Ecological factors facilitating city-dwelling in red-rumped parrots

2007 ◽  
Vol 34 (8) ◽  
pp. 624 ◽  
Author(s):  
Hélène Lowry ◽  
Alan Lill
Keyword(s):  
Interference Competition ◽  
Food Resource ◽  
Ecological Factors ◽  
Canopy Cover ◽  
Flock Size ◽  
Winter Food ◽  
Exotic Grass ◽  
Aggressive Interference ◽  
Autumn And Winter ◽  
Herb Species

The red-rumped parrot (Psephotus haematonotus), which appears to be undergoing range expansion, started colonising metropolitan Melbourne ~30 years ago. The factors that have facilitated this colonisation have not been evaluated. We investigated aspects of the parrot’s ecology at six parkland sites through late autumn and winter 2006 to elucidate these factors. The predominantly ground-feeding red-rumped parrot consumed mainly seeds of exotic grass and herb species, four of which were particularly important in providing a continuous winter food resource. Two of these species were common turf grasses and their visible and concealed seeds provided >50% of the diet. Sites occupied by parrots had relatively more native trees, tall trees and dense canopy cover than unoccupied sites; this may be important in providing suitable daytime and nocturnal roost sites. Little aggressive interference competition occurred with other ground-feeding birds. Mean population density in occupied sites was 1.3 parrots ha–1. Mean flock size was 10 ± 6 and, on average, males comprised 67 ± 19% of a flock’s members. We suggest that abundant, continuously available food (seed) resources, apparently limited competition for food and the presence of suitable roosting sites are probably important in facilitating winter occupancy of parkland by red-rumped parrots in Melbourne.

scholarly journals Canopy cover and anurans: nutrients are the most important predictor of growth and development

2016 ◽  
Vol 94 (3) ◽  
pp. 225-232 ◽  
Author(s):  
Freya E. Rowland ◽  
Sara K. Tuttle ◽  
María J. González ◽  
Michael J. Vanni
Keyword(s):  
Growth And Development ◽  
Large Scale ◽  
Food Resource ◽  
Canopy Cover ◽  
Resource Quality ◽  
Bottom Up ◽  
Growth And Survival ◽  
Primary Producer ◽  
Full Factorial ◽  
Potential Food

Bottom-up effects such as the availability of light and nutrients can have large impacts on primary producer quantity and quality, which is then translated into the growth and development of consumers. The use of “canopy cover” as a bottom-up predictive factor is a broad categorization, as canopy cover controls both the amount of light allowed into a pond and the nutrient load through leaf litter. To test how light and nutrients influence pond ecosystems, we manipulated inorganic nutrients and light in a 2 × 3 full-factorial, large-scale mesocosm experiment. Larval American Bullfrogs (Lithobates catesbeianus (Shaw, 1802)) were reared for 6 weeks at low densities and then assessed for development, growth, and survival at the end of the experiment. We also collected weekly samples of potential food resources (phytoplankton and periphyton) for the estimation of algal production and stoichiometric quality (carbon:nitrogen:phosphorus). Light had strong effects on food resource quality; however, resource quality did not significantly predict tadpole growth or development. Instead, nutrients seemed to be the most important factor as a stimulator of total algal primary production and some unknown pathway, which in turn affected tadpole development. Ours is the first study to investigate canopy cover using a comprehensive causal model, and our results suggest in regards to tadpole growth and development, canopy cover is important mainly as a source of nutrients to ponds.

scholarly journals Testing the Ability of Airborne LiDAR to Measure Forage Resources for Wild Ungulates in Conifer Forests

2019 ◽  
Vol 117 (5) ◽  
pp. 492-503 ◽  
Author(s):  
Iver T Hull ◽  
Lisa A Shipley
Keyword(s):  
Food Resource ◽  
Canopy Cover ◽  
Laser Pulses ◽  
Understory Vegetation ◽  
Airborne Lidar ◽  
Forest Understory ◽  
Conifer Forests ◽  
Vegetation Density ◽  
Wild Ungulates ◽  
Vegetation Biomass

