Aerial Foragers Research Articles

Sexually dimorphic swallows have higher extinction risk.

The effect of sexual selection on extinction risk remains unclear. In theory, sexual selection can lead to both increase and decrease extinction probability depending on the ecology of the study system. Thus, combining different groups might obscure patterns that can be found in groups that share similar ecological features. Using phylogenetic comparative analysis, we studied sexual plumage dimorphism in relation to the perceived risk of extinction in hirundines (subfamily: Hirundininae), in which all species are socially monogamous aerial foragers. Among the 72 species studied, five species are facing a perceived threat of extinction. Species with sexually dimorphic plumage had a higher risk of extinction than did species with sexually monomorphic plumage. Likewise, when focusing solely on tail ornamentation, species that exhibit a sexual dimorphism in tail length had a higher risk of extinction than did other species. In Hirundininae, which are affected a great deal by severe weather, sexual selection and the resultant sexual dimorphism would increase extinction risk.

Effect of light‐level geolocators on apparent survival of two highly aerial swift species

Light‐level geolocators are currently widely used to track the migration of small‐sized birds, but their potentially detrimental effects on survival of highly aerial species have been poorly investigated so far. We recorded capture–recapture histories of 283 common swifts Apus apus and 107 pallid swifts Apus pallidus breeding in 14 colonies in Italy, Spain, Sweden and Switzerland that were equipped with 10 different types of geolocators (‘geolocator birds’), and compared their survival with that of, respectively, 215 common and 101 pallid swifts not equipped with geolocators (‘control birds’). Data were analysed using both GLMMs with return rate as a proxy for survival and mark–recapture models to estimate survival while accounting for recapture probability. In all the analyses, geolocator birds showed reduced apparent survival compared to controls. Geolocator weight was always lower than 3% of body mass, and did not affect survival per se. Geolocators with a light‐stalk, which is used in some geolocator models to reduce light sensor shading by feathers, decreased apparent survival more than models without light‐stalk. Apparent survival of geolocator birds significantly varied among sites, being much higher in northern Europe. Despite in our analyses we could only partly account for variable recapture probabilities among sites and for inter‐annual variability in survival, our results generally showed that equipping swifts with geolocators decreased their survival prospects, but also that the magnitude of this effect may depend on species‐specific traits. These conclusions are in line with those of other studies on aerial foragers. We suggest that future studies tracking the movements of aerial insectivorous birds should use devices designed to minimize drag.

Activity of Insectivorous Bats is Related to Water Availability in a Highly Modified Mexican Temperate Forest

Artificial ponds are important foraging and drinking resources for bats at La Michilia, a temperate forest with a marked seasonal drought. Using acoustic data we tested the hypothesis that water availability restricts bat activity in the dry season to ponds, whereas in the rainy season resources are widely available and therefore used throughout the area. We compared bat activity at six ponds with that of a 500-meter transect perpendicular to each pond. We predicted that activity would be higher at ponds in the dry season, whereas in the rainy season activity should be equal or higher at transects. Also, all species guilds would use ponds in the dry season, whereas gleaners, edge aerial and open aerial foragers would be more frequent at transects in the rainy season. In no instance activity was higher at transects than at ponds during the rainy season. Open areas showed little or no bat activity in the dry season, but were very active in the rainy season. One transect located in dense forest and one near human dwellings were active both seasons. Open aerial foragers were present mostly on ponds in the dry season, and on ponds and transects in the rainy season; edge aerial bats were common in ponds in the dry season, but rare in transects in the rainy season. Trawling bats used ponds and transects in both seasons; and gleaners were rare over ponds and transects in both seasons. Because bats use the local habitat differently depending on season and feeding guild, and climate and seasonality vary greatly in Mexican temperate forests, conservation strategies can not be generalized, but should be implemented on a case-by-case basis.

Are invasive fire ants kept in check by native aerial insectivores?

