Migratory birds: technical information on risk factors

Risk factors for migratory birds

Mallards © Thinkstockphotos
Photo: © Thinkstockphotos.
Mallards

Depending on the location, the time of year and the type of activities, some operations could be subject to different risk factors associated with migratory birds.

The main sensitive periods to consider are the breeding season and the migration periods although for some migratory bird species, risks may also be associated with other times of the year, such as the post-breeding moult period and wintering stages.

The main sensitive locations include, for example, migratory bird breeding colonies and feeding areas around them as well as migration staging sites.

In the case of bird collisions with structures, generally the main risk factors are site sensitivity (areas of bird concentration, migratory pathways, surrounding landscaping and habitat type, particular meteorological conditions like fog, etc.) and structure design and size (reflectivity of glass panels, lighting used, use of guy wires, height, etc.).

Environment and Climate Change Canada provides information on the timing of migratory bird breeding in Canada and about other risk factors (see, for example, the Environment and Climate Change Canada publication: Wind Turbines and Birds: A Guidance Document for Environmental Assessment) in order to help individuals and companies assess their risk with regards to migratory birds and design relevant avoidance and mitigation measures.

Examples of risk factors associated with the take and disturbance of migratory birds, their nests and their eggs.

This table presents a summary of information extracted from the Avoidance Guidelines on Incidental Take published by Environment and Climate Change Canada. These examples are provided to help you with planning your activities.

Warning

The information presented here constitutes advice only. All persons must adhere to all pertinent laws (for example provincial or territorial laws), regulations and permit requirements including but not restricted to the Migratory Birds Convention Act, 1994 (MBCA) and the Migratory Birds Regulations (MBR). It is important to note that some species of birds protected under the MBCA have also been listed in Schedule 1 of the Species at Risk Act (SARA). These species receive protection from both the MBCA and SARA.

This advice does not provide an authorization for harming or killing migratory birds or for the disturbance, destruction or taking of nests or eggs under the Migratory Birds Regulations (MBR). It does not provide a guarantee that activities will avoid contravening the MBR or other laws and regulations. This is general information not intended to be relied on as official advice concerning the legal consequences of any specific activity. It is not a substitute for the MBCA, the MBR, or any other legislation.

Table 1. This table presents examples of lower and higher risk levels for the factor associated with management of incidental take of migratory birds in Canada.
Factor associated with management of incidental take
(More information)
Example of lower risk level Example of higher risk level
Knowledge of legal obligations Awareness of and understanding the relevant provisions of laws and regulations pertaining to the protection of birds, nests and eggs. Notably: the Migratory Birds Convention Act, 1994, the Migratory Birds Regulations and, where applicable, the Species at Risk Act. Unaware of legal responsibilities towards the protection of birds, nests and eggs.
Risk assessment and planning Completed a thorough risk assessment in a timeframe suitable to balance project needs with risk of incidental take of migratory birds. Little to no pre-planning or risk assessment around conservation issues related to migratory birds.
Preventive and mitigation measures

Measures are decided upon, implemented and monitored to avoid engaging in potentially destructive or disruptive activities at key locations or during key periods.

Records of decision and actions taken.

Measures (policies, procedures, plans, directive or compensatory plan) incorporated into a BMP.

Awareness of avoidance measures to be implemented on the part of proponents' representatives and field operations staff.

No specific measures planned and implemented to minimize the risk of detrimental effects and to help maintain sustainable populations of migratory birds.

No records.

No BMP.

Ignorance and /or no training.

 

Table 2. This table presents examples of lower and higher risk levels for the factor associated with protection of nests.
Factor associated with protection of nests
(More information)
Example of lower risk level Example of higher risk level
Timing Project occurs outside the general nesting period and won't affect nest to be reused the next year. Operations occur during the general nesting period or, throughout the year, could affect nest to be reused the next year (e.g., Great Blue Heron).
Likelihood of the presence of nests

Pertaining to the project, knowledge of available bird habitats, of migratory bird species and of the time periods during which they are likely to be encountered in such habitats.

Search for evidence of nesting using non-intrusive search methods to prevent disturbance.

No understanding of local bird presence in space or time.

