Publications for Dr Gillian Gilbert

Birds of conservation concern in Ireland 4: 2020–2026

This is the fourth review of the status of birds in Ireland. Two hundred and eleven species were assessed and assigned to the Red, Amber or Green list of conservation concern.

The criteria mainly follow previous assessments of conservation status at global and European levels; and within Ireland, include historical decline, trends in population and range, rarity, localised distribution and international importance. The availability of more data has allowed us to move closer towards the ideal time windows of existing criteria.

Results show 23 species moving onto the Red list and only six leaving it. Twelve species are newly Red-listed due to changed European or global status. Three are Red-listed due to declines within the expanded short-term breeding time period. There is no doubt that having 54 (25.6%) of Ireland’s regularly occurring bird species now on the Red list is alarming, with some species having shown dramatic declines and losses on this island.

Existing conservation concerns are reinforced, such as the further catastrophic decline of waders with six more wading bird species joining the Red list; and generalist birds of farmland, like Kestrel Falco tinnunculus now Red-listed.

When grouped by habitat, upland (50%) and farmland (35%) have the highest proportions of Red-listed species. Snipe Gallinago gallinago is now Red-listed with severe declines in its breeding and wintering populations and Swift Apus apus is Red-listed due to a decline in its breeding population. Good news comes from some recovery in the populations of species such as Black-headed Gull Larus ridibundus and European Herring Gull Larus argentatus which move from Red to Amber.

Date
01 May 2021
RSPB Authors
Dr Gillian Gilbert, Andrew Stanbury
Authors
Gilbert, Gillian Stanbury, Andrew Lewis, Lesley
Published in
Irish Birds
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Using indices of species’ potential range to inform conservation status

Assessments of conservation status are typically based on short-term extinction risk, but the value of indicators that compare the current state of species (e.g., abundance or distribution) to potential baselines is increasingly recognised. The use of baselines in conservation legislation is hindered by ambiguity in how baselines should be determined and interpreted, leading to inconsistent application. Here, we explored the use of species’ potential ranges as a consistent means of quantifying baselines for assessing species’ distributions, a key component of conservation status. Using breeding birds of Great Britain (GB) as a case study, we simulated where bird species would be expected to occur today in a modelled world without human land use. We calculated indices that contrasted these potential human-free ranges with realised ranges. Our analyses revealed that 42% of GB birds have wider realised than potential ranges and 28% have narrower realised than potential ranges. These indices could lead to reassessments of current conservation priorities. Eighteen species assigned ‘least concern’ status by the GB regional IUCN Red List had much narrower realised than potential ranges, suggesting that their ranges are in a more degraded state than currently recognised by Red List criteria. Some of these species are not under active conservation management and could be candidates for higher prioritisation. Our approach provides a systematic means of quantifying range baselines that is not reliant on variable historic data or expert opinion and, thereby, provides a step forward in resolving a major contemporary problem in conservation assessment: how to set baselines in conservation consistently. The insights produced are also of wider scientific and cultural relevance, revealing where species would likely exist today in the absence of historic human impacts. This could be used to identify areas where targeted restoration actions might lead to the return of historically extirpated species, or even to novel colonists.

Date
22 January 2021
RSPB Authors
Dr Gillian Gilbert, Prof Jeremy Wilson
Authors
Mason, Tom HE Stephens, Philip A Gilbert, Gillian Green, Rhys E Wilson, Jeremy D Jennings, Kate Allen, Judy RM Huntley, Brian Howard, Christine Willis, Stephen G
Published in
Ecological Indicators
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Livestock management in red-billed chough feeding habitat in Great Britain and the Isle of Man

