The biology of this nomadic and variable species raises cautions in interpreting population data. The Breeding Bird Survey (BBS) provides information on population trends but, with routes in fixed locations and a species that wanders great distances and that can breed in any season (Adkisson 1996), BBS results may not adequately assess the population. The Christmas Bird Count (CBC) covers a large portion of the wintering range in Canada. However, like the BBS, CBC counts are conducted in fixed locations and may not always capture important portions of the population. The overall trend suggested by both surveys is an increase in population relative to about 1970. The graphs of annual indices from the two surveys suggest a somewhat different pattern. The BBS graph shows an increase in numbers during the 1970s followed by relatively little overall change since then, notwithstanding the large interannual fluctuations. The CBC graph shows a relatively stable population until 2008, at which point numbers began to increase (see BBS and CBC Canada graphs below). Considering both surveys, the Red Crossbill, which includes all subspecies except the percna subspecies, is perhaps best assessed as having shown a moderate increase relative to the early 1970s and is at an acceptable level relative to its national population goal (see BBS Canada graph below). However, this assessment is considered to be of medium reliability due to the varying precision of the results and the complex biology of this species.
The percna subspecies was once common in Newfoundland but is now relatively rare (COSEWIC 2016b). Although few quantitative data are available, existing evidence indicates that the population has decreased dramatically. Even with the recent discovery of a breeding population on Anticosti Island, the subspecies' abundance has been reduced to 1,000-2,500 individuals (COSEWIC 2016b). Though a specific long-term goal has not yet been determined for the percna subspecies, the large decline clearly indicates that the population is below the lowest acceptable level.
Additional information on: Breeding Bird Survey (BBS) - Canadian analysis
Additional information on: Christmas Bird Count (CBC)
