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1.
Resource defense behavior is often explained by the spatial and temporal distribution of resources. However, factors such as competition, habitat complexity, and individual space use may also affect the capacity of individuals to defend and monopolize resources. Yet, studies frequently focus on one or two factors, overlooking the complexity found in natural settings. Here, we addressed defense and monopolization of nectar feeders in a population of free‐ranging ruby‐throated hummingbirds marked with passive integrated transponder (PIT tags). Our study system consisted of a 44 ha systematic grid of 45 feeders equipped with PIT tag detectors recording every visit made at feeders. We modeled the number of visits by competitors (NVC) at feeders in response to space use by a focal individual potentially defending a feeder, number of competitors, nectar sucrose concentration, and habitat visibility. Individuals who were more concentrated at certain feeders on a given day and who were more stable in their use of the grid throughout the season gained higher exclusivity in the use of those feeders on that day, especially for males competing against males. The level of spatial concentration at feeders and its negative effect on NVC was, however, highly variable among individuals, suggesting a continuum in resource defense strategies. Although the apparent capacity to defend feeders was not affected by competition or nectar sucrose concentration, the level of monopolization decreased with increasing number of competitors and higher nectar quality. Defense was enhanced by visibility near feeders, but only in forested habitats. The reverse effect of visibility in open habitats was more difficult to interpret as it was probably confounded by perch availability, from which a bird can defend its feeder. Our study is among the first to quantify the joint use of food resource by overlapping individuals unconstrained in their use of space. Our results show the importance of accounting for variation in space use among individuals as it translated into varying levels of defense and monopolization of feeders regardless of food resource distribution.  相似文献   

2.
ABSTRACT Radio frequency identification (RFID) technology can be used to implement automated bird‐monitoring systems and, therefore, could be of use to field ornithologists. However, the cost of a large‐scale RFID network can be prohibitive for those with limited research budgets. We describe a simple RFID reader/data logger that can be constructed for less than $40 (excluding tools and a battery). This device can be mounted on birdfeeders, nest boxes, nests, or any location repeatedly visited by birds fitted with small RFID tags (i.e., passive integrated transponder or PIT tags). To demonstrate the potential of this low‐cost RFID reader, we monitored the use of feeders by wintering songbirds in central New York and generated a data set consisting of more than 500,000 feeder visits over 5 mo. These data revealed several interesting behaviors, including high visitation rates by some individuals (>200 visits per day), long‐distance movements between feeders (emigration and immigration), and species‐specific patterns of feeder use. Although the system performed well in relatively harsh winter conditions, occasional battery failures and water damage led to some loss of data. Nevertheless, we amassed over 8000 h of monitoring by investing approximately 6 h of labor per week. In addition to recording tag numbers and time stamps, the RFID reader can interface with sensors and actuators, permitting the collection of additional data (such as body mass) and allowing control of motors or solenoids to interact with targeted individuals. RFID technology has great potential for use in a variety of ornithological studies, and we hope our device helps make this technology more accessible.  相似文献   

3.
The marked range shifts seen with global warming suggest that ranges are limited by temperature. Other findings, however, suggest winter survival is directly tied to food availability. We studied Carolina wrens Thryothorus ludovicianus at the northern edge of their range to understand the roles of temperature and food in limiting this species. We established 21 transects over 3 habitats (residential, city park, and rural) with varying degrees of human influence on temperature and food supply. The three habitat types showed variations in wren density, temperature, and feeder presence. While wren densities showed similar seasonal patterns in all habitats, significantly higher densities of birds were observed in the city park and residential habitats. Post‐winter densities of Carolina wrens were predicted by the presence of bird feeders, and not by January mean minimum temperatures. Our findings suggest the winter range limits for endotherms is more directly related to food supply, and only indirectly related to temperature. Therefore supplemental feeding and other changes in food supply may modify the range shifts predicted from temperature changes alone.  相似文献   

