Measuring the Impact of Parental Foraging by Starlings (Sturnus vulgaris) on Soil Invertebrate Prey Availability: An Exclosure Experiment

Oikos ◽  
1996 ◽  
Vol 76 (3) ◽  
pp. 511 ◽  
Author(s):  
Siân C. Whitehead ◽  
Jonathan Wright ◽  
Peter A. Cotton ◽  
Sian C. Whitehead
Keyword(s):  
Prey Availability ◽  
Sturnus Vulgaris ◽  
Soil Invertebrate ◽  
Invertebrate Prey ◽  
Exclosure Experiment ◽  
The Impact

Seasonal variations in intertidal density of invertebrate prey in a tropical lagoon and effects of shorebird predation

1994 ◽  
Vol 72 (10) ◽  
pp. 1755-1763 ◽  
Author(s):  
Francine Mercier ◽  
Raymond McNeil
Keyword(s):  
Seasonal Variations ◽  
Census Data ◽  
Invertebrate Prey ◽  
Exclosure Experiment ◽  
Tropical Environments ◽  
Energy Demands ◽  
Study Sites ◽  
Intertidal Surface ◽  
The Impact ◽  
Prey Depletion

We analyzed the relationship between the abundance of shorebirds and that of their intertidal invertebrate prey, and attempted to determine if shorebird predation significantly affects prey density. The study was conducted at three sites in the Chacopata Lagoon complex in northeastern Venezuela between January 1985 and September 1986, using shorebird census data, monthly sampling of intertidal invertebrates, and exclosure experiments. The invertebrates collected were divided into three groups: (i) polychaetes (≤50 mm in length), (ii) small bivalves (2 – 3 mm in length), and (iii) other species. The overall density of shorebirds foraging in the Chacopata Lagoon complex was very high, exceeding the densities reported for most other staging and overwintering areas by a wide margin. The abundance of shorebirds in the study area was related primarily to the density of polychaetes, their main prey. At two of the study sites, the arrival of fall migrants followed a significant increase in polychaete numbers. The increase in shorebird numbers in autumn was negligible at the third site, where polychaete density was lower than at the other sites. The impact of shorebird predation on their invertebrate prey varied seasonally, as did the extent of the foraging area available to them. The exclosure experiment revealed significant differences in the density of polychaetes inside and outside the exclosures only during, or shortly after, the fall migration period. The variability in the conclusions drawn from other studies examining prey depletion by shorebirds in tropical environments may be explained by differences in the length of sampling periods and seasonal variations in the numbers of foraging shorebirds, the energy demands of moult, fat deposition, and the intertidal surface area available for feeding. The impact of seasonal variables such as these should be taken into consideration when designing studies to measure prey depletion by shorebirds; such objectives may necessitate long-term studies.

scholarly journals Assessing population collapse of Drupella spp. (Mollusca: Gastropoda) 2 years after a coral bleaching event in the Republic of Maldives

Hydrobiologia ◽  
2021 ◽  
Author(s):  
L. Saponari ◽  
I. Dehnert ◽  
P. Galli ◽  
S. Montano
Keyword(s):  
Coral Bleaching ◽  
Prey Availability ◽  
Coral Cover ◽  
Environmental Data ◽  
High Plasticity ◽  
Bleaching Event ◽  
Coral Recovery ◽  
The Republic ◽  
The Impact ◽  
Line Intercept

AbstractCorallivory causes considerable damage to coral reefs and can exacerbate other disturbances. Among coral predators, Drupella spp. are considered as delayer of coral recovery in the Republic of Maldives, although little information is available on their ecology. Thus, we aimed to assess their population structure, feeding behaviour and spatial distribution around 2 years after a coral bleaching event in 2016. Biological and environmental data were collected using belt and line intercept transects in six shallow reefs in Maldives. The snails occurred in aggregations with a maximum of 62 individuals and exhibited a preference for branching corals. Yet, the gastropods showed a high plasticity in adapting feeding preferences to prey availability. Drupella spp. were homogenously distributed in the study area with an average of 9.04 ± 19.72 ind/200 m2. However, their occurrence was significantly different at the reef scale with the highest densities found in locations with higher coral cover. The impact of Drupella spp. appeared to be minimal with the population suffering from the loss of coral cover. We suggest that monitoring programs collect temporal- and spatial-scale data on non-outbreaking populations or non-aggregating populations to understand the dynamics of predation related to the co-occurrence of anthropogenic and natural impacts.

scholarly journals Expert knowledge assessment of threats and conservation strategies for breeding Hen Harrier and Short-eared Owl across Europe

