Canadian nesting zones are broad, general areas, corresponding roughly to Bird Conservation Regions (version 2014. updates have been made in 2022)

https://www.canada.ca/en/environment-climate-change/services/avoiding-harm-migratory-birds/general-nesting-periods/nesting-periods.html

The limits of nesting zones reflect:

- variations in species diversity

- variations in mean annual temperature

- similarities in the nesting periods within and between zones

Changes in the nesting period between adjacent nesting zones occur as a gradient.

When working near the boundary of a zone, you should also consider the nesting period of the adjacent zone..

More detail technical information are available here: https://publications.gc.ca/site/eng/9.843362/publication.html

Warning: This technical information on timing of nesting migratory birds are published by EC to support the planning of activities in order to reduce the risk of detrimental effects to migratory birds, their nests and eggs. This technical information constitutes advice only. This information does not provide an authorization for harming or killing migratory birds or for the disturbance, destruction or taking of nests or eggs as prohibited under the MBR. This information does not provide a guarantee that the 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. It is the responsibility of individuals and companies to assess their risk with regards to migratory birds and design relevant avoidance and mitigation measures.