Aerial predator-prey interactions may impact populations of many terrestrial species. Here, we use altitude loggers to study aerial foraging in a native insectivore, the purple martin (Progne subis), in the southern USA. Purple martins fed primarily on mating queens and males of the invasive red imported fire ant (Solenopsis invicta), and doubled their foraging efficiency by doing so. Across the USA, purple martins likely eat billions of fire ant queens each year, potentially impacting the spread of this species. Alternatively, predation on fire ants may help sustain populations of purple martins and other aerial insectivores.

Distribution and at-sea activity of a nocturnal seabird, the Bulwer's petrel Bulweria bulwerii, during the incubation period

Bulwer's petrels are nocturnal seabirds that mostly prey on mesopelagic fauna. As aerial foragers and shallow divers, their feeding opportunities are limited by near-surface availability of their prey, which is highly variable both temporally (reflecting diurnal and lunar cycles) and spatially. Here we studied how Bulwer's petrels cope with these constraints by analysing their at-sea distribution and activity during the incubation period. We tracked the movements of 20 birds from Selvagem Grande (NE Atlantic) during a complete lunar cycle, and recorded 30 foraging trips that lasted 11 days on average. Birds were both distributed around the colony and in waters close to the Azorean archipelago (mid-Atlantic) located 1700km away, and were significantly more active at night (especially just after sunset and before sunrise), when mesopelagic fauna is also closer to the sea surface due to their diel vertical migrations. Bulwer's petrels spent significantly more time flying during moonlight, although the effect of the moon was relatively weak (ca. 10–15% difference between moonlit and dark periods of the night), and not obvious when birds were foraging in mid-Atlantic waters, which were also targeted more often during full-moon. These results reveal key adaptations of the Bulwer's petrel to the highly dynamic ecology of its mesopelagic prey.

The winter foraging behaviour of birds in a mixed eucalypt forest and woodland on the Southern Tablelands of New South Wales

In this paper, I present data on the foraging behaviour of eucalypt forest and woodland birds at two sites on the Southern Tablelands of New South Wales during the non-breeding season (winter). The winter community was a subset of the summer community, with six guilds among 23 species identified by cluster analysis compared with seven guilds among 41 species in summer. Despite this difference, birds were abundant during winter, with more than 200 individuals of 29 species recorded during July censuses on the two 10 ha plots. Although a few birds fed on nectar, nectar was not abundant in winter and the nectar-foraging guild present in summer was absent in winter. Most birds that relied on large arthropods and aerial foragers left the area after summer and an aerial foraging guild was restricted to one species, the Grey Fantail. As in summer, species differed in foraging manoeuvres and substrates, as well as foraging heights and the plant species frequented to find food. The continued abundance and diversity of species/guilds through the winter is best explained by the variety of food resources available for birds; the complexity of foliage, bark, and ground substrates provided a wide range of foraging substrates over the entire vertical profile of the vegetation. Maintenance of this structural complexity is essential for the survival of eucalypt forest and woodland birds.

Multi-Season Regional Analysis of Multi-Species Occupancy: Implications for Bird Conservation in Agricultural Lands in East-Central Argentina.

Rapid expansion and intensification of agriculture create challenges for the conservation of biodiversity and associated ecosystem services. In Argentina, the total row crop planted area has increased in recent decades with the expansion of soybean cultivation, homogenizing the landscape. In 2003 we started the first long-term, large-scale bird monitoring program in agroecosystems of central Argentina, in portions of the Pampas and Espinal ecoregions. Using data from this program, we evaluated the effect of land use and cover extent on birds between 2003-2012, accounting for imperfect detection probabilities using a Bayesian hierarchical, multi-species and multi-season occupancy model. We tested predictions that species diversity is positively related to habitat heterogeneity, which in intensified agroecosystems is thought to be mediated by food availability; thus the extent of land use and cover is predicted to affect foraging guilds differently. We also infer about ecosystem services provisioning and inform management recommendations for conservation of birds. Overall our results support the predictions. Although many species within each guild responded differently to land use and native forest cover, we identified generalities for most trophic guilds. For example, granivorous gleaners, ground insectivores and omnivores responded negatively to high proportions of soybean, while insectivore gleaners and aerial foragers seemed more tolerant. Habitat heterogeneity would likely benefit most species in an intensified agroecosystem, and can be achieved with a diversity of crops, pastures, and natural areas within the landscape. Although most studied species are insectivores, potentially beneficial for pest control, some guilds such as ground insectivores are poorly represented, suggesting that agricultural intensification reduces ecological functions, which may be recovered through management. Continuation of the bird monitoring program will allow us to continue to inform for conservation of birds in agroecosystems, identify research needed to reduce key uncertainties, and anticipate the effects of changes in agriculture in central Argentina.

