species complex has been relatively well studied, very little is known about that of benthic Mesodinium species. In this study, we examined the growth response of the benthic ciliate Mesodinium coatsi to different cryptophyte prey using an established culture of this species. M. coatsi was able to ingest all of the offered cryptophyte prey types, but not all cryptophytes supported its positive, sustained growth. While M. coatsi achieved sustained growth on all of the phycocyanin‐containing Chroomonas spp. it was offered, it showed different growth responses to the phycoerythrin‐containing cryptophytes Rhodomonas spp., Storeatula sp., and Teleaulax amphioxeia. M. coatsi was able to easily replace previously ingested prey chloroplasts with newly ingested ones within 4 d, irrespective of prey type, if cryptophyte prey were available. Once retained, the ingested prey chloroplasts seemed to be photosynthetically active. When fed, M. coatsi was capable of heterotrophic growth in darkness, but its growth was enhanced significantly in the light (14:10 h light:dark cycle), suggesting that photosynthesis by ingested prey chloroplast leads to a significant increase in the growth of M. coatsi. Our results expand the knowledge of autecology and ecophysiology of the benthic M. coatsi.     

Post‐breeding population dynamics indicate upslope molt‐migration by Wilson's Warblers

Molt is an energetically costly process, and songbirds (Order Passeriformes) exhibit a diversity of strategies to maximize their survival and reproductive success while meeting the energetic demands of the annual prebasic molt. Nearctic‐Neotropic migrants in western North America commonly exhibit one of three strategies: (1) remain in breeding areas to molt, (2) migrate long distances to molt before continuing to wintering areas, or (3) migrate to wintering areas and then molt. Among species that molt in or near breeding areas, the nature of small‐scale movements to undergo molt remains largely unknown. We used banding data collected over a period of 27 yr and across an elevational gradient to examine the propensity of Wilson's Warblers (Cardellina pusilla) to molt and breed at the same or different locations in northern California and southern Oregon. We found that individual adult Wilson's Warblers were more likely to breed at lower elevations and molt at higher elevations, suggesting that some individuals move altitudinally after breeding to complete the definitive prebasic molt. Such altitudinal movements may be more common among Nearctic‐Neotropic migrants in western North America than previously thought.