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Western Marsh Harrier Preys on Herring Gull
Author(s): Gary R. Graves
Source: Journal of Raptor Research, 48(2):191-192. 2014.
Published By: The Raptor Research Foundation
DOI: http://dx.doi.org/10.3356/JRR-13-00088.1
URL: http://www.bioone.org/doi/full/10.3356/JRR-13-00088.1
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Received 10 September 2013; accepted 28 January 2014
Associate Editor: Joan L. Morrison
J. Raptor Res. 48(2):191–192
E 2014 The Raptor Research Foundation, Inc.
WESTERN MARSH HARRIER PREYS ON HERRING GULL
KEY WORDS: Western Marsh Harrier; Circus aeruginosus; Herring Gull; Larus argentatus; predation.
The Western Marsh Harrier (Circus aeruginosus) is one of
the better known raptors in the western Palearctic (Cramp
and Simmons 1980), and has been the subject of several
diet studies (Schipper 1973, Underhill-Day 1985, Clarke
et al. 1993, Brzekin´ski and Z˙mihorski 2009, Cardador
et al. 2012, Tornberg and Haapala 2013). Harriers feed
on a wide range of small mammals and birds. Most avian
prey is relatively small (10–675 g) but harriers occasionally
take prey as a large as 1000 g (e.g., Great Bittern [Botaurus
stellaris]; Tornberg and Haapala 2013). However, prey
items at the larger end of the mass spectrum tend to be
juvenile, sick, or disabled individuals (Schipper 1973).
Nesting harriers in Finland frequently took Black-headed
Gulls (Chroicocephalus ridibundus; 265 g) and less frequently
Mew Gulls (Larus canus, 415 g; Tornberg and Haapala
2013). To my knowledge, there are no published records
of Western Marsh Harrier preying on larger and more
aggressive species of gulls.
On 8 September 2013, I watched a congregation of sev-
eral thousand waterfowl, cormorants, shorebirds, Black-
headed Gulls, Great Black-backed Gulls (Larus marinus)
and Herring Gulls (Larus argentatus) from an observation
JUNE 2014 LETTERS 191
blind at Klydesøreservatet (55u34.89N, 12u31.89E) near
Copenhagen, Denmark. Two Western Marsh Harriers
made several passes over the mudflats and Phragmites beds
before my attention was drawn to a commotion of North-
ern Lapwings (Vanellus vanellus) and Black-headed Gulls
harassing a harrier that had captured a Herring Gull at
the end of a narrow spit (12:24 H). I observed the action
through a 20–603 scope from a distance of 205 m (mea-
sured with Google Earth Pro). The harrier had the gull’s
neck pinned to the mud with one foot, while the gull was
on its back, feebly beating its wings, and slowly kicking its
legs in a running fashion. The struggling gull failed to
right itself and the harrier carried it to higher ground
with the aid of a strong wind (approximately 28 km/
hr). At the higher site, the harrier’s feet and the gull’s
head were obscured by a dead thistle, so I could not see
how the harrier finally dispatched the gull, which contin-
ued to kick until 12:33 H. The harrier began consuming
bits of muscle soon afterwards and started plucking the
gull’s breast at 12:48 H. It fed until 12:52 H, stepped off
the gull’s carcass at 12:59 H, and preened nearby on the
ground until I left the area at 13:09 H. Having missed the
harrier’s initial strike, I do not know whether the gull was
acting normally beforehand or whether it showed signs of
disease or incapacitation. However, the length of time
(.9 min) required for the harrier to kill the gull suggest-
ed the gull was reasonably fit.
The harrier’s golden crown and throat, and the absence of
pale markings on the breast and leading edge of the wing
indicated that it was a juvenile. The gull was in second- or
third-year plumage, with dark mottling on the upper wing
coverts. Herring Gulls from nominate populations in Norway
vary in weight from 795 to 1440 g (Cramp and Simmons 1983),
overlapping the size range of female harriers (540–1269 g) but
not males (320–667 g; Cramp and Simmons 1980).
I thank two anonymous reviewers for helpful comments
and the Smoketree Trust for support.—Gary R. Graves
(email address: gravesg@si.edu), Department of Verte-
brate Zoology, MRC-116, National Museum of Natural His-
tory, Smithsonian Institution, P.O. Box 37012, Washing-
ton, D.C. 20013 U.S.A, and Center for Macroecology,
Evolution and Climate, University of Copenhagen, 2100
Copenhagen Ø, Denmark.
LITERATURE CITED
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Feeding behaviour and diet composition of Marsh Har-
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and Hen Harriers C. cyaneus on the Dutch coast in
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the birds of the western palearctic: hawks to bustards.
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Harrier Circus aeruginosus breeding on the isle of Hai-
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Received 12 November 2013; accepted 10 January 2014
J. Raptor Res. 48(2):192–193
E 2014 The Raptor Research Foundation, Inc.
PREDATION BY GEOFFROY’S CAT ON FERRUGINOUS PYGMY-OWL IN CALDE´N SEMIARID FOREST, ARGENTINA
KEY WORDS: Ferruginous Pygmy-Owl; Glaucidium brasilianum; Geoffroy’s cat; Leopardus geoffroyi; Argentina;
predation.
The Ferruginous Pygmy-Owl (Glaucidium brasilianum) has
a broad geographic distribution, occurring from the south-
western United States to Central America and South Amer-
ica (Holt et al. 1999, Proudfoot and Johnson 2000). It is
found in a variety of habitats from tropical and subtropical
dry forest to semiarid open forest; it nests in natural cavities
and is active diurnally (Proudfoot and Johnson 2000). Pre-
dation of Ferruginous Pygmy-Owl nestlings by raccoons
192 LETTERS VOL. 48, NO. 2