Climate similarity favors biological invasion, but a match between seasonality in the novel range and the timing of life cycle events of the invader also influences the outcome of species ...introduction. Yet, phenology effects on invasion success have generally been neglected. Here we study whether a phenological mismatch limits the non-native range of a globally successful invader, the Ring-necked parakeet, in Europe. Given the latitudes at which parakeets have established across Europe, they breed earlier than expected based on breeding dates from the native Asian range. Moreover, comparing the breeding dates of European populations to those of parakeets in the native Asian range, to five native breeding bird species in Europe and to the start of the growing season of four native European trees shows that the discrepancy between expected and actual breeding phenology is greater in northern Europe. In northern European populations, this temporal mismatch appears to have negative effects on hatching success, and on population growth rates in years that are colder than average in the first six months. Phenological mismatch also can explain why parakeets from African populations (that are more likely to breed in autumn) have been poor invaders compared to parakeets from Asia. These lines of evidence support the hypothesis that the reproductive phenology of the Ring-necked parakeet can be a limiting factor for establishment and range expansion in colder climates. Our results provide growing support for the hypothesis that the match between climate seasonality and timing of reproduction (or other important life cycle events) can affect the establishment success, invasive potential and distribution range of introduced non-native species, beyond the mere effect of climate similarity.
In the UK, alongside an expanding common buzzard population, there is increasing concern of raptor predation at pheasant release pens. Historically, losses of poults to raptor predation has been low, ...commonly (90 % of shoots) ≤1 % of birds released into pens, representing a small percentage of losses relative to all causes of mortality. A small number of shoots did suffer higher losses, estimated at >5 % at one in 30 estates and >10 % at some estates. Predation was lower (i) with increased poult age at release, (ii) in later releases, (iii) in pens with good vegetative cover, (iv) in pens within woods <50 acres and (v) in releases of <500 birds; there were also indications that predation was greater in high-density releases. Studies found no evidence for indirect losses (i.e. non-predation impacts of raptor activity, e.g. panic-induced smothering events). Mitigation measures include the following: (i) sufficient vegetative cover (supplemented if necessary, e.g. brash piles), (ii) minimise perching opportunities for raptors, (iii) stock older poults, (iv) stock at recommended densities, (v) reflective tape and scaring devices and (vi) diversionary feeding. Significant gaps in knowledge were identified, including (i) predation being incompletely evaluated in the context of contemporary buzzard populations, (ii) indirect effects not adequately studied, (iii) occurrence of ‘problem’ individual buzzards is unclear, (iv) adequate field trials of mitigation measures are lacking and (v) level of gamekeepers’ adherence to industry recommendations not known. Contemporary studies of these issues are necessary to understand the impacts and to inform management of buzzards at pheasant release pens.
Invasive alien species (IAS) are considered one of the greatest threats to biodiversity, particularly through their interactions with other drivers of change. Horizon scanning, the systematic ...examination of future potential threats and opportunities, leading to prioritization of IAS threats is seen as an essential component of IAS management. Our aim was to consider IAS that were likely to impact on native biodiversity but were not yet established in the wild in Great Britain. To achieve this, we developed an approach which coupled consensus methods (which have previously been used for collaboratively identifying priorities in other contexts) with rapid risk assessment. The process involved two distinct phases: Preliminary consultation with experts within five groups (plants, terrestrial invertebrates, freshwater invertebrates, vertebrates and marine species) to derive ranked lists of potential IAS. Consensus‐building across expert groups to compile and rank the entire list of potential IAS. Five hundred and ninety‐one species not native to Great Britain were considered. Ninety‐three of these species were agreed to constitute at least a medium risk (based on score and consensus) with respect to them arriving, establishing and posing a threat to native biodiversity. The quagga mussel, Dreissena rostriformis bugensis, received maximum scores for risk of arrival, establishment and impact; following discussions the unanimous consensus was to rank it in the top position. A further 29 species were considered to constitute a high risk and were grouped according to their ranked risk. The remaining 63 species were considered as medium risk, and included in an unranked long list. The information collated through this novel extension of the consensus method for horizon scanning provides evidence for underpinning and prioritizing management both for the species and, perhaps more importantly, their pathways of arrival. Although our study focused on Great Britain, we suggest that the methods adopted are applicable globally.
