The foraging profile of a wandoo woodland avifauna in early spring

Abstract This study reports on the foraging profile of a wandoo woodland avifauna at Dryandra in Western Australia, Australia. Despite its geographical isolation, wandoo woodland shares a large number of species with woodland bird communities in eastern Australia and there are broad similarities in community foraging profiles. Insect-eating birds using ground, bark, foliage, and aerial substrates dominate eucalypt bird communities. Nectar-feeding and seed/fruit-eating guilds are important components of the Australian avifauna, but have fewer species, and vary in composition and abundance as nectar, seed, and fruit availability changes seasonally and from year to year, and from one locality to another. Despite similarities, there are also differences between the foraging profile of the wandoo avifauna and those in eastern Australia. Specifically, the wandoo avifauna is characterized by a high proportion of ground-foraging species. In addition, many wandoo woodland birds appear to spread their foraging over a wider range of substrates (i.e., ground, bark, and foliage) than eastern species. Differences in habitat structure do not explain these differences in community foraging profiles, and there may be differences in the abundance, kind, and spatial distribution of resources between different eucalypt ecosystems. Possibly the eastern communities have lost ground-dwelling components of their avifauna since European settlement, while the woodlands at Dryandra retain a more intact avifauna. The reasons why some species and not others are lost from woodlands as a result of European land management practices are discussed.     

Influences of the season and the habitat structure on the foraging ecology of two coua species in the western dry forest of Madagascar

I studied the foraging ecology of Coquerel's Coua (Coua coquereli) and Giant Coua (Coua gigas), which occur in the dry forest in west Madagascar. This kind of forest is characterised by an alternating of a dry and a rainy season. The foraging behaviour was described in several dimensions: i.e. height and proportion of perching, rate of capture (estimating the food availability), foraging techniques, substrates used, type and size of the captured prey. Their foraging behaviour was different according to the season and to the proximity of water. Habitat structure was important to take in consideration to study their foraging behaviour. They tended to use the same pattern of techniques and substrates, but differed by the proportions they used these variables and also by the possibility to climb into the dense understorey vegetation. Seasonal variation has probably an important effect on the prey availability and the nature of prey captured. The diet of both species is also discussed. I suggest that change in habitat structure and resources levels could be important to take in consideration for the conservation of these forest birds.     

Effect of increased food abundance near forest edges on flocking patterns of Coal Tit Parus ater winter groups in mountain coniferous forests

CapsuleIndividuals concentrated near forest edges in bigger social groups than in forest interiors and foraged more on pine cones which were more abundant there.

Aims To evaluate differences in food distribution between forest edges and forest interiors and their effects on the non-breeding flocking patterns of Coal Tit populations inhabiting mountain coniferous forests.

Methods We collected cone production data at forests edges and interiors in mountain pine forests located in the Pyrenees (northeast Iberian peninsula). At the same sites, we also quantified Coal Tit abundance, flocking patterns and foraging behaviour by means of paired bird surveys during autumn and early winter.

Results We recorded a larger abundance of pine cones available on trees along forest edges compared with forest interiors. Coal Tit groups were of bigger size along forest edges, although the number of social groups detected did not differ from forest interiors. Our observations on foraging behaviour supported the hypothesis that differences in flock sizes and overall abundances associated with distance to the edge are due to differences in the availability of pine cones and to the heavier use of these foraging substrates by birds along forest edges.

Conclusions Our results suggest that by changing food distribution, edge effects on pine cone production may be significantly involved in local changes in the social structure of the Coal Tit. An increase in resource heterogeneity and local population density may have important implications at a population level, such as favouring mobility of individuals searching for food resources and thus a transient life, and increasing the costs of territory defence to resident individuals.     

