Until recently, little was known of the abundance and distribution of the Franklin's Gull in Canada (Beyersbergen et al. 2009), which makes assessing the national population status relative to 1970 difficult. During the breeding season, this species tends to remain close to its nesting colonies, often located in large, remote marshes. It is therefore not very well monitored by the roadside Breeding Bird Survey (BBS; see Ronconi et al. 2015). Nevertheless, the BBS remains the only source of long-term data for the species and indicates a large decrease in abundance since 1970, albeit with low precision, both in Canada and range-wide in North America. Using 1970 as the base year to track changes in abundance may introduce a bias because this species has changed its feeding behaviour as agricultural methods have changed. In the 1970s, Franklin's Gulls were much more likely to be feeding in roadside fields as farmers ploughed the soil, exposing cutworms and grasshoppers, which attracted gulls to the fields. Modern methods of zero tillage leave standing stubble in the field from the previous year, making it harder for the birds to locate insect prey. This means that the gulls may now feed over water, rather than in roadside fields. What additional data are available are mixed and rather anecdotal; Alberta, Saskatchewan, and Manitoba populations appear stable, while populations in British Columbia appear to be increasing (though the locations of the breeding colonies remain unknown; Burger and Gochfeld 2009). Targeted surveys in 2005-2007 found large, yearly variation in colony counts due to the shifting nature of these colonies. However, over 95% of the birds surveyed were found in only 16 of the 36 colonies active in 2007, when all known colonies were visited and counted (Beyersbergen et al. 2009). Overall, the population is perhaps best assessed as having shown a large decrease since the 1970s, based on BBS results but, because of the limitations and uncertainties outlined above, the reliability of this assessment is considered low. Franklin's Gull is currently below the lowest acceptable level relative to its national population goal (see Canada graph below). Future assessments will benefit from repeated, targeted monitoring of this species' nesting colonies.
Additional information on: Breeding Bird Survey (BBS) - Canadian analysis