4.
Supplementary feeding of birds, particularly in urban areas, is often associated with increased population size and fecundity. In the UK, the non‐native Grey Squirrel Sciurus carolinensis is common in rural and urban habitats. It exploits supplementary feeders and may induce interference competition by excluding birds, but empirical evidence of this is unavailable. Using controlled model presentation experiments, we demonstrate that Grey Squirrels could reduce bird use of supplementary feeders and induce interference competition. Total bird resource use was reduced by 98% and most species exhibited similar sensitivities. The likelihood and magnitude of interference competition will depend on how rapidly displaced birds find alternative food sources; it will be greatest where there are high Grey Squirrel densities and few supplementary feeders. Other studies suggest that supplementary feeding increases Grey Squirrel numbers, and the species is also predicted to expand its non‐native range across most of Europe. Our data indicate that Grey Squirrels may eventually alter the net effect of supplementary feeding on bird populations across the European continent; increased use of squirrel‐proof feeders may help to minimize such effects.  相似文献   

5.
In countries such as the UK, USA and Australia, approximately half of all households provide supplementary food for wild birds, making this the public's most common form of active engagement with nature. Year‐round supplementary feeding is currently encouraged by major conservation charities in the UK as it is thought to be of benefit to bird conservation. However, little is understood about how the provision of supplementary food affects the behaviour and ecology of target and non‐target species. Given the scale of supplementary feeding, any negative effects may have important implications for conservation. Potential nest predators are abundant in urban areas and some species frequently visit supplementary feeding stations. We assess whether providing supplementary food affects the likelihood of nest predation in the vicinity of the feeder, by acting as a point attractant for potential nest predators. We provided feeding stations (empty, peanut feeder, peanut feeder with guard to exclude potential nest predators) in an area of suburban parkland in the UK and monitored the predation rate of eggs placed in artificial nests located at distances that replicated the size of typical suburban gardens. Nest predators (Magpies Pica pica, Grey Squirrels Sciurus carolinensis) were frequent visitors to filled feeders, and predation caused by Magpies, European Jays Garrulus glandarius and Grey Squirrels was significantly higher when nests were adjacent to filled feeders. The presence of a feeder guard did not significantly reduce nest predation. As supplementary feeding is becoming increasingly common during the breeding season in suburban habitats, we suggest that providing point attractants to nest predators at this time may have previously unconsidered consequences for the breeding success of urban birds.  相似文献   

6.
Annual and seasonal trends in the use of garden feeders by birds in winter   总被引:3,自引:0,他引:3  
Provision of bird food in gardens is a common activity that may provide an alternative food source to birds in winter. Long-term survey data recording the weekly presence of all bird species using garden feeders in the winter were analysed to see if there was any evidence of trends in feeder use between 1970 and 2000 and whether these trends were correlated with breeding bird population trends. Of 41 species analysed, 21 showed significant increases in occurrence at garden feeders between 1970 and 2000. Many of these increases were evident only in the last 10 years. Several species showed significant positive correlations between trends in winter garden use and trends in relative population size in the previous breeding season. This was especially the case for species with population change (either increase or decrease) of the greatest magnitude. There was no evidence that seasonal shifts in garden feeder use were associated with population change in any species. Temperature was an important predictor of garden use but could not explain the year-to-year trends. However, as the number of feeding stations had increased over time the response of birds to the greater food availability in gardens may have been responsible for the widespread increases in occurrence of several species.  相似文献   

7.
Increasing evidence suggests that global warming significantly alters the range and phenology of plants and animals. Whereas thermophilous species usually benefit from rising temperatures, the living conditions of taxa adapted to cooler or continental climates are deteriorating. The woodland ringlet butterfly, Erebia medusa Fabricius (Lepidoptera: Nymphalidae) is one of the continental species that are supposed to be adversely affected by climate change, especially by rising winter temperatures. Here, we conduct an explorative study on the effects of low, moderate, and high winter temperatures on the pre‐adult and adult stages of E. medusa in a laboratory experiment. Compared to the two other temperature regimes, the warm winter treatment led to an earlier termination of diapause and higher larval weights at the end of the winter, but significantly lower survival rates. The after‐effects of the warm treatment included lower weight of the pupae and adult females, shorter forewings of adult males, and earlier emergence of both adult males and females. In natural environments, which are characterized by a much greater thermal variability and a much higher frequency of soil freeze‐thaw events compared to our experiment, the effects of rising winter temperatures might be stronger than in this study. Thus, we conclude that warmer winters pose a non‐negligible long‐term threat to E. medusa.  相似文献   

