. The Canadian field-naturalist. 1988 Blokpoel and Struger: Cherry Depredation by Ring-billed Gulls 431 N Toronto, Hamilton Harbour /wjnona. • City or town ^Ring-billed Gull colony Approximate area of ''cherry growing 50 km Figure 1. Map of the Niagara Peninsula and vicinity. Assuming that all cherry pits found at the six colonies were of cherries that would have been sold at 2 cents each if there had been no interference by gulls, the cherry pits found at the colonies represent an estimated retail loss of $23 480. Discussion Gulls feeding on cherries The comments by the observers suggested th
. The Canadian field-naturalist. 1988 Blokpoel and Struger: Cherry Depredation by Ring-billed Gulls 431 N Toronto, Hamilton Harbour /wjnona. • City or town ^Ring-billed Gull colony Approximate area of ''cherry growing 50 km Figure 1. Map of the Niagara Peninsula and vicinity. Assuming that all cherry pits found at the six colonies were of cherries that would have been sold at 2 cents each if there had been no interference by gulls, the cherry pits found at the colonies represent an estimated retail loss of $23 480. Discussion Gulls feeding on cherries The comments by the observers suggested that feeding by Ring-billed Gulls on cherries in 1985 was a new, rather than a hitherto unnoticed, activity in Ontario. At the colony sites we also found small numbers of regurgitated pits of plums and peaches. One grower reported that gulls were feeding on plums in his orchard and that they might also feed on peaches, pears and grapes. Estimate of financial damage Our estimate of the magnitude of damage based on estimated numbers of regurgitated cherry pits has several biases: (1) We did not visit five known colonies in the Niagara Peninsula area: Mohawk Island (in eastern Lake Erie 20 km west of Port Colborne, Figure I), Stony Point and Donnelly's Pier (at the easternmost tip of Lake Erie near Buffalo), and Buckhorn Island and Table Rock Island (in the Niagara River south of Tower Island). These colonies had an estimated total of IS 500 nests in. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ottawa Field-Naturalists' Club. Ottawa, Ottawa Field-Naturalists' Club
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