Barn SwallowHirundo rusticaparents work harder when foraging conditions are good

In altricial birds, the great effort involved in supplying food to nestlings can create trade‐offs in the allocation of resources between the current brood and parental self‐maintenance. In poor foraging conditions, parents have to adjust their energy expenditure in relation to the increased foraging costs. However, intra‐specific variation in parental energy expenditure has rarely been evaluated in the context of these trade‐offs. Here, we quantified the daily energy expenditure (DEE) of parent Barn SwallowsHirundo rusticaduring the nestling period in relation to foraging conditions while controlling for differences in brood size and nestling age. DEE varied substantially with environmental conditions, increasing by 10 kJ/day per 5 °C in ambient temperature, and by 11 kJ/day per hour in day length. Parent birds did not compensate for a poor aerial insect supply on cool days, but reduced their DEE. Parents only slightly buffered a negative energy balance during chick provisioning with stored body reserves. They did not sacrifice their own energy demands to keep up a high energy flow to the brood when foraging conditions were poor. Instead they worked harder when foraging conditions allowed a surplus intake, fully compensating for their additional efforts, and made maximum use of the rich food supply, allowing the brood to accrue body reserves to compensate for low food intake on cold days. This strategy of energy management may have evolved in the context of the adaptation to the aerial foraging mode and to the ephemeral nature of aerial food resources.

Effects of successive predator attacks on prey aggregations

We study the cumulative effect of successive predator attacks on the disturbance of a prey aggregation using a modelling approach. Our model intends to represent fish schools attacked by both aerial and underwater predators. This individual-based model uses long-distance attraction and short-distance repulsion between prey, which leads to prey aggregation and swarming in the absence of predators. When intermediate-distance alignment is added to the model, the prey aggregation displays a cohesive displacement, i.e., schooling, instead of swarming. Including predators, i.e. with repulsion behaviour for prey to predators in the model, leads to flash expansion of the prey aggregation after a predator attack. When several predators attack successively, the prey aggregation dynamics is a succession of expanding-grouping-swarming/schooling phases. We quantify this dynamics by recording the changes in the simulated prey aggregation radius over time. This radius is computed as the longest distance of individual prey to the aggregation centroid, and it is assumed to increase along with prey disturbance. The prey aggregation radius generally increases during flash expansion, then decreases during grouping until reaching a constant lowest level during swarming/schooling. This general dynamics is modulated by several parameters: the frequency, direction (vertical vs. horizontal) and target (centroid of the prey aggregation vs. random prey) of predator attacks; the distance at which prey detect predators; the number of prey and predators. Our results suggest that both aerial and underwater predators are more efficient at disturbing fish schools by increasing their attack frequency at such level that the fish cannot return to swarming/schooling. We find that a mix between aerial and underwater predators is more efficient at disturbing a fish school than a single type of attack, suggesting that aerial and underwater foragers may gain mutual benefits in forming foraging groups.

