Abstract
The Little Gull (Hydrocoloeus minutus) is a rare gull in most of North America; however, in spring it is relatively numerous at several sites in Ontario, as it migrates with its much more numerous relative, the Bonaparte’s Gull (Chroicocephalus philadelphia). The primary objective of this study was to document the spring migration phenology, abundance and behaviour of the Little Gull and the Bonaparte’s Gull at Oshawa Second Marsh (OSM), Ontario. Pursuit flights, roosting flights and migration departures by Little Gulls are also reported. The study took place from late March to late May, 1992–2022, at OSM. This site consistently hosted what was perhaps the largest predictable daily spring gathering of Little Gulls in North America. The earliest arriving individuals of both species appeared there in late March. Numbers of Little Gulls usually peaked during 22–28 April, and numbers of Bonaparte’s Gulls usually peaked from 29 April to 5 May; both species had left the area by mid-late May. The largest daily numbers of each species occurred on 26 April 2015: 158 Little Gulls and 5,783 Bonaparte’s Gulls. Daily counts of Little Gulls averaged 3.2% of counts of Bonaparte’s Gulls. Marsh rehabilitation efforts in 2015–2017, including the dramatic drawdown of water levels (to dry conditions), were associated with the complete abandonment of the site in spring by Little Gulls and greatly reduced numbers of Bonaparte’s Gulls since then. It is not known where the gulls have moved to during April–May or if they will return to their previous numbers at Oshawa Second Marsh.
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Recommended Citation
Hoar, Tyler; Weseloh, D.V. Chip; and Moore, David J.
(2023)
"Spring Migration Phenology, Abundance and Behaviour of Little and Bonaparte’s Gulls at Oshawa Second Marsh, Lake Ontario, Ontario, 1992–2022,"
Ontario Birds: Vol. 41
:
Iss.
1
, Article 6.
Available at:
https://digitalcommons.usf.edu/ontario_birds/vol41/iss1/6