In Great Britain, red-billed chough (Pyrrhocorax pyrrhocorax) breed in discrete populations along the west coast: on Islay and Colonsay, in the Inner Hebrides of Scotland; on the Isle of Man; in Wales; and in Cornwall. Chough are dependent on pastures grazed by sheep or cattle, and their survival therefore depends on sympathetic management of grassland. The Scottish population is in decline, and all other populations are growing or stable. Sixty-three farmers in these regions whose farms were known to support feeding chough were asked questions about their farm management using a structured, questionnaire-based personal interview. Islay farms were significantly larger and had more grazing area, with the lowest stocking densities. Welsh farms had the least cropping area and the smallest number of cattle. Cornwall had the smallest number of sheep per farm. Welsh farms were more likely to not house cattle during winter. Liver fluke in sheep and ticks and tick-borne disease were a higher concern on Islay than other regions, and abortion in sheep was of highest concern on the Isle of Man. Islay farmers applied between 4× and 13× as many synthetic pyrethroid (SP) treatments to cattle per year than farmers at other regions, and the application rate of triclabendazole (TCBZ) to sheep was higher on Islay than other regions. The rate of application of other products, including macrocyclic lactones, did not differ among regions. The study described here shows clear differences in the farm grazing management, in the priority given to animal health problems and in the frequency of application of veterinary parasiticides among four regions that provide feeding habitat for chough in the United Kingdom. These differences suggest that the viability of chough populations might be favored by higher-intensity grazing and low rates of application of veterinary parasiticides of either the TCBZ or SP, or both classes of parasiticides.

Date
03 March 2020
RSPB Authors
Dr Gillian Gilbert
Authors
Nicholas N. Jonssona, Gillian Gilbert and Fiona S. MacGillivray
Published in
Rangeland Ecology & Management
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Implications of the prevalence and magnitude of sustained declines for determining a minimum threshold for favourable population size

We propose a new approach to quantifying a minimum threshold value for the size of an animal population, below which that population might be categorised as having unfavourable status. Under European Union law, the concept of Favourable Conservation Status requires assessment of populations as having favourable or unfavourable status, but quantitative methods for such assessments have not yet been developed. One population threshold that is well established in conservation biology is the minimum viable population (MVP) defined as the size of a small but stable population with an acceptably low risk of extinction within a specified period. Our approach combines this small-population paradigm MVP concept with a multiplier, which is a factor by which the MVP is multiplied to allow for the risk of a sustained future decline. We demonstrate this approach using data on UK breeding bird population sizes. We used 43-year time-series data for 189 species and a qualitative assessment of population trends over almost 200 years for 229 species to examine the prevalence, duration and magnitude of sustained population declines. Our study addressed the problem of underestimation of the duration and magnitude of declines caused by short runs of monitoring data by allowing for the truncation of time series. The multiplier was derived from probability distributions of decline magnitudes within a given period, adjusted for truncation. Over a surveillance period of 100 years, we estimated that there was a 10% risk across species that a sustained population decline of at least sixteen-fold would begin. We therefore suggest that, in this case, a factor of 16 could be used as the multiplier of small-population MVPs to obtain minimum threshold population sizes for favourable status. We propose this ‘MVP Multiplier’ method as a new and robust approach to obtaining minimum threshold population sizes which integrates the concepts of small-population and declining-population paradigms. The minimum threshold value we propose is intended for use alongside a range of other measures to enable overall assessments of favourable conservation status.

Date
12 February 2020
RSPB Authors
Dr Gillian Gilbert, Prof Jeremy Wilson
Authors
Green, Rhys E Gilbert, Gillian Wilson, Jeremy D Jennings, Kate
Published in
Plos one
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Foraging habitat of a declining Scottish Red-billed Chough Pyrrhocorax pyrrhocorax population in the post-breeding period