Abstract Vegetation in the forest understory is a key food resource for wild ungulates like deer (Odocoileus spp.) because the amount of nutritious forage influences animal productivity and density. Therefore, measuring the abundance of understory vegetation available to wildlife populations is often a key objective for wildlife managers. Field-based methods for measuring understory vegetation across remote landscapes are time- and resource-intensive, so we compared estimates of understory vegetation density derived from airborne light detection and ranging (LiDAR) returns with vegetation biomass sampled directly on 65 field plots across 4 years and >250,000 hectares of xeric conifer forests in northeastern Washington. We found that LiDAR-derived estimates of understory vegetation density were only able to predict field-sampled vegetation biomass when the two sampling methods occurred within 3 years of each other, and overstory canopy cover was <50 percent. Our results demonstrate limitations in the ability of LiDAR, at the intensity and frequency currently applied for multiuse purposes, to measure the quantity of forage. However, further testing with synchronous field sampling and higher-density laser pulses holds promise.

Rangeland vegetation responses to traditional enclosure management in eastern Ethiopia

2013 ◽  
Vol 35 (1) ◽  
pp. 29 ◽  
Author(s):  
H. Haftay ◽  
T. Yayneshet ◽  
G. Animut ◽  
A. C. Treydte
Keyword(s):  
Open Access ◽  
Mass Density ◽  
Canopy Cover ◽  
Woody Species ◽  
Wiener Index ◽  
Woody Vegetation ◽  
Short Term ◽  
Eastern Ethiopia ◽  
Herb Species ◽  
Pastoral Economy

Enclosures are widely used by pastoralists in East Africa. However, the response of herbaceous and woody vegetation to enclosures seasonally grazed by livestock remains poorly understood. This study investigated the effectiveness of traditional enclosures in improving herbaceous and woody vegetation in the Somali Regional State of eastern Ethiopia. Vegetation composition (species composition, diversity and richness) and structure (herbage mass, density and canopy cover) were measured inside and outside a set of enclosures. The enclosures contained higher numbers of desirable species than the adjacent open-access grazing areas. Woody species richness was higher in the open-access grazing areas than in the enclosures, which is attributed to the manual removal of most of the undesirable shrubs and trees in the enclosures by pastoralists. Herbage mass was 2642 and 843 kg of dry matter ha–1 in the enclosures and open-access communal grazing areas, respectively. Herbaceous species diversity was higher in the enclosures than in the open-access communal grazing areas (Shannon–Wiener index: 1.8 v. 1.4, respectively). The enclosures were richer in herb species than the open-access grazing areas (13.5 v. 6.8, respectively), but values for woody species were not significantly different. Overall, we found that establishment of enclosures and the short-term protection from grazing they allow is an option for realising positive vegetation changes that support the local pastoral economy in the semiarid rangelands of eastern Ethiopia.

Interspecific relationships between two species of sympatric Afrotropical water snake in relation to a seasonally fluctuating food resource

2005 ◽  
Vol 22 (1) ◽  
pp. 91-100 ◽  
Author(s):  
Luca Luiselli
Keyword(s):  
Prey Size ◽  
Prey Availability ◽  
Interference Competition ◽  
Food Resource ◽  
Wet Season ◽  
Snake Species ◽  
Water Snake ◽  
Body Sizes ◽  
The Difference ◽  
Increased Activity