Active nest searches, except when the nests searched are known to be easy to locate without disturbing them.

Habitat Habitat is small and simple, such as: human-made structure (bridge, beacon, tower, and building), man-made setting or those with few potential nesting spots or few species of migratory birds, urban park made mostly of lawns with few isolated trees, a vacant lot with sparse vegetation. Habitat is large and/or complex with many potential nesting areas, such as woodland and scrubland.
Nest type Presence of nests that are easy to find and avoid (e.g. Great Blue Heron, Bank Swallow, Chimney Swift); easy-to-find cavity nests in snags (e.g. woodpeckers, goldeneyes or nuthatches); or nests of colonial-breeding species that can often be located from a distance (e.g. colony of terns or gulls). - This applies to nests of a few species Presence of nest difficult to locate (e.g. cryptic or small), such as nest of songbirds. - This applies to nests of most species

 

Table 3. This table presents examples of lower and higher risk levels for the factor associated with disturbance of nests and nesting birds.
Factor associated with disturbance of nests and nesting birds
(More information)
Example of lower risk level Example of higher risk level
Intensity of operation

Infrequent, quick and low intensity disturbance.

One or few sources of disturbance.

Low or below ambient noise in natural areas.

Frequent, lasting and large disturbance.

Several sources of disturbance.

Loud noise emissions, especially when above ambient in natural areas or greater than about 50 dB.

Landscape context Presence of birds accustomed to disturbance in the area or already breeding successfully in disturbed areas. Presence of birds intolerant to disturbance, such as those moving away from their nest, agitated or performing distraction displays or actively defending the nest.
Preventive and mitigation measures Disruptive activities around nest halted and nest protected with effective / efficient buffer zone / setback distances according to circumstances until the young have naturally and permanently left the vicinity of the nest. No protection measures to reduce the effect of disturbance sources or ineffective/inefficient buffer or setback distance.

 

Table 4. This table presents examples of lower and higher risk levels for the factor associated with bird at sea and fishing.
Factor associated with birds at sea and fishing
(More information)
Example of lower risk level Example of higher risk level
Risk assessment Awareness of potential risks of fishing methods to seabirds and knowledge of where and when the birds are concentrated. No understanding of how fishing practices create risks for birds.
Preventive and mitigation measures Measures are decided upon implemented and monitored to avoid engaging in potentially destructive or disruptive activities at key locations or during key periods. No record or best management practices implemented.

Timing of nesting of migratory birds in Canada

Environment and Climate Change Canada publishes technical information on general nesting periods to support the planning of activities in order to reduce the risk of detrimental effects to migratory birds, their nests and eggs. However, any time nests containing eggs or young are encountered, the immediate area should be avoided until the young have naturally left the vicinity of the nest (see Buffer zones and setbacks distances). This protection measure should be taken even if the nest has been found outside the dates of the general nesting period for the area published by Environment and Climate Change Canada. Once out of the nest, young birds are still vulnerable therefore precautionary measures are recommended.

In some cases, such as for migratory birds listed under the Species at Risk Act (SARA), more specific information on nesting periods may be available and should be considered. At all times, the onus remains with the individual or company to comply with all applicable legislation. See more information on requirements related to residence protection under SARA.

In Canada, the general nesting period may start as early as mid-March and may extend until the end of August. This is a general nesting period that covers most federally protected migratory bird species. This period varies regionally across Canada mainly due to differences in species assemblages, climate, elevation and habitat type. Generally, the nesting period is delayed in more northerly latitudes, corresponding to vegetation development and food availability. To help with determining regionally relevant periods where nesting is likely to occur, Environment and Climate Change Canada is publishing estimated regional nesting periods within large geographical areas across Canada referred to as "nesting zones". These periods are estimated for each zone and consider the time of first egg-laying until the young have naturally left the vicinity of the nest. Note that the technical information published on this web site may be updated - and possibly modified - as new data become available.

For more information please see General Nesting Periods of Migratory Birds in Canada.

Specific considerations:

Related to determining the presence of nests

Migratory bird nests can be found in a wide variety of habitats and locations. Depending on the species, nests may be found at many heights in trees, in tree cavities, in shrubs, on the ground (including in hayfields, crops and pastures), on cliffs, in burrows, in stockpiles of overburden from mines, in quarry banks, within wetlands, and on human-made structures such as bridges, ledges, and gutters.

