Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be increasing, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Wetlands International (2018) estimate the population at 1,000,000-1,490,000 individuals.
This species has undergone a small or statistically insignificant increase over the last 40 years in North America (data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007).
This species breeds in the northern USA and central-west Canada, migrates south through Central America and winters off the west coast southern Mexico, Central America and of South America, where it is particularly common from Ecuador to Chile (del Hoyo et al. 1996).
This species can be found on coasts, lakes, marshes, field and rubbish dumps. It feeds almost exclusively on earthworms or emerging chironomids, but also aquatic invertebrates, grasshoppers and incidental small rodents and small fish. Early arrivals to colonies may depend on grain or sunflower seeds before insects become available. In winter small fish make up an important part of the diet, as do fish offal and refuse. Breeding is highly synchronous, with individuals arriving at colonies in mid-April and laying in mid- to late May. It is a highly gregarious species, forming colonies from 100's to over 10'000 pairs at inland lands and marshes, with nesting requiring emergent vegetation (del Hoyo et al. 1996).
At present there are no factors thought to pose a genuine threat to this species.
Text account compilers
Calvert, R., Fisher, S., Butchart, S., Harding, M., Ekstrom, J.
BirdLife International (2019) Species factsheet: Larus pipixcan. Downloaded from http://www.birdlife.org on 25/08/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 25/08/2019.