Threats and Actions
This table summarizes the threats, threat scores, actions, and a justification for the assigned scores, following the IUCN classification scheme. Threat scores are based on the expert opinion of the authors of the Conservation Action Plan for Bicknell’s Thrush (see Appendix A for more details on methodology). This table can be downloaded as Excel, PDF, CSV, TSV, or ODS.
| Threat | Priority | Breeding/ Wintering/ Migration/ All | Exposition | Comments | Timing of threat | Timing impact score (0-3) | Scope of threat | Scope impact score (0-3) | Severity of threat | Severity impact score (0-3) | Total threat impact (0-9) | Justification of scoring | Action | Exposition | Action | Exposition | Action | Exposition | Action | Exposition | Action | Exposition | Action | Exposition | Action | Exposition | Action | Exposition | Action | Exposition | IUCN Threat Category |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Small-holder agriculture | High | W | Clearing forest to grow crops for subsistence and small-market agriculture results in loss and fragmentation of wintering habitat. Fields created in this system are permanent, and thus the continued operation of existing farms precludes habitat restoration. | Continuing | 3 | Affects the majority (50-90%) of the population | 2 | Causing or likely to cause very rapid declines (>30% over 10 years or three generations) | 3 | 8 | Small-holder farming renders areas unsuitable for wintering Bicknell's Thrush and could drive rapid declines. We did not have estimates of the amount of forest lost to small-holder farming, but suspected that this form of agriculture was more widespread than shifting agriculture. As such, we considered the scope of the threat posed by small-holder farming broader than for shifting agriculture. | 1.1 Land/water protection - Site/area protection | Acquire private properties that provide habitat for Bicknell's Thrush. | 2.1 Land/water management - Site/area management | Demarcate protected-area boundaries, increased enforcement of protected-area regulations. | 4.2 Education & awareness - Training | Improve institutional capacity for management of protected areas | 6.1 Livelihood, economic & other incentives - Linked enterprises & livelihood alternatives | Enhance opportunties for local ecotourism ventures; promote sustainable, shade-grown permanent crops like cacao or coffee, especially on degraded lands as a buffer to intact Bicknell's Thrush habitat | 6.4 Livelihood, economic & other incentives - Conservation payments | Direct payment for land-holders to protect habitat. | 8.1.6 Research - Actions | Research on drivers of land-use change and effectiveness of different interventions. | 8.1.6 Research - Actions | Research how to restore abandoned fields and develop best practices for habitat restoration. | 2.1.2 Annual and perennial non-timber crops - Small-holder agriculture | |||||
| Agro-industrial farming | High | W | Clearing forest to grow crops at an industrial scale, often for export, results in loss and fragmentation of wintering habitats. Fields created in this system are permanent, and thus the continued operation of existing farms precludes habitat restoration. | Continuing | 3 | Affects the minority (<50%) of the population | 1 | Causing or likely to cause very rapid declines (>30% over 10 years or three generations) | 3 | 7 | We applied the same rationale as for small-holder farming: agro-industrial farming results in loss of Bicknell's Thrush habitat because forests are cleared and replaced with vegetation (crops) that does not provide habitat. This threat is demonstrably ongoing, capable of causing rapid declines because it results in direct loss of habitat, and likely affects a non-neglible (i.e., >10%) minority of the population. | 1.1 Land/water protection - Site/area protection | Acquire private properties that provide habitat for Bicknell's Thrush. | 2.1 Land/water management - Site/area management | Demarcate protected-area boundaries, increased enforcement of protected-area regulations. | 4.2 Education & awareness - Training | Improve institutional capacity for management of protected area | 6.1 Livelihood, economic & other incentives - Linked enterprises & livelihood alternatives | Enhance opportunties for local ecotourism ventures; promote sustainable, permanent shade-grown crops like cacao or coffee, especially on degraded lands as a buffer to intact Bicknell's Thrush habitat | 6.3 Livelihood, economic & other Incentives - Market forces | Promote boycotts of crops grown within protected areas, certification of crops grown using sustainable practices (e.g., forest set-asides within plantations) | 6.4 Livelihood, economic & other incentives - Conservation payments | Direct payment for land-holders to protect habitat. | 6.4 Livelihood, economic & other incentives - Conservation payments | Direct payment land tenants with title or possessory interests within designated protected areas to relinquish property. | 8.1.6 Research - Actions | Research drivers of land-use change and effectiveness of different interventions. | 8.1.6 Research - Actions | Research how to restore abandoned fields and develop best practices. | 2.1.3 Annual and perennial non-timber crops - Agro-industry farming | |