Food hoarding behaviour of black-capped chickadees (Poecile atricapillus ) in relation to forest edges

In temperate forests, small birds avoid the use of forest edges in adverse winter weather suggesting high foraging costs in terms of energetic requirements. Since hoarding species will often retrieve caches during adverse winter weather, they may perceive forest edges, especially exposed ones, as low quality hoarding sites. We tested whether black-capped chickadees ( Poecile atricapillus) inhabiting fragmented forests modify and reduce hoarding activity near forest edges. We also tested whether hoarding behaviour will be most affected in sites with forest edges more exposed to extreme weather. Black-capped chickadees taking food from a feeder 30 m from the nearest forest edges hoarded items mostly towards the forest interior, whereas no preference in hoarding location was observed with birds taking food from a feeder placed >100 m from the edge. Furthermore, birds avoided direct flights towards forest edges and, at sites exposed to prevailing winds, hoarding trips were shorter than at other locations. These results suggest that individuals avoid hoarding near forest edges and there, they lower their investment in terms of hoarding effort. The observed difference in hoarding behaviour was more evident near forest edges delimiting wide unforested areas than in edges delimiting narrower unforested areas. Edge exposure to prevailing winds influenced hoarding behaviour much less. We suggest that hoarding birds may partially overcome the ecological costs of habitat loss and fragmentation due to abiotic edge effects. By hoarding food away from forest edges in good weather, they may use forest interiors as low-cost retrieval sites under adverse weather.     

Spatial Variability in Species Composition in Birds and Insects

If spatial patterns of change within a habitat were similar for both vertebrates and insects, then vertebrates would provide useful surrogates for designing reserves for the conservation of invertebrates. Data from two eucalypt habitats were analysed to determine levels of habitat richness, site richness and species turnover in birds and insects. For birds the relatively low species richness and turnover indicated that sites within the habitat were similar in composition. In wet eucalypt forests Diptera were very speciose with over 1,000 morphospecies sorted. Species turnover was slightly higher than for birds, indicating a large number of species change from site to site. In dry eucalypt woodland, insects trapped through the winter months were not speciose but turnover between sites was very large. This suggests reserves designed to conserve insects may need to be larger than for birds in order to include the high site variability and richness of insect communities.Spatial patterns of birds and insects were investigated further, to determine if sites that were closer together were more similar for both birds and insects. No patterns were found for birds in either habitat suggesting birds are not responding to changes in the environment at this scale. Diptera in wet eucalypt forest showed higher similarity between close sites than distant sites, while for winter insects in dry eucalypt woodland the relationship was significant when two outlier points were removed. Overall, birds are not good surrogates for insects in either habitat as no relationship between birds and insects in site-to-site similarity was found.     

Foraging Patch Selection in Winter: A Balance between Predation Risk and Thermoregulation Benefit

In winter, foraging activity is intended to optimize food search while minimizing both thermoregulation costs and predation risk. Here we quantify the relative importance of thermoregulation and predation in foraging patch selection of woodland birds wintering in a Mediterranean montane forest. Specifically, we account for thermoregulation benefits related to temperature, and predation risk associated with both illumination of the feeding patch and distance to the nearest refuge provided by vegetation. We measured the amount of time that 38 marked individual birds belonging to five small passerine species spent foraging at artificial feeders. Feeders were located in forest patches that vary in distance to protective cover and exposure to sun radiation; temperature and illumination were registered locally by data loggers. Our results support the influence of both thermoregulation benefits and predation costs on feeding patch choice. The influence of distance to refuge (negative relationship) was nearly three times higher than that of temperature (positive relationship) in determining total foraging time spent at a patch. Light intensity had a negligible and no significant effect. This pattern was generalizable among species and individuals within species, and highlights the preponderance of latent predation risk over thermoregulation benefits on foraging decisions of birds wintering in temperate Mediterranean forests.     