8.
Population‐level studies of how tit species (Parus spp.) track the changing phenology of their caterpillar food source have provided a model system allowing inference into how populations can adjust to changing climates, but are often limited because they implicitly assume all individuals experience similar environments. Ecologists are increasingly using satellite‐derived data to quantify aspects of animals' environments, but so far studies examining phenology have generally done so at large spatial scales. Considering the scale at which individuals experience their environment is likely to be key if we are to understand the ecological and evolutionary processes acting on reproductive phenology within populations. Here, we use time series of satellite images, with a resolution of 240 m, to quantify spatial variation in vegetation green‐up for a 385‐ha mixed‐deciduous woodland. Using data spanning 13 years, we demonstrate that annual population‐level measures of the timing of peak abundance of winter moth larvae (Operophtera brumata) and the timing of egg laying in great tits (Parus major) and blue tits (Cyanistes caeruleus) is related to satellite‐derived spring vegetation phenology. We go on to show that timing of local vegetation green‐up significantly explained individual differences in tit reproductive phenology within the population, and that the degree of synchrony between bird and vegetation phenology showed marked spatial variation across the woodland. Areas of high oak tree (Quercus robur) and hazel (Corylus avellana) density showed the strongest match between remote‐sensed vegetation phenology and reproductive phenology in both species. Marked within‐population variation in the extent to which phenology of different trophic levels match suggests that more attention should be given to small‐scale processes when exploring the causes and consequences of phenological matching. We discuss how use of remotely sensed data to study within‐population variation could broaden the scale and scope of studies exploring phenological synchrony between organisms and their environment.  相似文献   

9.
Juli Broggi  Esa Hohtola  Kari Koivula 《Ibis》2021,163(1):260-267
The plastic regulation of internal energy reserves is acknowledged as the main adaptive response to winter conditions of resident small birds in northern latitudes, a strategy that may be altered whenever human‐supplemented food is available. We investigated the effects of supplementary feeding on the energy management strategy of two wild passerine species, the Willow Tit Poecile montanus and Blue Tit Cyanistes caeruleus, wintering in boreal conditions by measuring body mass and the energy cost of living, i.e. basal metabolic rate. Individuals of both species were heavier, larger and exhibited a higher energy cost of living when captured at the feeders than were individuals captured away from feeders. Fed Willow Tits expended more energy in maintenance, although this difference disappeared once mass was accounted for. Conversely, Blue Tits at feeders had higher mass‐adjusted energy cost of living, but only at low ambient temperatures. The results indicate that winter feeding has species‐specific effects on overall energy management strategy and modifies the response to environmental conditions of wintering passerines.  相似文献   

10.
Knowledge of the latitudinal patterns in biotic interactions, and especially in herbivory, is crucial for understanding the mechanisms that govern ecosystem functioning and for predicting their responses to climate change. We used sap‐feeding insects as a model group to test the hypotheses that the strength of plant–herbivore interactions in boreal forests decreases with latitude and that this latitudinal pattern is driven primarily by midsummer temperatures. We used a replicated sampling design and quantitatively collected and identified all sap‐feeding insects from four species of forest trees along five latitudinal gradients (750–1300 km in length, ten sites in each gradient) in northern Europe (59 to 70°N and 10 to 60°E) during 2008–2011. Similar decreases in diversity of sap‐feeding insects with latitude were observed in all gradients during all study years. The sap‐feeder load (i.e. insect biomass per unit of foliar biomass) decreased with latitude in typical summers, but increased in an exceptionally hot summer and was independent of latitude during a warm summer. Analysis of combined data from all sites and years revealed dome‐shaped relationships between the loads of sap‐feeders and midsummer temperatures, peaking at 17 °C in Picea abies, at 19.5 °C in Pinus sylvestris and Betula pubescens and at 22 °C in B. pendula. From these relationships, we predict that the losses of forest trees to sap‐feeders will increase by 0–45% of the current level in southern boreal forests and by 65–210% in subarctic forests with a 1 °C increase in summer temperatures. The observed relationships between temperatures and the loads of sap‐feeders differ between the coniferous and deciduous tree species. We conclude that climate warming will not only increase plant losses to sap‐feeding insects, especially in subarctic forests, but can also alter plant‐plant interactions, thereby affecting both the productivity and the structure of future forest ecosystems.  相似文献   