| Incompatible forestry practices | High | B | Some forestry pratices may result in loss of breeding habitat. For example, several peer-reviewed studies have documented negative effects of pre-commercial thinning on breeding populations of Bicknell's Thrush. | Continuing | 3 | Affects the minority (<50%) of the population | 1 | Causing or likely to cause very rapid declines (>30% over 10 years or three generations) | 3 | 7 | We suspect that this threat affects <50% of the population because current estimates of the global population of Bicknell's Thrush indicate that the majority of the population breeds in high-elevation forests of the United States, which are not subject to forestry activities. | 5.3 Law & policy - Private sector standards & codes | Implement best management practices for forestry operations. | 5.2 Law & Policy - Policies & regulations | Implement policies that that require avoiding or limiting use of pre-commercial thinning in Bicknell's Thrush habitat and that promote compliance with existing rules and best management practices. | 8.1.2 Research - Population size, distribution & trends | Research distribution of Bicknell's Thrush in industrial forests of U.S. and Canada. | 8.1.5 Research - Threats | Determine whether retaining unthinned habitat promotes persistence of Bicknell's Thrush in landscapes where pre-commercial thinning is used. | 8.1.5 Research - Threats | Determine whether Bicknell's Thrush reproduce successfully in thinned stands that have regrown to the point of canopy closure. | 8.1.5 Research - Threats | Determine area of unthinned habitat necessary to meet conservation goals. | 8.1.5 Research - Threats | Determine at what point of maturity forest stands become unsuitable for nesting. | 5.3.5 Biological resource use - Logging and wood harvesting, unintentional effects: large scale | |||||
| Climate change | High | A | Future climate in much of the current breeding and wintering distribution may become unsuitable for forest types inhabited by Bicknell's Thrush. | Continuing | 3 | Affects the whole (>90%) population | 3 | Causing or likely to cause relatively slow, but significant, declines (<20% over 10 years or three generations) | 1 | 7 | Several modeling studies agree in predicting a reduction in the extent of suitable forest types on the breeding grounds due to increasing temperature. Several modeling studies also agree in predicting increasing aridity in the Greater Antilles, which may directly or indirectly affect quality and extent of wintering habitat. The entire population is at risk and the threat is ongoing, but effects will likely be manifested slowly. | 5.2 Law & Policy - Policies & regulations | Support policies that lead to reduced atmospheric concentrations of greenhouse gases. | 8.1.5 Research - Threats | Research effects of forecast changes in climate on distribution of breeding habitat for Bicknell's Thrush. | 8.1.6 Research - Actions | Identify areas of currently suitable habitat that may be resistant to climate change and that may act as refugia. | 8.1.6 Research - Actions | Research whether forest management can increase resistance of balsam-fir forests to climate change. | 11.1 Climate change and severe weather - habitat shifting and alteration | |||||||||||
| Wind-energy development | Medium | B | Construction of wind-energy facilities and associated infrastruture can result in loss of breeding habitat. | Continuing | 3 | Affects a negligible proportion of the population | 0 | Causing or likely to cause very rapid declines (>30% over 10 years or three generations) | 3 | 6 | Creation of wind-energy facilities can result in the permanent loss of breeding habitat and so represents a threat of moderate to high severity. At present, the threat is concentrated in certain areas, notably Québec. However, the scope of the threat has the potential to impact most of the breeding population because of the high overlap between Bicknell's Thrush breeding habitat and areas desirable for wind-energy generation. | 5.2 Law & Policy - Policies & regulations | Implement policies that require application of the mitigation hierarchy (avoid, minimize, or compensate) for any impacts to potential or actual breeding habitat. | 8.1.5 Research - Threats | Research effects of wind-energy facilities and associated infrastructure (e.g., mortality from collisions, impacts to breeding habitat). | 5.3 Law & policy - Private sector standards & codes | Develop best management practices for construction, operation, and maintenance of wind-energy facilities. | 3.3 Energy production and mining - Renewable energy | |||||||||||||
