The Oystercatcher Haemotopus
ostralegus is a very recognisable wader, with striking black and white
plumage, scarlet bill and bright pink legs (the name Haematopus means ‘blood foot’1, odd considering their
beak and eyes are redder). They’re also one of the most common and easily seen,
flying in loudly-peeping groups between feeding and roosting areas.
Oystercatchers live in many coastal habitats, from rocky
cliff bases to muddy estuaries across the British shoreline. Within the past 30
years some have moved inland upriver to gravel pits, flashes (shallow pools), and
pasture, a phenomenon first noticed in Scotland2. Some have even
followed the example of urban gulls, nesting in cities and feeding in playing
fields.
Oystercatchers are misnamed. Their original name was
‘Sea-pie’ after their pied feathers. Their current title is an Americanism, from
the naming of its cousin the American Oystercatcher H. palliatus in 1731, which eats small oysters3. Our oystercatchers rarely, if ever eat oysters,
but they do enjoy shellfish, especially mussels. Another appropriate older name
is ‘mussel cracker’3. Or it would be if they all cracked them...
The oystercatchers’ showy beak is very powerful *, allowing them to deal with hard-shelled prey, but their feeding habits differ. Some are ‘crackers’ or ‘hammerers’, bashing the shell until it smashes, whilst others are ‘stabbers’ prising the shells apart at the seam1,2,4. Their tools match their trade, stabbers having slimmer, flattened beaks and hammerers being shorter and thicker. Still others are worm-eaters with thin, pointed bills for probing their burrows4.
These types have puzzled ornithologists since the 1960’s. They were once thought to be learned through generations. Unlike other waders which feed themselves from day one, Oystercatchers teach their offspring how to eat. The parents can be devoted teachers, spending over 6 months schooling their young. However, oystercatchers nesting inland often leave for the coast before their young can fly with them so their habits cannot just be learned5.
The oystercatchers’ showy beak is very powerful *, allowing them to deal with hard-shelled prey, but their feeding habits differ. Some are ‘crackers’ or ‘hammerers’, bashing the shell until it smashes, whilst others are ‘stabbers’ prising the shells apart at the seam1,2,4. Their tools match their trade, stabbers having slimmer, flattened beaks and hammerers being shorter and thicker. Still others are worm-eaters with thin, pointed bills for probing their burrows4.
These types have puzzled ornithologists since the 1960’s. They were once thought to be learned through generations. Unlike other waders which feed themselves from day one, Oystercatchers teach their offspring how to eat. The parents can be devoted teachers, spending over 6 months schooling their young. However, oystercatchers nesting inland often leave for the coast before their young can fly with them so their habits cannot just be learned5.
The truth is even more fascinating. Oystercatchers can
switch their diets and are able to change their beak shape within days! This is thanks to their beak growing at three
times the rate of human fingernails, so it responds quickly to wear and
pressures (Just like our muscles and bone build up through strain and tear). In
a captive experiment, it took just 10 days for the beaks of mussel hammerers to
change to worm-eater form when their diet was switched. This makes the
oystercatcher very adaptable and able to exploit whatever prey is available4.
As well as molluscs and worms, oystercatchers also eat
insect larvae, shrimps, crabs, small fish and even occasionally the eggs
and chicks of small gulls (Though I could not find the original reference for
this-see comments reference 4).
They don’t always catch their own food, often stealing from smaller waders. Some are professional pirates, getting 60% of their food from other birds6. But the world is not their oyster, as black-headed gulls Choriocephalus ridibundus and even juvenile oystercatchers steal ready-opened molluscs from the stronger adults4.
They don’t always catch their own food, often stealing from smaller waders. Some are professional pirates, getting 60% of their food from other birds6. But the world is not their oyster, as black-headed gulls Choriocephalus ridibundus and even juvenile oystercatchers steal ready-opened molluscs from the stronger adults4.