11.
  1. Although considered a key functional trait, little is known about how zooplankton feeding mode affects top‐down regulation of phytoplankton communities. Indeed, copepods are expected to promote the dominance of toxic phytoplankton by selective removal of their edible competitors; however, empirical evidence comparing the effect among calanoid and cyclopoid copepods is lacking.
  2. We compared the top‐down effects of two copepods with contrasting feeding modes—the calanoid Notodiaptomus iheringi (current feeder) and the cyclopoid Thermocyclops decipiens (ambush feeder) — on the relative and absolute biomass of the filamentous cyanobacterium Raphidiopsis raciborskii co‐cultured with the nutritious eukaryotic phytoplankton Cryptomonas obovata in a week‐long laboratory assay.
  3. The current feeder had a stronger top‐down effect on the biomass of both prey throughout the experiment, with mass‐specific clearance rates 3–5× higher than ambush feeder. By the end of the experiment, the current feeder significantly reduced cyanobacteria biomass compared to controls while the ambush feeder did not. During the week‐long experiment, the current feeder switched from grazing on edible prey to cyanobacteria as the former became less abundant.
  4. Contrary to expectation, neither of the copepod species promoted cyanobacterial dominance by the end of the experiment. This is because both grazers, but especially the current feeder, initially increased but subsequently decreased the relative contribution of cyanobacteria to total phytoplankton biomass. Moreover, both copepods decreased the length of cyanobacteria filaments by c. 70%
  5. Current feeders can switch from edible prey to cyanobacteria when the abundance of shortened filaments surpasses the abundance of edible prey. While top‐down regulation of phytoplankton can be stronger for current feeding copepods, ambush feeding copepods can have a significant role during blooms by shortening cyanobacterial filaments. Hence, the broader role of contrasting copepod feeding traits on phytoplankton communities merits further study.
  相似文献   

12.
13.
Plant–pollinator interactions are critical to ecosystems. However, when artificial nectar feeders are available in an area, they could draw pollinators away from plants. We tested the effects of artificial nectar feeders in an Ecuadorian cloud forest on four aspects of bat–plant interactions: (1) bat relative abundance; (2) bat pollen loads; (3) flower visitation rates, and (4) breeding success of a bat‐pollinated species (Burmeistera glabrata). We divided the study site into areas close to (~30 m) and far from (~500 m) three different feeder sites. At each distance, we captured nectar bats (Anoura caudifer, Anoura cultrata, and Lonchophylla robusta) to estimate their relative abundance and to collect pollen from fur and fecal samples. We also videotaped flowers to estimate bat visitation rates and recorded different breeding success variables of B. glabrata. We found that areas close to feeders have higher relative bat abundance by a factor of 40. In spite of this, the presence of feeders did not affect bat pollen loads, nor the flower visitation rates and breeding success of B. glabrata. Interestingly, there were differences in pollen loads between the three bat species, in that L. robusta individuals rarely carried pollen and were only captured near feeders.  相似文献   

14.
The Hillesden experiment, established in 2005/2006 to test the delivery of biodiversity benefits under Environmental Stewardship, covers c. 1000 ha of arable farmland in central lowland England. It is a randomized block experiment with five replicates of three treatments: (1) CC: cross compliance, the control; (2) ELS: 1% of land removed from production for wildlife habitat provision; and (3) ELS‐X: 5% of land used for wildlife habitat, each treatment being applied to contiguous areas of 70–80 ha. Bird usage of winter food patches, comprising three different seed mixes, was monitored through the winter and was also related to seed yield. Winter and breeding season bird/territory abundance was recorded before and after the provision of the winter food patches. Bird use of the patches differed between seed mixes. There was large variation between individual patches in both seed yield and bird numbers and between individual bird species in their use of different seed mixes, suggesting that the availability of a range of patch types would be beneficial. Use of all patch types declined sharply in late January to February, indicating depletion and/or inability of birds to access shed seed. Winter bird abundance at a farm scale for all species combined, granivorous species and nine individual species increased for all monitored species when seed patches were available. At a treatment level, the increases tended to be greater in ELS‐X, where most of the patches were located. In the breeding season at a farm scale, the numbers of territories for all species combined and granivorous species increased significantly when seed patches had been available in the previous winter. There was little evidence of a treatment‐scale response. The provision of winter food appeared to increase winter bird abundance and to follow on into an overall increase in the breeding population, but if the latter effect is to be reflected elsewhere, this requires that sufficient breeding habitat is available to accommodate an increase.  相似文献   