| Shifting agriculture | Medium | W | Clearing and burning forest to create temporary agricultural fields that provide one or a few crop rotations before abandonment results in loss and fragmentation of wintering habitat. Although fields are abandonded within several years, consumption of organic soil during burning may preclude or slow natural forest regeneration. | Continuing | 3 | Affects a negligible proportion of the population | 0 | Causing or likely to cause very rapid declines (>30% over 10 years or three generations) | 3 | 6 | Shifting agriculture renders areas unsuitable for wintering Bicknell's Thrush, and could thus drive rapid declines, but we could not find evidence that the practice was widespread in core wintering habitat. For exampe, shifting agriculture has resulted in extensive forest loss on the southern slope of Sierra de Bahoruco, but much of this area is marginal habitat for Bicknell's Thrush. | 1.1 Land/water protection - Site/area protection | Acquire private properties that provide habitat for Bicknell's Thrush. | 2.1 Land/water management - Site/area management | Demarcate protected-area boundaries, increased enforcement of protected-area regulations. | 4.2 Education & awareness - Training | Improve institutional capacity for management of protected areas by training park staff. | 6.1 Livelihood, economic & other incentives - Linked enterprises & livelihood alternatives | Enhance opportunties for local ecotourism ventures; promote sustainable, permanent shade-grown crops like cacao or coffee, especially on degraded lands as a buffer to intact Bicknell's Thrush habitat | 6.4 Livelihood, economic & other incentives - Conservation payments | Direct payment for land-holders to protect habitat. | 6.4 Livelihood, economic & other incentives - Conservation payments | Direct payment land tenants with title or possessory interests within designated protected areas to relinquish property. | 8.1.6 Research - Actions | Research on drivers of land-use change and effectiveness of different interventions. | 8.1.6 Research - Actions | Research how to restore abandoned fields and develop best practices. | 2.1.1 Annual and perennial non-timber crops - Shifting agriculture | |||
| Charcoal production | Medium | W | Single-tree/small-group harvest for charcoal production results in degradation and loss of wintering habitat. | Continuing | 3 | Affects the minority (<50%) of the population | 1 | Causing or likely to cause rapid declines (20-30% over 10 years or three generations) | 2 | 6 | Cutting trees for the purpose of manufacturing charcoal poses an ongoing threat to wintering populations of Bicknell's Thrush. We assume that the threat is not widespread but that it can cause fairly rapid, if localized, declines. | 2.1 Land/water management - Site/area management | Demarcate protected-area boundaries, increased enforcement of protected-area regulations. | 4.2 Education & awareness - Training | Improve institutional capacity for management of protected areas by training park staff. | 6.1 Livelihood, economic & other incentives - Substitution | Provide alternative fuels. | 8.1.6 Research - Actions | Research how to restore abandoned charcoal-production areas and develop best practices for habitat restoration. | 5.3 Law & policy - Private sector standards & codes | Implement best-management practices for sustainable charcoal harvest. | 5.3.3 Biological resource use - Logging and wood harvesting - Unintentional effects: subsistence/small scale | |||||||||
| Invasive species | Medium | W | Invasive animals, especially pigs, that disturb forest understory may diminish quality of winter habitat. This threat also includes direct increases in mortality caused by introduced predators such as rats and mongoose. | Continuing | 3 | Affects the majority (50-90%) of the population | 2 | Causing or likely to cause relatively slow, but significant, declines (<20% over 10 years or three generations) | 1 | 6 | Invasive, exotic mammals including feral pigs, rats, and mongoose are widespread in forests that provide habitat to Bicknell's Thrush during the winter. The threat posed by these mammals is ongoing and likely to continue indefinitely and we assume that the severity of the threat is sufficient to produce measurable, albeit minor, changes in population size. | 2.2 Land/water management - Invasive/problematic species control | Where approriate, implement programs to reduce numbers of invasive animals. | 8.1.6 Research - Actions | Research effectiveness of control measures. | 8.1 Invasive and other problematic species, genes and diseases - Invasive non-native/alien species/disease | |||||||||||||||
| Mining | Medium | W | Although not a current threat, potential expansion of larimar and bauxite mining may result in loss of wintering habitat. | Only in the future (could happen in the short term) | 2 | Affects a negligible proportion of the population | 0 | Causing or likely to cause very rapid declines (>30% over 10 years or three generations) | 3 | 5 | The timing of this threat was uncertain, but we assumed that new mines, reactivation of old mines, or expansion of existing mines could happen in the short term. Although the severity of the threat posed by mining is significant because of the profound effect of mining on a forested landscape, we did not have reason to believe that the scope of the threat was broad. | 2.3 Land/water management - Habitat & natural process restoration | Reclaim and restore abandoned mines. | 5.2 Law & Policy - Policies & regulations | Implement policies that require application of the mitigation hierarchy (avoid, minimize, or compensate) for any impacts to potential or actual wintering habitat. | 3.2 Energy production and mining - Mining and quarrying | |||||||||||||||
