MALLARD FEEDING FRENZY
Shaun Micklewright
During a visit to Trimpley Reservoir in mid February 2003 I was
surprised to record a significant increase in the numbers of
Mallards Anas platyrhynchos present on the main reservoir.
Although present throughout the year on the reservoirs and
adjacent River Severn, with the maximum number of birds recorded
around 30, I was quite surprised to observe approximately 140
feeding around the rocky shore of the reservoir. The water level
was approximately two meters below full capacity, exposing a dark
tide mark which I first thought was a type of alga, but on closer
inspection I was amazed to discover it was caused by thousands of
Zebra Mussels Dreissena polymorpha tightly encrusted on the rocks
and concrete banks. The Mallards appeared to be prizing them off
(no mean feat) with gusto and swallowing them whole in what I can
only describe as a feeding frenzy.
The Birds of the Western Palaearctic concise edition describes
Mallard food/feeding requirements as 'omnivorous and
opportunistic with a range of food and feeding methods'. I have
yet to find any reference specifically related to Zebra Mussel as
part of Mallard diet although both Tufted Duck Aythya fuligula
and Scaup Aythya marila regularly feed on them when they are
available.
All records of Zebra Mussels would be most welcome (see
Worcestershire Record No 11 November 2001). The Trimpley record
is a first for this site and, more worryingly, a potential
headache for water abstraction engineers.
Editor's note
The main BWP (Cramp 1977) states animal food includes "insects,
molluscs, crustaceans, annelids, amphibians, fish, and
occasionally even birds and mammals size range up to 5 cms but
usually 1mm to 1 cm". Bulk of diet is usually vegetable
material but mallards are nothing if not opportunistic feeders!
No mention of zebra mussels although BWP volume one was written
27 years ago and there may be more recent reports.
Reference:
D.W.SNOW, C.M.PERRINS 1998 The Birds of the Western Palearctic.
Concise Edition. OUP
CRAMP S et al 1977 The Birds of the Western Palearctic. Volume 1.
OUP
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