A meta-analysis of the effects of geolocator application on birds

Abstract An increasing trend in use of tracking devices such as geolocators is based on the assumption that the information gathered from such devices provides reliable information about the migratory behavior of free-living birds. This underlying assumption is rarely tested, as evidenced by the absence in many studies of controls, in particular treated controls, and so far never with a reasonable statistical power. Published studies have shown reduced survival prospects or delayed breeding in some species, suggesting that there may be reason to doubt that tracking devices provide unbiased information. Therefore, we conducted a meta-analysis of studies applying geolocators to wild birds to determine whether geolocators affected fitness components. Ge-olocators had an overall negative effect on fitness components, in particular survival, and ecological variables. Effect size was larger for aerial foragers than for other species. Moreover the leg band attachment method was more detrimental for birds than the leg-loop backpack harness. A meta-regression model of effect size showed independent negative effects of geolocators on aerial foragers, smaller species, species with smaller migration distances and in studies where geolocators were attached with a ring. These results suggest that geolocator studies should be interpreted with caution, but also raise questions whether it is ethically defensible to use geolocators on aerial foragers or small species without carrying out robust pilot studies.

Changes in Avian and Plant Communities of Aspen Woodlands over 12 Years after Livestock Removal in the Northwestern Great Basin

Riparian and quaking aspen (Populus tremuloides) woodlands are centers of avian abundance and diversity in the western United States, but they have been affected adversely by land use practices, particularly livestock grazing. In 1990, cattle were removed from a 112,500-ha national wildlife refuge in southeastern Oregon. Thereafter, we monitored changes in vegetation and bird abundance in years 1-3 (phase 1) and 10-12 (phase 2) in 17 riparian and 9 snow-pocket aspen plots. On each 1.5-ha plot, we sampled vegetation in 6 transects. Three times during each breeding season, observers recorded all birds 50 m to each side of the plot's 150-m centerline for 25 minutes. We analyzed data with multivariate analysis of variance and paired t tests with p values adjusted for multiple comparisons. In both periods, riparian and snow-pocket aspen produced extensive regeneration of new shoots (stems/ha and 7079 stems/ha, respectively). By phase 2, a 64% increase in medium-diameter trees in riparian stands indicated successful recruitment into the overstory, but this pattern was not seen in snow-pocket stands, where the density of trees was over 2 times greater. By phase 2 in riparian and snow-pocket stands, native forb cover had increased by 68% and 57%, respectively, mesic shrub cover had increased by 29% and 58%, and sagebrush cover had decreased by 24% and 31%. Total avian abundance increased by 33% and 39% in riparian and snow-pocket aspen, respectively, ground or understory nesters increased by 133% and 67% and overstory nesters increased by 34% and 33%. Similarly, ground or understory foragers increased by 25% and 32%, aerial foragers by 55% and 57%, and overstory foragers by 66% and 43%. We interpreted the substantial regeneration of aspen shoots, increased densities of riparian forbs and shrubs, and increased avian abundances as a multitrophic-level response to the total removal of livestock and as substantial movement toward recovery of biological integrity.

Nest Predation Risk and Growth Strategies of Passerine Species: Grow Fast or Develop Traits to Escape Risk?

Different body components are thought to trade off in their growth and development rates, but the causes for relative prioritization of any trait remains a critical question. Offspring of species at higher risk of predation might prioritize development of locomotor traits that facilitate escaping risky environments over growth of mass. We tested this possibility in 12 altricial passerine species that differed in their risk of nest predation. We found that rates of growth and development of mass, wings, and endothermy increased with nest predation risk across species. In particular, species with higher nest predation risk exhibited relatively faster growth of wings than of mass, fledged with relatively larger wing sizes and smaller mass, and developed endothermy earlier at relatively smaller mass. This differential development can facilitate both escape from predators and survival outside of the nest environment. Tarsus growth was not differentially prioritized with respect to nest predation risk, and instead all species achieved adult tarsus size by age of fledging. We also tested whether different foraging modes (aerial, arboreal, and ground foragers) might explain the variation of differential growth of locomotor modules, but we found that little residual variation was explained. Our results suggest that differences in nest predation risk among species are associated with relative prioritization of body components to facilitate escape from the risky nest environment.