Capsule A declining Red-billed Chough Pyrrhocorax pyrrhocorax population, observed during the post-breeding period, used dung and soil-based habitat features as frequent and consistent food sources, but this had not changed from when the population was healthy. Aims To quantify use of different food sources by Red-billed Choughs in the post-fledging period and to measure any changes since 1989. To find habitat characteristics of soil-based foraging positions, and to highlight food sources that were used more by first-year birds. Methods In 2013 on Islay, Inner Hebrides, we recorded the foraging habitat of Red-billed Choughs at different spatial scales in the same location and using the same methods as a study in 1989. We made more detailed measures of foraging habitat in 2011–13 across other areas of Islay. Results At a large scale, dune pasture was the most preferred foraging habitat. There were indications of a change in preference with time in line with availability of seasonal habitats, such as cut silage and barley stubbles, and preference for foraging in fields with greater livestock density. Within preferred habitats, the most used sources of food at a small patch scale were dung and the soil around rocky outcrops; overall, this had not changed when compared between the declining 2013 population and healthy 1989 population. Soil at chough foraging locations was relatively drier and characterized by short, sparse, vegetation and a slight slope. We found that young birds foraged twice as frequently in dung compared to adults, while adults foraged twice as much in soil. Conclusions During the post-fledging period, consistent, reliable dung and soil-based features provide sources of invertebrate food for choughs, are as important now as they were 24 years before. These are at least equally as important as the opportunity and variety provided by seasonally available sources such as cut silage and barley stubble.

Date
20 May 2019
RSPB Authors
Dr Gillian Gilbert
Authors
Gilbert, Gillian MacGillivray, Fiona McKay, Clive Robertson, Helen
Published in
Bird Study
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Adverse effects of routine bovine health treatments containing triclabendazole and synthetic pyrethroids on the abundance of dipteran larvae in bovine faeces

Macrocyclic lactone treatments for livestock can have detrimental effects on the arthropod populations in livestock faeces. For the last twenty years, avoidance of these products has been a standard recommendation on livestock farms that are managed for wildlife by the Royal Society for Protection of Birds (RSPB). However, the continued decline in the populations of birds (in particular the red-billed chough Pyrrhocorax pyrrhocorax) that are dependent on dung invertebrates on islands in the Inner Hebrides of Scotland prompted us to investigate the effects of livestock treatments that are commonly used on these islands. We conducted a replicated field plot study over two years to quantify the effects of livestock treatments containing copper, deltamethrin and triclabendazole on invertebrate density in pooled, artificial faecal pats on the island of Islay. We found that the density of arthropod larvae was significantly reduced by the triclabendazole and deltamethrin treatments in both years and by as much as 86% when the treatments were combined. Copper-containing boluses did not consistently affect abundance of arthropod larvae. These results suggest that veterinary treatment of livestock might contribute to a reduction in the food supply of chough.

Date
04 March 2019
RSPB Authors
Dr Gillian Gilbert
Authors
Gilbert, G. MacGillivray, F. S. Robertson, H. L. Jonsson, N. N.
Published in
Scientific Reports
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The diet of a declining Red-billed Chough Pyrrhocorax pyrrhocorax population on Islay, Scotland

Capsule: We quantify Red-billed Chough Pyrrhocorax pyrrhocorax diet from faecal samples collected on Islay. Dung invertebrates formed the majority of prey biomass in dune pasture and...

Date
01 August 2018
RSPB Authors
Dr Gillian Gilbert
Authors
MacGillivray, F.S., Gilbert, G. & McKay, C.R.
Published in
Bird Study 65 (3): 422-425
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Bird-habitat relationships in reedswamps and fens

This chapter focuses on the habitat relationships of birds that are closely associated with reedswamps and fens in western Europe. These are normally waterlogged habitats with vegetation frequently ...

Date
01 December 2012
RSPB Authors
Dr Gillian Gilbert
Authors
Gilbert, G. & Smith, K.W.
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Grasshopper warbler Locustella naevia breeding habitat in Britain

Capsule Structural aspects were common across a range of different habitat types and there was evidence that this breeding habitat was limited in extent. Aims To characterize Grasshopper Warbler breed...

Date
02 April 2012
RSPB Authors
Dr Gillian Gilbert
Authors
Gilbert, G.
Published in
Bird Study
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Eurasian Bittern distribution and abundance in the UK during the 2009/10 winter

By collating records from a number of sources, primarily via BirdGuides, BirdTrack and county bird recorders, it was found that there were a minimum of 600 wintering Eurasian Bitterns Botaurus stellar...

Date
02 November 2011
RSPB Authors
Simon Wotton, Dr Gillian Gilbert
Authors
Wotton, S., Grantham, M., Moran, N. & Gilbert, G.
Published in
British Birds
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