| Communication towers | Medium | B | Communication towers and associated infrastructure result in loss of high-elevation forests on breeding grounds and may result in direct mortality due to collisions. | Continuing | 3 | Affects a negligible proportion of the population | 0 | Causing or likely to cause rapid declines (20-30% over 10 years or three generations) | 2 | 5 | Erecting communications towers is an ongoing activity that can result in the permanent loss of breeding habitat and so represents a threat of moderate to high severity. The scope of the threat at present is modest and we assume that relatively few new towers will be erected in the future given the trend towards co-location with existing infrastructure. | 5.2 Law & Policy - Policies & regulations | Implement policies that require application of the mitigation hierarchy (avoid, minimize, or compensate) for any impacts to potential or actual breeding habitat. | 5.3 Law & policy - Private sector standards & codes | Develop and implement best-management practices for construction, operation, and maintenance of communication towers and associated infrastructure. | 4.2 Transportation and service corridors - Utility and service lines | |||||||||||||||
| Altered fire regimes | Medium | W | Wintering habitat is threatened by a lack of resources to control fire coupled with likely increase in fire frequency due to climate change and increasing human use of forests. | Continuing | 3 | Affects the minority (<50%) of the population | 1 | Causing or likely to cause relatively slow, but significant, declines (<20% over 10 years or three generations) | 1 | 5 | Broadleaf montane forests that constitute wintering habitat are not fire-adapted, but may be increasingly at risk if climate change results in more frequent and more intense drought as predicted by climate models. We assumed that most ignitions will occur in pine forest and spread to broadleaf forest, and thus that most wintering populations were relatively secure due to their isolation from fire-prone pine forests. Those populations at risk, however, might experience slow but significant declines. | 4.2 Education & awareness - Training | Increase number of firefighters trained in wildland fire suppresion. | 4.3 Education & awareness - Awareness & communications | Conduct wildland fire education in communities near vulnerable protected areas. | 2.1 Land/water management - Site/area management | Assess available equipment for wildland fire suppression and facilitate equipment acquisition where needed. | 2.3 Land/water management - Habitat & natural process restoration | Adopt fire-management practices that reduce risk of large, intense fires, especially at pine/broadleaf forest ecotone. | 7.1.1. Fire and fire suppression - Increase in fire frequency/intensity | |||||||||||
| Excessive browsing by moose | Medium | B | Large moose populations in Cape Breton Highlands, Nova Scotia are converting forested areas once suitable for Bicknell's Thrush into grassy clearings. | Continuing | 3 | Affects a negligible proportion of the population | 0 | Causing or likely to cause rapid declines (20-30% over 10 years or three generations) | 2 | 5 | Several studies have documented that browsing by unusually large populations of moose is preventing forest regeneration in Cape Breton Highlands and favoring grassy clearings over dense stands of regenerating balsam fir that would provide habitat for Bicknell's Thrush. This threat may cause local declines or extirpations, but we did not have evidence that the problem was widespread. | 2.2 Land/water management - Invasive/problematic species control | Continue experimental cull program. | 8.1.6 Research - Actions | Research effectiveness of different control techniques. | 8.2.2 Invasive & other problematic species, genes & diseases - Problematic native species/diseases - Named species | |||||||||||||||
| Acid precipitation | Medium | B | Acid precipitation harms spruce trees, thus potentially degrading breeding habitat, and depletes soil calcium, which may causes a decline in reproductive success. Acidification can also increase amounts of methyl mercury in the soil. | Continuing | 3 | Affects the minority (<50%) of the population | 1 | Causing or likely to cause negligible declines | 0 | 4 | Acid precipitation has abated somewhat in parts of the breeding range, although complete ecosystem recovery will require more stringent limits on emissions. The deleterious effects on high-elevation spruce forests seem to have diminished, and we could find no evidence suggesting that acid precipitation was currently implicated in measureable population declines. | 5.2 Law & Policy - Policies & regulations | Support policies that lead to reduced emissions of sulfur dioxide and nitrogen oxide. | 8.1.5 Research - Threats | Research current effects of acid precipitation on Bicknell's Thrush. | 9.5.1 Pollution - Airborne pollutants - Acid rain | |||||||||||||||