2020 ◽  
pp. 1-18
Author(s):  
DARÍO FERNÁNDEZ-BELLON ◽  
JOHN LUSBY ◽  
JULES BOS ◽  
TONIO SCHAUB ◽  
ALAN MCCARTHY ◽  
...  
Keyword(s):  
Protected Areas ◽  
Habitat Management ◽  
Expert Knowledge ◽  
Prey Availability ◽  
Active Management ◽  
Conservation Strategy ◽  
Conservation Strategies ◽  
Conservation Threats ◽  
The Impact ◽  
Hen Harrier

Summary Hen Harrier Circus cyaneus and Short-eared Owl Asio flammeus are open-country birds of prey with overlapping distributions. Although both species face similar conservation threats across their ranges, work to date has largely been undertaken at a national scale with few attempts to collate and assess factors relevant to their conservation at an international scale. Here we use an expert knowledge approach to evaluate the impact of conservation threats and the effectiveness of conservation strategies for each species across Europe. We report results of responses to a questionnaire from 23 Hen Harrier experts from nine countries and 12 Short-eared Owl experts from six countries. The majority of responses for both species reported declines in breeding numbers. The perceived impact of threats was broadly similar for both species: ecological factors (predation, extreme weather and prey availability), changes in land use (habitat loss and agricultural intensification) and indirect persecution (accidental nest destruction) were considered to be the greatest threats to breeding Hen Harrier and Short-eared Owl. Short-eared Owl experts also highlighted lack of knowledge and difficulties associated with monitoring as a major conservation challenge. Despite broad-scale similarities, geographical variation was also apparent in the perceived importance of conservation threats, with some threats (such as direct persecution, large-scale afforestation or habitat degradation) requiring country-specific actions. Implementation of different conservation strategies also varied between countries, with the designation of protected areas reported as the most widespread conservation strategy adopted, followed by species and habitat management. However, protected areas (including species-specific protected areas) were perceived to be less effective than active management of species and habitats. These findings highlight the overlap between the conservation requirements of these two species, and the need for collaborative international research and conservation approaches that prioritise pro-active conservation strategies subject to continued assessment and with specific conservation goals.

The diet of a forest-dependent frog species, Odorrana morafkai (Anura: Ranidae), in relation to habitat disturbance

2020 ◽  
Vol 41 (1) ◽  
pp. 29-41
Author(s):  
Duong Thi Thuy Le ◽  
Jodi J.L. Rowley ◽  
Dao Thi Anh Tran ◽  
Huy Duc Hoang
Keyword(s):  
Rainy Season ◽  
Prey Availability ◽  
Feeding Strategy ◽  
Habitat Disturbance ◽  
Habitat Modification ◽  
Prey Composition ◽  
Frog Species ◽  
Disturbed Habitats ◽  
The Impact ◽  
Prey Items

Abstract While deforestation is one of the greatest drivers of biodiversity loss, our understanding of the effects of habitat modification on species is limited. We investigated the diet of a forest-dwelling frog species, Morafka’s frog (Odorrana morafkai), in a highland forest in Vietnam in relation to habitat disturbance, sex and season. We surveyed the species at 45 sites in forest of varying disturbance and examined its diet using stomach flushing, estimating prey availability via trapping. We detected significantly fewer O. morafkai in highly disturbed habitats compared to moderately disturbed or non-disturbed habitats. We revealed that O. morafkai is a dietary generalist, identifying 28 prey types, primarily invertebrates. Prey composition, the number of prey items per stomach and prey volume per stomach did not vary between disturbance levels. Diet did not vary significantly between sexes, except that females had a higher prey volume. Prey composition in the species varied between seasons, with Coleoptera and Orthoptera dominating the diet in the rainy season and Lepidoptera in the dry season. The number of prey items per stomach and prey volume were significantly higher in the rainy season. There was a significant correlation between prey availability and diet composition. The low number of O. morafkai detected in highly disturbed habitats suggests that this habitat may not be optimal for the species, despite having a generalist feeding strategy and presumed high mobility. This study provides a window into the impact of an increasing threat, habitat disturbance, on forest-dependent amphibian species.

Feeding habits of cockfish, Callorhinchus callorhynchus (Holocephali: Callorhynchidae), in Patagonian waters (Argentina)

1996 ◽  
Vol 47 (6) ◽  
pp. 801 ◽  
Author(s):  
EE Di Giacomo ◽  
MR Perier
Keyword(s):  
Prey Size ◽  
Prey Availability ◽  
Feeding Habits ◽  
Food Composition ◽  
Commercial Fishing ◽  
Bivalve Molluscs ◽  
Invertebrate Prey ◽  
Selective Foraging ◽  
Predator Size ◽  
Two Factors

