Stashing behaviour in a Herring Gull

Title:Stashing behaviour in a Herring Gull
Author(s):Tom Dickins, Miles Thompson
Outlet:British Birds
Abstract Summary:At around midday on 6th June 2019, in warm, bright conditions, we were watching a small Kittiwake (Rissa tridactyla) colony on the west coast of Lundy, Devon. Our attention was drawn to an adult Herring Gull (Larus argentatus) on the rocks below with a live Common Guillemot Uria aalge chick. We estimated that the chick was just a few days old, which fitted with data from a sample plot at a larger colony about 200 m south of our vantage point (Grant Sherman, pers. comm.). The gull stabbed at the chick, grabbed it and shook it, and moved it around various ledges and banged it against the rocks. After a short period, the chick died. The gull meanwhile continued these behaviours. At first they appeared random but after a while we wondered whether this was a sequence of ‘processing’ the chick before consuming it. About 20-25 minutes into this event, the gull began attempts to swallow the chick whole. At each failure the chick was processed further, and we were reasonably convinced that this was designed to pulverise the chick’s internal structure to make it easier to swallow. We were surprised that the gull could not swallow the chick and wondered if the gull had fed recently.

Presently, a second Herring Gull arrived and perched above the first. This led to the first gull moving the chick and then chasing off the new arrival. Later, another Herring Gull arrived and took up the same position – we suspect it was the original interloper. This again led to the first chasing it off, but then (c. 45 minutes into the bout) the gull took the chick and stashed it in nearby rocks. Once the interloper had left, the first gull did not return for at least another 15 minutes. The stashing behaviour was very deliberate, and the chick was moved to a crevice much less obvious from the air. We are unaware of stashing behaviour in gull species and would be interested to learn more about this action. It clearly occurred under threat of kleptoparasitism, which is well documented in this species (Spencer et al. 2016).
Reference:Dickins, T., & Thompson, M. (2020). Stashing behaviour in a Herring Gull. British Birds, 113(April 2020), 233-239.
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