Direct impacts of climatic warming on heat stress in endothermic species: seabirds as bioindicators of changing thermoregulatory constraints

There is now abundant evidence that contemporary climatic change has indirectly affected a wide-range of species by changing trophic interactions, competition, epidemiology and habitat. However, direct physiological impacts of changing climates are rarely reported for endothermic species, despite being commonly reported for ectotherms. We review the evidence for changing physiological constraints on endothermic vertebrates at high temperatures, integrating theoretical and empirical perspectives on the morphology, physiology and behavior of marine birds. Potential for increasing heat stress exposure depends on changes in multiple environmental variables, not just air temperature, as well as organism-specific morphology, physiology and behavior. Endotherms breeding at high latitudes are vulnerable to the forecast, extensive temperature changes because of the adaptations they possess to minimize heat loss. Low-latitude species will also be challenged as they currently live close to their thermal limits and will likely suffer future water shortages. Small, highly-active species, particularly aerial foragers, are acutely vulnerable as they are least able to dissipate heat at high temperatures. Overall, direct physiological impacts of climatic change appear underrepresented in the published literature, but available data suggest they have much potential to shape behavior, morphology and distribution of endothermic species. Coincidence between future heat stress events and other energetic constraints on endotherms remains largely unexplored but will be key in determining the physiological impacts of climatic change. Multi-scale, biophysical modeling, informed by experiments that quantify thermoregulatory responses of endotherms to heat stress, is an essential precursor to urgently-needed analyses at the population or species level.

The ecological importance of wetlands for aerial insectivores (swifts, martins and swallows) along the Tyrrhenian coast

We studied phenology and density of migrant aerial insectivore birds (Riparia riparia, Hirundo rustica, Delichon urbicum, Apus sp.) from a coastal landscape mosaic of central Italy, in order to detect differences in habitat use and seasonal dynamics of each species. Two habitat types were surveyed: wetlands (a mosaic of reed beds and rush beds) and altered habitats, consisting of orchards and urban areas. We used the point count method from January to June, in a set of randomly selected sampling points. A comparison between all species showed that swifts reached the highest mean point density, while sand martin showed the lowest values, mainly in altered habitats. Initially, all the breeding species were numerous in wetlands; subsequently they shifted toward altered habitats (mainly used as breeding sites), where they were observed up to the end of the counts. Along the Tyrrhenian coast, wetlands are exploited as soon as these aerial foragers arrive in the study area and then shift to the surrounding altered (i.e., urbanized or land reclaimed) zones for nesting after some ten-days.

Modeling forest songbird species richness using LiDAR-derived measures of forest structure

Conservation of biodiversity requires information at many spatial scales in order to detect and preserve habitat for many species, often simultaneously. Vegetation structure information is particularly important for avian habitat models and has largely been unavailable for large areas at the desired resolution. Airborne LiDAR, with its combination of relatively broad coverage and fine resolution provides existing new opportunities to map vegetation structure and hence avian habitat. Our goal was to model the richness of forest songbirds using forest structure information obtained from LiDAR data. In deciduous forests of southern Wisconsin, USA, we used discrete-return airborne LiDAR to derive forest structure metrics related to the height and density of vegetation returns, as well as composite variables that captured major forest structural elements. We conducted point counts to determine total forest songbird richness and the richness of foraging, nesting, and forest edge-related habitat guilds. A suite of 35 LiDAR variables were used to model bird species richness using best-subsets regression and we used hierarchical partitioning analysis to quantify the explanatory power of each variable in the multivariate models. Songbird species richness was correlated most strongly with LiDAR variables related to canopy and midstory height and midstory density (R 2 = 0.204, p < 0.001). Richness of species that nest in the midstory was best explained by canopy height variables (R 2 = 0.197, p < 0.001). Species that forage on the ground responded to mean canopy height and the height of the lower canopy (R 2 = 0.149, p < 0.005) while aerial foragers had higher richness where the canopy was tall and dense and the midstory more sparse (R 2 = 0.216, p < 0.001). Richness of edge-preferring species was greater where there were fewer vegetation returns but higher density in the understory (R 2 = 0.153, p < 0.005). Forest interior specialists responded positively to a tall canopy, developed midstory, and a higher proportion of vegetation returns (R 2 = 0.195, p < 0.001). LiDAR forest structure metrics explained between 15 and 20% of the variability in richness within deciduous forest songbird communities. This variability was associated with vertical structure alone and shows how LiDAR can provide a source of complementary predictive data that can be incorporated in models of wildlife habitat associations across broad geographical extents.