Morphology of the main digestive features of cockfish, Callorhinchus callorhynchus, is described and linked to feeding habits. Composition of the diet and size-selective foraging of this species on scallops was studied in northern Patagonian waters and analysed in relation to depth, sex and size. Three species of bivalve molluscs (Pitar rostratus, Aequipecten tehuelchus and Ennucula puelcha) and flabelligerid polychaetes were predominant in the diet of males. The scallop Zygochlamys patagonica dominated the diet of females. The diet of juveniles consisted of small gastropods (Olivella sp.), bivalves with fragile shells (e.g. Pandora cistula), amphipods and polychaetes. Differences in food composition between sexes and between juveniles and adults are attributed to two factors: extrinsic (concerning prey availability) and intrinsic (concerning the morphology and behaviour of the predator). Size-selective foraging on two species of scallops, Aequipecten tehuelchus (subject to commercial fishing) and Zygochlamys patagonica, was found in adults; it is argued that maximum scallop prey size is constrained by the strength of the crushing apparatus of the cockfish. The diet of the cockfish is compared with that of other holocephalans. It is concluded that species of Callorhinchus can be generally characterized as benthic foragers that specialize in crushing shelled invertebrate prey.

scholarly journals Mid-winter temperatures, not spring temperatures, predict breeding phenology in the European starling Sturnus vulgaris

2015 ◽  
Vol 2 (1) ◽  
pp. 140301 ◽  
Author(s):  
Tony D. Williams ◽  
Sophie Bourgeon ◽  
Allison Cornell ◽  
Laramie Ferguson ◽  
Melinda Fowler ◽  
...  
Keyword(s):  
Clutch Size ◽  
Prey Availability ◽  
Sturnus Vulgaris ◽  
Winter Temperature ◽  
Laying Date ◽  
Breeding Phenology ◽  
European Starlings ◽  
Winter Temperatures ◽  
Lag Times ◽  
High Degree

In many species, empirical data suggest that temperatures less than 1 month before breeding strongly influence laying date, consistent with predictions that short lag times between cue and response are more reliable, decreasing the chance of mismatch with prey. Here we show in European starlings ( Sturnus vulgaris ) that mid-winter temperature ca 50–90 days before laying (8 January–22 February) strongly ( r 2 = 0.89) predicts annual variation in laying date. Mid-winter temperature also correlated highly with relative clutch size: birds laid later, but laid larger clutches, in years when mid-winter temperatures were lower. Despite a high degree of breeding synchrony (mean laying date 5–13 April = ±4 days; 80% of nests laid within 4.8 days within year), European starlings show strong date-dependent variation in clutch size and productivity, but this appears to be mediated by a different temporal mechanism for integration of supplemental cue (temperature) information. We suggest the relationship between mid-winter temperature and breeding phenology might be indirect with both components correlating with a third factor: temperature-dependent development of the starling's insect (tipulid) prey. Mid-winter temperatures might set the trajectory of growth and final biomass of tipulid larvae, with this temperature cue providing starlings with information on breeding season prey availability (though exactly how remains unknown).

Does hypoxia reduce habitat quality for Lake Erie walleye (Sander vitreus)? A bioenergetics perspective

2011 ◽  
Vol 68 (5) ◽  
pp. 857-879 ◽  
Author(s):  
Stephen B. Brandt ◽  
Marco Costantini ◽  
Sarah Kolesar ◽  
Stuart A. Ludsin ◽  
Doran M. Mason ◽  
...  
Keyword(s):  
Habitat Quality ◽  
Lake Erie ◽  
Prey Availability ◽  
Spatial Arrangement ◽  
Spatially Explicit ◽  
Sander Vitreus ◽  
Light Conditions ◽  
The Impact ◽  
Favorable Temperature ◽  
East West

In Lake Erie, the duration and extent of hypoxia (dissolved oxygen (DO)  ≤ 2 mg·L–1) has increased in recent years, yet little is known on the corresponding impact on its fish, particularly the highly valued walleye ( Sander vitreus ) fishery. Here, we quantified the impact of hypoxia on walleye habitat quality, using a spatially explicit growth rate potential (GRP) modeling approach, which integrates the spatial arrangement of biological (prey availability) and environmental (DO, temperature, irradiance) measures. Data were collected along two types of transects: 60 km north–south transects (each sampled once during day and night) and 5 km east–west transects (sampled every 4 h for 24 h) during August (pre-hypoxia), September (peak-hypoxia), and October (post-hypoxia) 2005. Overall, the average monthly amount of high quality habitat (GRP > 0 g·g–1·day–1) for walleye declined slightly with hypoxia (<2.0%); however, hypoxia appeared to enhance habitat quality by concentrating prey in favorable temperature, DO, and light conditions. In September, percentages of walleye growth rates were at the upper end of the range, much more so than during August or October. Although an understanding of walleye distributions, foraging, and growth in relation to hypoxia is needed, our results do not suggest that hypoxia is negatively influencing walleye through reduced habitat quality.

