Carrying capacity in overwintering birds: when are spatial models needed?

Goss‐Custard, J. D.; Stillman, Richard A.; Caldow, R. W. G.; West, Andrew; Guillemain, Matthieu

doi:10.1046/j.1365-2664.2003.00785.x

Cited by 40 publications

(39 citation statements)

References 13 publications

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“…We adapted a model derived by Goss‐Custard et al. (2003) to predict the amount of time for which a forager population can be supported when consuming a food resource that grows at a constant proportional rate (see Table 1 for the derivation of the parameters used to model the swan– R. pseudofluitans system).…”

Section: Methodsmentioning

confidence: 99%

Effects of mute swan grazing on a keystone macrophyte

O’Hare¹,

Stillman

Mcdonnell

et al. 2007

Freshwater Biology

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1. This study describes the early summer foraging behaviour of mute swans (Cygnus olor) on the River Frome, a highly productive chalk stream in southern England in which Ranunculus penicillatus pseudofluitans is the dominant macrophyte. 2. A daily maximum of 41 ± 2.5 swans were present along the 1.1 km study reach during the study period (late May to the end of June). The river was the primary feeding habitat. Feeding activity on the river at dawn and dusk was much lower than during daylight, but we cannot rule out the possibility that swans fed during the hours of darkness. 3. The effects of herbivory on R. pseudofluitans biomass and morphology were quantified. Biomass was lower in grazed areas and swans grazed selectively on leaves in preference to stems. A lower proportion of stems from grazed areas possessed intact stem apices and flowering of the plant was reduced in grazed areas. 4. A model, based on the swans' daily consumption, was used to predict the grazing pressure of swans on R. pseudofluitans. The model accurately predicted the number of bird days supported by the study site, only if grazing was assumed to severely reduce R. pseudofluitans growth. The proportion of the initial R. pseudofluitans biomass consumed by a fixed number of swans was predicted to be greater when the habitat area was smaller, initial R. pseudofluitans biomass was lower and R. pseudofluitans was of lower food value. 5. We concluded that the flux of N and P through the study reach was largely unaffected by swan activity. The quality of R. pseudofluitans mesohabitat (the plant as habitat for invertebrates and fish) was significantly reduced by grazing which also indirectly contributed to reduced roughness (Manning's n) and by inference water depth. Wetted habitat area for fish and invertebrates would also be lowered over the summer period as a consequence of the reduction in water depth. It was estimated that, while grazing, an individual swan may eat the same mass of invertebrates per day as a 300-g trout. 6. There is a need to manage the conflict between mute swans and the keystone macrophyte, R. pseudofluitans, in chalk streams, and the modelling approach used here offers a potentially useful tool for this purpose.

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Section: Methodsmentioning

confidence: 99%

Effects of mute swan grazing on a keystone macrophyte

O’Hare¹,

Stillman

Mcdonnell

et al. 2007

Freshwater Biology

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“…The steady‐state upper limit on a population's abundance, often called its carrying capacity, is a key quantity in theoretical and applied ecology (Vasconcellos & Gasalla ; Goss‐Custard et al . ; Hayward et al . ).…”

Section: Introductionmentioning

confidence: 99%

Carrying capacity in a heterogeneous environment with habitat connectivity

et al. 2017

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A large body of theory predicts that populations diffusing in heterogeneous environments reach higher total size than if non-diffusing, and, paradoxically, higher size than in a corresponding homogeneous environment. However, this theory and its assumptions have not been rigorously tested. Here, we extended previous theory to include exploitable resources, proving qualitatively novel results, which we tested experimentally using spatially diffusing laboratory populations of yeast. Consistent with previous theory, we predicted and experimentally observed that spatial diffusion increased total equilibrium population abundance in heterogeneous environments, with the effect size depending on the relationship between r and K. Refuting previous theory, however, we discovered that homogeneously distributed resources support higher total carrying capacity than heterogeneously distributed resources, even with species diffusion. Our results provide rigorous experimental tests of new and old theory, demonstrating how the traditional notion of carrying capacity is ambiguous for populations diffusing in spatially heterogeneous environments.

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“…According to previous reports, the amount of food consumption by shorebirds is about 13%-23% in the breeding regions, and about 12% in the over-wintering regions (Meire et al, 1994;Goss-Custard et al, 2003). The feeding intensity is usually higher in breeding / overwintering areas than in stopover sites.…”

Section: Carrying Capacity For Shorebirdsmentioning

confidence: 92%

Carrying capacity for shorebirds during migratory seasons at the Jiuduansha Wetland, Yangtze River Estuary, China

Zhou

Shi

2008

Front. Biol. China

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The carrying capacity of food resources for migrating shorebirds was estimated at a stopover site in the Yangtze River Estuary during the two migratory seasons (spring and autumn). From March to May and September to November 2005, the macrobenthos resources of the Jiuduansha Wetland were investigated, and most of the macrobenthos species in the newlyformed shoal were found to be appropriate food for shorebirds. Biomass measurements showed that the total food resource was about 4541.20 kg AFDW (Ash-Free Dry Weight) in spring and about 2279.64 kg AFDW in autumn. Calculations were also done in the available habitats (intertidal bare mudflat and Scirpus 6 mariqueter/ Scirpus triqueter zones) for the shorebirds. The food resources in the available areas were about 3429.03 kg AFDW in spring and about 1700.92 kg AFDW in autumn. Based on the classification (by lean weight, basic metabolic rate and body length) of the shorebird community, and using the energy depletion model, it was theorized that all of the food resources in the Jiuduansha Wetland could support about 3.5 million shorebirds during spring season and 1.75 million shorebirds during autumn season. The shorebird carrying capacities in terms of the available food were about 2.6 million and 1.3 million birds during the two respective migration seasons. Considering the effect of intake rate, the potential carrying capacity was about 0.13-0.26 million shorebirds in the study area. The main factor restricting use of the area by shorebirds was the scarcity of available habitats for roosting at high tide rather than availability of food supply. We recommend restoring some wading pools in the dense Phragmites australis and Spartina alterniflora zones for shorebirds to roost in, to improve shorebirds' utilization efficiency of the resources in the Jiuduansha Wetland.

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Carrying capacity in overwintering birds: when are spatial models needed?

Cited by 40 publications

References 13 publications

Effects of mute swan grazing on a keystone macrophyte

Effects of mute swan grazing on a keystone macrophyte

Carrying capacity in a heterogeneous environment with habitat connectivity

Carrying capacity for shorebirds during migratory seasons at the Jiuduansha Wetland, Yangtze River Estuary, China

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