Grazing by mute swans
Cygnus olor can cause significant yield loss on individual fields of autumn-sown oilseed rape. In England, during 2002–2004, we tested the effectiveness of suspended high ...visibility tape in deterring grazing on 12 fields. On 8 fields tape was deployed over the whole field, whilst the other 4 fields were split into separate treatment (taped) and control halves (untaped). On all fields, trials involved sequential pre-treatment (no tape) and treatment phases (tape deployed), during which counts were conducted of swan droppings and swan numbers at approximately 2-week intervals. On all treated plots, following application of the tape, dropping counts were significantly reduced (median=99%, range 89–100%) as were swan numbers (median=97%, range=85–100%). The deterrent represents a highly effective control measure for reducing crop damage. In its current format, however, the technique is cost-effective only on the most heavily grazed fields.
The introduction of exotic species to ecosystems can have severe consequences for populations of native organisms, but logistical limitations and shortage of historical data often hinder attempts to ...quantify the ecological implications of such relationships. The establishment and rapid expansion of Ring-necked Parakeets Psittacula krameri in England therefore presents a rare opportunity to apply novel analytical methods to existing extensive national bird monitoring data from the UK Breeding Bird Survey for an invasive species. A previous study from Belgium suggests that Ring-necked Parakeets have the potential to reduce the abundance of Eurasian Nuthatch Sitta europaea through competition for nesting cavities. Our analysis provides no evidence for a significant impact through competition on Nuthatch populations or those of any other cavity-nesting species within the Parakeet's current range in the UK. However, we cannot exclude the possibility that competitive exclusion could be occurring at a minority of sites at which availability of nest cavities is limiting. This may yet have significant implications for future conflict if Parakeets continue to increase in numbers and range.
A hedgehog (Erinaceus europaeus) survey was conducted in four regions of west and south-west England during the summer of 2006. In each region, surveys were conducted in a series of 15–18 survey ...areas each of which contained 1–4 paired amenity grassland (recreation ground, sports field, and village green) and permanent pasture survey sites. Each pair of survey sites was surveyed for hedgehogs using night-time lamped searches during two separate survey periods. Located hedgehogs were sexed, weighed, and aged. The density of hedgehogs on individual sites was based on the maximum number of hedgehogs recorded during any one of the two surveys. The occurrence of hedgehogs on pasture (2 % of fields) was much lower than that on amenity grassland (26 % of fields), resulting in mean densities of hedgehogs that were significantly greater on amenity grassland than on pasture in all four regions. The density of hedgehogs was 0.47 ± 0.09 ha⁻¹ on amenity grassland and 0.04 ± 0.02 ha⁻¹ on pasture (mean ± standard error). This study represents a geographically extensive and locally intensive hedgehog field survey in England and produces results that are spatially and temporally concurrent with wildlife surveys of another ecologically linked species, the badger (Meles meles).
Walked spotlight transect surveys with distance sampling were used to estimate regional population densities of badger (Meles meles), fox (Vulpes vulpes) and brown hare (Lepus europaeus) in ...south-west England (Cornwall, Devon, Gloucestershire, Herefordshire) and Wales (Pembrokeshire, Borders, North Wales). All regions were surveyed during spring 2006 with English regions re-surveyed in autumn 2006. In each region, surveys were conducted in a random sample of 19.6 km2 areas (mean areas per region: spring = 19, autumn = 25). Within each survey area, a semi-random transect was established in each of a random sample of fields (open habitat almost exclusively pasture). Transects were subsequently walked at night with spotlights (mean transects per survey area: spring = 21, autumn = 21). Each area was surveyed twice during a season. Total transect length per region ranged from 137 to 193 km in spring and 230 to 250 km in autumn. The mean density of species per region was: badger 1.5–4.8 km−2, fox 1.0–4.0 km−2, hare 0.4–4.6 km−2. The study has provided baseline estimates of regional densities against which any future equivalent surveys can be compared. It has also illustrated the practical application of large-scale walked distance sampling to surveys of British mammals.
Yield loss due to grazing by mute swans was measured on nine fields of autumn-sown oilseed rape located in five regions of England. Using a paired-plot design, a significant reduction in yield (total ...dry weight of seed) was observed on three of the fields: 18%, 23% and 24%, respectively. On the first of these fields yield reduction was not simply due to fewer seeds being produced, as the weight of individual seeds was also significantly lower on grazed plots, with a reduction in thousand seed weight of 13%. Between fields (
n=9), yield loss was positively correlated with the number of swans per ha, and the number of days of swan grazing per ha. Significant levels of yield loss occurred only on fields grazed by >5 swans per ha. The density of swans grazing per ha can thus be used to predict potentially significant yield loss and provides an indicator of the level of swan grazing activity at which growers should consider deploying measures to reduce grazing.
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