It is difficult to locate most nests. Nest sites are often hidden and adult birds avoid approaching their nests in a manner that would attract predators to their eggs or young. Moreover, the amount and complexity of habitat to be searched often limits the success of surveys intended to locate all active nests. The nests of a few species are easier to locate, particularly those in isolated trees, on human-made structures and/or in colonies.

To determine the likelihood that migratory birds, their nests or eggs are present in a particular location, use a scientifically sound approach that considers the available bird habitats, which migratory bird species are likely to be encountered in such habitats, and the time periods when they would likely be present. This will help you plan work activities to avoid having an impact on nesting birds. If further investigation is required to determine the presence of breeding birds, consider conducting an area search for evidence of nesting (e.g., presence of birds in breeding habitat through observation of singing birds, alarm calls, distraction displays) using non-intrusive search methods to prevent disturbance to migratory birds. In the case of songbirds, for example, “point counts” (a technique to locate singing territorial males) may provide a good indication of the presence of nests of these birds in an area. Please contact Environment and Climate Change Canada’s Canadian Wildlife Service office in your region for further technical information about investigation methods for non-song bird species (notably, waterfowl, waterbirds and shorebirds).

In most cases, nest search techniques are not recommended because, in most habitats, the ability to detect nests remains very low while the risk of disturbing active nests is high. Flushing nesting birds increases the risk of predation of the eggs or young, or may cause the adults to abandon the nest or the eggs. Therefore, except when the nests searched are known to be easy to locate without disturbing them, active nest searches are generally not recommended; they have a low probability of locating all nests, and are likely to cause disturbance to nesting birds. In many circumstances, incidental take is likely to still occur during industrial or other activities even when active nest searches are conducted prior to these activities.

In some cases, nest surveys may be carried out successfully by skilled and experienced observers using appropriate methodology, and in the event that activities would take place in simple habitats (often in man-made settings) with only a few likely nesting spots or a small community of migratory birds. Examples of simple habitats include:

  • an urban park consisting mostly of lawns with a few isolated trees;
  • a vacant lot with few possible nest sites;
  • a previously cleared area where there is a lag between clearing and construction activities (and where ground nesters may have been attracted to nest in cleared areas or in stockpiles of soil, for instance); or
  • a structure such as a bridge, a beacon, a tower or a building (often chosen as a nesting spot by robins, swallows, phoebes, Common Nighthawks, gulls and others).

Nest searches can also be considered when looking for:

  • conspicuous nest structures (such as nests of Great Blue Herons, Bank Swallows, Chimney Swifts);
  • cavity nesters in snags (such as woodpeckers, goldeneyes, nuthatches); or
  • colonial-breeding species that can often be located from a distance (such as a colony of terns or gulls).

Buffer zones and setback distances

Birds usually perceive humans as potential predators and may leave their nests in response to being approached, or abort nesting because of stressful situations. In general, there is a negative relationship between the type and magnitude of disturbance experienced by a nesting bird or colony and its breeding success. For example, disturbed birds tend to spend more time off the nest which could increase the likelihood of predation on eggs or nestlings, exposure of nests and eggs to cold temperatures or wet conditions, fewer episodes of chick feeding, premature fledging or abandonment of nestlings and physiological stress. If nests containing eggs or young of migratory birds are located or discovered, disturbance in the nesting area should cease until nesting is completed (i.e., the young have permanently left the vicinity of the nest, which could range from a few days to a few weeks depending on the species and stage of development).

Any nest found should be protected with a buffer zone determined by a setback distance appropriate to the species, the level of the disturbance and the landscape context, until the young have permanently left the vicinity of the nest. The appropriate setback distance varies greatly according to the circumstances. For example, a buffer of only a few metres is a safety measure that is likely to reduce the risk of disturbing a migratory bird nesting in your backyard. However, a larger buffer may be more appropriate in the case of industrial operations.

