Population status

Bonaparte's Gull
(Chroicocephalus philadelphia)

The Bonaparte’s Gull winters widely throughout the Great Lakes south to Mexico and the Caribbean Islands (Burger and Gochfeld 2002). The Christmas Bird Count (CBC) offers good coverage of those individuals wintering in temperate regions, but poorer coverage of more southerly wintering birds. Though CBC results combine data from the United States and Canada, most individuals breed in Canada, so these results should be fairly representative of the population’s status in Canada. The Breeding Bird Survey does not adequately cover the northern portion of this species’ breeding range, and so is not considered here. Based on the CBC results for North America, the Bonaparte’s Gull has increased largely in Canada. However, the precision of the trend estimate is only moderate, and there have been large fluctuations in the population, which complicates this assessment and suggests a flag of medium reliability. Interestingly, an assessment of birds in the Salish Sea, British Columbia, indicates the species experienced a decline of 4.5%/year, from 1994-2010, similar to many fish-eating birds in the region (Vilchis et al. 2015). The Bonaparte’s Gull is currently at an acceptable level relative to its national population goal (see graph below).


Population goal and acceptable levels of variation

Species/groupGoalLower levelUpper level
Bonaparte's GullMean abundance (2008-2012)10th percentile of observed abundance (1970-2012)Not applicable

Picture of logo Christmas Bird Count (CBC)

Additional information on: Christmas Bird Count (CBC)

Table 1: Population trends by geographic area
Geographic areaTime PeriodAnnual Trend Table 1 - footnote 1 Limits
North America Select to view graph of the geographic area: North America 1970-2016; Christmas Bird Count (CBC)1970-20161.6-1.25.1

British Columbia Coastal Waterbird Survey

Additional information on: British Columbia Coastal Waterbird Survey

Table 2: Population trends by geographic area
Geographic areaTime PeriodAnnual Trend Table 2 - footnote 1 Limits
British Columbia coast1999-20160.4-94.41691.4