Invertebrate prey availability limits reproductive success but not breeding population size in suburban House Sparrows Passer domesticus

Ibis ◽  
2015 ◽  
Vol 157 (3) ◽  
pp. 601-613 ◽  
Author(s):  
Will J. Peach ◽  
John W. Mallord ◽  
Nancy Ockendon ◽  
Chris J. Orsman ◽  
William G. Haines
Keyword(s):  
Reproductive Success ◽  
Population Size ◽  
Prey Availability ◽  
Passer Domesticus ◽  
Breeding Population ◽  
House Sparrows ◽  
Invertebrate Prey

scholarly journals Prey choice and habitat use of people exploiting intertidal resources

2002 ◽  
Vol 29 (2) ◽  
pp. 238-252 ◽  
Author(s):  
W.F. de Boer ◽  
A.-F. Blijdenstein ◽  
F. Longamane
Keyword(s):  
Prey Species ◽  
Prey Availability ◽  
Spring Tide ◽  
Dry Weight ◽  
Intake Rate ◽  
Mangrove Forests ◽  
Prey Choice ◽  
Relative Value ◽  
The Mean ◽  
The Impact

The impact of human exploitation depends mostly on the size of the catch and the species targeted. The value of a species is an important explanatory variable in understanding human impact. Co-management of resources should take into account these different resource values, when evaluating exploitation strategies. The prey choice and foraging behaviour of women and children searching for crabs and shells on the intertidal area at Inhaca Island, South Mozambique, were investigated using optimal foraging theory. This theoretical framework offers the possibility to understand the reasoning of an exploitation strategy and the preference for certain prey species. The number of people was registered, catches were analysed, and timing and substrate choice were recorded. The value of species was estimated using contingency tables. Women were more efficient than children, as their catch was heavier, and the mean weight/animal was larger. The density of women and their timing were positively correlated to prey availability. During neap tide, they spread their visit over more of the low water period and collected crabs by digging in the mangrove forests. No digging occurred during spring tide when a larger area was exposed, the total abundance of species increased, and more species became available. Women then switched to a second strategy, targeting swimming crabs in the tidal channel. Mean neap and spring tide catches were equal (133 g ash-free dry weight per person), but spring catches comprised significantly fewer animals per catch (42 against 123 per person), and mean animal weight was larger (5.4 against 3.0 g ash-free dry-weight per person). Diet breadth was narrower during spring tide, and decreased significantly with increased catch weight. Species with profitabilities (energy intake/handling time) lower than the mean intake rate of 0.024–0.028 g ash-free dry weight s−1 were generally excluded from the diet. The prey preference was positively related to the relative value ranks of the prey species, as measured by ranking of species by women. Women maximized the cumulative relative value ranks during spring tide, instead of total weight. Using this analysis, differences in prey choice and spatial differences in exploitation can be understood as a strategy aimed at maximizing intake and the relative value of a prey species.

First results from an experiment excluding three sizes classes of herbivores from tundra vegetation in southern Yamal, Russia

2016 ◽  
Vol 6 (2) ◽  
pp. 132-140
Author(s):  
Capucine Baubin ◽  
Dorothée Ehrich ◽  
Virve Ravolainen ◽  
Svetlana Sokovina Abdulmanova ◽  
Svetlana Ektova ◽  
...  
Keyword(s):  
Grazing Pressure ◽  
Yamal Peninsula ◽  
Exclosure Experiment ◽  
Plant Groups ◽  
Tundra Vegetation ◽  
First Results ◽  
Herbivore Faeces ◽  
Growing Conditions ◽  
Plant Herbivore ◽  
The Impact

Plant-herbivore relationships are important for the functioning of tundra ecosystems. Here, we report the first results from an exclosure experiment that, something very few studies have done, separated the impact of three sizes of herbivores (small, medium and large) on nine functional groups of plants in the low arctic tundra of the Yamal Peninsula (Russia). Herbivore faeces counts in the exclosures and pictures from automatic cameras proved that the experimental setup worked. The majority of plant groups did not respond to exclusion of herbivores, supporting our expectation that vegetation responses in tundra are generally too slow to be measured during one growing season. The plant groups with highest growth rates and palatability (forbs and grasses) increased their biomass in meadows associated to tall willow shrubs when reindeer were excluded. This result was expected based on studies from other arctic regions. Our results also suggested that willow meadows and forb tundra, which are focal habitat for herbivores, are resilient and have the capacity to increase their biomass over a short term. We expect this experiment to provide valuable information on how different plant functional types and habitats with different growing conditions and importance to herbivores respond to relaxed grazing pressure from a variety of tundra herbivores.

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