Great Black-backed Gull (Larus marinus)

(last update: July 12, 2015)

Great Black-backed Gull adult December

Source:

Population Status, Distribution, and Trends of Gulls and Kittiwakes Breeding in Eastern Canada, 1998–2007 -
Occasional Paper Number 120, Canadian Wildlife Service, December 2012 (PDF)

by: R. C. Cotter, J.-F. Rail, A. W. Boyne, G. J. Robertson, D. V. C. Weseloh, K. G. Chaulk.

Chapter 4.4 Great Black-backed Gull

It is the largest gull in North America. This predominantly marine gull is the least abundant of the four main larids, with an estimated population of 30,980 pairs (61,960 individuals) (Table 1). Reflecting its marine origins, 79% of all Great Black-backed Gulls were found in Atlantic Canada (24,410 pairs) and 13% along the Gulf of St. Lawrence in Québec (4123 pairs) (Table 1; Figures 10, 11); only 8% (2447 pairs) of its population nested along fresh or brackish water, mostly along the St. Lawrence River and Estuary in Québec. Very few nest in the Great Lake system in Ontario; during a comprehensive gull census in 1999–2000 only 36 pairs were counted, and the majority of these were on the Lower Great Lakes system (especially Lake Ontario with 22 pairs). In 2004–2006, there was a die-off of Great Black-backed Gulls due to an outbreak of Type E botulism, and in 2007 only one pair was counted on Lake Ontario (Weseloh 2007a).

The coast and off-shore islands of Labrador, Newfoundland, and eastern Nova Scotia (i.e., East Coast) harbour over half of all Great Black-backed Gulls breeding pairs (57%, 17,653 of 30,980 pairs; Table 1) and colonies (64%, 486 of 763 colonies; Table 3). In each province, with the exception of Ontario, the Great Black-backed Gull has more colonies than any other gull species. Of the 763 colonies recorded during recent censuses, only 21 had 250 or more pairs (Tables 4, 6–9) while 92 had 100 or more pairs (Figure 12). Nova Scotia has 13 of these large colonies, including the two largest--Boot Island in the Bay of Fundy with 753 pairs (censused in 2002) and Outer Island in Shelburne County with 628 pairs (in 2002) (Table 6). The third largest colony was found on Île du Chenal (Grande-Entrée lagoon) on Îles-de-la-Madeleine in the Gulf of St. Lawrence in Québec, with 549 pairs (in 2007) (Table 9), while the fourth largest colony was found on Prince Edward Island at Poverty Beach, with 435 pairs (in 2004) (Table 7). The average colony size was slightly larger for the Maritimes, 62 pairs (n=289 colonies), than for Québec, 40 pairs (n=164 colonies) (Table 3).

Figure 10: Distribution of Great Black-backed Gull breeding colonies (number of pairs) in eastern Canada (number of colonies in parentheses). This is a map of eastern Canada showing the location of each Great Black-backed Gull nesting colony. Each red dot represents one colony, and the size of the dot represents the number of breeding pairs. There are three dot sizes: from small to large they represent 1 to 9 pairs, 10 to 99 pairs, and 100 to 999 pairs. The number of colonies in each size class is presented in parenthesis to the right of the size class.

Figure 11: Proportion (%) of the total breeding population estimate of the Great Black-backed Gull in eastern Canada, by province (A) and waterbody (B). This is a graph for the Great Black-backed Gull with, in part A, a pie chart showing the proportion (%) of its total breeding population that occurs in each province in eastern Canada and, in part B, a pie chart showing the proportion (%) of its total breeding population that occurs in each main waterbody (Great Lakes, Gulf of St. Lawrence, St. Lawrence River and Estuary, Bay of Fundy, and East Coast) in eastern Canada.

Figure 12: Frequency of colony size classes (number of pairs) of the Great Black-backed Gull in eastern Canada, by geographic region (A) and waterbody (B). This is a graph for the Great Black-backed Gull with, in part A, a bar chart showing the number of colonies per colony size class in Atlantic Canada, Québec, and Ontario and, in part B, a bar chart showing the number of colonies per colony size class in each main waterbody (Great Lakes, Gulf of St. Lawrence, St. Lawrence River and Estuary, Bay of Fundy, and East Coast) in eastern Canada . There are three colony size classes: from small to large (on the graph, from left to right), 1 to 9 pairs, 10 to 99 pairs, and 100 to 999 pairs. The number of colonies in each size class is presented on top of each bar.

Table 1: Estimated number of pairs of Ring-billed Gulls, Herring Gulls, Great Black-backed Gulls, and Black-legged Kittiwakes nesting in eastern Canada

1 This total is a minimum because Labrador has been only partially surveyed for nesting gulls; furthermore, this total includes 771 pairs from mixed Herring Gull and Great-Black-backed Gull colonies for which species was not identified.
2 Includes a Black-legged Kittiwake colony (Cape St. Mary's; 10,000 pairs) that was last censused in 1979.
3 Includes a Ring-billed Gull colony (Pointe de Sandy Beach; 1172 pairs; BIOMQ) that was surveyed in 2004; in 2002 this colony was unoccupied.
4 All Migratory Bird Sanctuaries were surveyed in 2005; colony data from Mingan Archipelago National Park Reserve and elsewhere date from 1990–1999.
5 Most colonies surveyed between 2001 and 2007, however a few were last surveyed in 1990 or 1995.

Table 3: Number and average size of Herring Gull and Great Black-backed Gull colonies in eastern Canada

1 na=not available; for most colonies only an approximate size was recorded (i.e., small, medium, large, or very large; see Methods).