Birds respond differently to different levels of disturbance, which could be determined based on the intensity, duration, frequency and proximity of the activity, but also on the cumulative effects of multiple activities in the vicinity of a nest. Therefore, setbacks should incorporate this dynamic by identifying larger setbacks for types of activities which cause greater amounts of disturbance. Significant sources of disturbance include: removal of vegetation and/or soil operations, drilling, loud noise, vibration, (e.g., seismic blasting from operations), or regular approach by humans or vehicles. Disturbance could also be associated with noise, especially when the noise is 10 dB above ambient noise levels in the natural environment or greater than about 50dB.

Birds can get used to disturbances and their degree of tolerance is largely a function of landscape context. Birds which choose to inhabit developed areas are less susceptible to disturbance and likely do not need buffers to the same extent as birds which inhabit more natural or remote settings. Birds can also be less tolerant if the nest is exposed and located in a landscape with sparse vegetation density and/or with lack of topographic relief (like the Prairie or tundra) compared to when the nest is hidden and/or in a more complex setting, like a forest or bush habitat. The risk of disturbance is also greater with larger birds (such as herons or cranes) that are generally less tolerant than songbirds (such as robins or sparrows). For songbirds, which generally have inconspicuous nests, setbacks may not be the most practical means of providing nest protection. For such species, alternative nest protection can still be provided without needing to know the precise nest location by protecting prescribed areas of high-quality habitat in the vicinity of known breeding activity. For heron colonies and other stick-nesting birds, which generally have conspicuous nests, setbacks are often used to provide nest protection.

Setback distances are often determined scientifically, based on the distance at which nesting birds react to human disturbance; expert opinion, however, is often used to supplement scientific data. Alert distance and flush distance are two benchmark measurements of disturbance distance that are often used to develop a baseline equation to help determine a setback distance. Alert distance is the distance at which the bird adopts an alert posture or emits alarm calls. Flush distance is the distance at which a bird takes flight or moves away from a threat, performs distraction displays (e.g., feigning a broken wing or sitting down on a non-nesting site to draw attention away from the nest), or actively defends the nest.

To help with the determination of appropriate setback distances for your circumstances, here are examples of setback ranges for different types of birds: 1-5m up to 10-50m or more for most nests of songbirds and other small birds; 10-25m up to 50m or more for swallow colonies, and 10-30m up to 50m or more for most waterfowl nests. The shorter distances are more reflective of urban backyards and the longer distances are more reflective of rural or natural habitats. The following examples are for sensitive species or species at risk: up to 500m or more for Trumpeter Swan; 50-100m up to 200m or more for Pileated or Red-Headed woodpecker cavities; 100-150m up to 300m or more for nests of Piping Plover; 100m up to a 1000m or more for nests of Sandhill Crane. Remember that these general examples should serve as a general starting point and must be adjusted after assessing relevant factors, such as those described above. A larger buffer may be needed to minimize the risk of disturbance caused by industrial operations and for species at risk. For guidance regarding seabird and waterbird colonies, please refer to Guidelines to Avoid Disturbance to Seabird and Waterbird Colonies in Canada.

 

Warning:

Note that it is the responsibility of the individual or organization undertaking the activities to determine set-back distances. The information presented above constitutes advice only. This advice does not provide an authorization for harming or killing migratory birds or for the disturbance, destruction or taking of nests or eggs under the Migratory Birds Regulations (MBR). It does not provide a guarantee that activities will avoid contravening the MBR or other laws and regulations. This is general information that should not be relied on as official advice concerning the legality of any specific activity. It is not a substitute for the Migratory Birds Convention Act, 1994, the MBR, or any other legislation. In particular instances, specific recommendations or requirements may apply and may be found in such documents as Species at Risk Recovery Strategies or other official documents. Please contact Environment and Climate Change Canada’s Canadian Wildlife Service office in your region for further technical information.

In all cases, the nest itself should never be marked using flagging tape or other similar material as this increases the risk of nest predation. If necessary, flagging tape can be placed at the limits of the buffer zone.

