O is for Oystercatcher

OYSTERCATCHER (HAEMATOPUS OSTRALEGUS)

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 seam^1,2,4. 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.

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.

Chicks that do survive to adulthood may live long and prosper. Some oystercatchers have been recorded at 30-40 years old^1,4.

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’

N is for Nuthatch

NUTHATCH (SITTA EUROPAEA)

With its powder blue upperside, blended cream and rusty orange underside and charcoal bandit mask , the Nuthatch Sitta europaea looks as if it has been coloured with pastilles, but is surprisingly difficult to see in its shady habitat. The nuthatch is truly a woodland bird, and with good reason. Like a woodpecker (which it resembles) it finds food on and under tree bark, hopping up, down and around the trunk and branches in search of insects. The nuthatch is the only British bird capable of climbing down a tree trunk head first. They achieve this through not relying on their tail as a prop, as woodpeckers and treecreepers Certhia familiaris do, and by having especially large, strong feet which they position one behind the other to act as a pivot and support¹.

The nuthatch reveals itself by its insistent piping call or the crackling sound of it pecking and peeling bark. Even then, they are difficult to keep track of as they scoot and weave behind the tree in and out of view.  However, they are quite tame and will call or feed a couple of meters away.

The nuthatch also eats seeds and nuts in autumn and winter when insects become scarce, cracking them by shoving them into a bark crevice and thrusting down with its powerful beak. This habit earned them their original, more powerful name ‘Nut hacker’ which has since become corrupted².

Nuthatches are partial to peanuts and seeds from garden feeders and bird tables, where they aggressively chase off other small birds, especially other nuthatches. Though they are increasingly seen in gardens where they are most easily observed, they only visit those near woodlands. Nuthatches stay very close to their birthplace, and even patches of suitable natural woodland may not be colonised if they are too far from others³. However, nuthatches are slowly moving North with warmer British weather, and were first recorded breeding in Scotland in 1989⁴

Perhaps because they don’t move far and because they nest in scarce tree holes, territory is very important to nuthatches. Neighbouring pairs have frequent stand-offs. Usually these are just posturing, but sometimes they escalate into fights when their beaks often inflict serious injury or death⁴.  Juvenile nuthatches have to wait in the wings in low-quality territories until a position in a breeding territory becomes available⁵. Though they are a small bird and reach adulthood at just 1 year, nuthatches have been recorded at 7 years old⁶.

Nuthatches are crafty birds. They store seeds and nuts for the winter by pushing them into gaps in tree bark or wood. Come nesting time, they will plug up their nest hole with mud, which hardens like concrete until only their bodies can pass through. This keeps out nest predators such as woodpeckers and competitors like starlings Sturnus vulgaris, but they can be over-enthusiatic, filling up the joins in nestboxes and even encasing them entirely ^1,3!
 I have also once seen one of a pair of nuthatches in Worcester use a piece of bark to prise off another part and wondered if this counted as tool use. This behaviour (this time with a small stick) has been photographed before.  Its American relative, the brown-headed nuthatch is renowned for using tools in a similar way.

Next time you’re in a woodland, make an effort to listen out for this agile and crafty character around a tree trunk near you.

References

1- Dominic Couzens. (2012) Garden Birds Confidential. Bounty Books.

2- Fransesca Greenoak. (1979) All the Birds of the Air. A. Brown and Sons.

3- Peter Holden and J.T.R. Sharrock. (1989) The RSPB book of British Birds. PAPERMAC, London.

4-Tim Harrison and Mike Toms. (2012) BTO Garden Bird of the Month – November: Nuthatch. Available from: http://www.discoverwildlife.com/blog/bto-garden-bird-month-%E2%80%93-november-nuthatch

5- Erik Matthysen.(1990) Behavioural and ecological correlates of territory quality in the Eurasian Nuthatch (Sitta europaea). The Auk, 107 (1), 86-95. Available from: http://www.jstor.org/discover/10.2307/4087805?uid=3738032&uid=2129&uid=2&uid=70&uid=4&sid=21102756365933

6- R.A. Robinson.(2005) BTO BirdFacts: profiles of birds occurring in Britain & Ireland: Nuthatch Sitta europaea Available from: http://blx1.bto.org/birdfacts/results/bob14790.htm

M is for Moorhen

MOORHEN (GALLINULA CHLOROPUS)

“Look there’s a moorhen.” said my schoolteacher.
“What’s a moorhen?” someone replied
“It’s a little, black duck.” he said.

The Moorhen is not a duck. Neither is it a chicken, but with their cocked tail and habit of strutting and pecking in the grass it is easy to see the resemblance. They are a rail, related to the Coot Fulica atra which they are often confused with.