Changes in the flocking behaviour of wintering English titmice with time,weather and supplementary food

Over the course of one winter, the food supply of birds living in a deciduous woodland in southern England was supplemented and unsupplemented during alternating periods. In the presence of substantial predation pressure from hawks, the sociality of blue tits, Parus caeruleus, and great tits, P. major, showed significant partial correlations with several weather and temporal factors when the woodland was unsupplemented. Such correlations between social behaviour and abiotic factors diminished significantly when the birds had access to extra food. Blue tits and great tits without access to supplemental food flocked significantly more often with other species while foraging than when they were food-supplemented. Long-tailed tits, Aegithalos caudatus, ignored the artificial food and foraged in mixed-species flocks to the same extent in both unsupplemented and food-supplemented periods. Results disprove the hypothesis that mixed-species foraging groups are caused by increased predation protection alone, and they support the hypotheses that mixed-species foraging groups are caused by increased foraging efficiency alone or by a combination of increased foraging efficiency and increased protection from predators.     

东北山地次生林鸟类多样性的研究

山地次生林是东北地区半山区重要的生态环境。随着森林的采伐,次生林越来越多,与人类的关系也越来越密切。有关次生林鸟类多样性的研究,国内报道甚少。我们于1983—1984年4—7月在吉林省蛟     

Persistence of the threatened Knysna warbler Bradypterus sylvaticus in an urban landscape: do gardens substitute for fire?

Food resources can limit populations of insectivorous birds. Previous studies have shown strong correlations between bird population densities and their invertebrate food, with declining populations being attributed to loss of prey. This might also be the case for the threatened Knysna warbler (Bradypterus sylvaticus), which in the last 20 years has declined precipitously on the Cape Peninsula, South Africa. The bird is abandoning natural, protected forests, retreating to narrow belts of suburban, riverine woodland with dense, tangled understoreys. The potential invertebrate food availability in natural forests and suburban woodland was assessed against what is known of the bird’s preferred prey. The invertebrate food resource spectrum and abundance were determined using three sampling techniques in both natural forest and suburban woodland. Despite greater overall abundance of invertebrates in suburban woodland, the warbler’s preferred prey items were equally abundant in both habitats. This suggests that reduced food supply does not explain abandonment of natural forests by the warbler. Rather, it is concluded that the availability of suitable nesting substrata, which are more abundant in suburban woodland, has driven the biotope shift. This is an unusual case of a localized and threatened bird species faring better under transformed conditions than in natural habitats.     

Prescribed Fire Effects on Wintering,Bark-Foraging Birds in Northern Arizona

ABSTRACT We examined effects of prescribed fire on 3 wintering, bark-foraging birds, hairy woodpeckers (Picoides villosus), pygmy nuthatches (Sitta pygmaea), and white-breasted nuthatches (S. carolinensis), in ponderosa pine (Pinus ponderosa) forests of northern Arizona, USA. During winters of 2004–2006, we compared bird density, foraging behavior, and bark beetle activity among burned treatment and unburned control units. Hairy woodpecker density was 5 times greater in burn units, whereas white-breasted nuthatches and pygmy nuthatches had similar densities between treatments. Compared to available trees, trees used by foraging hairy woodpeckers had 9 times greater odds of having bark beetles in control units and 12 times greater odds in burn units. Tree diameter appeared to be the main factor bark-foraging birds used in selecting winter foraging trees. Our results suggest that forest managers can use prescribed fire treatments without detrimental effects to wintering nuthatches, while providing additional food to hairy woodpeckers.     

Foraging ecology of an assemblage of birds in lowland rainforest in northern Queensland

This paper presents an analysis of the foraging ecologies and hence means of partitioning resources amongst the twenty-eight most conspicuous species of birds in lowland tropical rainforest at Lacey's Creek, North Queensland. The height and site of foraging and the type of behaviour used by the species were compared. The height at which species foraged appeared to be more important for separating species than the site of foraging or the behaviour used. There appeared to be a greater proportion of species with generalized foraging behaviour at Lacey's Creek than in bird communities in the neotropics. Frugivorous species had very similar foraging ecologies but there were differences in the species of fruit eaten by some species. There were seasonal shifts in foraging by some species. It is postulated that the relative shortage of terrestrial species at Lacey's Creek compared with highland forest in North Queensland is due to the harsh dry season in the lowlands. The structure of this bird community appeared to be strongly affected by seasonality of climate.     