| Ski-area expansion | Low | B | Ski-area construction or expansion can result in loss of breeding habitat. | Continuing | 3 | Affects a negligible proportion of the population | 0 | Causing or likely to cause negligible declines | 0 | 3 | Expansion of existing ski areas is extremely limited, but we include in this threat the unauthorized creation of gladed skiing runs. Although these actions may reduce local habitat quality, we had no evidence or reason to believe that it affected large numbers of birds or that it would lead to severe declines. | 5.2 Law & Policy - Policies & regulations | Implement policies that require application of the mitigation hierarchy (avoid, minimize, or compensate) for any impacts to potential or actual breeding habitat. | 5.3 Law & policy - Private sector standards & codes | Work with ski areas and user groups to implement existing best management practices. | 1.3 Residential and commercial development - Tourism and recreation areas | |||||||||||||||
| Reforestation with exotic plants | Low | W | Reforesting cleared areas on the wintering grounds with quick-growing exotic softwoods for carbon markets precludes use by Bicknell's Thrush. Although not a net loss of habitat, represents an opportunity cost because that area remains uninhabitable by Bicknell's Thrush. | Continuing | 3 | Affects a negligible proportion of the population | 0 | Causing or likely to cause negligible declines | 0 | 3 | Although this threat is ongoing, we could not find evidence that it is widespread. In addition, because it does not result in a net loss of habitat - it replaces one form of unsuitable land cover with another form of unsuitable land cover - we determined that the severity of the threat was low. | 5.2 Law & Policy - Policies & regulations | Implement policies that prohibit use of exotic species in reforestation efforts within areas that could support habitat for Bicknell's Thrush. | 8.1.6 Research - Actions | Identify suitable native species for use in reforestation and research horticultural requirements. | 4.2 Education & awareness - Training | Train forest agents to transfer knowledge to users about research on reforestation with native species. | 5.3 Law & policy - Private sector standards & codes | Encourage adoption of standards for carbon offsets that promote use of native species. | 2.2.2 Agriculture and aquaculture - Wood and pulp plantations - Agro-indsutry plantations | |||||||||||
| Incidental take during forestry activities | Low | B | Forestry activities conducted during the breeding season may inadvertently cause mortality of eggs or nestlings. | Continuing | 3 | Affects a negligible proportion of the population | 0 | Causing or likely to cause negligible declines | 0 | 3 | Some number of Bicknell's Thrush nests may fail each year due to the direct effects of forestry operations, but had no reason to belive that the threat was widespread or that it was of sufficient severity to cause population declines. | 5.3 Law & policy - Private sector standards & codes | Develop and implement best management practices for forestry operations. | 5.2 Law & Policy - Policies & regulations | Implement policies that require conducting forestry operations outside of breeding season in Bicknell's Thrush habitat. | 5.3.4 Biological resource use - Logging and wood harvesting - Unintentional effects: large scale | |||||||||||||||
| Human recreation | Low | B | Recreational activities such as hiking or birdwatching in breeding habitat may disturb individual birds and reduce reproductive success. | Continuing | 3 | Affects a negligible proportion of the population | 0 | No decline | 0 | 3 | Many people engage in recreational activities in Bicknell's Thrush breeding habitat but no evidence exists that human disturbance is a widespread or important threat. One study of impacts of recreation in part of the breeding range found no effect on Bicknell's Thrush. | 4.3 Education & awareness - Awareness & communications | Outreach campaigns to recreational user groups about Bicknell's Thrush and its habitat. | 6.1 Human intrusion and disturbance - Recreational Activities | |||||||||||||||||
| Incidental take during research | Low | A | Researchers may inadvertently harm individual birds during species research. | Continuing | 3 | Affects a negligible proportion of the population | 0 | No decline | 0 | 3 | The extent of incidental mortality caused by research is unknown, but is believed to be low given the small number of individuals exposed to invasive research techniques (e.g., banding or attaching geo-locators). | 4.2 Education & awareness - Training | Adhere to the Ornithological Council's Guidlines for the Use of Wild Birds in Research. | 6.3 Human intrusions and disturbance - Work and other activities | |||||||||||||||||