Short‐term responses of birds to prescribed fire in fire‐suppressed forests of California

AbstractPrescribed fire is one tool for restoring fire‐suppressed forests, but application of fire during spring coincides with breeding and arrival of migrant birds. We examined effects of low‐severity prescribed fires on counts of birds in a managed forest in the Sierra Nevada of California immediately, 1 year, and 3–6 years after fire was applied in spring. Of 26 species analyzed, counts of 3 species increased after fire (Pacific‐slope flycatcher [Empidonax difficilis], brown creeper [Certhia americana], and American robin [Turdus migratorius]), and 6 species decreased after fire (Anna's hummingbird [Calypte anna], Hutton's vireo [Vireo huttoni], warbling vireo [Vireo gilvus], golden‐crowned kinglet [Regulus satrapa], Nashville warbler [Vermivora ruficapilla], hermit warbler [Dendroica occidentalis]). Black‐throated gray warbler (Dendroica nigrescens) increased in the first year following fire but decreased 3–6 years after fire. When grouped into guilds, habitat association and foraging guild best explained responses to fire, with the greatest changes occurring for oak‐associated species (negative), riparian‐associated species (positive), aerial foragers (positive), and bark foragers (positive). Lastly, when we compared our counts to those collected during the 1910s, changes were consistent with those predicted from fire suppression and species' affinity for burned forests, suggesting that results from contemporary fire studies should be interpreted within an ecological context that includes effects of fire suppression. We found that low‐severity prescribed fires applied in spring served to drive the bird community towards pre‐suppression conditions. © 2011 The Wildlife Society.

Optimizing inventories of diverse sites: insights from Barro Colorado Island birds

Summary 1. Diverse sites have long‐attracted ecologists, yet the overwhelming variety of species can confound attempts to enumerate species richness. Various predictive methods estimate species richness by comparing the rate at which species are first detected with the rate at which they are detected again, yielding richness estimates of known precision without exhaustive sampling. 2. While frequently used for arthropods, predictive methods are rarely applied to vertebrate surveys where species identity is often a priority. Expressing observed richness as a function of estimated richness, an estimate of survey completeness can be derived, offering the potential for inventories of standardized precision for comparison and further analysis. 3. To realize this potential, I conducted 402 h of bird surveys on Barro Colorado Island (Panama) and performed a series of retrospective analyses to address three questions: (i) How much effort is required to achieve complete inventories (maximum completeness)? (ii) What is the least amount of effort required to yield robust richness estimates (maximum efficiency)? and (iii) How much effort is required to optimize sampling, balancing completeness and efficiency? 4. Whereas the richness estimate for all species required thirty 6‐h samples to attain maximum completeness, once migrants, waterbirds and non‐forest‐dependent species were excluded, the richness of forest‐dependent residents could be estimated to the same precision with fifteen samples and to 80% completeness with four samples. 5. Of the 186 bird species detected, 70 represented unique or duplicate records, seen in only one or two sampling periods. These low detectability species were dominated by migrants (28) and raptors (14) and also included seven waterbirds, five nocturnal species and four aerial foragers, justifying the widespread practice of excluding these groups from surveys of forest assemblages. 6. In addition to demonstrating the reliability of predictive approaches, this study demonstrates the practicality of results‐based stopping rules for sampling diverse sites, especially for targeted groups of species. Combining predictive methods with targeted sampling represents an efficient and rigorous design, increasing the number of sites that can be sampled and enhancing the overall power and value of the study.

