Definition of the nesting periods: The nesting chronology of birds includes several successive phases, including: finding a place to breed, choosing a mate, building a nest, laying and incubating the eggs and rearing the young inside and outside the nest. In this query tool, the nesting chronology given is starting with the laying of the first egg and ending with the departure of the last young from the nest. Thus, the earliest nesting dates do not take into account the nest building period and the latest nesting dates do not take into consideration the period of dependence of young outside the nest.

Accuracy of nesting dates: In general, the uncertainty around the estimated nesting dates given could vary within a period of up to 10 days or more due to the natural variability in the timing of nesting events between regions, individuals and years and due to the sampling and the constraints associated with the method used. Moreover, since the timing of nesting in this query tool applies to large geographical areas, it is possible that nesting periods in a given location could have different start dates and/or durations than the estimated dates due to micro-climatic conditions in specific areas (e.g., high elevation sites or coastal sites), as well as inter-annual variation due to factors such as an early spring or a cold, wet summer. In this query tool, the nesting dates provided are estimations from predictive models that identify the main nesting period. Before and after these dates the probability of encountering an active nest is lower, but not null. For more technical information concerning the methodology behind these estimations, please read the “About” tab in the query tool.

Protection of bird nests and eggs: The nesting period is critical in the life cycle of birds to maintain sustainable populations. That is why most bird’s nests and eggs are protected in Canada. The technical information provided by this query tool is for general information only. It is the full responsibility of every one to assess the risk of their activities with regards to avoidance and mitigation of inadvertent disturbance or destruction of bird nests and eggs. The information provided by this query tool does not provide a guarantee of the presence or absence of active nests or that the activities will avoid disturbing or destroying the nest or the eggs of a bird. Any time bird nests containing eggs or young are encountered, the immediate area should be avoided until the young have naturally left the vicinity of the nest. This protection measure should be taken even if the nest has been found outside the dates provided by this query tool. Once out of the nest, young birds are still vulnerable; therefore, precautionary measures are recommended. More information about the protection of federally protected migratory bird species, their nests and eggs and the general timing of nesting of migratory birds can be found from Environment Canada Web pages at: www.ec.gc.ca/paom-itmb.