| Development of stopover habitat | Not ranked | M | Development in coastal areas may result in loss of stopover habitat. | Unknown | NA | Unknown | NA | Unknown | NA | NA | Geolocator studies indicate that Bicknell's Thrush regularly stopover in coastal North Carolina and possibly in the Bahamas and Cuba. Development in these areas, which we assume would most likely come in the form of tourist resorts, might pose a threat although we do not have any evidence that this is currently happening nor can we estimate the number of birds potentially affected or the severity of the threat posed. | 8.1.3 Research - Life history & ecology | Identify stopover sites and habitat use during stopover. | 5.2 Law & Policy - Policies & regulations | Implement policies that require application of the mitigation hierarchy (avoid, minimize, or compensate) for any impacts to stopover habitat. | 1.3 Residential and commercial development - Tourism and recreation areas | |||||||||||||||
| Resort development | Not ranked | W | Development of resorts may result in a loss of wintering habitat. | Unknown | NA | Unknown | NA | Unknown | NA | NA | The possibility of resort development in wintering areas was raised during the IBTCG meeting, but we have no other information on this threat. | 8.1.3 Research - Life history & ecology | Conduct risk analysis of wintering habitat to identify areas at risk of development. | 1.3 Residential and commercial development - Tourism and recreation areas | |||||||||||||||||
| Livestock grazing | Not ranked | W | Cows and goats grazing in protected areas on the wintering grounds may reduce habitat quality. | Continuing | 3 | Unknown | NA | Causing or likely to cause negligible declines | 0 | NA | This issue was raised at the IBTCG meeting, but we could find no further information about the timing, scope, or severity of this threat. | 2.1 Land/water management - Site/area management | Demarcate protected-area boundaries, increased enforcement of protected-area regulations. | 8.1.5 Research - Threats | Resarch extent of threat posed by livestock use of Bicknell's Thrush habitat in protected areas. | 2.3.4 Livestock farming and ranching - Scale unknown/unrecorded | |||||||||||||||
| Collision with wind turbines during migration | Not ranked | M | Construction of wind-energy facilities and associated infrastruture may result in loss of stopover habitat. Migrating individuals may be vulnerable to mortality from collisions with turbines. | Unknown | NA | Unknown | NA | Unknown | NA | NA | Collisions with wind turbines during migration is a possible risk that is ongoing, but we were unaware of any data that would allow us to identify the scope or severity of the threat. | 8.1.5 Research - Threats | Research effects of wind-energy facilities and associated infrastructure (e.g., mortality from collisions, impacts to stopover habitat). | 5.3 Law & policy - Private sector standards & codes | Develop best-management practices for construction, operation, and maintenance of wind-energy facilities. | 3.3 Energy production and mining - Renewable energy | |||||||||||||||
| Wind-energy development | Not ranked | W | Construction of wind-energy facilities and associated infrastruture may result in loss of wintering habitat. | Unknown | NA | Unknown | NA | Unknown | NA | NA | We are unaware of any existing or planned wind-energy facilities in wintering habitat, although we recognize that the potential for such developments exists. We had no information that would allow us to identify the scope or severity of the threat. | 8.1.5 Research - Threats | Research effects of wind-energy facilities and associated infrastructure (e.g., mortality from collisions, impacts to winter habitat). | 5.3 Law & policy - Private sector standards & codes | Develop best-management practices for construction, operation, and maintenance of wind-energy facilities. | 3.3 Energy production and mining - Renewable energy | |||||||||||||||
| Communication towers | Not ranked | W | Communication towers and associated infrastructure result in loss of wintering habitat and may cause direct mortality due to collisions. | Unknown | NA | Unknown | NA | Unknown | NA | NA | Erecting communications towers is an ongoing activity that can result in the permanent loss of montane forest used as wintering habitat and so represents a threat of moderate to high severity. However, we have no information that would allow us to identify the timing or scope of this threat as it pertains to the wintering grounds. | 8.1.5 Research - Threats | Research effects of communication towers and associated infrastructure (e.g., mortality from collisions, impacts to wintering habitat). | 4.2 Transportation and service corridors - Utility and service lines | |||||||||||||||||