A Quantitative Analysis of Flight Feather Replacement in the Moustached Tree Swift Hemiprocne mystacea, a Tropical Aerial Forager

The functional life span of feathers is always much less than the potential life span of birds, so feathers must be renewed regularly. But feather renewal entails important energetic, time and performance costs that must be integrated into the annual cycle. Across species the time required to replace flight feather increases disproportionately with body size, resulting in complex, multiple waves of feather replacement in the primaries of many large birds. We describe the rules of flight feather replacement for Hemiprocne mystacea, a small, 60g tree swift from the New Guinea region. This species breeds and molts in all months of the year, and flight feather molt occurs during breeding in some individuals. H. mystacea is one to be the smallest species for which stepwise replacement of the primaries and secondaries has been documented; yet, primary replacement is extremely slow in this aerial forager, requiring more than 300 days if molt is not interrupted. We used growth bands to show that primaries grow at an average rate of 2.86 mm/d. The 10 primaries are a single molt series, while the 11 secondaries and five rectrices are each broken into two molt series. In large birds stepwise replacement of the primaries serves to increase the rate of primary replacement while minimizing gaps in the wing. But stepwise replacement of the wing quills in H. mystacea proceeds so slowly that it may be a consequence of the ontogeny of stepwise molting, rather than an adaptation, because the average number of growing primaries is probably lower than 1.14 feathers per wing.

Short-term effects of group-selection harvesting on breeding birds in a northern hardwood forest

We used a before-after, control-impact design (one year pre-harvest, two years post-harvest) and unlimited-radius point counts to study the effects of typical group-selection harvesting (0.5 gaps ha −1 placed near seed trees within a standard single-tree selection harvest) and intensive group-selection harvesting (4 gaps ha −1 placed on a grid with no harvesting between gaps) on the composition and abundance of breeding birds in tolerant hardwood forests in Algonquin Provincial Park, Ontario. Percent similarity between pre- and post-harvest bird communities was 5–9% lower in selection harvested stands than in reference stands. Differences in percent similarity among the three treatments were not significant, however, suggesting that the changes in the bird community in stands harvested with group selection were not substantially different than those in reference stands. Abundance of aerial foragers and tree-and-shrub nesters increased in response to typical and intensive group selection in the second year post-harvest. By contrast, bark foragers and cavity-nesters decreased in the first year post-harvest and then increased in the second year post-harvest in response to typical group selection. Abundance of 16 (73%) of 22 species was not affected by harvesting. Blue Jay ( Cyanocitta cristata), Chestnut-sided Warbler ( Dendroica pensylvanica), Least Flycatcher ( Empidonax minimus), and White-throated Sparrow ( Zonotrichia albicollis) increased in response to intensive group selection in the first or second year post-harvest, whereas Chestnut-sided Warbler, Hairy Woodpecker ( Picoides villosus), and White-throated Sparrow increased in response to typical group selection in the first or second year post-harvest. Ovenbird ( Seiurus aurocapilla) decreased slightly in response to typical group selection in the second year post-harvest. Our short-term data suggest that intensive, rather than typical, group-selection harvesting is preferred for maintaining densities of cavity-nesting birds and Ovenbird; whether these advantages continue through the remainder of the cutting cycle and beyond requires further investigation.

Resource partitioning between the breeding migrant Cyprus Wheatear, Oenanthe cypriaca, and the passage migrant Spotted Flycatcher, Muscicapa striata, in Cyprus

The foraging behaviour of the passage migrant Spotted Flycatcher, Muscicapa striata (Pallas, 1764), was compared with the breeding migrant Cyprus Wheatear, Oenanthe cypriaca (Homeyer, 1884), in Cyprus during May 2009. M. striata preferred higher perches, had shorter distances to the next perch, made more aerial sallying per minute and less perch-pounce foraging, and showed a higher overall foraging rate per minute. Based on a principal component analysis, M. striata was characterised by high perches and exclusively aerial foraging, while O. cypriaca was characterised by perch-pounce foraging and larger distances to the next perch. Despite some niche overlap, both species differed in some aspects. Six direct encounters between O. cypriaca and M. striata have been observed, and O. cypriaca was always the winner. M. striata showed a higher foraging speed which is in line with observations in resident-migrant bird assemblages in Africa, where migrants also often had a higher foraging speed. By contrast, the breeding species O. cypriaca was more flexible in its foraging strategies.