In this paper, the ecological relationships and the resource partitioning patterns in a two-species system of sympatric aquatic snakes (Grayia smythii and Afronatrix anoscopus) from a riverine forest area in southern Nigeria, West Africa, were tested. The monthly availability of their food resources in the field, and the monthly variation in the feeding relationships between these snakes and their preys, were also studied. Food items of 1245 snakes, i.e. 554 Grayia smythii, and 691 Afronatrix anoscopus, were examined. The mean body length of Grayia smythii was significantly larger than that of Afronatrix anoscopus in any interspecific comparison, i.e. males versus males, females versus females, and females versus males; however, in both species the females attained significantly larger body sizes than the males. 676 prey items were obtained from the stomachs of Afronatrix anoscopus, and 390 from those of Grayia smythii. Both species of snake exhibited an increased activity in the open during the wet months, and this increased activity was positively correlated to the higher abundance of prey during the wet season. In both species the diet consisted of a great variety of different amphibian and fish species. Direct interference competition was not observed. The month-by-month dietary patterns exhibited by the two snake species were similar. Mean prey size was significantly larger in the larger species, and the difference in prey size between the two snake species increased during the dry season, i.e. during the period of reduced prey availability. The monthly availability of the three main food types for these snakes varied, and were significantly more abundant during the wet season (April–September). A positive relationship between prey availability and prey use by snakes strongly suggests that the two snake species are predatory generalists, utilizing prey in relation to their abundance in the field.

Differential effects of predation risk and competition over vigilance variables and feeding success in Eurasian siskins (Carduelis spinus)

Behaviour ◽  
2013 ◽  
Vol 150 (14) ◽  
pp. 1665-1687 ◽  
Author(s):  
Jordi Pascual ◽  
Juan Carlos Senar
Keyword(s):  
Food Intake ◽  
Predation Risk ◽  
Foraging Behaviour ◽  
Interference Competition ◽  
Ecological Factors ◽  
Intake Rate ◽  
Similar Length ◽  
Feeding Success ◽  
High Predation ◽  
Food Intake Rate

Many investigations have studied the effects of predation risk and competition over vigilance and feeding success, but they have proven to be difficult to discriminate. Moreover, none of the studies that have avoided the confusion has considered all the vigilance variables, food intake rate and time spent in the foraging patch. In this study, we designed an experiment with Eurasian siskinsCarduelis spinusforaging on three bird table feeders: one with low predation risk and competition, one with low predation risk and high competition and one with high predation risk and intermediate competition. Birds responded to increasing interference competition by increasing mean scan durations (probably due to the birds having to be vigilant for both other flock members and predators) and maintaining the length of mean inter-scan durations, while they responded to increasing predation risk by reducing mean inter-scan durations (probably in order to detect the predator sooner) while maintaining similar length of mean scan durations. Birds were often ejected from the feeder or departed because of disturbances, so time spent on feeders was reduced both because of competition and predation risk. Pecking rates were affected by competition but not by predation risk. Our results clearly show that birds vigilance strategy while foraging might be very different when they are mainly concerned with scanning for predators or when they primarily monitor competing flock companions. In addition, they stress the importance of recording all the vigilance and feeding variables when studying the effect of ecological factors over the foraging behaviour of birds.

Effects of winter food supplementation on reproduction, body mass, and numbers of small mammals in montane Australia

2000 ◽  
Vol 78 (10) ◽  
pp. 1775-1783 ◽  
Author(s):  
Peter B Banks ◽  
Chris R Dickman
Keyword(s):  
Body Mass ◽  
Small Mammals ◽  
Interference Competition ◽  
Peanut Butter ◽  
Survival Rates ◽  
Food Supplementation ◽  
High Quality ◽  
Additional Food ◽  
Winter Food ◽  
Antechinus Stuartii