| Communication towers | Not ranked | M | Collisions with communications towers during migration result in mortality. | Unknown | NA | Unknown | NA | Unknown | NA | NA | Most bird species are vulnerable to mortality caused by collision with communication towers, and we assume that this includes Bicknell's Thrush. However, we are unaware of any data that would allow us to identify the scope or severity of this threat. | 8.1.5 Research - Threats | Research effects of communication towers and associated infrastructure (e.g., mortality from collisions, impacts to stopover habitat). | 4.2 Transportation and service corridors - Utility and service lines | |||||||||||||||||
| Altered disturbance regimes | Not ranked | B | Reduction in anthropogenic (logging) and natural (fire, insect outbreaks) disturbances may result in a decline in the amount of suitable breeding habitat. | Concern expressed in first CAP that weak market for wood products would drastically reduce extent of forestry operations in Canada and Maine. | Now suspended (could come back in the long term) | 1 | Unknown | NA | Unknown | NA | NA | The first Conservation Action Plan noted concern that natural and anthropogenic disturbances that create breeding habitat might occur less frequently in the future. Contrary to this expectation, the forest-products industry remains viable in most of Canada and the State of Maine and spruce budworms are once again epidemic in parts of the breeding range, and thus we considered this threat to be suspended. | 7.3 Natural system modification - Other ecosystem modifications | ||||||||||||||||||
| Invasive plants | Not ranked | W | The invasive native fern Dicranopteris pectinata forms thickets in forest clearings that may inhibit regeneration of forest suitable for wintering Bicknell's Thrush. | Continuing | 3 | Unknown | NA | Unknown | NA | NA | Empirical evidence and anecdotal observation indicate that the fern Dicranopteris pectinata inhibits forest regeneration in the Dominican Republic. As such, it may hinder habitat restoration and thus limit recovery of Bicknell's Thrush populations. However, we could not find information that allowed us to score the scope or severity of the threat. | 8.1.5 Research - Threats | Determine extent of threat posed by Dicranopteris pectinata. | 2.3 Habitat & natural process restoration | Where needed, use restoration techniques outlined Slocum et al. (2006). | 8.2 Invasive and other problematic species, genes and diseases - Problematic native species | |||||||||||||||
| Pesticides | Not ranked | W | Mosquito control in the Dominican Republic may have unintended, negative effects on Bicknell's Thrush. | Unknown | NA | Unknown | NA | Unknown | NA | NA | This issue was raised at the IBTCG meeting, but we could find no further information about the timing, scope, or severity of this threat. | 8.1.5 Research - Threats | Research consequences of mosquito control on Bicknell's Thrush. | 9.3.3 Pollution - Agricultural & forestry effluents - Herbicides and pesticides | |||||||||||||||||
| Lead poisoning | Not ranked | A | Lead present in montane forest soils may have sub-lethal physiological effects on Bicknell's Thrush. | Continuing | 3 | Unknown | NA | Unknown | NA | NA | This issue was raised in the first CAP, but we could find no further information about the timing, scope, or severity of this threat. | 8.1.5 Research - Threats | Research extent and consequences of lead exposure on Bicknell's Thrush. | 9.5 Pollution - Airborne pollutants | |||||||||||||||||
| Mercury poisoning | Not ranked | A | Mercury released during coal burning and waste incineration accumulates in the blood of Bicknell's Thrush and may cause sub-lethal physiological or behavioral effects. | Continuing | 3 | Affects the majority (50-90%) of the population | 2 | Unknown | NA | NA | Mercury occurs at elevated levels in blood of Bicknell's Thrush, and individuals are exposed to mercury on both wintering and breeding grounds, but we have no information about the consequences of exposure on individual vital rates or population growth rate. | 8.1.5 Research - Threats | Research consequences of mercury exposure on Bicknell's Thrush. | Law & Policy - Policies & regulations | Support policies that lead to reduced emissions of mercury. | 9.5 Pollution - Airborne pollutants | |||||||||||||||
| Ozone pollution | Not ranked | B | Ground-level ozone can accumulate in the air at high elevations. Exposure to elevated ozone levels has deleterious effects on human health, and unknown effects on the health of Bicknell's Thrush. | Unknown | NA | Unknown | NA | Unknown | NA | NA | High concentrations of ozone occur at high elevations in the northeastern US, but whether this poses a threat to Bicknell's Thrush is unclear and we could find no information addressing effects of ground-level ozone on wildlife populations. | 8.1.5 Research - Threats | Research consequences for Bicknell's Thrush of exposure to ground-level ozone. | 9.5.3 Pollution - Airborne pollutants - Ozone | |||||||||||||||||