The moorhen appears black, with a flashing white undertail and white stripe along the wing, but a closer look reveals its wings are dark brown. Offsetting their plumage, their pointed beak is a bright waxy red and yellow (The coot by contrast is all black with a white beak). When on land, the moorhen reveals its long, gangly legs and toes which spread its weight on aquatic vegetation or silty banks and propel it through the water.
The moorhen’s  loud, high-pitched voice is also very distinct. Their explosive ‘Pruuuk!’ call from a hiding place has often made me jump.

Moorhens are a familiar wetland bird, found almost anywhere there is fresh water from park lakes and marshes to small ponds, sometimes in gardens.  They are quite skittish and prefer to stay around bankside plants to hide from predators, though they often venture onto open lawns to feed. They are rarely seen flying, since they usually do it at night.They are generally most active in the evening.
Moorhens are omnivores, eating a variety of foods in water and on land,from algae, shoots, roots, fruits and seeds to invertebrates, small fish and amphibians, and human scraps if available.

For a waterbird, moorhens have unusual habits. They often roost, and even nest in tree branches and during freezing winters they may venture far from water to find food, sometimes ending up around garden bird tables¹.

Added to this, their breeding behaviour is quite remarkable among birds. To the casual observer, everything appears normal, since it is difficult to separate the sexes. Closer study shows that moorhens reverse normal avian gender roles.  It is the male who tends the eggs and young the most, whilst females compete for good father material. The male is also responsible for holding the family’s territory, providing a safe home to rear the chicks².

Another quirk to moorhen family life is cooperative breeding². Young from the year’s first brood may stay and help their parents raise later broods. Only two other British birds are known to do this, the Long-tailed Tit Aegithalos caudatus and the Swallow  Hirundo rustica. The parents obviously benefit from the reduced workload, and more chicks survive, but what’s in it for the stay-at-home teenager? By staying with it’s parents, the cooperative youngster avoids conflict with strangers in other territories, but also indirectly improves its gene pool. Since it shares genes with its younger siblings and can’t breed itself until adulthood, the helper actually improves its lifetime reproductive success (known as its ‘inclusive fitness’). See here for further explanation and photographs of this behaviour.

The moorhen’s nest is made of twigs, other plant parts and often plastic rubbish. It is usually built away from the banks to be out of reach of predators, either in the water or up to 8 metres above it in a tree.  Although it appears messy, the nest is meticulously woven together.
The chicks are very comical with messy black down, partly bald heads and feet that seem too big for their bodies, making them charmingly clumsy walkers. Juvenile moorhens are grey-brown with pale beaks reaching maturity at just one year old.

Though they seem dainty and skittish, Moorhens are ferocious fighters amongst their own kind.  Two aggressors rush towards each other and turn in a head-down display fanning their white undertails to show off their size. If neither backs down, they start a ferocious grapple, clawing each other’s heads and breasts with their long toes like fighting cockerels and ultimately aiming to dunk each other underwater. Most fights you will see during the breeding season are ‘cat fights’ between females over a choice boyfriend, whilst males fight over territory². See a dramatic video of both partners fighting here (video would not embed).

So next time you’re by the water and see a moorhen, look through the unassuming cover and admire the unique bird within, that will do anything for its family.

References

1-      RSPB Community Forum. (2010) Moorhen in the Garden!. Available from: http://www.rspb.org.uk/community/wildlife/homesforwildlife/f/905/p/7822/61771.aspx

2-      Africa Gómez. The surprising Moorhen. Available from: http://therattlingcrow.blogspot.co.uk/2010/03/surprising-moorhen.html

 

L is for Larus

LARUS (Lariid gulls)

Ok, this is cheating. This entry could have been focussed on the Lesser Black Backed Gull Larus fuscus, but it is difficult to talk about this species without comparison to others in the genus*.  

Any trip to the British coast will have a background of ‘gull-ness’, both the soundtrack of their territorial ‘trumpet calls’ and the image of pale ‘V’-shaped birds flying across the blue sea (No ship painting is worth its salt without gulls in), and of course the presence waiting for you to drop a chip. Love them or loathe them, they are the classic sea bird (Indeed the name Larus means ‘a sea bird’) and they add a certain romance to a beach holiday.

But look closer and you’ll notice different species. The larger gulls are distinguishable by the shade of their wings. The classic blue-grey ‘Sea gull’^ᵻ the Herring Gull L. argentatus (meaning ‘decorated with silver’), the darker grey Lesser Black-backed Gull L. fuscus (meany ‘dusky’) and the pitch black, Greater Black-backed Gull L. marinus, the largest gull in the world.  They are fairly similar, with a dagger-like yellow bill, red spot on the lower jaw (which acts as a feeding signal to their young), black-and-white tipped wings and a furrowed brow. The juveniles are a spotty brown. You may see another Lariid, the Common gull L. canus which is smaller with a slimmer, all yellow bill and rounded head. They are named from the middle English meaning plain, not abundant². A recent arrival, The Mediterranean gull L. melanocephalus , has a black head in summer, reduced to a spot in winter and a thick red beak (not to be confused with the black-headed gull Choriocephalus ridibundus).