15.
Supplementary food given to birds can have contemporary effects by reducing the risk of starvation, increasing survival and altering movements and reproductive performance. There is, however, a widely held perception that birds benefit from extra food over winter, but that it is better that they 'look after themselves' during breeding. Here we describe a landscape-scale experiment showing for the first time that the effects of increasing food availability only during the winter can be carried over to the subsequent breeding season. Even though food supplementation stopped six weeks prior to breeding, birds living on sites provisioned over winter had advanced laying dates and increased fledging success compared with birds living on unprovisioned sites. Thus, supplemental feeding of wild birds during winter, in a manner mimicking householders provisioning in gardens and backyards, has the potential to alter bird population dynamics by altering future reproductive performance. With levels of bird feeding by the public continuing to increase, the impacts of this additional food supply on wild bird populations may be considerable.  相似文献   

16.
We examined the feasibility of automating the collection of hummingbird mass data facilitated by low‐cost, low‐power radio frequency identification (RFID) technology. In a field study in southern Ontario, wild hummingbirds were captured, subcutaneously implanted with passive integrated transponder (PIT) tags, and released over a three‐year period. Tagged hummingbirds were detected at specially designed feeder stations outfitted with low‐cost, low‐power RFID readers coupled with a perch secured to a digital balance. When tagged birds visited the feeder, transponder detection initiated the recording of the perched hummingbird's mass at regular intervals continuing as long as the bird remained. This permitted a nearly continuous record of mass during each visit. Mass data collected from tagged hummingbirds showed consistent trends at multiple temporal scales: the individual feeder visit, single days, and even whole seasons. These results further confirm that RFID technology is safe for use in the smallest birds. The effective detection range is a function of RFID reader power, antenna, and tag size. Yet, we find that careful arrangement of feeders and detectors allows for reliable detection even when detection range is low. When coupled with additional technologies, such as a precision electronic balance, this approach can yield robust serial measures of physiological parameters such as mass, an indicator of energy balance over time.  相似文献   

17.
Wild bird feeding often results in high densities of birds, potentially facilitating transmission of disease. Wild birds are major reservoirs of many zoonotic diseases, and although a number of avian disease outbreaks have been linked to bird feeders, urban bird‐feeding and its role in disease systems remains poorly studied. We examined the impacts of typical supplementary feeding practices on the health status of feeder‐visiting birds at experimental feeding stations in an urban area of New Zealand. Over an 18‐month period, we screened birds captured at feeding and non‐feeding properties for three pathogens and four groups of parasites to determine whether feeding altered disease dynamics. We also assessed body condition. All pathogens and parasites were detected in at least one garden bird species. Feeding stations tested positive for Salmonella enterica Typhimurium on ~7% of occasions, confirming that structures used in feeding are a potential transmission pathway. Feeding influenced some parasite infection parameters; these effects varied among host species. In silvereyes Zosterops lateralis, helminth prevalence and abundance were lower at feeding properties compared to non‐feeding properties. In contrast, Eurasian blackbirds Turdus merula at feeding properties had a higher abundance of helminths. House sparrows Passer domesticus at feeding properties had a higher abundance of feather lice. Furthermore, our feeding regime significantly affected body condition in house sparrow and silvereye, though no associations between parasite parameters and body condition indices were found. Our results demonstrate that feeding practices can have varied effects on avian health, including no observable effects for some disease agents in some host species. Disease risks are present, however, thus understanding and reducing these risks should be a key goal for all stakeholders to protect birds that use feeders and other wildlife.  相似文献   