We used a food-supplementation experiment to test the hypothesis that small-mammal populations are food-limited during winter in southeastern Australia. We trapped small mammals along 120- to 150-m transects at 12 creek and 12 ridgetop sites (representing high- and low-quality habitats) for 2 months prior to winter and 2 months during winter. High-quality food (peanut butter, honey, oats, and dried cat food) was provided ad libitum for 7 weeks during winter at four sites in each habitat. Eight sites were provided with empty feeding tubes and eight were untreated. Seven weeks of food supplementation caused numerical increases of 4.0- and 5.0-fold for the rodents Rattus fuscipes and Rattus lutreolus, respectively. Increases were due largely to immigration, and were only observed in the high-quality creek habitats (R. lutreolus were exclusively captured at creek sites). Food supplementation also led to an increase in body mass and reversed the hiatus in winter breeding for rodents. These results suggest that populations of both species are limited by winter food availability. However, survival rates (indexed from recapture rates) were not affected by food supplementation. Mean body mass of the marsupial Antechinus stuartii also increased with food supplementation, but other demographic parameters showed no response; numbers declined at creek sites after additional food was provided. Trapping-revealed measures of interspecific association showed that A. stuartii avoided areas of high rat numbers after additional food was provided. It is thus likely that interference competition from the much larger and more abundant rodents forced A. stuartii out of the food-supplemented creek sites, hence mediating the direct effects of food supplementation on this species.

Seasonal oestrous cycle activity of captive female koalas in south-east Queensland

2015 ◽  
Vol 37 (2) ◽  
pp. 245 ◽  
Author(s):  
K. Ballantyne ◽  
A. Lisle ◽  
A. Mucci ◽  
S. D. Johnston
Keyword(s):  
Resource Availability ◽  
Food Resource ◽  
Reproductive Function ◽  
Genetic Management ◽  
Confounding Effect ◽  
Influence Of Temperature ◽  
Reproductive Management ◽  
Captive Populations ◽  
Autumn And Winter ◽  
Sexually Mature

This study investigated the seasonality of behavioural oestrus in a captive koala population in south-east Queensland. A total of 33 sexually mature koalas were examined over a 4-year period (2009–12) to determine the possible influence of temperature, photoperiod and rainfall on the incidence of expression of behavioural oestrus without the confounding effect of lactation or limiting food resource availability. Although signs of behavioural oestrus were detected throughout the year, an obvious seasonality was apparent, with significantly fewer females displaying behavioural oestrus in late autumn and winter (May–August) than September to April (P < 0.0001). While average monthly photoperiod (P < 0.0001) and average monthly temperature (P < 0.0001) were significantly related to oestrous behaviour, rainfall was not (P > 0.05). A better understanding of the seasonality of reproductive function in the female koala will facilitate the use of reproductive management-assisted breeding technology to enable improved genetic management in captive populations.

scholarly journals Relationships of shredders, leaf processing and organic matter along a canopy cover gradient in tropical streams

2017 ◽  
Vol 77 (1) ◽  
Author(s):  
Anna C.F. Aguiar ◽  
Vinicius Neres-Lima ◽  
Timothy P. Moulton
Keyword(s):  
Organic Matter ◽  
Large Body ◽  
Food Resource ◽  
Canopy Cover ◽  
Tropical Streams ◽  
Leaf Biomass ◽  
Leaf Breakdown ◽  
Leaf Packs ◽  
Leaf Processing ◽  
Breakdown Rates

