The Breeding Bird Survey (BBS) is the most reliable survey for the Tree Swallow, although the northern portion of the breeding range is less well covered. Results from the BBS indicate that there has been a long-term decrease in abundance, resulting in an overall loss of 56% of the Canadian population since about 1970. Of the eight Bird Conservation Regions (BCRs) with reasonably reliable BBS data (displayed below), the three eastern (Lower Great Lakes/St. Lawrence Plain, Boreal Hardwood Transition, and Atlantic Northern Forest BCRs) and the British Columbian BCRs show moderate or large decreases in population, whereas the central regions (Boreal Taiga Plains and Prairie Potholes BCRs) show a stable population and a large increase, respectively. BBS results from throughout North America suggest that the continental population has decreased by about 40% since 1970. The Tree Swallow is below the lowest acceptable level relative to its national population goal (see BBS Canada graph below).
Additional information on: Breeding Bird Survey (BBS) - Canadian analysis