Intersexual niche segregation among three bark-foraging birds of eucalypt forests

All three species of specialized bark-climbing birds in eucalypt forests of north-eastern New South Wales exhibited sexual differences in their foraging behaviour. The degree of these differences was weakest in the least social species and strongest in the most social species, suggesting that intersexual niche segregation is an adaptation to reduce intraspecific competition for food. In the least social White-throated Treecreeper, the slightly longer-billed males foraged on dead branches more than females only during the breeding season when pair members were forced to share the same area. In the group-living Red-browed Treecreeper and Varied Sittella, males foraged lower and used rough-barked trunks and limbs more than females throughout the year. Sexual differences in the foraging substrates of Sittellas may have been related to sexual dimorphism of the bill, but in the monomorphic Red-browed Tree-creeper, male dominance was probably important. Some evidence suggests that further subdivision of the niche may occur in the highly social Sittella along the vertical dimension according to age and/or reproductive status. This report argues that intersexual niche segregation is just as likely to develop under conditions of increased interspecific competition as under reduced competition.     

Resource partitioning among three woodpecker species Dendrocopos spp. during the breeding season

Food composition, prey size utilization and foraging behaviour of three sympatric woodpecker species ( Dendrocopos major, D. medius, D. minor ) were studied in an oak forest near Budapest during the breeding season in 1983 and 1984. Considering these three aspects of feeding, the great spotted woodpecker is a generalist species. Food composition of this species resembled the arthropod supply on the bark of trees more than those of the other two species. The bark of the trees seems to be a relatively unproductive microhabitat in the breeding season, so woodpecker species use, to different degrees, the food supply of the foliage as well. The food and the foraging behaviour of the middle spotted woodpecker show that this species feeds on prey living both on barks and in the foliage; it occupies-an intermediate position between the great and the lesser spotted woodpeckers. Prey size did not correlate with predator size suggesting that woodpeckers adapted not to the summer resources but rather the winter ones.     

Patterns of resource use in an assemblage of birds in the canopy of a temperate alluvial forest

In our study, we assessed patterns of resource use in an assemblage of birds by observing their foraging behaviour from a crane in the canopy of a temperate alluvial forest. We selected 12 bird species and addressed seasonal changes in feeding activity during a 2-month period in spring focussing on average staying time and utilisation of crown strata in two tree species, the common oak (Quercus robur) and the sycamore maple (Acer pseudoplatanus). We further examined ecological characteristics of the trees (i. e., crown density) that are likely to influence resource use in birds. The selected birds differed in their preference for the tree species. Most birds preferred common oaks. This preference was probably associated with higher food abundance related to substrate characteristics (i.e., roughness of bark) which offer more microhabitats for arthropods and thus permit higher densities of potential prey. Some bird species switched feeding preferences within the study period from sycamore maples to common oaks in association with tree phenology. We found two main foraging techniques. All birds searched for prey at short distance (≤50 cm) and gleaned food from substrate except the Pied Flycatcher that foraged by hovering and searched over longer distances (>50 cm). Overall, we demonstrate in our study that canopy access with mobile crane systems provides excellent opportunities to observe canopy birds and enables detailed analysis of their foraging behaviour. The main result of our study reveals fine-grained resource partitioning of birds within the canopy as an important factor structuring assemblages, with species-specific and in part also seasonal differences in stratification and substrate use.     