Related to disturbance of breeding colonies

Common Murres © Thinkstockphotos
Photo: © Thinkstockphotos.
Common Murres

Colonies of seabirds and waterbirds are particularly vulnerable to the effects of human disturbance. Disturbance can cause colonial-breeding birds to abandon their nests or young, or to use valuable energy reserves for defense, instead of incubating eggs and feeding their young. In addition, disturbance to the colony may prevent adult birds from returning to protect and feed their young, and expose eggs or chicks to predation and to the lethal effects of heat, cold and rain. Human activities in the vicinity of breeding colonies, such as fishing and boating or low-altitude flying, should be kept far enough away to avoid flushing birds from their nests, or cause them to dive at you in an attempt to drive you away from the colony. In all cases where you may be disturbing seabirds or waterbirds, move away as quickly and quietly as possible.

Environment and Climate Change Canada recommends that people do not enter seabird and waterbird colonies, maintain appropriate buffer zones around colonies, and avoid disturbing migratory birds during the breeding season. For more specific information including minimum distances and distances for anchoring large vessels, please refer to Guidelines to Avoid Disturbance to Seabird and Waterbird Colonies in Canada. In addition, protected areas such as National Wildlife Areas, Migratory Bird Sanctuaries and National Parks may have specific restrictions regarding buffer zones on land and in water, as well as flight restrictions. For more information, please contact Environment and Climate Change Canada’s Canadian Wildlife Service office in your region.

Related to birds at sea

Seabird populations are threatened by many factors including introduced predators on nesting colonies, contaminants, marine oil pollution and litter, climate change, tourism, disease, and aquaculture activities. Seabirds may be encountered at sea at any time of year and in almost any location, however, many seabirds tend to concentrate in particular areas; the birds are at greater risk if there are interactions between seabirds and human activities in those areas.

Environment and Climate Change Canada conducts research and monitoring to determine the areas and time periods where seabirds congregate. This is done to raise awareness of the potential risks to seabirds from human activities, and to identify the areas and time periods when those risks may be higher. The information from this research and monitoring is also provided in order to facilitate risk management decisions by those who carry out activities in areas where seabirds are found. The first phase of this work was a study to determine areas of increased density for species vulnerable to fisheries bycatch in Canada's Pacific Ocean. For additional information, please refer to the section on Birds at sea or contact Environment and Climate Change Canada’s Canadian Wildlife Service office in your region.

Related to maintenance of human-built structures

Activities such as cleaning, application and removal of protective coatings (e.g., paints), and demolition should not take place during the breeding season on structures where migratory birds are nesting, as there is a risk of disturbing or destroying eggs or nestlings.

Where maintenance activities must take place during the breeding season, netting or other appropriate systems may be temporarily installed prior to the arrival of birds in the spring, in order to prevent birds from initiating nesting on the structure.

Generally, if migratory birds nesting in buildings are a cause for concern, it is recommended that you identify how the birds enter the building and block those entries after nesting is completed and before the birds come back to nest the following season. Should there be additional concerns, please contact Environment and Climate Change Canada’s Canadian Wildlife Service office in your region.

Related to water-level regulation

Red-necked Grebe on a floating nest © Photos.com
Photo : © Photos.com.
Red-necked Grebe on a floating nest

The management of dams and project construction and maintenance may necessitate modifications to water levels in reservoirs, ponds or other wetlands. For example, it may be required to remove beaver dams in order to regulate water-levels. Under such circumstances, project managers should determine whether waterfowl, waterbirds and/or other birds are nesting in or near the wetland, and avoid regulating water-levels that could result in flooding or drying out nests until the birds have raised their young. Water-level modifications may, for example, be scheduled prior to or after the breeding season.

Related to exposed soil banks

Bank Swallows © Nolan Pelland, Marathon, Ontario
Photo : © Nolan Pelland.
Bank Swallows, Marathon, Ontario

Particular care should be taken in selecting erosion prevention and control measures if migratory birds are found nesting in stockpiles of overburden or on exposed soil banks in sand pits or quarries. During the breeding season it is important that nests not be disturbed by erosion prevention and control measures or by excavation and construction activities. For species such as Bank Swallows, which nest in burrows dug into exposed soil banks, the period when nests are considered active includes not only when birds are incubating eggs and taking care of flightless chicks, but also the short roosting period after chicks have learned to fly and nests continue to be used.

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