Terrestrial allochthonous organic matter represents a structuring element and an important source of energy and carbon to fauna in small forested streams. However, the role of this matter as a food resource for benthic macroinvertebrates, and consequently, for shredders and their performance in riverine processes, is not clear in low-order tropical streams. Aiming to investigate the relationship between shredders and leaves, we analyzed along a gradient of 8-93% canopy cover biomass and abundance of shredders, accumulated leaves and breakdown rates of local leaves to verify if these parameters were related to shade conditions and to each other. Three hypotheses were tested: i) shredder biomass, accumulated leaves and breakdown rates are related to canopy cover and exhibit higher values in shaded sites; ii) shredder biomass is positively related to accumulated leaves and breakdown rates; and iii) due to the relatively large body size of the important shredders, the association of shredders with leaves and importance to leaf processing should be better expressed in terms of guild biomass than abundance. Shredder biomass varied between 846 and 1506 mg DM m‑2 and accumulated leaves varied between 479 and 1120 g AFDM m-2 across sites. Leaf breakdown rate (k), the only measured variable that varied significantly among sites, varied between -0.0015 and -0.0238 day-1. Neither shredder biomass nor leaf biomass were associated with the shading gradient.  On the other hand, shredder abundance and biomass, mainly represented by Triplectides (Trichoptera, Leptoceridae), was positively related to accumulated leaves within sites and to breakdown rates assessed by leaf packs. Leaf breakdown, as assessed by the experimental leaf packs, was associated with shredder biomass, but not with shredder abundance. This result suggests that macroinvertebrates are important for leaf detritus processing and that their biomass reflects their activity, presumably because it is related to their secondary production and perhaps non-consumptive action. Their activity was observed at the scale of leaf packs and not at the scale of variation in canopy cover because apparently canopy did not modulate availability of leaves, which were apparently not limiting to the shredders.   

Do differences in ecological conditions influence grouping behaviour in a solitary ungulate, the Japanese serow?

Behaviour ◽  
2019 ◽  
Vol 156 (3-4) ◽  
pp. 245-264 ◽  
Author(s):  
H. Takada ◽  
M. Minami
Keyword(s):  
Group Size ◽  
Habitat Structure ◽  
Alpine Meadow ◽  
Resource Competition ◽  
Food Resource ◽  
Ecological Factors ◽  
Ecological Conditions ◽  
Evolution Of Sociality ◽  
Japanese Serow ◽  
The Cost

Abstract One aim of animal behaviour research is to explain why animals live in groups. The grouping behaviour of solitary mammals is important for understanding the ecological factors promoting the evolution of sociality. We present field data of Japanese serow, a primitive solitary ungulate, in forest and alpine meadow habitats. We found no differences in group size of all age–sex classes between the forest and alpine meadow habitats, and both populations were mainly solitary. The current findings suggest that group size in the serow is not affected by ecological conditions, including habitat structure, forage abundance, and population density. However, female associations involving up to three females occurred in the alpine meadow habitat throughout the year, whereas such groupings were not observed in the forest habitat. This finding suggests that abundant food supply in the alpine meadow promoted female associations by decreasing the cost of food resource competition.

scholarly journals Taxonomic and phylogenetic composition show biotic resistance to exotic invasion in acid seep springs

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
David F. Barfknecht ◽  
David J. Gibson
Keyword(s):  
Phylogenetic Diversity ◽  
Biotic Resistance ◽  
Environmental Filtering ◽  
Canopy Cover ◽  
Taxonomic Diversity ◽  
Freshwater Wetlands ◽  
Phylogenetic Structure ◽  
Exotic Invasion ◽  
Phylogenetic Composition ◽  
Exotic Grass

Abstract Background Few studies have incorporated the evolutionary insights provided by analysis of phylogenetic structure along with community composition to assess the effects of exotic invasion on freshwater wetlands. Here, we assess the taxonomic and phylogenetic relationships among acid seep springs to investigate the potential homogenization or resistance of communities due to invasion of an exotic grass. Results Multivariate community analyses indicated differences in community and phylogenetic composition and dispersion among acid seep springs, associated with gradients in soil moisture, canopy cover, and phylogenetic diversity. By contrast, univariate analyses showed differences in taxonomic diversity but not phylogenetic diversity among acid seep springs. Conclusions Despite exotic invasion, individual acid seep springs remained taxonomically and phylogenetically distinct from each other. Taxonomic and phylogenetic diversity metrics revealed different aspects of composition, reinforcing the importance of including both in analyses of plant communities for understanding community assembly following exotic invasion and for management purposes. Within acid seep springs, taxonomic and phylogenetic composition appear to be driven more through environmental filtering by light and moisture than by the competitive effects following invasion of an exotic grass in support of Elton’s biotic resistance hypothesis.

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