Intersexual segregation in foraging microhabitat use by Magellanic Woodpeckers (Campephilus magellanicus): Seasonal and habitat effects at the world's southernmost forests

Animals facing seasonal food shortage and habitat degradation may adjust their foraging behaviour to reduce intraspecific competition. In the harsh environment of the world's southernmost forests in the Magellanic sub‐Antarctic ecoregion in Chile, we studied intersexual foraging differences in the largest South American woodpecker species, the Magellanic Woodpecker (Campephilus magellanicus). We assessed whether niche overlap between males and females decrease when food resources are less abundant or accessible, that is, during winter and in secondary forests, compared to summer and in old‐growth forests, respectively. We analysed 421 foraging microhabitat observations from six males and six females during 2011 and 2012. As predicted, the amount of niche overlap between males and females decreased during winter, when provisioning is more difficult. During winter, males and females (i) used trees with different diameter at breast height (DBH); (ii) fed in trunk sections with different diameters; and (iii) fed at different heights on tree trunks or branches. Vertical niche partitioning between sexes was found in both old‐growth and secondary forests. Such a niche partitioning during winter may be a seasonal strategy to avoid competition between sexes when prey resources are less abundant or accessible. Our results suggest that the conservation of this forest specialist, dimorphic and charismatic woodpecker species requires considering differences in habitat use between males and females.     

Raiders of the lost bark: orangutan foraging strategies in a degraded landscape

Deforestation is rapidly transforming primary forests across the tropics into human-dominated landscapes. Consequently, conservationists need to understand how different taxa respond and adapt to these changes in order to develop appropriate management strategies. Our two year study seeks to determine how wild Sumatran orangutans (Pongo abelii) adapt to living in an isolated agroforest landscape by investigating the sex of crop-raiders related to population demographics, and their temporal variations in feeding behaviour and dietary composition. From focal animal sampling we found that nine identified females raided cultivated fruits more than the four males. Seasonal adaptations were shown through orangutan feeding habits that shifted from being predominantly fruit-based (56% of the total feeding time, then 22% on bark) to the fallback food of bark (44%, then 35% on fruits), when key cultivated resources such as jackfruit (Artocarpus integer), were unavailable. Cultivated fruits were mostly consumed in the afternoon and evening, when farmers had returned home. The finding that females take greater crop-raiding risks than males differs from previous human-primate conflict studies, probably because of the low risks associated (as farmers rarely retaliated) and low intraspecific competition between males. Thus, the behavioral ecology of orangutans living in this human-dominated landscape differs markedly from that in primary forest, where orangutans have a strictly wild food diet, even where primary rainforests directly borders farmland. The importance of wild food availability was clearly illustrated in this study with 21% of the total orangutan feeding time being allocated to feeding on cultivated fruits. As forests are increasingly converted to cultivation, humans and orangutans are predicted to come into conflict more frequently. This study reveals orangutan adaptations for coexisting with humans, e.g. changes in temporal foraging patterns, which should be used for guiding the development of specific human-wildlife conflict mitigation strategies to lessen future crop-raiding and conflicts.     

Small-scale variability in a mosaic tropical rainforest influences habitat use of long-tailed macaques

Pristine habitats have generally been considered to be the most important ecological resource for wildlife conservation, but due to forest degradation caused by human activities, mosaics of secondary forests have become increasingly prominent. We studied three forest types in a mosaic tropical forest consisting of short secondary forest (SS), tall secondary forest (TS) and freshwater swamp forest (SF). These forests differed in stand structure and floristic composition, as well as phenological productivity of fruits, flowers and young leaves. We examined habitat use of long-tailed macaques (Macaca fascicularis) in relation to indices of phenological activity. The macaques used the SS for feeding/foraging more than the TS and the SF. This was because the SS had higher productivity of fruit, which is a preferred food resource for macaques. Stem densities of young leaves in the SS and the TS also influenced habitat use, as they provided more clumped resources. Use of SF was limited, but these forests provided more species-rich resources. Our results showed that M. fascicularis responded to small-scale variability in phenological activity between forest types found in a heterogeneous mosaic forest, with young secondary regrowth forests likely providing the most important food resources. Mosaic landscapes may be important as they can buffer the effects of temporal food resource variability in any given forest type. In our increasingly human-altered landscapes, a better understanding of the role of secondary forest mosaics is crucial to the conservation and management of wildlife habitats and the animals they support.     