| Altered predator-prey relationships | Not ranked | B | Climate change may disrupt an important interaction between red squirrels and Bicknell's Thrush on the breeding grounds. In a warmer climate, balsam fir may produce cones every year, instead of every other year, allowing large, permanent populations of red squirrel, an important nest predator, to become established across the breeding range. | Unknown | NA | Unknown | NA | Causing or likely to cause very rapid declines (>30% over 10 years or three generations) | 3 | NA | Uncertainty exists concerning the timing of this threat and its scope, especially given anecdotal evidence that populations in other parts of the range coexist with red squirrels. | 8.1.5 Research - Threats | Research whether climate change alters balsam fir cone cycle and red squirrel population dynamics in such a way as to affect Bicknell's Thrush population dynamics and whether these effects occur across the breeding range. | 11.1 Climate change and severe weather - habitat shifting and alteration - predators | |||||||||||||||||
| Altered phenology due to climate change | Not ranked | B | Warmer springs within the breeding range may advance the phenology of important prey species of Bicknell's Thrush, but not the date at which Bicknell's Thrush return to the breeding grounds, causing a mismatch between the timing of maximum prey availability and Bicknell's Thrush nesting. | Unknown | NA | Unknown | NA | Unknown | NA | NA | Although studies of other species have implicated phenological mismatches as a cause of steep and rapid declines, mismatched phenology does not always result in population-level impacts. This suggests the consequences of changing phenology may be species-specific, and no information is available regarding this phenomenon in Bicknell’s Thrush. Additional research is needed to clarify the risk posed by this threat. | 8.1.5 Research - Threats | Research whether phenological mismatch has consequences for population dynamics. | 11.1 Climate change and severe weather - habitat shifting and alteration - prey phenology | |||||||||||||||||
| Altered interspecific relationships due to climate change | Not ranked | B | Climate change may result in a greater degree of habitat overlap between Swainson's Thrush and Bicknell's Thrush and increased interspecific competition. | Unknown | NA | Unknown | NA | Unknown | NA | NA | Empirical documentations of competition between the species, and evidence of population-level impacts to Bicknell’s Thrush, are lacking. Indeed, in parts of Canada, the two species coexist without any evident negative consequences for Bicknell's Thrush. | 8.1.5 Research - Threats | Research whether competition with Swainson's Thrush has fitness consequences for Bicknell's Thrush and whether degree of overlap between two species is increasing. | 11.1 Climate change and severe weather - habitat shifting and alteration - competitors | |||||||||||||||||
| Forest pests and pathogens | Not ranked | B | Forest pests, such as balsam wooly adelgid, normally limited by cold climate may expand into montane forests and lead to loss and degradation of breeding habitat. | Unknown | NA | Unknown | NA | Unknown | NA | NA | Empirical information on the timing, scope, and severity of this threat is lacking. | 8.1.5 Research - Threats | Conduct threat assessment to examine potential impact of forest pests on Bicknell's Thrush. | 11.1 Climate change and severe weather - habitat shifting and alteration - forest pests and pathogens | |||||||||||||||||
| Drought | Not ranked | W | Increased frequency and severity of drought throughout the Caribbean Basin may diminish quality of winter habitat and increase risk of forest fire. | Unknown | NA | Unknown | NA | Unknown | NA | NA | Additional research is needed to document the direct effects of drought and quantify its timing, scope, and severity. Indirect effects of increasing aridity, such as increased risk of forest fire in wintering habitat or shifts in the distribution of wintering habitat, are addressed under other threats. | 8.1.5 Research - Threats | Research effects of drought on quality of Bicknell's Thrush habitat. | 11.2 Climate change and severe weather - droughts | |||||||||||||||||
| Severe weather | Not ranked | B | Greater frequency of inclement weather, such as heavy rain or wind, during the breeding season may lead to increased nest failure and reduced reproductive success. | Unknown | NA | Unknown | NA | Unknown | NA | NA | Documentation of this phenomenon, as well as continued downscaling of climate models, is needed to evaluate the risk posed by changes in the frequency of inclement weather. | 8.1.5 Research - Threats | Continue monitoring relevant demographic rates in long-term research sites. | 11.4 Climate change and severe weather - storms and flooding | |||||||||||||||||
| Severe weather | Not ranked | M | Greater frequency of severe storms may cause increased mortality during migration. | Unknown | NA | Unknown | NA | Unknown | NA | NA | Greater frequency of severe storms could cause increased mortality during migration and lead to declines in population size. At present, however, the degree of risk posed by this threat is unknown, and additional research is needed. | 8.1.5 Research - Threats | Research survival during migration and expand efforts to track birds during migration. | 11.4 Climate change and severe weather - storms and flooding |