Oystercatchers nest in bare scrapes on a prominent feature
such as a rock or in the open on shingle or short grass where they can easily
spot predators and their pebble-like eggs are camouflaged. Urban oystercatchers
take advantage of gravelled areas, including flat roofs.
Males protect the nest and are a force to be reckoned with. They react quickly to any passing nest predator, be it gull, corvid, raptor or human, flying up and chasing them away whilst shouting abuse. Other birds don’t want to get involved with the powerful beak. When I visited Skomer Island with friends in summer, oystercatchers were constantly setting off after the many gulls and Buzzards Buteo buteo. However, gull predation still greatly limits breeding success7.
Not all chicks are lucky enough to have their parent’s protection, since oystercatchers sometimes ‘egg dump’ –laying their eggs in the nest of another, like a gull. Whilst the female probably hopes her chick will be reared by its adopted parents like a cuckoo, its chances of survival are slim8.
Males protect the nest and are a force to be reckoned with. They react quickly to any passing nest predator, be it gull, corvid, raptor or human, flying up and chasing them away whilst shouting abuse. Other birds don’t want to get involved with the powerful beak. When I visited Skomer Island with friends in summer, oystercatchers were constantly setting off after the many gulls and Buzzards Buteo buteo. However, gull predation still greatly limits breeding success7.
Not all chicks are lucky enough to have their parent’s protection, since oystercatchers sometimes ‘egg dump’ –laying their eggs in the nest of another, like a gull. Whilst the female probably hopes her chick will be reared by its adopted parents like a cuckoo, its chances of survival are slim8.
Chicks that do survive to adulthood may live long and
prosper. Some oystercatchers have been recorded at 30-40 years old1,4.
Oystercatchers are certainly a unique wader. This pied piper
of our shorelines may be common and
perhaps taken for granted, but is hugely adaptable and intriguing
*In fact, it has the heaviest beak of all living waders.
References
1- R.A. Robinson.(2005) BTO
BirdFacts: profiles of birds occurring
in Britain & Ireland: Oystercatcher Haematopus ostralegus
[Linnaeus, 1758]. Available from:
http://blx1.bto.org/birdfacts/results/bob4500.htm
2- Peter Holden and J.T.R. Sharrock. (1989) The RSPB book of British Birds.
PAPERMAC, London.
3- Fransesca Greenoak. (1979) All the Birds of the Air. A.
Brown and Sons.
4- Darren Naish. (2010) The incredible bill of the
oystercatcher. Tetrapod Zoology.
Available from: http://scienceblogs.com/tetrapodzoology/2010/07/11/incredible-bill-of-oystercatcher/
5-William.J. Sutherland.
(1987) Why do animals specialize? Nature 325, 483-484. Cited by: Darren
Naish. (2010) The incredible bill of the oystercatcher. Tetrapod Zoology. Available from: http://scienceblogs.com/tetrapodzoology/2010/07/11/incredible-bill-of-oystercatcher/
6- Nicholas Hammond
and Bruce Pearson. (1994) Waders. Hamlyn,
London. Cited by: Darren Naish. (2010) The incredible bill of the
oystercatcher. Tetrapod Zoology.
Available from: http://scienceblogs.com/tetrapodzoology/2010/07/11/incredible-bill-of-oystercatcher/
7-M.P. Harris and S.Wanless. (1997) The effect of removing large
numbers of gulls Larus spp. on an island population of oystercatchers Haematopus ostralegus: Implications for
management. Biological Conservation 82
(2), Pages 167–171. Available from: http://www.sciencedirect.com/science/article/pii/S0006320797000190
8- Science Daily and Dr Clive Craik. (2011). Birds Dumping Eggs On the Neighbors. Available
from: http://www.sciencedaily.com/releases/2011/05/110524203605.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily+%28ScienceDaily%3A+Latest+Science+News%29&utm_content=Google+Feedfetcher
See also Mike Mottram’s entry on filming an urban oystercatcher nest in ‘Diaries of a Cheshire Wildlife Watcher’
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