Acquisition of foraging skills by Heron Island Silvereyes Zosterops later alis chlorocephala

Age-related differences in foraging efficiency and behaviour were investigated in a population of colour-ringed Silvereyes Zosterops lateralis . First-year birds were less efficient foragers than older birds with second-year birds being intermediate. First- and second-year birds had lower success rates than older birds overall, and for most capture techniques and substrates. First-year birds never attempted breeding while about half of the second-year birds and all of the older birds did. Both learning and selection effects may have been involved in causing the age-related differences in foraging behaviour. Foraging skills appear to improve during the first 2 years of life and selection could remove the least efficient foragers from the population in winter when food is short. That second-year birds, some of which had already attempted breeding, were not significantly more efficient foragers than first-year birds suggests that reproduction is not delayed until adult levels of foraging efficiency have been attained.     

Habitat selection in the White-plumed Honeyeater and the Fuscous Honeyeater at an area of sympatry

Multivariate analysis on 15 habitat variables and quantitative data on foraging and interactive behaviour were used to investigate habitat selection in the White-plumed Honeyeater (Lichenostomus penicillatus) and the Fuscous Honeyeater (Lichenostomus fuscus) at an area of sympatry in woodland in New England Tablelands. Thirty-nine plots from four sites were used to examine significant differences in habitat utilization during the breeding period. The White-plumed Honeyeater associated strongly with narrow belts of riverine Casuarina while the Fuscous Honeyeater was associated with Eucalyptus in the extensive eucalypt woodland. The narrow ecotone was used by both species, but the two occurred together only in an extremely narrow zone. Changes in foraging activities were observed between this overlap zone and non-overlap zone. Both niche breadth and overlap in relation to four measures of foraging were reduced in plots where species were in joint occurrence compared with where they were not, although overlap in most measures of foraging remained high. The number of encounters between the two highly aggressive and abundant species was not great. Thus, the species appear generally to avoid each other. The observed spacing pattern may result from prior experience of intense aggressive interactions. Distinct habitat features could provide easily recognized cues for the maintenance of local horizontal separation. Other factors such as slight differences in morphology, habitat preference, foraging and physiology may enhance differences in habitat selection.     

Bird communities of dry forests and oak woodland of western Mexico

Bird species-richness and densities were studied in spring and autumn of 1991 and 1992 in dry forest and oak woodland in western Mexico. Classification of the vegetation resulted in the identification of six dry forest types: from thorn forests, dominated by Acacia , through broad-leaved tree forest (typical dry forest of western Mexico) and small-leaved tree forest to Ipomoea forest. Oak woodland and mixed woodland, which are a transition between dry forest and the more mesic oak woodland, formed two further forest types. In the study area as a whole, bird densities were higher in autumn, following the rainy season, than in spring, which is the dry season, and the beginning of the breeding season. Densities in the two autumns were very similar (mean 93 ± 7.8 birds per 2.8 ha) but differed significantly between spring 1991 (57 ± 2.2 per 2.8 ha) and spring 1992 (70 ± 3.2 per 2.8 ha), possibly due to unseasonal rain in 1992. In autumn, bird densities were highest in thorn forests and lowest in broad-leaved tree forests and oak woodland. In spring 1991, bird densities were highest in Prosopis thorn forest and mixed woodland, and lowest in oak woodland. Bird species-richness was low in oak woodland, in both seasons, and high in mixed woodland and Ipomoea forest in spring. Bird species composition between forest types was more similar in the spring than autumn. The spring similarity in species composition is explained by the presence of generalist species in times of food scarcity during the dry season, and by the homogeneity of the predominantly leafless vegetation. Comparison with the bird species composition of a dry forest in Venezuela and the Pacific coast of Mexico indicates that the sites in the present study have an intermediate number of species. Although the present study recorded a smaller number of bird species than on the Pacific coast, 16 were different, expanding the total for Mexican dry forest by 14% from 118 to 134.