Of course, you don’t have to go to the coast any more to see gulls in Britain. They’re now common in our cities, parks and rubbish dumps.  Herring gulls only moved into cities during the 1940’s³. Since then both Herring and Lesser Black Backs have increasingly exploited the artificial cliffs of flat-roof buildings for nesting (Much to the dismay of many human occupants), whilst commons forage on playing fields. The Great black-back is more coastal and hasn’t taken to landlubbing ways.

Gulls are able to adapt to new lifestyles with their generalist diet. They are omnivores, gulping down a variety of land and water invertebrates, small vertebrates, some plantstuffs, carrion and human scraps . On the coast they are mainly fish eaters, hence the herring gull was named as feeding flocks signalled the location of herring Clupea spp. shoals to fisherman, whilst the lesser black back was known as the ‘Coddy moddy’ for following young cod Gadus morhua².  Gulls can swallow large fish whole to gorge themselves (I once saw Japanese tourists feed a whole medium battered cod to a herring gull in one!).
The Great black back is a ferocious predator of larger animals including rabbits and seabirds. The common gull takes smaller fish and invertebrates, and unusually eats grain, hence the Devonshire name ‘Barley bird’².
Gulls have developed new behaviours to get their food, such as pirating from other seabirds, pattering the ground with their feet to bring up earthworms, dropping shellfish onto rocks to crack them and puncturing bin bags. They find a bonanza of easy pickings at rubbish dumps, but their adventurous tastes get them into trouble with inedible objects. One gull was found to have swallowed a mobile phone⁴!  The increasing amounts of plastic waste in our oceans is a huge problem for many seabirds.

With gulls increasingly moving into our living space, they seem to be doing well. The Lesser Black Back, traditionally a summer migrant wintering in Southern Europe, is even increasingly staying over⁵. However, the bigger picture is not good. The Herring gull is on the red list of threatened British birds, and the Black-backs and Common are classed as Amber^3,6. Rather than expanding, gulls are being pushed to move inland as overfishing depletes their natural food sources⁷. Whilst landfills once attracted them in needy times, inland gulls are now doing better than coastal dwellers, even though we try to deter them as a nuisance⁷. The fact is, if we want our seaside soundtrack to last, Britain’s gulls need all the support they can get.

*All of Britain’s gulls except the Kittiwake Rissa tridactyla used to be classed in the Larus genus, but a genetic study revealed this to be inaccurate¹. Thus the Black-headed Gull Choriocephalus ridibundus and the Little Gull Hydrocoloeus minutes are now classed separately.

^ᵻThe term 'Seagull' is technically wrong. It is not opposed to anything (i.e. there are no land gulls, river gulls etc) and most gulls do not rely on the sea. It’s often said only to truly apply to the kittiwake, a strictly oceanic species, but the name originally applied to the Common gull².

References

11-      J.-M. Ponsa, A. Hassanina, and P.-A. Crochet. (2005) Phylogenetic relationships within the Laridae (Charadriiformes: Aves) inferred from mitochondrial markers. Available from: http://www.researchgate.net/publication/7692222_Phylogenetic_relationships_within_the_Laridae_%28Charadriiformes_Aves%29_inferred_from_mitochondrial_markers

22-      Fransesca Greenoak. (1979) All the Birds of the Air. A. Brown and Sons.

33-      RSPB. (2013) Advice: Urban Gulls. Available from: http://www.rspb.org.uk/advice/gardening/unwantedvisitors/gulls/urbangulls.aspx

44-     C.J.Camphuysen, S.Boekhout, A.Gronert, V.Hunt , T van Nus. and J. Ouwehand, (2008). Bizarre prey items: odd food choices in herring gulls and lesser black-backed gulls at Texel.  Sula 21, 49-61. Cited by: Darren Naish. (2009) Mobile phones, medals, a doll’s legs, an entire army… is there anything a gull won’t swallow? Available from: http://scienceblogs.com/tetrapodzoology/2009/12/19/gull-swallows-phone/

55-      R.A. Robinson./ (2005) BTO BirdFacts: profiles of birds occurring in Britain & Ireland: Gulls: Lesser Black-backed Gull Larus fuscus   [Linnaeus, 1758]. Available from: http://blx1.bto.org/birdfacts/results/bob5910.htm

66-      R.A. Robinson. (2005) BTO BirdFacts: profiles of birds occurring in Britain & Ireland. (BTO Research Report 407). BTO, Thetford. Available from: http://www.bto.org/birdfacts

77-BBC. (2012) Who What Why: Why are there so many seagulls in cities? BBC News Magazine. Available from: http://www.bbc.co.uk/news/magazine-19490866