18.
Piscivorous birds frequently display sex‐specific differences in their hunting and feeding behavior, which lead to diverging impacts on prey populations. Cormorants (Phalacrocoracidae), for example, were previously studied to examine dietary differences between the sexes and males were found to consume larger fish in coastal areas during autumn and winter. However, information on prey partitioning during breeding and generally on sex‐specific foraging in inland waters is missing. Here, we assess sex‐specific prey choice of Great Cormorants (Phalacrocorax carbo) during two subsequent breeding seasons in the Central European Alpine foreland, an area characterized by numerous stagnant and flowing waters in close proximity to each other. We developed a unique, noninvasive approach and applied it to regurgitated pellets: molecular cormorant sexing combined with molecular fish identification and fish‐length regression analysis performed on prey hard parts. Altogether, 364 pellets delivered information on both, bird sex, and consumed prey. The sexes differed significantly in their overall prey composition, even though Perca fluviatilis, Rutilus rutilus, and Coregonus spp. represented the main food source for both. Albeit prey composition did not indicate the use of different water bodies by the sexes, male diet was characterized by higher prey diversity within a pellet and the consumption of larger fish. The current findings show that female and male cormorants to some extent target the available prey spectrum at different levels. Finally, the comprehensive and noninvasive approach has great potential for application in studies of other piscivorous bird species.  相似文献   

19.
Effective management and conservation of migratory bird populations require knowledge and incorporation of their movement patterns and space use throughout the annual cycle. To investigate the little‐known migratory patterns of two grassland bird species, we deployed 180 light‐level geolocators on Grasshopper Sparrows (Ammodramus savannarum) and 29 Argos‐GPS tags on Eastern Meadowlarks (Sturnella magna) at Konza Prairie, Kansas, USA, and six US Department of Defense (DoD) installations distributed across the species' breeding ranges. We analyzed location data from 34 light‐level geolocators and five Argos‐GPS tags attached for 1 year to Grasshopper Sparrows and Eastern Meadowlarks, respectively. Grasshopper Sparrows were present on the breeding grounds from mid‐April through early October, substantially longer than previously estimated, and migrated on average ~2,500 km over ~30 days. Grasshopper Sparrows exhibited strong migratory connectivity only at a continental scale. The North American Great Lakes region likely serves as a migratory divide for Midwest and East Coast Grasshopper Sparrows; Midwest populations (Kansas, Wisconsin, and North Dakota; n = 13) largely wintered in Texas or Mexico, whereas East Coast populations (Maryland and Massachusetts, n = 20) wintered in the northern Caribbean or Florida. Our data from Eastern Meadowlarks provided evidence for a diversity of stationary and short‐ and long‐distance migration strategies. By providing the most extensive examination of the nonbreeding movement ecology for these two North American grassland bird species to date, we refine information gaps and provide key insight for their management and conservation.  相似文献   

20.
Tracking studies normally focus on long‐distance migrants, meaning that our understanding about short‐distance migration remains limited. In this study, we present the first individual tracks of the Eurasian golden plover Pluvialis apricaria, a short‐distance migrant, which were tracked from a Scandinavian breeding population using geolocators. In addition, golden plovers are known for their cold spell‐induced winter movements, and this study provides some first individual tracking data on this type of movements. In three cases the plovers spent the winter in NW Europe and in four cases they departed during winter from NW Europe to spend the rest of the winter in Iberia or Morocco (one bird that was tracked during two subsequent migration cycles moved to Iberia in the first winter but remained in NW Europe during the second winter). The four winter departures were associated with a cold spell in NW Europe during which maximum temperatures dropped to freezing. Cold spell‐induced winter movements were notably long and fast. The birds that remained at their NW European wintering site did not experience such cold spell. However, the plovers did not always move in response to freezing temperatures, as demonstrated by the individual that was tracked for a second season, when it experienced four cold spells at its wintering site in NW France without leaving. Little information was obtained about spring migration, but one bird had a prominent counter‐clockwise loop migration pattern through E Europe. Due to their cold spell winter movements, golden plovers exhibit great flexibility in migration patterns, resulting in a notably large spread in final wintering areas.  相似文献   

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